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2022 use of coronary computed tomographic angiography for patients presenting with acute chest pain to the emergency department: An expert consensus document of the Society of cardiovascular computed tomography (SCCT)

Endorsed by the American College of Radiology (ACR) and North American Society for cardiovascular Imaging (NASCI)
Published:September 28, 2022DOI:https://doi.org/10.1016/j.jcct.2022.09.003

      Abstract

      Coronary computed tomography angiography (CTA) improves the quality of care for patients presenting with acute chest pain (ACP) to the emergency department (ED), particularly in patients with low to intermediate likelihood of acute coronary syndrome (ACS). The Society of Cardiovascular Computed Tomography Guidelines Committee was formed to develop recommendations for acquiring, interpreting, and reporting of coronary CTA to ensure appropriate, safe, and efficient use of this modality. Because of the increasing use of coronary CTA testing for the evaluation of ACP patients, the Committee has been charged with the development of the present document to assist physicians and technologists. These recommendations were produced as an educational tool for practitioners evaluating acute chest pain patients in the ED, in the interest of developing systematic standards of practice for coronary CTA based on the best available data or broad expert consensus. Due to the highly variable nature of medical care, approaches to patient selection, preparation, protocol selection, interpretation or reporting that differs from these guidelines may represent an appropriate variation based on a legitimate assessment of an individual patient's needs.

      Abbreviations

      ACLS
      advanced cardiac life support
      ACP
      acute chest pain
      ACS
      acute coronary syndrome
      BMI
      body mass index
      CABG
      coronary artery bypass grafting
      CAC
      coronary artery calcium
      CAD
      coronary artery disease
      CAD-RADS
      Coronary Artery Disease Reporting and Data System
      CMR
      cardiovascular magnetic resonance imaging
      CTA
      computed tomographic angiography
      cTn
      Conventional cardiac troponin
      CTP
      Myocardial CT perfusion
      ECG
      electrocardiogram
      ED
      emergency department
      FFR-CT
      CT-based fractional flow reserve
      GFR
      glomerular filtration rate
      HRP
      high-risk (vulnerable) plaque
      Hs-Tn
      High-sensitivity cardiac troponin
      ICA
      invasive coronary angiography
      IV
      intravenous
      LV
      left ventricle
      MACE
      major adverse cardiovascular events
      MI
      myocardial infarction
      MIP
      maximum intensity projections
      MPI
      myocardial perfusion imaging
      MPR
      multi-planar reconstructions
      NSTEMI
      non-ST-segment elevation myocardial infarction
      SCAD
      spontaneous coronary artery dissection
      SCCT
      Society of Cardiovascular Computed Tomography
      SIS
      segment involvement score
      SPECT
      single photon-emission computed tomography
      STEMI
      ST-segment-elevation myocardial infarction
      TRO
      triple rule-out computed tomographic angiography

      1. Introduction

      Diagnosis and triage of emergency department (ED) patients with suspected acute coronary syndrome (ACS) consume a large and increasing amount of healthcare resources. It has been estimated that over 9 million ED patients with acute chest pain (ACP) are seen annually in the United States alone, with related healthcare costs of $13–15 billion.
      ,
      • Bhuiya F.A.
      • Pitts S.R.
      • McCaig L.F.
      Emergency department visits for chest pain and abdominal pain: United States, 1999-2008.
      ED overcrowding is associated with adverse outcomes for ACP patients, and consequently rapid triage has both health and economic consequences.
      • Pines J.M.
      • Pollack Jr., C.V.
      • Diercks D.B.
      • Chang A.M.
      • Shofer F.S.
      • Hollander J.E.
      The association between emergency department crowding and adverse cardiovascular outcomes in patients with chest pain.
      Further, the consequences of missing ACS are both a source of morbidity and mortality in such patients and remain a source of significant malpractice litigation. Therefore, expeditious, safe evaluation of ACP is a pressing need to increase ED efficiency, contain costs and improve outcomes.
      Coronary CTA is a proven strategy to safely expedite diagnosis and limit resource utilization for patients presenting with acute chest pain in the ED with no known prior coronary artery disease. The clinical value of coronary CTA in this setting is well-validated in numerous randomized-controlled trials
      • Dedic A.
      • Lubbers M.M.
      • Schaap J.
      • et al.
      Coronary CT angiography for suspected ACS in the era of high-sensitivity troponins: randomized multicenter study.
      • Goldstein J.A.
      • Chinnaiyan K.M.
      • Abidov A.
      • et al.
      The CT-STAT (coronary computed tomographic angiography for systematic triage of acute chest pain patients to treatment) trial.
      • Hoffmann U.
      • Truong Q.A.
      • Schoenfeld D.A.
      • et al.
      Coronary CT angiography versus standard evaluation in acute chest pain.
      • Levsky J.M.
      • Spevack D.M.
      • Travin M.I.
      • et al.
      Coronary computed tomography angiography versus radionuclide myocardial perfusion imaging in patients with chest pain admitted to telemetry: a randomized trial.
      • Linde J.J.
      • Hove J.D.
      • Sorgaard M.
      • et al.
      Long-term clinical impact of coronary CT angiography in patients with recent acute-onset chest pain: the randomized controlled CATCH trial.
      • Litt H.I.
      • Gatsonis C.
      • Snyder B.
      • et al.
      CT angiography for safe discharge of patients with possible acute coronary syndromes.
      • Sørgaard M.H.
      • Linde J.J.
      • Kühl J.T.
      • et al.
      Value of myocardial perfusion assessment with coronary computed tomography angiography in patients with recent acute-onset chest pain.
      • Bittner D.O.
      • Mayrhofer T.
      • Bamberg F.
      • et al.
      Impact of coronary calcification on clinical management in patients with acute chest pain.
      • Goldstein J.A.
      • Gallagher M.J.
      • O'Neill W.W.
      • Ross M.A.
      • O'Neil B.J.
      • Raff G.L.
      A randomized controlled trial of multi-slice coronary computed tomography for evaluation of acute chest pain.
      • Miller A.H.
      • Pepe P.E.
      • Peshock R.
      • et al.
      Is coronary computed tomography angiography a resource sparing strategy in the risk stratification and evaluation of acute chest pain? Results of a randomized controlled trial.
      • Gray A.J.
      • Roobottom C.
      • Smith J.E.
      • et al.
      Early computed tomography coronary angiography in patients with suspected acute coronary syndrome: randomised controlled trial.
      with an expanded evidence base since the original iteration of these guidelines.
      • Raff G.L.
      • Chinnaiyan K.M.
      • Cury R.C.
      • et al.
      Hoffmann U and Society of Cardiovascular Computed Tomography Guidelines C. SCCT guidelines on the use of coronary computed tomographic angiography for patients presenting with acute chest pain to the emergency department: a report of the Society of Cardiovascular Computed Tomography Guidelines Committee.
      Coronary CTA offers rapid evaluation of the degree of coronary stenosis and atherosclerosis, allows significant reduction in time-to-discharge, and ensures high risk patients are appropriately triaged to cardiac catheterization.
      • Raff G.L.
      • Chinnaiyan K.M.
      • Cury R.C.
      • et al.
      Hoffmann U and Society of Cardiovascular Computed Tomography Guidelines C. SCCT guidelines on the use of coronary computed tomographic angiography for patients presenting with acute chest pain to the emergency department: a report of the Society of Cardiovascular Computed Tomography Guidelines Committee.
      • Farkouh M.E.
      • Douglas P.S.
      The management of acute chest pain: what lies beyond the emergency department doors?.
      • Kumar V.
      • Weerakoon S.
      • Dey A.K.
      • et al.
      The evolving role of coronary CT angiography in Acute Coronary Syndromes.
      Rapid chest pain triage also limits nosocomial infection transmission between patients and medical staff, which is of particular importance during the Covid-era.
      • Choi A.D.
      • Abbara S.
      • Branch K.R.
      • et al.
      Society of cardiovascular computed tomography guidance for use of cardiac computed tomography amidst the COVID-19 pandemic endorsed by the American College of Cardiology.

      1.1 Value of coronary CTA in the ED

      In the ED setting, the high accuracy of coronary CTA is driven by its high sensitivity and negative predictive value for detecting or excluding obstructive coronary artery disease, particularly among patients with low-to-intermediate pretest risk for ACS.
      • Hulten E.
      • Pickett C.
      • Bittencourt M.S.
      • et al.
      Outcomes after coronary computed tomography angiography in the emergency department: a systematic review and meta-analysis of randomized, controlled trials.
      • Knuuti J.
      • Ballo H.
      • Juarez-Orozco L.E.
      • et al.
      The performance of non-invasive tests to rule-in and rule-out significant coronary artery stenosis in patients with stable angina: a meta-analysis focused on post-test disease probability.
      • Samad Z.
      • Hakeem A.
      • Mahmood S.S.
      • et al.
      A meta-analysis and systematic review of computed tomography angiography as a diagnostic triage tool for patients with chest pain presenting to the emergency department.
      • Staniak H.L.
      • Bittencourt M.S.
      • Pickett C.
      • et al.
      Coronary CT angiography for acute chest pain in the emergency department.
      In the Perfusion Imaging and CT-Understanding Relative Efficacy (PICTURE) trial,
      • Budoff M.J.
      • Li D.
      • Kazerooni E.A.
      • Thomas G.S.
      • Mieres J.H.
      • Shaw L.J.
      Diagnostic accuracy of noninvasive 64-row computed tomographic coronary angiography (CCTA) compared with myocardial perfusion imaging (MPI): the PICTURE study, A prospective multicenter trial.
      coronary CTA demonstrated per-patient sensitivity of 92% and specificity of 87% for significant coronary stenosis using invasive catheter angiography (ICA) as a reference standard, compared with stress myocardial perfusion imaging (per-patient sensitivity of 55% and specificity of 78%).
      Over the past decade, coronary CTA has established itself as a first-line imaging strategy for rapid triage of patients with low-to-intermediate risk ACP in the ED.
      • Dedic A.
      • Lubbers M.M.
      • Schaap J.
      • et al.
      Coronary CT angiography for suspected ACS in the era of high-sensitivity troponins: randomized multicenter study.
      • Goldstein J.A.
      • Chinnaiyan K.M.
      • Abidov A.
      • et al.
      The CT-STAT (coronary computed tomographic angiography for systematic triage of acute chest pain patients to treatment) trial.
      • Hoffmann U.
      • Truong Q.A.
      • Schoenfeld D.A.
      • et al.
      Coronary CT angiography versus standard evaluation in acute chest pain.
      • Levsky J.M.
      • Spevack D.M.
      • Travin M.I.
      • et al.
      Coronary computed tomography angiography versus radionuclide myocardial perfusion imaging in patients with chest pain admitted to telemetry: a randomized trial.
      • Linde J.J.
      • Hove J.D.
      • Sorgaard M.
      • et al.
      Long-term clinical impact of coronary CT angiography in patients with recent acute-onset chest pain: the randomized controlled CATCH trial.
      • Litt H.I.
      • Gatsonis C.
      • Snyder B.
      • et al.
      CT angiography for safe discharge of patients with possible acute coronary syndromes.
      ,
      • Bittner D.O.
      • Mayrhofer T.
      • Bamberg F.
      • et al.
      Impact of coronary calcification on clinical management in patients with acute chest pain.
      • Goldstein J.A.
      • Gallagher M.J.
      • O'Neill W.W.
      • Ross M.A.
      • O'Neil B.J.
      • Raff G.L.
      A randomized controlled trial of multi-slice coronary computed tomography for evaluation of acute chest pain.
      • Miller A.H.
      • Pepe P.E.
      • Peshock R.
      • et al.
      Is coronary computed tomography angiography a resource sparing strategy in the risk stratification and evaluation of acute chest pain? Results of a randomized controlled trial.
      ,
      • Hamilton-Craig C.
      • Fifoot A.
      • Hansen M.
      • et al.
      Diagnostic performance and cost of CT angiography versus stress ECG–a randomized prospective study of suspected acute coronary syndrome chest pain in the emergency department (CT-COMPARE).
      In the multicenter randomized-controlled CT-STAT trial,
      • Goldstein J.A.
      • Chinnaiyan K.M.
      • Abidov A.
      • et al.
      The CT-STAT (coronary computed tomographic angiography for systematic triage of acute chest pain patients to treatment) trial.
      699 patients with TIMI risk scores ≤4 were randomized to coronary CTA (n ​= ​361) or rest-stress myocardial perfusion imaging (MPI) (n = 338) and demonstrated a significant reduction in time-to-diagnosis with a coronary CTA approach (2.9 hours vs 6.2 hours, p ​< ​0.0001) and a low rate of major adverse cardiovascular events (MACE) in patients with a normal coronary CTA. Similar results were observed in ACRIN PA,
      • Litt H.I.
      • Gatsonis C.
      • Snyder B.
      • et al.
      CT angiography for safe discharge of patients with possible acute coronary syndromes.
      a randomized-controlled trial to compare coronary CTA in the ED to standard care, in which 30-day MACE was 0% among subjects discharged from the ED with a negative coronary CTA (95% confidence interval, 0 to 0.57). In the 2012 ROMICAT II trial,
      • Hoffmann U.
      • Truong Q.A.
      • Schoenfeld D.A.
      • et al.
      Coronary CT angiography versus standard evaluation in acute chest pain.
      1000 low-to-intermediate risk subjects were randomized 1:1 to coronary CTA or standard care, and demonstrated a significant reduction in ED length-of-stay among patients in the CTA arm (23.2 hours vs 30.8 hours, p ​< ​0.001). Further, there were more direct-from-ED discharges in the CTA arm (47% vs 12%, p ​< ​0.001) with comparable safety (28-day MACE 0.4% for CTA vs 1.2% for standard care, p ​= ​0.18), confirming improved efficiency of coronary CTA without a compromise in patient outcomes.
      More recently, the CT-COMPARE trial
      • Hamilton-Craig C.
      • Fifoot A.
      • Hansen M.
      • et al.
      Diagnostic performance and cost of CT angiography versus stress ECG–a randomized prospective study of suspected acute coronary syndrome chest pain in the emergency department (CT-COMPARE).
      randomized low-to-intermediate risk patients with acute chest pain to coronary CTA (n ​= ​322) or exercise ECG (n ​= ​240). Coronary CTA was associated with 20% reduction in hospital costs, and a 34% reduction in length-of-stay (13.5 hrs vs 20.7 hrs, p ​< ​0.0001). The long-term clinical value of coronary CTA in the ED was evaluated in the 2013 CATCH trial, which randomized 600 patients 1:1 to coronary CTA or functional testing and followed patients for a median duration of 18.7 months. Over this interval, the composite endpoint for MACE (including cardiac death, myocardial infarction, hospitalization for unstable angina, and late symptom-driven revascularization) was less frequent in the coronary CTA arm compared to functional testing (5 vs 14 events, p ​= ​0.04).

      1.1.1 Summary

      A wealth of data over the past decade, including 8 randomized controlled trials and 5 meta-analyses, validate coronary CTA as a first-line imaging strategy for rapid triage of low-to-intermediate risk ACP in the ED.
      • Dedic A.
      • Lubbers M.M.
      • Schaap J.
      • et al.
      Coronary CT angiography for suspected ACS in the era of high-sensitivity troponins: randomized multicenter study.
      ,
      • Levsky J.M.
      • Spevack D.M.
      • Travin M.I.
      • et al.
      Coronary computed tomography angiography versus radionuclide myocardial perfusion imaging in patients with chest pain admitted to telemetry: a randomized trial.
      ,
      • Linde J.J.
      • Hove J.D.
      • Sorgaard M.
      • et al.
      Long-term clinical impact of coronary CT angiography in patients with recent acute-onset chest pain: the randomized controlled CATCH trial.
      ,
      • Sørgaard M.H.
      • Linde J.J.
      • Kühl J.T.
      • et al.
      Value of myocardial perfusion assessment with coronary computed tomography angiography in patients with recent acute-onset chest pain.
      ,
      • Bittner D.O.
      • Mayrhofer T.
      • Bamberg F.
      • et al.
      Impact of coronary calcification on clinical management in patients with acute chest pain.
      ,
      • Hulten E.
      • Pickett C.
      • Bittencourt M.S.
      • et al.
      Outcomes after coronary computed tomography angiography in the emergency department: a systematic review and meta-analysis of randomized, controlled trials.
      ,
      • Samad Z.
      • Hakeem A.
      • Mahmood S.S.
      • et al.
      A meta-analysis and systematic review of computed tomography angiography as a diagnostic triage tool for patients with chest pain presenting to the emergency department.
      ,
      • Hamilton-Craig C.
      • Fifoot A.
      • Hansen M.
      • et al.
      Diagnostic performance and cost of CT angiography versus stress ECG–a randomized prospective study of suspected acute coronary syndrome chest pain in the emergency department (CT-COMPARE).
      • Nudi F.
      • Lotrionte M.
      • Biasucci L.M.
      • et al.
      Comparative safety and effectiveness of coronary computed tomography: systematic review and meta-analysis including 11 randomized controlled trials and 19,957 patients.
      • Chaikriangkrai K.
      • Palamaner Subash Shantha G.
      • Jhun H.Y.
      • et al.
      Prognostic value of coronary artery calcium score in acute chest pain patients without known coronary artery disease: systematic review and meta-analysis.
      • Foy A.J.
      • Dhruva S.S.
      • Peterson B.
      • Mandrola J.M.
      • Morgan D.J.
      • Redberg R.F.
      Coronary computed tomography angiography vs functional stress testing for patients with suspected coronary artery disease: a systematic review and meta-analysis.
      • Gray A.J.
      • Roobottom C.
      • Smith J.E.
      • et al.
      The RAPID-CTCA trial (Rapid Assessment of Potential Ischaemic Heart Disease with CTCA) — a multicentre parallel-group randomised trial to compare early computerised tomography coronary angiography versus standard care in patients presenting with suspected or confirmed acute coronary syndrome: study protocol for a randomised controlled trial.
      • Levsky J.M.
      • Haramati L.B.
      • Spevack D.M.
      • et al.
      Coronary computed tomography angiography versus stress echocardiography in acute chest pain.

      1.2 Coronary CTA in the era of high-sensitivity troponins

      Detecting early myocardial injury with high sensitivity troponin (hs-cTn) assays has become more common throughout the U.S. and internationally. High-sensitivity troponins are preferred over prior generations of conventional cardiac troponin (cTn) tests because they enable faster detection or exclusion of myocardial injury and increase diagnostic accuracy for ACS.
      • Cullen L.
      • Mueller C.
      • Parsonage W.A.
      • et al.
      Validation of high-sensitivity troponin I in a 2-hour diagnostic strategy to assess 30-day outcomes in emergency department patients with possible acute coronary syndrome.
      ,
      • Twerenbold R.
      • Boeddinghaus J.
      • Nestelberger T.
      • et al.
      Clinical use of high-sensitivity cardiac troponin in patients with suspected myocardial infarction.
      However, false positive results and borderline results are a concern as many other cardiac and non-cardiac etiologies can account for elevated hs-cTn measurements beyond epicardial CAD, including myocarditis, arrhythmia, cardiotoxicity, chronic kidney disease, heart failure, sepsis, rhabdomyolysis, chronic obstructive pulmonary disease, and pulmonary embolism.
      • Long B.
      • Long D.A.
      • Tannenbaum L.
      • Koyfman A.
      An emergency medicine approach to troponin elevation due to causes other than occlusion myocardial infarction.
      The 2016 BEACON trial
      • Dedic A.
      • Lubbers M.M.
      • Schaap J.
      • et al.
      Coronary CT angiography for suspected ACS in the era of high-sensitivity troponins: randomized multicenter study.
      aimed to compare a strategy of early coronary CTA versus standard care for suspected ACS following hs-cTn testing. Five hundred patients were randomized 1:1 to coronary CTA or standard care, and followed for the primary endpoint of 30-day rate of obstructive CAD requiring revascularization. While the primary endpoint was similar in both study arms (9% coronary CTA vs 7% standard care, p ​= ​0.40), CTA was associated with less outpatient testing (4% vs 10%, p ​< ​0.01) and lower direct medical costs (€337 vs. €511, p ​< ​0.01). Further, there were nonsignificant trends toward fewer repeat ED visits (5% vs 8%), and repeat hospitalizations (3% vs 6%) among patients in the CTA arm. A secondary analysis of ROMICAT II data demonstrated that hs-cTn and advanced CTA features (including stenosis ≥50% and the presence of high-risk plaque) had a significant improvement in accuracy for ACS when compared to conventional cardiac troponin testing.
      • Ferencik M.
      • Liu T.
      • Mayrhofer T.
      • et al.
      Hs-troponin I followed by CT angiography improves acute coronary syndrome risk stratification accuracy and work-up in acute chest pain patients: results from ROMICAT II trial.
      High-risk plaque features on coronary CTA allowed for more accurate risk stratification, particularly among patients with intermediate hs-cTn levels below the 99th percentile. In the PRECISE-CTCA trial,
      • Lee K.K.
      • Bularga A.
      • O'Brien R.
      • et al.
      Troponin-guided coronary computed tomographic angiography after exclusion of myocardial infarction.
      patients who presented to the ED with acute chest pain and intermediate hs-cTn concentrations (between 5 ng/L and the sex-specific 99th percentile) were 3× more likely to have CAD compared to those with low hs-cTn concentrations, suggesting further testing with coronary CTA in this population could aid in higher precision risk-stratification. Collectively, these data suggest hs-cTn and coronary CTA likely have complementary roles, and together may offer a superior chest pain triage strategy compared to any test used in isolation.

      1.2.1 Summary statement

      Coronary CTA is complementary to hs-cTn assays in the ED by improving specificity for ACS and identifying vulnerable anatomy.

      1.3 Coronary CTA in high-risk patients

      Recent evidence suggests an expanded role of coronary CTA for patients at higher pretest risk for ACS, including select patients with non-ST elevation myocardial infarction (NSTEMI) when a non-invasive strategy is preferred (e.g. bleeding risk, vascular access issues, patient preference).
      • Kumar V.
      • Weerakoon S.
      • Dey A.K.
      • et al.
      The evolving role of coronary CT angiography in Acute Coronary Syndromes.
      Potential benefits of coronary CTA within this higher-risk population include 1) rapid and accurate exclusion of obstructive CAD, 2) identification of high-risk plaque and atherosclerosis burden to improve future risk prediction, and 3) reduction in costs and resource utilization for cases where ICA can be safely avoided. An observational component of the randomized-controlled VERDICT trial
      • Linde J.J.
      • Kelbæk H.
      • Hansen T.F.
      • et al.
      Coronary CT angiography in patients with non-ST-segment elevation acute coronary syndrome.
      examined the accuracy of coronary CTA in 1023 patients with documented non-ST elevation ACS, and determined CTA maintains high accuracy to rule out clinically significant CAD (stenosis ≥50%) with a per-patient negative predictive value 91% and positive predictive value 88%. In addition, 33% of patients with non-ST elevation ACS had no clinically significant CAD (stenosis <50%), suggesting an opportunity for coronary CTA to safely defer ICA in nearly 1/3 of high-risk patients. In a follow-up study evaluating long-term outcomes after a median follow-up time of 4.2 years, coronary CTA was equivalent to ICA for the assessment of long-term risk.
      • Kofoed Klaus F.
      • Engstrøm T.
      • Sigvardsen Per E.
      • et al.
      Kelbæk H and Køber lars V. Prognostic value of coronary CT angiography in patients with non–ST-segment elevation acute coronary syndromes.
      Similar results were observed in CARMENTA,
      • Smulders M.W.
      • Kietselaer B.
      • Wildberger J.E.
      • et al.
      Initial imaging-guided strategy versus routine care in patients with non-ST-segment elevation myocardial infarction.
      a single-center, prospective, randomized-controlled trial designed to investigate whether cardiac magnetic resonance imaging (CMR) or coronary CTA could serve as an effective gatekeeper for ICA in NSTEMI patients presenting to the ED. Early coronary CTA safely reduced referrals for invasive coronary angiography by 34% compared to routine clinical care, with no increase in MACE after 1 year. More recently, in the RAPID-CTCA prospective multi-center randomized-controlled trial,
      • Gray A.J.
      • Roobottom C.
      • Smith J.E.
      • et al.
      Early computed tomography coronary angiography in patients with suspected acute coronary syndrome: randomised controlled trial.
      ,
      • Gray A.J.
      • Roobottom C.
      • Smith J.E.
      • et al.
      The RAPID-CTCA trial (Rapid Assessment of Potential Ischaemic Heart Disease with CTCA) — a multicentre parallel-group randomised trial to compare early computerised tomography coronary angiography versus standard care in patients presenting with suspected or confirmed acute coronary syndrome: study protocol for a randomised controlled trial.
      1748 patients at intermediate-to-high risk for ACS were randomized to coronary CTA with standard care versus standard care alone. Pretest risk was established on the basis of prior CAD, abnormal ECG, or elevated cardiac biomarkers. While the primary outcome of all-cause death or MI at 1 year was similar in both arms (5.8% in the CTA group vs 6.1% in standard care), coronary CTA significantly reduced referrals for invasive coronary angiography (HR 0.81, 95% CI 0.72–0.92), underscoring a potential role as a gatekeeper among higher risk patients.

      1.3.1 Summary

      Recent evidence supports a potential role for coronary CTA in select non-ST-elevation ACS patients when an invasive strategy is not preferred due to clinical variables (e.g. high bleeding risk, patient preference, vascular access issues, etc).

      1.4 Functional testing with CT

      CT-based fractional flow reserve (FFR-CT) and stress myocardial CT perfusion (CTP) are established techniques for evaluating the hemodynamic significance of coronary stenosis.
      • Sørgaard M.H.
      • Linde J.J.
      • Kühl J.T.
      • et al.
      Value of myocardial perfusion assessment with coronary computed tomography angiography in patients with recent acute-onset chest pain.
      ,
      • Dewey M.
      • Rochitte C.E.
      • Ostovaneh M.R.
      • et al.
      Prognostic value of noninvasive combined anatomic/functional assessment by cardiac CT in patients with suspected coronary artery disease — comparison with invasive coronary angiography and nuclear myocardial perfusion imaging for the five-year-follow up of the CORE320 multicenter study.
      • Feuchtner G.M.
      • Plank F.
      • Pena C.
      • et al.
      Evaluation of myocardial CT perfusion in patients presenting with acute chest pain to the emergency department: comparison with SPECT-myocardial perfusion imaging.
      • Grandhi G.R.
      • Batlle J.C.
      • Maroules C.D.
      • et al.
      Combined stress myocardial CT perfusion and coronary CT angiography as a feasible strategy among patients presenting with acute chest pain to the emergency department.
      • Ko S.M.
      • Choi J.W.
      • Song M.G.
      • et al.
      Myocardial perfusion imaging using adenosine-induced stress dual-energy computed tomography of the heart: comparison with cardiac magnetic resonance imaging and conventional coronary angiography.
      • Rief M.
      • Chen M.Y.
      • Vavere A.L.
      • et al.
      Coronary artery disease: analysis of diagnostic performance of CT perfusion and MR perfusion imaging in comparison with quantitative coronary angiography and SPECT-multicenter prospective trial.
      • Rochitte C.E.
      • George R.T.
      • Chen M.Y.
      • et al.
      Computed tomography angiography and perfusion to assess coronary artery stenosis causing perfusion defects by single photon emission computed tomography: the CORE320 study.
      • Chinnaiyan K.M.
      • Safian R.D.
      • Gallagher M.L.
      • et al.
      Clinical use of CT-derived fractional flow reserve in the emergency department.
      • Douglas P.S.
      • Pontone G.
      • Hlatky M.A.
      • et al.
      Clinical outcomes of fractional flow reserve by computed tomographic angiography-guided diagnostic strategies vs. usual care in patients with suspected coronary artery disease: the prospective longitudinal trial of FFR(CT): outcome and resource impacts study.
      • Fairbairn T.A.
      • Nieman K.
      • Akasaka T.
      • et al.
      Real-world clinical utility and impact on clinical decision-making of coronary computed tomography angiography-derived fractional flow reserve: lessons from the ADVANCE Registry.
      • Ferencik M.
      • Lu M.T.
      • Mayrhofer T.
      • et al.
      Non-invasive fractional flow reserve derived from coronary computed tomography angiography in patients with acute chest pain: subgroup analysis of the ROMICAT II trial.
      • Martin S.S.
      • Mastrodicasa D.
      • van Assen M.
      • et al.
      Value of machine learning-based coronary CT fractional flow reserve applied to triple-rule-out CT angiography in acute chest pain.
      • Nørgaard B.L.
      • Leipsic J.
      • Gaur S.
      • et al.
      Diagnostic performance of noninvasive fractional flow reserve derived from coronary computed tomography angiography in suspected coronary artery disease: the NXT trial (Analysis of Coronary Blood Flow Using CT Angiography: next Steps).
      • Patel M.R.
      • Nørgaard B.L.
      • Fairbairn T.A.
      • et al.
      1-Year impact on medical practice and clinical outcomes of FFR(CT): the ADVANCE registry.
      • Stuijfzand W.J.
      • van Rosendael A.R.
      • Lin F.Y.
      • et al.
      Stress myocardial perfusion imaging vs coronary computed tomographic angiography for diagnosis of invasive vessel-specific coronary physiology: predictive modeling results from the computed tomographic evaluation of atherosclerotic determinants of myocardial ischemia (CREDENCE) trial.
      Both strategies offer incremental value over coronary CTA, improving its diagnostic accuracy by increasing specificity and positive predictive value.
      • Rochitte C.E.
      • George R.T.
      • Chen M.Y.
      • et al.
      Computed tomography angiography and perfusion to assess coronary artery stenosis causing perfusion defects by single photon emission computed tomography: the CORE320 study.
      ,
      • Nørgaard B.L.
      • Leipsic J.
      • Gaur S.
      • et al.
      Diagnostic performance of noninvasive fractional flow reserve derived from coronary computed tomography angiography in suspected coronary artery disease: the NXT trial (Analysis of Coronary Blood Flow Using CT Angiography: next Steps).
      ,
      • Parikh R.
      • Patel A.
      • Lu B.
      • Senapati A.
      • Mahmarian J.
      • Chang S.M.
      Cardiac computed tomography for comprehensive coronary assessment: beyond diagnosis of anatomic stenosis.
      They are most appropriate in situations where the presence or absence of ischemia may guide patient management, as with an intermediate-grade stenosis on coronary CTA (i.e. 40-80% stenosis).
      • Narula J.
      • Chandrashekhar Y.
      • Ahmadi A.
      • et al.
      2021 expert consensus document on coronary computed tomographic angiography: a report of the society of cardiovascular computed tomography.
      ,
      • Patel A.R.
      • Bamberg F.
      • Branch K.
      • et al.
      Society of cardiovascular computed tomography expert consensus document on myocardial computed tomography perfusion imaging.
      While the clinical utility of these strategies in the ED setting is not fully recognized, there is evidence both FFR-CT and CTP offer more comprehensive evaluation of coronary anatomy and physiology, potentially eliminating unnecessary invasive coronary angiograms.

      1.4.1 FFR-CT

      FFR-CT offers evaluation of lesion-specific physiology from a coronary CTA dataset using computational flow dynamic modeling and some hemodynamic assumptions. It has been shown to improve the specificity and accuracy for functionally significant coronary artery disease in patients with stable (chronic) coronary syndromes. In the NXT trial,
      • Nørgaard B.L.
      • Leipsic J.
      • Gaur S.
      • et al.
      Diagnostic performance of noninvasive fractional flow reserve derived from coronary computed tomography angiography in suspected coronary artery disease: the NXT trial (Analysis of Coronary Blood Flow Using CT Angiography: next Steps).
      which compared the diagnostic performance of FFR-CT ≤0.80 vs coronary CTA stenosis >50% among patients with stable chest pain, the specificity for detecting stenosis ≥50% on invasive coronary angiography and invasive FFR ≤0.80 improved from 34% (CTA) to 79% (FFR-CT).
      Negative FFR-CT results are associated with good prognosis and may serve as a gatekeeper for cardiac catheterization. In the ADVANCE multicenter registry
      • Fairbairn T.A.
      • Nieman K.
      • Akasaka T.
      • et al.
      Real-world clinical utility and impact on clinical decision-making of coronary computed tomography angiography-derived fractional flow reserve: lessons from the ADVANCE Registry.
      of over 5000 patients, there was 0% 90-day death or MI in all patients with FFR-CT >0.80. One-year follow-up
      • Patel M.R.
      • Nørgaard B.L.
      • Fairbairn T.A.
      • et al.
      1-Year impact on medical practice and clinical outcomes of FFR(CT): the ADVANCE registry.
      data from the registry also demonstrated a low 0.6% rate of death and MI with FFR-CT >0.80. In the PLATFORM registry
      • Douglas P.S.
      • Pontone G.
      • Hlatky M.A.
      • et al.
      Clinical outcomes of fractional flow reserve by computed tomographic angiography-guided diagnostic strategies vs. usual care in patients with suspected coronary artery disease: the prospective longitudinal trial of FFR(CT): outcome and resource impacts study.
      of 584 patients with new onset chest pain, FFR-CT reduced the use of invasive coronary angiography among patients undergoing coronary CTA, with superior discrimination for invasive FFR <0.80 compared to CTA alone (p ​< ​0.0001). However, the majority of patients enrolled in these studies presented with stable chest pain and did not undergo evaluation in the ED.
      Recent evidence suggests FFR-CT may provide clinically meaningful value in the ED setting. In a post hoc analysis of ROMICAT II,
      • Ferencik M.
      • Lu M.T.
      • Mayrhofer T.
      • et al.
      Non-invasive fractional flow reserve derived from coronary computed tomography angiography in patients with acute chest pain: subgroup analysis of the ROMICAT II trial.
      FFR-CT in the ED setting was able to downgrade severely stenotic lesions (>70% stenosis) on coronary CTA by more than half. Further, over 1/3 of patients with mild (25–49%) stenosis were noted to have hemodynamically significant flow limitation (FFR-CT <0.80). A more recent single-center observational study evaluated the feasibility, safety, clinical outcomes, and costs associated with FFR-CT in the ED setting.
      • Chinnaiyan K.M.
      • Safian R.D.
      • Gallagher M.L.
      • et al.
      Clinical use of CT-derived fractional flow reserve in the emergency department.
      The investigators found no significant difference in MACE when FFR-CT was added to coronary CTA compared with coronary CTA alone (2.7% vs 4.3%, p ​= ​0.310), and no deaths or myocardial infarctions occurred with negative FFR-CT when revascularization was deferred.

      1.4.2 CTP

      Myocardial CTP following vasodilator stress has been significantly validated over the last decade to identify functionally significant CAD.
      • Sørgaard M.H.
      • Linde J.J.
      • Kühl J.T.
      • et al.
      Value of myocardial perfusion assessment with coronary computed tomography angiography in patients with recent acute-onset chest pain.
      ,
      • Feuchtner G.M.
      • Plank F.
      • Pena C.
      • et al.
      Evaluation of myocardial CT perfusion in patients presenting with acute chest pain to the emergency department: comparison with SPECT-myocardial perfusion imaging.
      ,
      • Ko S.M.
      • Choi J.W.
      • Song M.G.
      • et al.
      Myocardial perfusion imaging using adenosine-induced stress dual-energy computed tomography of the heart: comparison with cardiac magnetic resonance imaging and conventional coronary angiography.
      • Rief M.
      • Chen M.Y.
      • Vavere A.L.
      • et al.
      Coronary artery disease: analysis of diagnostic performance of CT perfusion and MR perfusion imaging in comparison with quantitative coronary angiography and SPECT-multicenter prospective trial.
      • Rochitte C.E.
      • George R.T.
      • Chen M.Y.
      • et al.
      Computed tomography angiography and perfusion to assess coronary artery stenosis causing perfusion defects by single photon emission computed tomography: the CORE320 study.
      ,
      • Parikh R.
      • Patel A.
      • Lu B.
      • Senapati A.
      • Mahmarian J.
      • Chang S.M.
      Cardiac computed tomography for comprehensive coronary assessment: beyond diagnosis of anatomic stenosis.
      ,
      • Patel A.R.
      • Bamberg F.
      • Branch K.
      • et al.
      Society of cardiovascular computed tomography expert consensus document on myocardial computed tomography perfusion imaging.
      Both static and dynamic CT perfusion protocols have been described, as well as dual-energy CT perfusion which offers the highest contrast differentiation but requires specific scanner hardware. Static CTP is technically simple and offers rapid analysis and interpretation with comparatively low radiation exposure. Expert consensus guidelines on proper utilization and performance of CTP were recently published by the SCCT.
      • Patel A.R.
      • Bamberg F.
      • Branch K.
      • et al.
      Society of cardiovascular computed tomography expert consensus document on myocardial computed tomography perfusion imaging.
      Several studies have examined the diagnostic utility of myocardial CTP in the ED setting. In the Baptist Health of South Florida trial
      • Feuchtner G.M.
      • Plank F.
      • Pena C.
      • et al.
      Evaluation of myocardial CT perfusion in patients presenting with acute chest pain to the emergency department: comparison with SPECT-myocardial perfusion imaging.
      of 76 patients presenting to the ED with ACP, the addition of rest myocardial CTP to coronary CTA improved accuracy and increased positive predictive value from 67% to 90%. In another prospective trial of 145 patients of the same group,
      • Grandhi G.R.
      • Batlle J.C.
      • Maroules C.D.
      • et al.
      Combined stress myocardial CT perfusion and coronary CT angiography as a feasible strategy among patients presenting with acute chest pain to the emergency department.
      direct costs and length-of-stay with a combined stress CTP/CTA protocol were compared to SPECT myocardial perfusion imaging among ACP patients at intermediate risk for ACS. Mean length-of-stay was 28% shorter and mean direct costs were 44% lower with stress CTP/CTA compared to SPECT. In the CATCH-2 trial,
      • Sørgaard M.H.
      • Linde J.J.
      • Kühl J.T.
      • et al.
      Value of myocardial perfusion assessment with coronary computed tomography angiography in patients with recent acute-onset chest pain.
      300 patients hospitalized for ACP were randomized 1:1 to combined myocardial CTP and coronary CTA or coronary CTA alone, and the primary endpoint was frequency of coronary revascularization among patients referred for invasive coronary angiography. While there was no difference in the primary endpoint, combined stress CTP/CTA protocol resulted in significantly fewer referrals for invasive coronary angiography compared to CTA alone (14% vs 30%, p ​< ​0.0001), with similar outcomes after a median follow-up of 1.5 years, highlighting a potential gatekeeping role for CTP/CTA protocol.

      1.4.3 Summary

      Coronary CTA combined with FFR-CT or CTP may offer a comprehensive evaluation of coronary anatomy and physiology, potentially eliminating unnecessary invasive coronary angiograms.

      1.5 Atherosclerosis burden

      Large-scale clinical outcomes data have related plaque burden on coronary CTA to adverse CAD outcomes. Data from the CONFIRM registry
      • Schulman-Marcus J.
      • Hartaigh B.
      • Gransar H.
      • et al.
      Sex-specific associations between coronary artery plaque extent and risk of major adverse cardiovascular events: the CONFIRM long-term registry.
      ,
      • Shaw L.J.
      • Hausleiter J.
      • Achenbach S.
      • et al.
      Coronary computed tomographic angiography as a gatekeeper to invasive diagnostic and surgical procedures: results from the multicenter CONFIRM (coronary CT angiography evaluation for clinical outcomes: an international multicenter) registry.
      demonstrated that absence of CAD on coronary CTA is associated with a very favorable prognosis, and as coronary plaque burden increases, so does the risk of MACE and all-cause mortality. In a cohort of 3242 patients followed over a median duration of 3.6 years, a greater extent of coronary plaque on CTA conferred higher risk of MACE independent of stenosis.
      • Bittencourt M.S.
      • Hulten E.
      • Ghoshhajra B.
      • et al.
      Prognostic value of nonobstructive and obstructive coronary artery disease detected by coronary computed tomography angiography to identify cardiovascular events.
      Patients with non-obstructive plaque and extensive plaque burden (defined by a segment involvement score >4) had a similar adjusted hazard ratio for MACE as did patients with obstructive CAD and lower plaque burden (segment involvement score ≤4).

      1.6 High-risk plaque

      Coronary CTA can detect high-risk plaque features associated with greater risk of plaque rupture and ACS, independent of stenosis severity.
      • Motoyama S.
      • Ito H.
      • Sarai M.
      • et al.
      Plaque characterization by coronary computed tomography angiography and the likelihood of acute coronary events in mid-term follow-up.
      • Narula J.
      • Nakano M.
      • Virmani R.
      • et al.
      Histopathologic characteristics of atherosclerotic coronary disease and implications of the findings for the invasive and noninvasive detection of vulnerable plaques.
      • Puchner S.B.
      • Liu T.
      • Mayrhofer T.
      • et al.
      High-risk plaque detected on coronary CT angiography predicts acute coronary syndromes independent of significant stenosis in acute chest pain: results from the ROMICAT-II trial.
      • Taron J.
      • Foldyna B.
      • Mayrhofer T.
      • et al.
      Risk stratification with the use of coronary computed tomographic angiography in patients with nonobstructive coronary artery disease.
      • Williams M.C.
      • Moss A.J.
      • Dweck M.
      • et al.
      Coronary artery plaque characteristics associated with adverse outcomes in the SCOT-heart study.
      This is particularly important in the ED setting, as most precursors of ACS and culprit lesions are non-obstructive.
      • Shaw L.J.
      • Blankstein R.
      • Bax J.J.
      • et al.
      Society of cardiovascular computed tomography/north American society of cardiovascular imaging – expert consensus document on coronary CT imaging of atherosclerotic plaque.
      ,
      • Chang H.J.
      • Lin F.Y.
      • Lee S.E.
      • et al.
      Coronary atherosclerotic precursors of acute coronary syndromes.
      High-risk plaque features include positive remodeling, low attenuation (<30 Hounsfield Units), napkin ring sign, and spotty calcification.
      • Shaw L.J.
      • Blankstein R.
      • Bax J.J.
      • et al.
      Society of cardiovascular computed tomography/north American society of cardiovascular imaging – expert consensus document on coronary CT imaging of atherosclerotic plaque.
      In a post hoc analysis of ROMICAT II data, high-risk features on CTA increased the likelihood of ACS with a relative risk of 32.0, and this increased risk was independent of stenosis severity and clinical risk assessment.
      • Puchner S.B.
      • Liu T.
      • Mayrhofer T.
      • et al.
      High-risk plaque detected on coronary CT angiography predicts acute coronary syndromes independent of significant stenosis in acute chest pain: results from the ROMICAT-II trial.
      In the ICONIC trial,
      • Chang H.J.
      • Lin F.Y.
      • Lee S.E.
      • et al.
      Coronary atherosclerotic precursors of acute coronary syndromes.
      a nested case-control study from the CONFIRM registry, quantitative coronary plaque evaluation, including assessment of high-risk plaque and plaque composition, identified high-risk patients at risk for ACS above and beyond stenosis severity and aggregate plaque burden. Further, results from the CREDENCE trial
      • Stuijfzand W.J.
      • van Rosendael A.R.
      • Lin F.Y.
      • et al.
      Stress myocardial perfusion imaging vs coronary computed tomographic angiography for diagnosis of invasive vessel-specific coronary physiology: predictive modeling results from the computed tomographic evaluation of atherosclerotic determinants of myocardial ischemia (CREDENCE) trial.
      demonstrated that comprehensive plaque measures on coronary CTA improved prediction of vessel-specific coronary physiology more so than stress-induced myocardial perfusion defects, among patients referred for nonemergent invasive coronary angiography. In light of this evidence, a recent expert consensus document
      • Shaw L.J.
      • Blankstein R.
      • Bax J.J.
      • et al.
      Society of cardiovascular computed tomography/north American society of cardiovascular imaging – expert consensus document on coronary CT imaging of atherosclerotic plaque.
      was developed by the SCCT for the reporting atherosclerosis on coronary CTA.

      1.6.1 Summary statement

      High-risk plaque on coronary CTA may provide additional prognostic value beyond stenosis severity, although it remains unclear how plaque morphology should influence decision-making in the ED setting.

      1.7 Societal endorsements

      Numerous professional societies have embraced coronary CTA as a first-line triage strategy for chest pain in select patients. In the 2015 Multi-Society Appropriate Utilization of Cardiovascular Imaging in Emergency Department Patients with Chest Pain document,
      • Rybicki F.J.
      • Udelson J.E.
      • Peacock W.F.
      • et al.
      2015 ACR/ACC/AHA/AATS/ACEP/ASNC/NASCI/SAEM/SCCT/SCMR/SCPC/SNMMI/STR/STS appropriate utilization of cardiovascular imaging in emergency department patients with chest pain.
      coronary CTA was designated “appropriate” in ACP patients with low or intermediate pretest likelihood of ACS, and for patients with equivocal initial diagnosis of NSTEMI where initial troponin is equivocal or elevated without additional evidence of ACS. In 2016, the National Institute for Health and Clinical Excellence within the United Kingdom updated their chest pain guidelines,
      recommending that all patients with typical or atypical angina without STEMI be referred directly for coronary CTA as a first-line test, reserving functional testing as a second-order test for patients with non-diagnostic or inconclusive CT exams. However, it should be noted that the updated NICE guidelines excluded patients with acute chest pain.
      In the 2020 European Society of Cardiology guidelines for the management of ACS in patients without persistent ST-segment elevation,
      • Collet J.P.
      • Thiele H.
      • Barbato E.
      • et al.
      2020 ESC Guidelines for the management of acute coronary syndromes in patients presenting without persistent ST-segment elevation.
      coronary CTA received a “Class I” endorsement (“Level A″ quality of evidence) for early triage of patients with low-to-intermediate risk chest pain with normal ECG and negative troponins, and in patients with inconclusive or equivocal troponins. The evidence also prompted inclusion of coronary CTA as a usually appropriate initial imaging strategy in the American College of Radiology Appropriateness Criteria on acute nonspecific chest pain with low probability of coronary artery disease.
      • Beache G.M.
      • Mohammed T.H.
      • Hurwitz Koweek L.M.
      • et al.
      Appropriateness Criteria® acute nonspecific chest pain-low probability of coronary artery disease..
      Most recently, updated chest pain guidelines
      • Gulati M.
      • Levy P.D.
      • Mukherjee D.
      • et al.
      2021 AHA/ACC/ASE/CHEST/SAEM/SCCT/SCMR guideline for the evaluation and diagnosis of chest pain: a report of the American College of Cardiology/American heart association joint committee on clinical practice guidelines.
      from the American College of Cardiology and the American Heart Association elevated the role of coronary CTA for the non-invasive assessment of patients with either acute or stable chest pain. Coronary CTA is the only non-invasive testing modality issued a “Class I” endorsement by the ACC/AHA for patients with acute or stable chest pain, supported by “Level A” quality of evidence. Other modalities also received a Class I endorsement, but “Level B” quality of evidence.

      1.7.1 Summary

      Coronary CTA is endorsed by multiple professional societies as a first-line triage strategy for ACP in the ED, including the American College of Cardiology/American Heart Association and the European Society of Cardiology.
      • Rybicki F.J.
      • Udelson J.E.
      • Peacock W.F.
      • et al.
      2015 ACR/ACC/AHA/AATS/ACEP/ASNC/NASCI/SAEM/SCCT/SCMR/SCPC/SNMMI/STR/STS appropriate utilization of cardiovascular imaging in emergency department patients with chest pain.
      ,
      • Collet J.P.
      • Thiele H.
      • Barbato E.
      • et al.
      2020 ESC Guidelines for the management of acute coronary syndromes in patients presenting without persistent ST-segment elevation.
      ,
      • Gulati M.
      • Levy P.D.
      • Mukherjee D.
      • et al.
      2021 AHA/ACC/ASE/CHEST/SAEM/SCCT/SCMR guideline for the evaluation and diagnosis of chest pain: a report of the American College of Cardiology/American heart association joint committee on clinical practice guidelines.

      2. Site requirements

      2.1 Needs assessment

      A preliminary needs assessment should be undertaken prior to initiating a new coronary CTA program for the evaluation of ACP patients.
      • Maroules C.D.
      • Blaha M.J.
      • El-Haddad M.A.
      • Ferencik M.
      • Cury R.C.
      Establishing a successful coronary CT angiography program in the emergency department: official writing of the fellow and resident leaders of the society of cardiovascular computed tomography (FiRST).
      This assessment should be conducted jointly by representatives from Emergency Medicine, Radiology, and Cardiology, and as applicable, the medical center administration. There also should be evidence that sufficient case volume and multi-departmental buy in will be likely to maintain performance and interpretation expertise, and that the resources are available to achieve rapid, high-quality studies, and interpretations available during sufficient service hours to benefit patients.

      2.2 Equipment

      CT scanner equipment should include multi-detector scanners with a minimum of 64 detector-rows and appropriate cardiac software.
      • Abbara S.
      • Blanke P.
      • Maroules C.D.
      • et al.
      SCCT guidelines for the performance and acquisition of coronary computed tomographic angiography: a report of the society of cardiovascular computed tomography guidelines committee: endorsed by the north American society for cardiovascular imaging (nasci).
      Modern CT scanners provide higher temporal resolution (ranging from 66 to 150 msec), allowing for coronary CTA imaging with less contrast, lower radiation, and fewer artifacts. Patient-specific tube potential and current adjustment should be available.
      • Bischoff B.
      • Hein F.
      • Meyer T.
      • et al.
      Impact of a reduced tube voltage on CT angiography and radiation dose: results of the PROTECTION I study.
      Patient safety equipment including advanced cardiovascular life support (ACLS) equipment should be present in the patient preparation and scanner areas. Scanners should be equipped to perform prospectively triggered axial scanning with ECG-gated tube current modulation. Low dose acquisition modes such as volumetric acquisition or high-pitch scan mode are advantageous and should be utilized if available and appropriate. The use of iterative or model-based reconstruction to facilitate radiation dose reduction is also strongly recommended. Periodic review of the site's radiation levels and comparison with published references should be performed at least twice a year.
      • Stocker T.J.
      • Deseive S.
      • Leipsic J.
      • et al.
      Hausleiter J and investigators PV. Reduction in radiation exposure in cardiovascular computed tomography imaging: results from the PROspective multicenter registry on radiaTion dose Estimates of cardiac CT angIOgraphy iN daily practice in 2017 (PROTECTION VI).
      Image interpretation should be performed with 3D post-processing software capable of displaying reconstructed axial data, multi-planar reconstructions (MPRs) including curved MPRs and maximum intensity projections (MIPs).
      • Leipsic J.
      • Abbara S.
      • Achenbach S.
      • et al.
      SCCT guidelines for the interpretation and reporting of coronary CT angiography: a report of the Society of Cardiovascular Computed Tomography Guidelines Committee.

      2.3 Staff

      ED programs should be initiated only at sites with sufficient experience and case volume, with an expected minimum of 200 coronary CTA cases within the previous year or additional outside support for training the local staff and implementation of the program. At least one technologist with prior experience of at least 100 coronary CTA scans is recommended to initiate the program. Properly trained ACLS certified nursing or similar qualified staff should supervise premedication of patients, consistent with institutional policy. A rapid response team and/or an ACLS certified physician should be readily available for prompt response to urgent or emergent complications. The scanner and staffing service hours must satisfy ED minimum requirements.

      2.4 Training & interpreting physician requirements

      All coronary CTA exams should be performed and interpreted by physicians adequately trained in cardiac CT, who have achieved at least Independent Practitioner status as defined in recent training guidelines issued by SCCT.
      • Choi A.D.
      • Thomas D.M.
      • Lee J.
      • et al.
      2020 SCCT guideline for training Cardiology and Radiology trainees as independent practitioners (level II) and advanced practitioners (level III) in cardiovascular computed tomography: a statement from the society of cardiovascular computed tomography.
      This includes at least 250 mentored coronary CTA exams, among other criteria. Radiologists interpreting coronary CTA exams should also follow American College of Radiology (ACR) training standards.
      ACR-NASCI-SPR practice parameter for the performance and interpretation of cardiac computed tomography (CT). Resolution 45..
      Due to the severe consequences of missed ACS, additional physician experience is recommended for physicians reading ED coronary CTA scans. Interpreting physicians should be promptly available in person or by phone for consultation about patient preparation and scan protocoling. A qualified physician should also interpret the non-cardiac anatomy on all scans either as the primary reader or as a collaborating physician.

      2.5 Quality assurance

      A quality assurance program is recommended with quality targets, including: a diagnostic-quality scan rate of ≥95%, a quarterly median radiation dose rate within the reference level (dose-length product 110-338 mGy-cm)
      • Stocker T.J.
      • Deseive S.
      • Leipsic J.
      • et al.
      Hausleiter J and investigators PV. Reduction in radiation exposure in cardiovascular computed tomography imaging: results from the PROspective multicenter registry on radiaTion dose Estimates of cardiac CT angIOgraphy iN daily practice in 2017 (PROTECTION VI).
      and a quarterly comparative review of cases with both coronary CTA and invasive angiography that demonstrates a median accuracy of at least 75% per-patient.

      2.6 Implementation

      Developing an algorithm for the appropriate triage of ACP patients into well-established clinical pathways is critical for successful program implementation. For example, a five-tiered chest pain pathway can be utilized for patients with no known CAD, as depicted in Table 2a. All patients and all imaging strategies should be included in the algorithm that should be understood and agreed upon by stakeholders including ED physicians, radiologists, cardiologists, nursing, hospitalists, and medical center administration.

      3. Patient selection

      3.1 Evaluating pre-test likelihood of ACS

      Patient selection is primarily guided by the patient's history, clinical presentation, ECG and initial biomarker assessment (Fig. 1). Clinically appropriate patients should have reasonable clinical suspicion of ACS. A careful history and physical examination should precede any cardiac testing, to exclude alternative non-coronary diagnoses and to help define the pre-test likelihood of ACS. ECG should be acquired and reviewed for STEMI within 10 minutes of arrival to the ED. Cardiac troponin or hs-cTn should be measured as soon as possible. High sensitivity troponin assays are preferred for establishing a diagnosis of acute myocardial infarction due to their improved performance over contemporary cTn.
      • Twerenbold R.
      • Boeddinghaus J.
      • Nestelberger T.
      • et al.
      Clinical use of high-sensitivity cardiac troponin in patients with suspected myocardial infarction.
      ,
      • Long B.
      • Long D.A.
      • Tannenbaum L.
      • Koyfman A.
      An emergency medicine approach to troponin elevation due to causes other than occlusion myocardial infarction.
      Clinicians should be familiar with 99th percentile upper reference limit for the hs-cTn or conventional cTn assay used at their local institution.
      Fig. 1
      Fig. 1Patient-centric algorithm for acute chest pain in the ED.
      Risk stratification tools for ACS can help categorize patients into low-, intermediate- and high-risk. Commonly used tools in Emergency Medicine include the HEART pathway,
      • Mahler S.A.
      • Riley R.F.
      • Hiestand B.C.
      • et al.
      The HEART pathway randomized trial.
      EDACS,
      • Than M.P.
      • Pickering J.W.
      • Aldous S.J.
      • et al.
      Effectiveness of EDACS versus ADAPT accelerated diagnostic pathways for chest pain: a pragmatic randomized controlled trial Embedded within practice.
      and ADAPT
      • Than M.
      • Aldous S.
      • Lord S.J.
      • et al.
      Cullen L and Richards AM. A 2-hour diagnostic protocol for possible cardiac chest pain in the emergency department: a randomized clinical trial.
      (based on the TIMI risk score), which incorporate the results of troponin testing and have established value in clinical practice (Table 1). Risk stratification should be performed in parallel with serial troponin measurements to exclude myocardial injury. For hs-cTn assays, baseline sample collection should be obtained followed by a repeat measurement in 1–3 hours, unless the baseline test is below the limit of detection in a low-risk patient. . For conventional troponin assays, repeat sample collections are generally advised between 3 and 6 hours (see Table 2a).
      Table 1Sample risk stratification tools for patients in the ED with suspected ACS.
      HEART pathway
      • Mahler S.A.
      • Riley R.F.
      • Hiestand B.C.
      • et al.
      The HEART pathway randomized trial.
      EDACS
      • Than M.P.
      • Pickering J.W.
      • Aldous S.J.
      • et al.
      Effectiveness of EDACS versus ADAPT accelerated diagnostic pathways for chest pain: a pragmatic randomized controlled trial Embedded within practice.
      ADAPT (mADAPT)
      • Than M.
      • Aldous S.
      • Lord S.J.
      • et al.
      Cullen L and Richards AM. A 2-hour diagnostic protocol for possible cardiac chest pain in the emergency department: a randomized clinical trial.
      Variables used
      • History
      • Age
      • TIMI score
      • ECG
      • Sex
      • No ischemic ECG changes
      • Age
      • Risk factors
      • Troponin (0, 2 hrs)
      • Risk factors
      • History
      • Troponin (0, 3 hrs)
      • Troponin (0, 2 hrs)
      Scoring
      • History
      • Age (2–20 points)
      TIMI score (1 point each)
      •  ○Highly suspicious (2 pts)
      •  ○18–45 (2 pts)
      • Age ≥65
      •  ○Moderately suspicious (1 pt)
      •  ○46–50 (4 pts)
      • ≥3 CAD risk factors
      •  ○Slightly or non-suspicious (0 pts)
      •  ○51–55 (6 pts)
      •  ○Family Hx
      • ECG
      •  ○56–60 (8 pts)
      •  ○Hypertension
      •  ○Significant ST-depression (2 pts)
      •  ○61–65 (10 pts)
      •  ○↑ cholesterol
      •  ○Nonspecific repolarization (1 pt)
      •  ○66–70 (12 pts)
      •  ○Diabetes mellitus
      •  ○Normal (0 pts)
      •  ○71–75 (14 pts)
      •  ○Active smoker
      • Age
      •  ○76–80 (16 pts)
      • Known CAD (stenosis ≥50%)
      •  ○≥65 yrs (2 pts)
      •  ○81–85 (18 pts)
      • Aspirin use in past 7 days
      •  ○>45-<65 yrs (1 pt)
      •  ○≥86 (20 pts)
      • Recent (≤24hr) severe angina
      •  ○≤ 45 yrs (0 pts)
      • Male sex (6 pts)
      • ST deviation ≥0.5 mm
      • Risk factors (DM, current or recent (<1 month) smoker, HTN, HLP, family history of CAD, & obesity)
      • Known CAD or ≥3 CAD risk factors (DM, current or recent (<1 month) smoker, HTN, HLP, family history of CAD, & obesity) (4 pts)
      •  ○≥ 3 risk factors or history of CAD (2 pts)
      • Diaphoresis (3 pts)
      •  ○1 or 2 risk factors (1 pt)
      • Pain radiates to the arm or shoulder (5 pts)
      •  ○No risk factors (0 pts)
      • Pain occurred or worsened with inspiration (−4 pts)
      • Troponin
      • Pain is reproduced by palpation (−6 pts)
      •  ○≥3× normal limit (2 pts)
      •  ○>1-<3 normal limit (1 pt)
      •  ○≤ normal limit (0 pts)
      TroponincTn or hs-cTnhs-cTncTn or hs-cTn
      Risk Thresholds
      Low risk
      • HEART score <3
      • EDACS score <16
      • TIMI score 0 (<1 for mADAPT)
      • Negative 0, 3-hr cTn
      • Negative 0, 2-hr hs-cTn
      • Negative 0, 2-hr cTn or hs-cTn
      • Negative 0, 2-hr hs-cTn
      • No ischemic ECG changes
      • No ischemic ECG changes
      Intermediate risk
      • HEART score 4-6
      • Not defined
      • TIMI score 2-4
      High risk
      • HEART score 7-10
      • Not defined
      • TIMI score 5-7
      Table 2aRecommended chest pain pathways: Patients with No known CAD.
      Table thumbnail fx1
      *Triple rule-out CTA can substitute for coronary CTA if there is reasonable risk for both ACS and either PE or AAS (see Table 4). The CT scanner used must be cardiac-capable with a minimum of 64 multidetector units, and offer reasonable likelihood for diagnostic quality.
      **Using a pre-test clinical decision assessment tool (Table 1).
      Red: usually not appropriate.
      Yellow: may be appropriate.
      Green: usually appropriate.
      STEMI should be managed according to recent guidelines,
      • O'Gara P.T.
      • Kushner F.G.
      • Ascheim D.D.
      • et al.
      2013 ACCF/AHA guideline for the management of ST-elevation myocardial infarction.
      with prompt ICA as the only appropriate imaging study. Patients with documented NSTEMI should also follow guidelines-directed management,
      • Amsterdam E.A.
      • Wenger N.K.
      • Brindis R.G.
      • et al.
      2014 AHA/ACC guideline for the management of patients with non-ST-elevation acute coronary syndromes: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines.
      with consideration of early coronary CTA in limited scenarios.

      3.2 Clinical considerations

      Clinical scenarios are provided in Table 2 to illustrate a sample diagnostic pathway that integrates appropriate coronary CTA utilization for patients with suspected or definite ACS. Institutional practices will vary, and all management decisions should be tailored to individual patients based on clinical judgment. In selecting the optimal diagnostic test for a patient, it is important to recognize that coronary CTA provides information about coronary atherosclerosis burden, plaque morphology, and stenosis severity. CT may also permit evaluation of regional and global ventricular function and wall motion at low radiation doses, which adds incremental value for the diagnosis of ACS beyond evaluation of coronary anatomy.
      • Seneviratne S.K.
      • Truong Q.A.
      • Bamberg F.
      • et al.
      Incremental diagnostic value of regional left ventricular function over coronary assessment by cardiac computed tomography for the detection of acute coronary syndrome in patients with acute chest pain: from the ROMICAT trial.
      By contrast, functional testing (including ECG-only stress testing and stress testing with the use of imaging such as echocardiography or SPECT MPI) evaluates for regional myocardial ischemia due to inadequate coronary flow reserve. There are advantages and disadvantages to each approach.
      Table 2bPatients with documented CAD, post-revascularization.
      Table thumbnail fx2
      *Triple rule-out CTA can substitute for coronary CTA if there is reasonable risk for both ACS and either PE or AAS (see Table 4). The CT scanner used must be cardiac-capable with a minimum of 64 multidetector units, and offer reasonable likelihood for diagnostic quality.
      Red: usually not appropriate.
      Yellow: may be appropriate.
      Green: usually appropriate.

      3.3 General safety and diagnostic quality considerations

      The principal safety considerations for coronary CTA include radiation exposure, allergic reactions to iodinated contrast agents, and contrast-induced nephropathy. The risk of contrast-induced nephropathy is very low, and recent guidelines from the American College of Radiology (ACR) recommend limiting eGFR screening prior to iodinated contrast administration to patients who are older than 60 years, history of renal disease, history of hypertension and taking antihypertensive medication, and diabetes mellitus.
      ACR committee on drugs and contrast media
      ACR manual on contrast media.
      The use of any exposure to radiation should always be weighed against the potential risk of cancer, according to the “as low as reasonably achievable” principle. For example, increased radiation sensitivity in pre-menopausal women or younger patients or patient characteristics known to impair image quality (i.e., inability to take beta-blockers, lack of cooperation, or high body mass index) may favor alternative test strategies. Although high body mass index adversely affects coronary CTA image quality, that is also true for alternative modalities, and ultimately clinical judgment by the referring clinician is required for optimal test selection.

      3.4 Shared decision-making

      Chest pain pathways should be patient-centric, with patients included in shared decision-making. Patients should be provided the risks and benefits of different diagnostic strategies, including radiation exposure, costs, and alternative testing options. A sample decision aid is provided to guide this discussion (Supplement A). Provider cultural competency training is also recommended to encourage best outcomes in patients of diverse racial and ethnic backgrounds. Translation services should be utilized to address potential language barriers with patients for whom English may not be their primary language.

      4. Clinical scenarios/diagnostic pathway

      Patient scenarios are provided to illustrate a sample diagnostic pathway that integrates appropriate coronary CTA utilization with standard care for patients with suspected or definite ACS (Table 2a). Institutional practice will vary and all management decisions should be individualized for patients based on physicians’ clinical judgment. The appropriateness of an imaging examination is measured as “usually appropriate” (green score), “may be appropriate” (yellow score), and “usually not appropriate” (red score). More granular appropriateness such as a 1 (lowest appropriateness) - 9 (highest appropriateness) ranking is not considered. For example, a patient who presents with STEMI by ECG criteria would rarely undergo combined coronary CTA and CTP in lieu of going to the cardiac catheterization lab (Table 2b). Instead of numerically assigning a score of 1, the imaging study for this clinical scenario is designated simply as “red”.
      Prior to test selection, recent chest CT examinations should be reviewed for an estimate of CAC burden. Prior coronary angiograms (both CTA and invasive angiography) should also be reviewed for evidence of CAD, and prior stress test results reviewed for evidence of ischemia, to refine pre-test probability and guide appropriate test selection.

      4.1 Patients with No known CAD

      • 1.
        STEMI: In patients with documented STEMI, urgent cardiac catheterization is proven to be beneficial, with door-to-balloon time less than 90 minutes.
        • O'Gara P.T.
        • Kushner F.G.
        • Ascheim D.D.
        • et al.
        2013 ACCF/AHA guideline for the management of ST-elevation myocardial infarction.
        CT imaging should not delay “door-to-balloon” time. As such, all CT imaging is considered inappropriate, categorized as “usually not appropriate” and designated a “red” score. While not formally considered in Table 2a, portable chest radiography may be appropriate (yellow) to exclude secondary pathology that will be treated before or during catheterization, such as pneumothorax or abnormal line placement.
        • Amsterdam E.A.
        • Wenger N.K.
        • Brindis R.G.
        • et al.
        2014 AHA/ACC guideline for the management of patients with non-ST-elevation acute coronary syndromes: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines.
      • 2.
        Leading Diagnosis NSTEMI: This scenario includes patients with 1) ST changes on ECG that are suggestive of myocardial ischemia, but without ST-elevation; and 2) elevated cTn or hs-cTn. The favored management is invasive coronary angiography within 24 hours.
        • Amsterdam E.A.
        • Wenger N.K.
        • Brindis R.G.
        • et al.
        2014 AHA/ACC guideline for the management of patients with non-ST-elevation acute coronary syndromes: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines.
        Coronary CTA is seldom indicated first-line in the setting of NSTEMI to determine whether invasive evaluation is appropriate. Recent evidence suggests a possible role to rapidly exclude obstructive CAD when the pretest likelihood is low, or when there is desire to avoid unnecessary invasive coronary angiography (i.e., during the Covid-19 pandemic).
        • Choi A.D.
        • Abbara S.
        • Branch K.R.
        • et al.
        Society of cardiovascular computed tomography guidance for use of cardiac computed tomography amidst the COVID-19 pandemic endorsed by the American College of Cardiology.
        ,
        • Linde J.J.
        • Kelbæk H.
        • Hansen T.F.
        • et al.
        Coronary CT angiography in patients with non-ST-segment elevation acute coronary syndrome.
        ,
        • Smulders M.W.
        • Kietselaer B.
        • Wildberger J.E.
        • et al.
        Initial imaging-guided strategy versus routine care in patients with non-ST-segment elevation myocardial infarction.
        ,
        • Kühl J.T.
        • Hove J.D.
        • Kristensen T.S.
        • et al.
        Coronary CT angiography in clinical triage of patients at high risk of coronary artery disease.
        ,
        • MacLachlan H.
        • Thomas R.
        • Langtree J.
        • Hare C.
        • Mitchell A.R.
        Is there a role for a local inpatient CT coronary angiography service in selected patients with acute coronary syndrome? A cohort analysis of inpatient tertiary centre referrals for invasive coronary angiography.
      • 3.
        High Risk for ACS: This scenario includes patients at high pretest risk for CAD, but with no definite evidence of ACS by ECG and troponins. In patients considered high-risk by risk stratification tools (i.e., HEART score >6, TIMI risk score >4 (Table 1), but with normal or nonischemic ECG, and normal or equivocal troponins, coronary CTA may be appropriate, particularly at centers with local expertise and established high-quality coronary CTA programs. Alternatively, high-risk patients may be considered for functional testing or invasive angiography. Coronary CTA offers an opportunity to safely defer invasive angiography in patients with normal or nonobstructive CAD, which can represent up to 50% of this patient population.
        • Gray A.J.
        • Roobottom C.
        • Smith J.E.
        • et al.
        The RAPID-CTCA trial (Rapid Assessment of Potential Ischaemic Heart Disease with CTCA) — a multicentre parallel-group randomised trial to compare early computerised tomography coronary angiography versus standard care in patients presenting with suspected or confirmed acute coronary syndrome: study protocol for a randomised controlled trial.
        ,
        • Gray A.J.
        Early coronary CT angiography in patients with suspected or provisionally diagnosed acute coronary syndrome - RAPID CTCA.
        Among patients found to have nonobstructive disease, early recognition with coronary CTA offers the opportunity to optimize preventive therapy and medical management prior to ED discharge.
        • Williams M.C.
        • Dweck M.R.
        • Newby D.E.
        Coronary computed tomography angiography to triage patients with non-ST-segment elevation acute coronary syndrome.
      • 4.
        Low-to-Intermediate Risk for ACS: Coronary CTA is most effective in patients with a low-to-intermediate pretest likelihood of ACS. This includes patients with normal or nonischemic ECG changes, and normal or equivocal baseline cTn, or baseline hs-cTn below the 99th percentile. Using risk stratification tools, low-to-intermediate pretest risk is defined by HEART scores 1–6, and TIMI risk scores 1–4. This category also includes patients with inadequate or mildly abnormal functional testing during the index ED visit or within the previous 1 year.
      The majority of randomized-controlled trial evidence supporting coronary CTA in the ED enrolled patients within the low-to-intermediate risk category risk.
      • Goldstein J.A.
      • Chinnaiyan K.M.
      • Abidov A.
      • et al.
      The CT-STAT (coronary computed tomographic angiography for systematic triage of acute chest pain patients to treatment) trial.
      ,
      • Hoffmann U.
      • Truong Q.A.
      • Schoenfeld D.A.
      • et al.
      Coronary CT angiography versus standard evaluation in acute chest pain.
      ,
      • Linde J.J.
      • Hove J.D.
      • Sorgaard M.
      • et al.
      Long-term clinical impact of coronary CT angiography in patients with recent acute-onset chest pain: the randomized controlled CATCH trial.
      ,
      • Litt H.I.
      • Gatsonis C.
      • Snyder B.
      • et al.
      CT angiography for safe discharge of patients with possible acute coronary syndromes.
      ,
      • Goldstein J.A.
      • Gallagher M.J.
      • O'Neill W.W.
      • Ross M.A.
      • O'Neil B.J.
      • Raff G.L.
      A randomized controlled trial of multi-slice coronary computed tomography for evaluation of acute chest pain.
      ,
      • Hamilton-Craig C.
      • Fifoot A.
      • Hansen M.
      • et al.
      Diagnostic performance and cost of CT angiography versus stress ECG–a randomized prospective study of suspected acute coronary syndrome chest pain in the emergency department (CT-COMPARE).
      in this group of patients coronary CTA is most efficient; approximately 5–15% of patients will have obstructive CAD warranting further evaluation with invasive coronary angiography, while the majority of patients can be safely discharged from the ED with normal or nonobstructive disease.
      • 5.
        Very Low Risk for ACS: This category refers to patients who are considered low-risk by risk stratification tools, with normal or nonischemic ECG, and normal baseline hs-cTn. Within this patient population, the 30-day risk of MACE is less than 1%.
        • Allen B.R.
        • Christenson R.H.
        • Cohen S.A.
        • et al.
        Diagnostic Performance of High-Sensitivity Cardiac Troponin T Strategies and Clinical Variables in a Multisite US Cohort
        For many of these patients, further diagnostic testing for CAD is not necessary as the yield would likely be low. However, coronary CTA may be appropriate in some very low risk patients to confidently exclude CAD and provide risk stratification; for example, patients with recurrent ED visits for chest pain who desire further testing to confidently rule-out CAD. Testing during the index ED visit could expedite a more thorough coronary evaluation, including the presence of non-obstructive plaque and also evaluate for other potential sources of chest pain. Further, coronary CTA is considered appropriate in the 2015 multi-society appropriate use criteria for ED cardiac imaging in very low risk patients, defined by TIMI risk score zero and negative early hs-cTn.
        • Rybicki F.J.
        • Udelson J.E.
        • Peacock W.F.
        • et al.
        2015 ACR/ACC/AHA/AATS/ACEP/ASNC/NASCI/SAEM/SCCT/SCMR/SCPC/SNMMI/STR/STS appropriate utilization of cardiovascular imaging in emergency department patients with chest pain.
        Shared decision making cannot be overemphasized in this patient population, so patients are well informed of the potential risks and benefits of additional testing.

      4.2 CAC testing

      Coronary artery calcium (CAC) testing with non-contrast CT is rarely appropriate as a stand-alone test for the evaluation of ACP in the ED. While there is established utility for CAC testing in asymptomatic patients with intermediate risk of CAD,
      • Ghoshhajra B.B.
      • Hedgire S.S.
      • Hurwitz Koweek L.M.
      • et al.
      Appropriateness Criteria® asymptomatic patient at risk for coronary artery disease: 2021 update. Journal of the American College of Radiology.
      there is limited data on CAC as a stand-alone test for symptomatic patients in whom ACS is a leading differential diagnosis. When CAC ​= ​0, the rate of obstructive CAD is low (less than 1%) and long-term prognosis is favorable.
      • Chaikriangkrai K.
      • Palamaner Subash Shantha G.
      • Jhun H.Y.
      • et al.
      Prognostic value of coronary artery calcium score in acute chest pain patients without known coronary artery disease: systematic review and meta-analysis.
      ,
      • Laudon D.A.
      • Behrenbeck T.R.
      • Wood C.M.
      • et al.
      Computed tomographic coronary artery calcium assessment for evaluating chest pain in the emergency department: long-term outcome of a prospective blind study.
      However, CAC ​= ​0 cannot exclude ACS, which can occur in 1–3% of patients who have noncalcified plaque.
      • Bittner D.O.
      • Mayrhofer T.
      • Bamberg F.
      • et al.
      Impact of coronary calcification on clinical management in patients with acute chest pain.
      ,
      • Pursnani A.
      • Chou E.T.
      • Zakroysky P.
      • et al.
      Use of coronary artery calcium scanning beyond coronary computed tomographic angiography in the emergency department evaluation for acute chest pain: the ROMICAT II trial.
      However, obtaining CAC prior to coronary CTA can be useful as an opportunity to quantify coronary plaque burden and modify the CTA protocol when heavy plaque burden is detected (i.e., use of sharp reconstruction filter, iterative reconstruction, increased acquisition time, and/or retrospective technique). However, the decision to perform a non-contrast CT scan for CAC scoring prior to coronary CTA should be made by each institution, based on their workflow and patient population.

      4.3 Sequential testing with FFR-CT or stress CTP

      The addition of FFR-CT
      • Chinnaiyan K.M.
      • Safian R.D.
      • Gallagher M.L.
      • et al.
      Clinical use of CT-derived fractional flow reserve in the emergency department.
      ,
      • Patel M.R.
      • Nørgaard B.L.
      • Fairbairn T.A.
      • et al.
      1-Year impact on medical practice and clinical outcomes of FFR(CT): the ADVANCE registry.
      ,
      • Graby J.
      • Metters R.
      • Kandan S.R.
      • et al.
      Real-world clinical and cost analysis of CT coronary angiography and CT coronary angiography-derived fractional flow reserve (FFR(CT))-guided care in the National Health Service.
      ,
      • Curzen N.
      • Nicholas Z.
      • Stuart B.
      • et al.
      Fractional flow reserve derived from computed tomography coronary angiography in the assessment and management of stable chest pain: the FORECAST randomized trial.
      or stress myocardial CTP
      • Sørgaard M.H.
      • Linde J.J.
      • Kühl J.T.
      • et al.
      Value of myocardial perfusion assessment with coronary computed tomography angiography in patients with recent acute-onset chest pain.
      ,
      • Grandhi G.R.
      • Batlle J.C.
      • Maroules C.D.
      • et al.
      Combined stress myocardial CT perfusion and coronary CT angiography as a feasible strategy among patients presenting with acute chest pain to the emergency department.
      ,
      • Patel A.R.
      • Bamberg F.
      • Branch K.
      • et al.
      Society of cardiovascular computed tomography expert consensus document on myocardial computed tomography perfusion imaging.
      to coronary CTA may be appropriate in situations where the determination of lesion specific ischemia or myocardial ischemia would be helpful to guide management, including the following scenarios:
      • Coronary artery stenosis of unknown hemodynamic significance (40–70%)
      • Severe coronary calcification

      4.4 Patients with known CAD and prior revascularization

      Coronary CTA is appropriate for the early triage of symptomatic patients with known CAD and prior PCI, provided: 1) the coronary stent is ​≥ ​3-mm in diameter and within a proximal coronary segment; 2) the ECG is normal or nonischemic; and 3) the baseline cTn or hs-cTn is normal or equivocal. In some scenarios it may be appropriate to perform coronary CTA in patients with stents less than 3-mm, particularly in patients known to have thin stent struts (<100-μm) in proximal, non-bifurcation locations.
      Measures to improve the accuracy of stent imaging are encouraged, including strict heart rate control (goal <60 bpm), iterative or model-based reconstruction, sharp kernel reconstruction, and mono-energetic reconstructions (when available). Protocols to optimize stent imaging should be locally developed and followed.
      • Narula J.
      • Chandrashekhar Y.
      • Ahmadi A.
      • et al.
      2021 expert consensus document on coronary computed tomographic angiography: a report of the society of cardiovascular computed tomography.
      Coronary CTA is also appropriate in select patients with known CAD who have had prior coronary artery bypass grafting (CABG), particularly if the primary objective is to evaluate graft patency. These patients should have a normal or nonischemic ECG and normal or equivocal baseline cTn or hs-cTn.

      4.4.1 Combined coronary CTA ​+ ​FFR-CT

      At the time of this writing, there is limited evidence on the feasibility and clinical utility of FFR-CT in ACP patients with prior revascularization; as such, FFR-CT is considered “usually not appropriate” (red) in this scenario.

      4.4.2 Combined coronary CTA ​+ ​CTP

      The combination of myocardial CTP and coronary CTA may be appropriate for the evaluation of patients with prior revascularization in the ED. In such cases, CTP is recommended if the presence and severity of ischemia would impact patient management and CTP is feasible. There is evidence to support the use of CTP in the ED setting,
      • Sørgaard M.H.
      • Linde J.J.
      • Kühl J.T.
      • et al.
      Value of myocardial perfusion assessment with coronary computed tomography angiography in patients with recent acute-onset chest pain.
      ,
      • Feuchtner G.M.
      • Plank F.
      • Pena C.
      • et al.
      Evaluation of myocardial CT perfusion in patients presenting with acute chest pain to the emergency department: comparison with SPECT-myocardial perfusion imaging.
      ,
      • Grandhi G.R.
      • Batlle J.C.
      • Maroules C.D.
      • et al.
      Combined stress myocardial CT perfusion and coronary CT angiography as a feasible strategy among patients presenting with acute chest pain to the emergency department.
      although studies have specifically evaluated its utility among patients with prior revascularization in other settings. However, the clinical value of alternative stress myocardial perfusion imaging (i.e. SPECT and CMR) following PCI and CABG is well established.
      • Georgoulias P.
      • Valotassiou V.
      • Tsougos I.
      • Demakopoulos N.
      Myocardial perfusion SPECT imaging in patients after percutaneous coronary intervention.
      ,
      • Giedd K.N.
      • Bergmann S.R.
      Myocardial perfusion imaging following percutaneous coronary intervention: the importance of restenosis, disease progression, and directed reintervention.

      5. Patient preparation

      Achieving high diagnostic accuracy with the lowest possible radiation dose requires careful preparation of coronary CTA patients. CT imaging is sensitive to motion, requiring slow, steady heart rates and patient cooperation. Higher heart rates require scan protocols that are less sensitive to movement, such as retrospective ECG-gated scan protocols, but these result in higher radiation doses. The precise targets for adequate scans depend on the scanner technology available. The essential steps in preparing patients for coronary CTA include: evaluation, education, medication and re-evaluation after pre-medication.
      • Halliburton S.S.
      • Abbara S.
      Practical tips and tricks in cardiovascular computed tomography: patient preparation for optimization of cardiovascular CT data acquisition.
      The principles of patient preparation and sample institutional guidelines (Table 3) should be modified as needed, using clinical judgment and can be tailored to scanner technology and institutional experience.
      Table 3Shared decision-making and patient preparation: Sample institutional guidelines.
      Shared decision-making
      • Once Coronary CTA is deemed appropriate, shared decision-making between the clinician and patient is encouraged to review pros and cons of coronary CTA and to improve understanding and facilitate risk communication
      • Alternative diagnostic strategies should be discussed, including no further testing, observation and/or functional testing, if available
      • Decision aids are encouraged, for example “Cardiac CT: Is It Right for Me?” (Supplement)
      • Emphasize the importance of outpatient follow-up after discharge from the ED, particularly if non-obstructive coronary plaque is identified
      Nursing assessments
      • Ensure patients are screened for contraindications to contrast-enhanced CT imaging
      • Describe what can be expected during the exam: medications, positioning, and sensations. Assess ability and willingness to cooperate.
      • Assess heart rate variability and blood pressure, and effects of breath hold on the heart rate
      Heart-rate control
      • Prescribe heart rate-lowering medication, if appropriate, with the intent to achieve a stable target heart rate ≤60 beats/min
      • Sample institutional protocol:
      1. Oral metoprolol: give 30–60 min prior to imaging, then reassess; systolic blood pressure >90 mmHg
      • Baseline HR 55–60: give 25 mg
      • Baseline HR 61–65: give 50 mg
      • Baseline HR > 66: give 100 mg
      2. IV metoprolol: while patient is on the scanner table, give 5 mg over slow IV push every 5 min, up to 20–25 mg total; systolic blood pressure >90 mmHg
      3. Ivabradine:
      • Oral ivabradine 15mg or 7.5 mg (in chronic beta blockade) 75 min prior to imaging
      4. IV diltiazem: not recommended first-line for heart rate control unless there is contraindication to beta-blockers; do not combine with beta-blockers; systolic blood pressure >90 mmHg
      • Give 5 mg IV over 2 minutes; re-dose every 10 minutes to a max dose of 30 mg
      Coronary vasodilation
      • Sample protocols:
      1. Apply ½ inch nitropaste to chest 60 min prior to imaging
      2. Give 0.4–0.8 mg sublingual nitroglycerin (tabs or spray) 5 min prior to contrast
      • Omit nitroglycerin in patients with contraindications (ie aortic stenosis, recent intake of phosphodiesterase inhibitors, etc)

      5.1 Patient evaluation

      Patients should be evaluated by staff (for example a CT technologist or patient nurse), to ensure that no absolute contraindications exist to the examination. If uncertain, staff should confer with the attending physician. It should be clear that the patient understands the nature of the examination and can cooperate with breath-holding instructions. Baseline vital signs should be used to design a pre-scan medication protocol to achieve heart rate targets based on the scanner model to be used. Staff should ascertain the patient's previous medications. If the baseline heart rate is within target range, a mild stress, e.g., 30 seconds of hard hand-grip on a towel, may be considered to ensure heart rate does not rise unduly.
      • Cauwenberghs N.
      • Cornelissen V.
      • Christle J.W.
      • et al.
      Impact of age, sex and heart rate variability on the acute cardiovascular response to isometric handgrip exercise.

      5.2 Patient education

      Patients should be fully informed about the nature of the examination, its objectives, possible risks including radiation dose, their required cooperation and the sensations they are likely to feel. This is a critical component of shared decision-making. It is suggested that radiation dose be compared to annual background dose (approximately 3 mSv in the United States). Patients should be given a chance to request an alternative diagnostic strategy if they feel unable or unwilling to proceed. This educational process should be repeated after premedication, just before scanning, to ensure patients remember instructions on breath-holding and are prepared for the sensations likely to occur from nitroglycerin and contrast administration.

      5.3 Patient pre-medication

      The majority of patients referred for coronary CTA require pre-medication with beta-blockers to establish heart rate control and reduce heart rate variability. SCCT guidelines for the performance and acquisition of coronary CTA should be followed.
      • Abbara S.
      • Blanke P.
      • Maroules C.D.
      • et al.
      SCCT guidelines for the performance and acquisition of coronary computed tomographic angiography: a report of the society of cardiovascular computed tomography guidelines committee: endorsed by the north American society for cardiovascular imaging (nasci).
      Generally, a target heart rate of 60 beats per minute or less is usually appropriate. A detailed example of pre-medication orders is listed in Table 3. Institutional protocols will vary depending on target heart rates required by the scanner model to be used; preferably a set of standardized orders should be made available to staff.
      Oral metoprolol administration is the usual practice, with 50–100 mg by mouth 1 hour prior to imaging.
      • Abbara S.
      • Blanke P.
      • Maroules C.D.
      • et al.
      SCCT guidelines for the performance and acquisition of coronary computed tomographic angiography: a report of the society of cardiovascular computed tomography guidelines committee: endorsed by the north American society for cardiovascular imaging (nasci).
      Slow-release formulations of oral metoprolol should not be used. At the time of scanning, supplementation with IV metoprolol can be used to achieve target heart rates (5 mg IV, followed by repeated 5 mg doses as necessary, typically up to 20–25mg total).
      Ivabradine, a direct I(f) current inhibitor,
      • Celik O.
      • Atasoy M.M.
      • Erturk M.
      • et al.
      Comparison of different strategies of ivabradine premedication for heart rate reduction before coronary computed tomography angiography.
      can be used in addition to or in lieu of beta-blockers for heart rate control prior to coronary CTA. It is available in oral and IV formulations and can lower heart rate without affecting myocardial contractility or blood pressure. This makes ivabradine an attractive alternative to metoprolol in patients with low blood pressure. A sample protocol is 15 mg orally 60–75 minutes prior to scanning.
      • Guler E.C.
      • Yam Y.
      • Jia K.
      • et al.
      Effectiveness of point-of-care oral ivabradine for cardiac computed tomography.
      Ivabradine may be more effective than metoprolol in patients treated with chronic beta-blockers. However, it is ineffective in patients who are not in sinus rhythm, as it acts through direct inhibition of the sinoatrial node.

      5.4 Recommendations

      • Establishment of institution-specific guidelines for diagnostic heart rate and rhythm based on scanner technology and staff capability, and following SCCT Guidelines
        • Abbara S.
        • Blanke P.
        • Maroules C.D.
        • et al.
        SCCT guidelines for the performance and acquisition of coronary computed tomographic angiography: a report of the society of cardiovascular computed tomography guidelines committee: endorsed by the north American society for cardiovascular imaging (nasci).
      • Verification of acceptable GFR (>30) and negative pregnancy testing as appropriate
      • Patient evaluation with vital signs measurement prior to coronary CTA and ∼30 minutes after imaging
      • Use of fenestrated, high-flow IV access, ensuring the IV used is rated to administer flow rates required for coronary CTA (e.g., 5–7 mL/s).
      • Patient interview to determine ability to follow instructions, educate about breath holding and other aspects of procedure
      • Measurement of baseline vital signs
      • Administration of oral beta blockers at institutionally approved dose ranges if baseline heart rate does not fall into approved range. Intravenous beta blockers and oral ivabradine may be supplemental to or an alternative to oral beta blockers depending on institutional guidelines.
      • Some institutions with high temporal resolution CT scanners may elect to scan patients without heart rate-controlling medication, as long as diagnostic image quality can be achieved.
      • If heart rate not in acceptable range, consultation with supervising physician for additional beta blocker dosage
      • Nitroglycerin 5 minutes prior to scan unless blood pressure out of range or history of prior adverse reaction, or other contraindications to its use
      • In case of previous mild-moderate contrast allergy, provided clinical decision is made against alternative testing, antihistamine/corticosteroid preparation over 6–12 hours according to institutional guidelines
      • Intravenous saline for blood pressure support before and during beta blocker dosage if necessary to achieve target heart rate if no contraindication is present

      5.5 Contraindications

      Scenarios when coronary CTA may be difficult or nondiagnostic are presented in Table 5, along with strategies to improve quality. Scenarios when the risks associated with coronary CTA may not outweigh the benefits are presented in Table 6, with strategies to improve safety.
      Table 5Scenarios when Coronary CTA may be difficult or nondiagnostic, and strategies to improve quality
      Scenarios are scanner-dependent and may not be problematic when using modern CT scanner platforms.
      .
      ScenarioStrategies to improve image quality
      High heart rate
      • Re-dose oral metoprolol prior to imaging (50–100 mg additional)
      • Re-dose IV metoprolol prior to imaging (5 mg increments, up to 20 mg total)
      • Consider IV or oral ivabradine
      • Avoid dehydration; consider oral or IV hydration
      • Consider anxiolytics prior to imaging (ie 0.5 mg alprazolam)
      • Scan protocol modifications
        Scenarios are scanner-dependent and may not be problematic when using modern CT scanner platforms.
        :
      •  ○Consider retrospective ECG gating with ECG-based tube-current modulation
      •  ○Consider prospective ECG triggering with widened acquisition window (“padding”) (ie 35–80% of the R-R interval)
      • Consider multi-segment reconstruction to improve temporal resolution
      Atrial fibrillation and other irregular rhythms
      • Scan protocol modifications:
      •  ○Consider retrospective ECG gating with ECG-based tube-current modulation, and triggering at a fixed time after the R-peak (250 msec) to capture end-systolic data
      • Utilize scanner-specific arrhythmia protocols as applicable (ie ECG editing)
      High coronary calcium score (>1000)
      • Sun Z.
      • Ng C.K.C.
      • Xu L.
      • Fan Z.
      • Lei J.
      Coronary CT angiography in heavily calcified coronary arteries: improvement of coronary lumen visualization and coronary stenosis assessment with image postprocessing methods.
      • Utilize dual-energy CT if available (virtual monoenergetic images at high energies, >100 keV)
      • Reconstruct images at higher spatial resolution (0.5–0.6 mm x 0.25–0.3 mm, 50% overlap)
      • Utilize an edge-enhancing sharp kernel (ie, I46f)
      • Utilize higher levels of iterative reconstruction
      • Review coronary CTA images with wide window width (1200–1500 HU)
      • Review coronary CTA images with high window center (300–400 HU)
      • Consider higher tube potential (120–140 kVp)
      • Decision to proceed to coronary CTA should be based on patient factors (e.g. heart rate, likelihood of diagnostic image quality)
      • Consider functional/alternative testing if diagnostic image quality is unlikely
      Patients with known coronary stents
      • Goerne H.
      • de la Fuente D.
      • Cabrera M.
      • Chaturvedi A.
      • Vargas D.
      • Young P.M.
      Saboo SS and rajiah P. Imaging features of complications after coronary interventions and surgical procedures.
      • Utilize dual-energy CT if available (virtual monoenergetic images at high energies, >100 keV)
      • Reconstruct images at higher spatial resolution (0.5–0.6 mm x 0.25–0.3 mm, 50% overlap)
      • Utilize an edge-enhancing sharp kernel (ie, I46f)
      • Utilize higher levels of iterative reconstruction
      • Review coronary CTA images with wide window width (1200–1500 HU)
      • Review coronary CTA images with high window center (300–400 HU)
      • Consider higher tube potential (120–140 kVp)
      Morbid obesity (body mass index ≥40 kg/m2)
      • Ensure high-flow IV contrast injection (6–7 cc/sec)
      • Ensure high concentration iodine solution is utilized to improve vascular contrast
      • Consider higher tube potential (120–140 kVp)
      • Ensure arms are raised above the head
      • Utilize higher levels of iterative reconstruction
      • Review reconstructed images with a thicker slice width (1.0–1.5 mm) to reduce image noise
      • Review images with a soft or smooth reconstruction kernel to reduce image noise
      Inability to raise arms over the head
      • Ensure high-flow IV contrast injection (6–7 cc/sec)
      • Ensure high concentration iodine solution is utilized to improve vascular contrast
      • Consider higher tube potential (120–140 kVp)
      Tachypnea
      • Consider nasal cannula oxygen to improve patient comfort
      • Practice breath-holds prior to CT scanning to ensure the patient is an appropriate candidate
      • Consider fast-acquisition protocols, including prospectively ECG triggered high-pitch helical scanning, if available, or retrospectively ECG-gated scanning
      Difficult IV access
      • Establish 18- or 20-gauge peripheral IV with ultrasound guidance. Peripherally inserted central venous catheters (PICC) are not recommended.
      • Consider a test bolus with 10–20 cc of contrast followed by a saline bolus at the anticipated injection rate to ensure sufficient access and vascular enhancement
      Communication barriers (ie language, hearing disability)
      • Communication aids should be utilized prior to and during the CT scan to establish patient consent and facilitate understanding
      • In-person or electronic language interpretations services should be utilized
      • Engage family members and caregivers during patient preparation
      Anxious patient
      • Encourage the patient to rest comfortably for at least 30 min prior to scanning
      • Coach the patient prior to CT scanning on expectations
      • Engage family members and caregivers during patient preparation
      • Consider anxiolytics prior to imaging (ie 0.5 mg alprazolam)
      a Scenarios are scanner-dependent and may not be problematic when using modern CT scanner platforms.
      Table 6Scenarios when risks associated with Coronary CTA may not outweigh the benefits, and strategies to improve safety
      Scenarios are scanner-dependent and may not be problematic when using modern CT scanner platforms.
      .
      ScenarioStrategies to improve safety
      Pediatric & young adult patients
      • Coronary CTA should only be performed if the results have the potential to impact patient management or prognosis
      • Explicit breath-holding instructions and breath-hold training should be provided prior to scanning
      • Coronary CTA to delineate the course of a coronary anomaly can tolerate greater noise, and can therefore be performed with lower radiation exposure (ie low kVp, high-pitch helical scanning)
      • Utilize anatomy-based tube current adaptation, if available, to adjust tube current on the basis of patient size in order to limit radiation exposure
      • Scan range should be as short as reasonably possible
      • Utilize higher levels of iterative reconstruction to reduce image noise, so lower kVp and mA can be accommodated
      • If a pediatric patient requires anesthesia, institutional anesthesia guidelines should be followed, including NPO prior to the exam
        • Abbara S.
        • Blanke P.
        • Maroules C.D.
        • et al.
        SCCT guidelines for the performance and acquisition of coronary computed tomographic angiography: a report of the society of cardiovascular computed tomography guidelines committee: endorsed by the north American society for cardiovascular imaging (nasci).
      Pregnancy
      • Coronary CTA should only be performed if the results have the potential to impact patient management or prognosis (ie SCAD); patient informed consent is recommended
      • Scan range should be as short as reasonably possible
      • Utilize higher levels of iterative reconstruction to reduce image noise, permitting lower kVp imaging and lower contrast volume
      • Consider breast displacement to lower radiation exposure and improve CT image quality
      Renal insufficiency (eGFR <60)
      • Consider iso-osmolar iodine contrast agents (ie, iodixanol)
      • Minimize the volume and frequency of contrast administration (avoid repeat injection within 72 hrs)
      • Avoid nephrotoxic medications 48 hrs before contrast administration, including nonsteroidal anti-inflammatory drugs (NSAIDs)
      • Avoid dehydration
      • Consider isotonic IV fluid administration as per published guidelines
        ACR committee on drugs and contrast media
        ACR manual on contrast media.
      Mild-moderate iodinated contrast allergy
      • Coronary CTA should only be performed if the results have the potential to impact patient management or prognosis
      • Administer pre-medication for contrast allergy. Sample premedication protocols include:
        • Beckett K.R.
        • Moriarity A.K.
        • Langer J.M.
        Safe use of contrast media: what the radiologist needs to Know.
      •  ○4-h (emergent) protocol: Hydrocortisone 200mg IV or methylprednisolone 40 mg IV every 4 hours until contrast; in addition to diphenhydramine 50 mg IV 1 hour prior to contrast
      •  ○13-h (elective) protocol: Prednisone 50 mg by mouth, 13, 7, and 1 hour prior to contrast; in addition to diphenhydramine 50 mg by mouth 1 hour prior to contrast
        • Greenberger P.
        • Patterson R.
        Prednisone-diphenhydramine regimen prior to use of radiographic contrast media.
      • In general, emergent pre-medication protocols are less desirable; used when there is insufficient time to achieve peak corticosteroid effect \
      • Corticosteriods and diphenhydramine may increase heart rate slightly and diminish image quality in some patients
      Use of sildenafil (Viagra) or (Levitra) within the prior 24 hours, or use of tadalafil (Cialis) within the prior 48 hours
      • Avoid nitroglycerin pre-medication, which will decrease coronary diameter and image quality
        • Takx R.A.P.
        • Suchá D.
        • Park J.
        • Leiner T.
        • Hoffmann U.
        Sublingual nitroglycerin administration in coronary computed tomography angiography: a systematic review.
      • Optimize other parameters that impact image quality (ie heart rate control, breath-hold training, vascular contrast)
      • Avoid dehydration; consider oral or IV hydration
      • Reconstruct images at higher spatial resolution (0.5–0.6 mm x 0.25–0.3 mm, 50% overlap) to quantify coronary stenosis
      Low blood pressure
      • Avoid dehydration; consider oral or IV hydration
      • Consider ivabradine in lieu of beta-blockers to achieve target heart rate
      • Monitor the patient and vital signs at regular intervals for 1 hour after scanning to ensure stability prior to discharge
      Other relative contraindication to beta-blockers (ie, mild-moderate allergy, moderate-severe asthma/COPD)
      • Consider ivabradine in lieu of beta-blockers to achieve target heart rate (ie 15 mg or 7.5 mg by mouth 1 hour prior to scanning)
      • Consider calcium channel blockers (diltiazem) in lieu of beta-blockers to achieve target heart rate
      • For history of allergic reaction, consider pre-medication protocol (described above)
      a Scenarios are scanner-dependent and may not be problematic when using modern CT scanner platforms.
      Relative contraindications to coronary CTA in the ED include:
      • History of allergic reaction to iodinated contrast after adequate steroid/antihistamine preparation.
      • Estimated GFR<30 unless on chronic dialysis, or evidence of acute kidney injury.
      • Patient factors leading to potentially non-diagnostic scans, which will vary with scanner technology and site capabilities, including HR ​> ​site maximum for reliably diagnostic scans after pre-medication, markedly irregular rhythm, high coronary calcium burden, and large body size.
      • Inability to cooperate and follow commands during the CT acquisition
      • Pregnancy or uncertain pregnancy status in pre-menopausal women. Coronary CTA may be useful to exclude spontaneous coronary artery dissection (SCAD) which predominantly occurs in young women without traditional CAD risk factors.
        • Gupta S.
        • Meyersohn N.M.
        • Wood M.J.
        • et al.
        Role of coronary CT angiography in spontaneous coronary artery dissection.

      6. SCAN protocol selection

      Scan acquisitions should be consistent with SCCT Guidelines for Performance of Coronary Computed Tomography.
      • Abbara S.
      • Blanke P.
      • Maroules C.D.
      • et al.
      SCCT guidelines for the performance and acquisition of coronary computed tomographic angiography: a report of the society of cardiovascular computed tomography guidelines committee: endorsed by the north American society for cardiovascular imaging (nasci).
      In planning a coronary CTA, knowledge of the indications for the scan and of patient characteristics is of paramount importance. The indication of possible ACS has specific requirements. For example, while non-contrast calcium scoring can provide useful data, there is a significant proportion of patients with zero calcium scores who have ACS and significant coronary stenosis due to the presence of non-calcified plaque.
      • Henneman M.M.
      • Schuijf J.D.
      • Pundziute G.
      • et al.
      Noninvasive evaluation with multislice computed tomography in suspected acute coronary syndrome: plaque morphology on multislice computed tomography versus coronary calcium score.
      ,
      • Gottlieb I.
      • Miller J.M.
      • Arbab-Zadeh A.
      • et al.
      The absence of coronary calcification does not exclude obstructive coronary artery disease or the need for revascularization in patients referred for conventional coronary angiography.
      When CAC ​= ​0, long-term prognosis is generally favorable.
      • Chaikriangkrai K.
      • Palamaner Subash Shantha G.
      • Jhun H.Y.
      • et al.
      Prognostic value of coronary artery calcium score in acute chest pain patients without known coronary artery disease: systematic review and meta-analysis.
      ,
      • Laudon D.A.
      • Behrenbeck T.R.
      • Wood C.M.
      • et al.
      Computed tomographic coronary artery calcium assessment for evaluating chest pain in the emergency department: long-term outcome of a prospective blind study.
      However, it may not add incremental prognostic value to coronary CTA, and CAC ​= ​0 alone cannot exclude ACS.
      • Pursnani A.
      • Chou E.T.
      • Zakroysky P.
      • et al.
      Use of coronary artery calcium scanning beyond coronary computed tomographic angiography in the emergency department evaluation for acute chest pain: the ROMICAT II trial.
      Coronary CTA protocols should provide the highest diagnostic quality with the lowest radiation dose. A carefully thought-out institutional algorithm for protocol selection will allow management of most patients; however, physicians must be available to assist what can be difficult decisions in individual patients. The main patient factors to consider are type of scan (i.e., coronaries only, “triple rule out”, evaluation of bypass grafts, etc.), heart rate and rhythm, and body habitus of the patient.
      • Raff G.L.
      • Chinnaiyan K.M.
      • Share D.A.
      • et al.
      Radiation dose from cardiac computed tomography before and after implementation of radiation dose-reduction techniques.

      6.1 Patient-tailored scan protocols

      Patient-specific scan protocoling is recommended to minimize radiation dose while still achieving diagnostic quality. This results in modification of scan length, timing and infusion rate of the contrast bolus, and alteration of tube potential and tube current based on patient characteristics. A sample protocol selection guide is presented in Table 4.
      Table 4Scan protocol selection for Coronary CTA.
      General principles
      • Scan acquisition should be consistent with SCCT Guidelines for Performing Coronary CTA
        • Abbara S.
        • Blanke P.
        • Maroules C.D.
        • et al.
        SCCT guidelines for the performance and acquisition of coronary computed tomographic angiography: a report of the society of cardiovascular computed tomography guidelines committee: endorsed by the north American society for cardiovascular imaging (nasci).
      • Institutional scan protocol guidelines should be established and staff trained in routine scan protocol selection, based on scanner hardware and software, as well as staff capabilities.
      • Scan protocols should prioritize achievement of diagnostic scan quality with the lowest achievable radiation dose based on individual patient characteristics.
      • Protocol selection should consider achieved heart rate and rhythm after maximal patient preparation, patient body habitus, and the quality of IV acesss for high-flow contrast injection.
      Protocol selections
      ParameterTailor parameter to:Recommendations
      Tube potential (kVp)Body habitus
      • Preference should be given to using 100 kVp for most adults when the patient's weight is below 100 kg and the body mass index (BMI) is below 30 kg/m2
      • Consider lower tube potential (eg, 80 kVp) in favorable situations, including when the patient's weight is below 60 kg or chest diameter <32cm
        • Wu Q.
        • Wang Y.
        • Kai H.
        • et al.
        Application of 80-kVp tube voltage, low-concentration contrast agent and iterative reconstruction in coronary CT angiography: evaluation of image quality and radiation dose. Int J Clin Pract.
      • Consider 120 kVp for larger patients BMI >30 kg/m2 or chest diameter >38cm
      • Automated methods for kVp selection based on attenuation values in the scout images are encouraged to facilitate low radiation exposure
      Tube current (mAs)Body habitus
      • Larger patients generally require higher tube current to reduce image noise to an acceptable level
      • Customize tube current using an automated current selection algorithm based on the scanned body profile (eg, topogram), if available
      Scan modeHeart rate & heart rate variability; modify based on CT scanner model
      • Prospectively ECG-triggered axial scanning in mid-diastole should be considered as the default scan mode of choice in patients with adequate heart rate control (ie, regular heart rate ≤65 beats/min)
      •  ○Prospectively ECG-triggered axial scanning in late systole should be considered as an alternative to retrospectively ECG-gated scanning in patients with sinus rhythm with heart rates >65 beats/min
      • Retrospectively ECG-gated scanning may be used as necessary to achieve diagnostic image quality in patients with higher heart rates (eg, > 70 beats/min) or significant heart rate variability
      •  ○ECG-based tube current modulation should generally be applied during retrospectively ECG-gated scanning to lower radiation exposure
      • Scanner-specific low-dose protocols, such as prospectively ECG-triggered high-pitch helical scanning and wide z-axis single heartbeat scanning should be considered for patients in whom acceptable image quality is expected at ultra low radiation dose (cooperative, regular heart rate <60 beats/min, BMI <30 kg/m2)
      • Scanner-specific protocols that account for arrythmias are encouraged for patients with irregular rhythms and in patients who are unable to reliably hold their breath; this includes retrospectively ECG-gated scanning with ECG-based tube current modulation and max tube current in systole 200–440 msec after the R-peak
        • Meyersohn N.M.
        • Szilveszter B.
        • Staziaki P.V.
        • et al.
        Coronary CT angiography in the emergency department utilizing second and third generation dual source CT.
      Scan protocol: coronary CTA vs TRO-CTAConcomitant clinical risk for PE or AAS
      • In general, TRO-CTA is discouraged unless there is reasonable clinical suspicion for both ACS and either PE or AAS.
      • Consider TRO-CTA if the likelihood of PE is not low:
        • Rybicki F.J.
        • Udelson J.E.
        • Peacock W.F.
        • et al.
        2015 ACR/ACC/AHA/AATS/ACEP/ASNC/NASCI/SAEM/SCCT/SCMR/SCPC/SNMMI/STR/STS appropriate utilization of cardiovascular imaging in emergency department patients with chest pain.
        ,
        • Burris 2nd, A.C.
        • Boura J.A.
        • Raff G.L.
        • Chinnaiyan K.M.
        Triple Rule Out Versus Coronary CT Angiography in Patients With Acute Chest Pain: Results From the ACIC Consortium
      •  ○History of DVT, malignancy, immobility, age >65 with tachycardia, and
      •  ○Indeterminate biomarkers (i.e. D-dimer)
      • Consider TRO-CTA if the likliehood of AAS is not low:
        • Rybicki F.J.
        • Udelson J.E.
        • Peacock W.F.
        • et al.
        2015 ACR/ACC/AHA/AATS/ACEP/ASNC/NASCI/SAEM/SCCT/SCMR/SCPC/SNMMI/STR/STS appropriate utilization of cardiovascular imaging in emergency department patients with chest pain.
        ,
        • Burris 2nd, A.C.
        • Boura J.A.
        • Raff G.L.
        • Chinnaiyan K.M.
        Triple Rule Out Versus Coronary CT Angiography in Patients With Acute Chest Pain: Results From the ACIC Consortium
      •  ○History of Marfan's syndrome, aortic valve disease, aortic aneurysm, or recent aortic surgery, or
      •  ○Symptom of abrupt onset ripping/stabbing/tearing pain, or
      •  ○Physical exam finding of pulse or blood pressure deficit, or a new murmur of aortic insufficiency
      Scan length can be determined in two ways: by the initial topogram or by the non-contrast calcium scoring CT scan. Scan length is decreased as much as possible, to include the heart from above the level of the highest coronary artery (often the left anterior descending) to below the level of the posterior descending artery. Scan length is increased as necessary for evaluation of bypass grafts (to include origin of the left internal mammary artery) or the aorta and pulmonary arteries (in triple-rule-out CTA).
      • Vrachliotis T.G.
      • Bis K.G.
      • Haidary A.
      • et al.
      Atypical chest pain: coronary, aortic, and pulmonary vasculature enhancement at biphasic single-injection 64-section CT angiography.
      ,
      • Takakuwa K.M.
      • Halpern E.J.
      Evaluation of a "triple rule-out" coronary CT angiography protocol: use of 64-Section CT in low-to-moderate risk emergency department patients suspected of having acute coronary syndrome.
      Routine use of 100 kV tube potential is generally possible in patients when the patient's weight is below 100 kg and the body mass index ≤30 kg/m sq. It should be noted that radiation dose varies approximately as the square of the change in tube potential, as opposed to linearly with tube current or scan length. On the other hand, very high body mass (≥40 kg/m2) may require a higher tube potential (140 kV) with better tissue penetration and a reduction in image noise to achieve diagnostic quality. In addition to BMI-based tube voltage selection, automated methods for tube voltage selection based on attenuation values in the scout images are recommended to lower radiation exposure and preserve image quality. In smaller adults and pediatric patients, reducing tube potential to 80 kVp can lower radiation exposure and maintain diagnostic image quality, while substantially lowering radiation exposure 30–50%.
      • Abbara S.
      • Blanke P.
      • Maroules C.D.
      • et al.
      SCCT guidelines for the performance and acquisition of coronary computed tomographic angiography: a report of the society of cardiovascular computed tomography guidelines committee: endorsed by the north American society for cardiovascular imaging (nasci).
      In such cases, the supervising physician should be involved in decision making about this choice. In adjusting tube current to body habitus, many scanner models provide automated adjustment from a profile taken from the topogram or by other means. Further, iterative and model-based reconstruction techniques reduce image noise, allowing for imaging at lower kVp and lower tube current with preservation of diagnostic image quality.

      6.2 Modes of data acquisition

      Prospectively ECG-triggered axial acquisition should be considered the default scan mode of choice in patients with sufficient heart rate control, including patients with regular rhythms and heart rates less than 65 beats per minute. At higher heart rates (ie, 66–72 beats per minute), the acquisition window can be widened (“padding”) to increase the likelihood of imaging during coronary diastasis. If retrospectively-gated scans are necessary (generally due to high or irregular heart rates), ECG-gated tube current modulation should generally be used unless specific clinical situations exist. Low-dose scan modes such as high-pitch or wide-detector volumetric scans should be used, if available, in patients meeting standards for target heart rates and body habitus.
      • Hausleiter J.
      • Bischoff B.
      • Hein F.
      • et al.
      Feasibility of dual-source cardiac CT angiography with high-pitch scan protocols.
      • Achenbach S.
      • Marwan M.
      • Ropers D.
      • et al.
      Coronary computed tomography angiography with a consistent dose below 1 mSv using prospectively electrocardiogram-triggered high-pitch spiral acquisition.
      • Flohr T.G.
      • Klotz E.
      • Allmendinger T.
      • Raupach R.
      • Bruder H.
      • Schmidt B.
      Pushing the envelope: new computed tomography techniques for cardiothoracic imaging.
      • Goetti R.
      • Feuchtner G.
      • Stolzmann P.
      • et al.
      High-pitch dual-source CT coronary angiography: systolic data acquisition at high heart rates.
      • Scharf M.
      • Bink R.
      • May M.S.
      • et al.
      High-pitch thoracic CT with simultaneous assessment of coronary arteries: effect of heart rate and heart rate variability on image quality and diagnostic accuracy.
      • Choi S.I.
      • George R.T.
      • Schuleri K.H.
      • Chun E.J.
      • Lima J.A.
      • Lardo A.C.
      Recent developments in wide-detector cardiac computed tomography. Int J Cardiovasc Imaging.
      • de Graaf F.R.
      • Schuijf J.D.
      • Delgado V.
      • et al.
      Clinical application of CT coronary angiography: state of the art.
      • de Graaf F.R.
      • Schuijf J.D.
      • van Velzen J.E.
      • et al.
      Diagnostic accuracy of 320-row multidetector computed tomography coronary angiography to noninvasively assess in-stent restenosis.
      • de Graaf F.R.
      • Schuijf J.D.
      • van Velzen J.E.
      • et al.
      Diagnostic accuracy of 320-row multidetector computed tomography coronary angiography in the non-invasive evaluation of significant coronary artery disease.
      • Kang E.J.
      • Lee K.N.
      • Kim D.W.
      • et al.
      Triple rule-out acute chest pain evaluation using a 320-row-detector volume CT: a comparison of the wide-volume and helical modes. Int J Cardiovasc Imaging.
      The most modern CT scanners can image the entire heart within a single beat and with a radiation dose <1 mSv in patients with slow sinus rhythm.
      • Cecco C.N.D.
      • Meinel F.G.
      • Chiaramida S.A.
      • Costello P.
      • Bamberg F.
      • Schoepf U.J.
      Coronary artery computed tomography scanning.

      6.3 Triple-rule-out CTA (TRO)

      In select patients presenting to the ED with ACP, there may be more than one life-threatening clinical suspicion; for example, when a patient with multiple cardiac risk factors also has a positive D-dimer test and clinical symptoms suggesting pulmonary embolism. CT technology permits increasing the field of view to include the entire thorax and using techniques to simultaneously opacify the aorta, pulmonary arteries and the coronary arteries. This so-called “triple-rule-out” protocol may be used to exclude disease of all three vascular beds.
      • Ayaram D.
      • Bellolio M.F.
      • Murad M.H.
      • et al.
      Triple rule-out computed tomographic angiography for chest pain: a diagnostic systematic review and meta-analysis.
      ,
      • Halpern E.J.
      Triple-rule-out CT angiography for evaluation of acute chest pain and possible acute coronary syndrome.
      TRO is highly accurate for detecting significant coronary artery disease, with comparable accuracy and diagnostic yield to dedicated coronary CTA.
      • Ayaram D.
      • Bellolio M.F.
      • Murad M.H.
      • et al.
      Triple rule-out computed tomographic angiography for chest pain: a diagnostic systematic review and meta-analysis.
      ,
      • Burris 2nd, A.C.
      • Boura J.A.
      • Raff G.L.
      • Chinnaiyan K.M.
      Triple Rule Out Versus Coronary CT Angiography in Patients With Acute Chest Pain: Results From the ACIC Consortium
      ,
      • Wnorowski A.M.
      • Halpern E.J.
      Diagnostic yield of triple-rule-out CT in an emergency setting.
      Depending on scanner model, TRO CTA can be performed with an extended contrast infusion to maintain pulmonary artery opacification (using a similar contrast infusion rate as coronary CTA, e.g. 5–7 mL/sec) followed by a reduced rate (3 mL/sec) or a late phase infusion of reduced contrast concentration. Alternatively, if high-pitch scan mode is available, a two-pass protocol can be implemented in which single contrast bolus is rapidly imaged in two acquisitions through the chest: the first pass timed to enhance the pulmonary arteries, then subsequently to enhance the aorta and coronary arteries (second pass).
      • Burris 2nd, A.C.
      • Boura J.A.
      • Raff G.L.
      • Chinnaiyan K.M.
      Triple Rule Out Versus Coronary CT Angiography in Patients With Acute Chest Pain: Results From the ACIC Consortium
      Compared to conventional coronary CTA, TRO is associated with a higher diagnostic yield for pulmonary embolism and aortic dissection, and may detect a significant noncoronary diagnosis in 8–14% of patients that can explain the patient's ACP, including pathologic findings that may not be identified on coronary CTA.
      • Wnorowski A.M.
      • Halpern E.J.
      Diagnostic yield of triple-rule-out CT in an emergency setting.
      ,
      • Takakuwa K.M.
      • Halpern E.J.
      • Gingold E.L.
      • Levin D.C.
      • Shofer F.S.
      Radiation dose in a "triple rule-out" coronary CT angiography protocol of emergency department patients using 64-MDCT: the impact of ECG-based tube current modulation on age, sex, and body mass index.
      Further, TRO may safely eliminate the need for further testing in up to 75% of patients.
      • Halpern E.J.
      Triple-rule-out CT angiography for evaluation of acute chest pain and possible acute coronary syndrome.
      However, the examination comes with increased radiation and contrast dose, and potentially higher incidence of nondiagnostic coronary evaluation, which varies based on the type of CT scanner and scan protocol.
      • Rybicki F.J.
      • Udelson J.E.
      • Peacock W.F.
      • et al.
      2015 ACR/ACC/AHA/AATS/ACEP/ASNC/NASCI/SAEM/SCCT/SCMR/SCPC/SNMMI/STR/STS appropriate utilization of cardiovascular imaging in emergency department patients with chest pain.
      ,
      • Burris 2nd, A.C.
      • Boura J.A.
      • Raff G.L.
      • Chinnaiyan K.M.
      Triple Rule Out Versus Coronary CT Angiography in Patients With Acute Chest Pain: Results From the ACIC Consortium
      ,
      • Gruettner J.
      • Fink C.
      • Walter T.
      • et al.
      Coronary computed tomography and triple rule out CT in patients with acute chest pain and an intermediate cardiac risk profile. Part 1: impact on patient management.
      With modern CT scanners and scan protocols, the radiation and contrast penalties associated with TRO are less substantial than previously described.
      • Halpern E.J.
      Triple-rule-out CT angiography for evaluation of acute chest pain and possible acute coronary syndrome.
      Nevertheless, judicious use of TRO is recommended, and its potential risks and benefits should be discussed with the patient prior to imaging.
      The 2015 multi-society appropriate use criteria for cardiovascular imaging in the ED
      • Rybicki F.J.
      • Udelson J.E.
      • Peacock W.F.
      • et al.
      2015 ACR/ACC/AHA/AATS/ACEP/ASNC/NASCI/SAEM/SCCT/SCMR/SCPC/SNMMI/STR/STS appropriate utilization of cardiovascular imaging in emergency department patients with chest pain.
      designates TRO “appropriate” in ED patients with ACP for whom a leading diagnosis is problematic or not possible, and in whom the overall likelihood of ACS, pulmonary embolism or acute aortic syndrome is not low (Table 4). This may include patients with history of deep vein thrombosis, malignancy, or immobility; indeterminate biomarkers (e.g., D-dimer); history of Marfan syndrome, aortic valve disease, aortic aneurysm, or recent aortic surgery; symptoms of abrupt onset ripping/stabbing/tearing pain; or physical exam findings of pulse or blood pressure deficit, or a new murmur of aortic insufficiency.
      • Burris 2nd, A.C.
      • Boura J.A.
      • Raff G.L.
      • Chinnaiyan K.M.
      Triple Rule Out Versus Coronary CT Angiography in Patients With Acute Chest Pain: Results From the ACIC Consortium
      If the primary clinical diagnosis under consideration is pulmonary embolism or acute aortic syndrome, strong consideration should be given to dedicated CTA of the pulmonary arteries or aorta, respectively, as a first-line imaging test, so as to avoid a potential delay in diagnosis with TRO CTA, which often requires heart control prior to scan acquisition.

      6.4 Contrast injection

      A high iodine concentration contrast agent is infused at a high flow rate (5–7 mL/sec) to optimize coronary imaging. An 18- or 20-gauge IV is recommended to accommodate the high flow rate, and should be placed within an antecubital vein. Hand and forearm IV access is less favored due to greater potential for compartment syndrome in the event of contrast extravasation. The volume of contrast needed is determined by the scan duration. Contrast administration protocols vary among institutions, with use of contrast injection followed by a saline chaser (biphasic protocol), or contrast injection followed by injection of a saline/contrast mixture (ie 30% contrast, 70% saline) in turn followed by a 100% saline chaser (triphasic protocol).
      • Abbara S.
      • Blanke P.
      • Maroules C.D.
      • et al.
      SCCT guidelines for the performance and acquisition of coronary computed tomographic angiography: a report of the society of cardiovascular computed tomography guidelines committee: endorsed by the north American society for cardiovascular imaging (nasci).
      ,
      • Scholtz J.-E.
      • Ghoshhajra B.
      Advances in cardiac CT contrast injection and acquisition protocols.
      Scanning is initiated either by a “timing bolus” method (in which a test bolus is injected and the time to maximum opacification of the aortic root is determined), or a “bolus tracking” method (in which the scan begins automatically after a preset CT attenuation threshold is reached in the aortic root).
      • Abbara S.
      • Blanke P.
      • Maroules C.D.
      • et al.
      SCCT guidelines for the performance and acquisition of coronary computed tomographic angiography: a report of the society of cardiovascular computed tomography guidelines committee: endorsed by the north American society for cardiovascular imaging (nasci).
      ,
      • Scholtz J.-E.
      • Ghoshhajra B.
      Advances in cardiac CT contrast injection and acquisition protocols.
      Once scan quality is deemed adequate, the patient is taken off the scanner table and transferred back to the ED following a brief observation period to ensure hemodynamic and clinical stability.

      6.5 Recommendations

      • Scan acquisition should follow SCCT guidelines for the performance and acquisition of coronary CTA.
        • Abbara S.
        • Blanke P.
        • Maroules C.D.
        • et al.
        SCCT guidelines for the performance and acquisition of coronary computed tomographic angiography: a report of the society of cardiovascular computed tomography guidelines committee: endorsed by the north American society for cardiovascular imaging (nasci).
      • Institutional scan protocol guidelines should be established, and staff trained in routine scan protocol selection, based on scanner hardware and software, as well as staff capabilities. Physicians should be readily available to answer questions on protocol selection.
      • In patients undergoing CT for the exclusion of ACS, contrast-enhanced coronary CTA should always be obtained, and a preceding noncontrast calcium score is optional though recommended.
      • Scanner-based automated tube potential and tube current selection algorithms are preferred, if available.
      • When automated tube potential selection is not available, 100 kV tube potential is recommended when the patient's weight is below 100 kg and the body mass index ≤30 kg/m sq.
      • Scan protocol selection should be customized to the patient's heart rate and rhythm and body habitus, choosing the lowest dose mode based on patient characteristics and scanner model.
      • Contrast should be administered through an 18- or 20-gauge IV in an antecubital (or more central) vein. Hand and forearm IV access is less favored due to the increased risk of compartment syndrome in the event of contrast extravasation.
      • Iterative or model-based reconstruction should be used to reduce radiation dose and improve quality.
      • Generally, prospectively ECG-triggered axial acquisition should be considered the default scan mode in most patients with sufficient heart rate control, including patients with regular rhythm and heart rates less than 65 beats per minute
      • Newer low-dose scan modes (e.g., wide-detector prospective or high-pitch spiral acquisition) should be utilized if the patient's heart rate and characteristics are likely to provide diagnostic image quality.
      • TRO can be considered in lieu of coronary-only CTA in select patients for whom the comparative likelihood of ACS, pulmonary embolism, or acute aortic syndrome is uncertain.

      7. Interpretation & reporting

      The interpretation and reporting of coronary CTA in the ED should make use of the Coronary Artery Disease Data and Reporting System (CAD-RADS)
      • Cury R.C.
      • Abbara S.
      • Achenbach S.
      • et al.
      CAD-RADS(TM) coronary artery disease - reporting and data system. An expert consensus document of the society of cardiovascular computed tomography (SCCT), the American College of Radiology (ACR) and the north American society for cardiovascular imaging (NASCI). Endorsed by the American College of Cardiology.
      and conform to SCCT Guidelines for Interpretation and Reporting of Coronary CTA.
      • Leipsic J.
      • Abbara S.
      • Achenbach S.
      • et al.
      SCCT guidelines for the interpretation and reporting of coronary CT angiography: a report of the Society of Cardiovascular Computed Tomography Guidelines Committee.
      In addition, there are particular considerations pertinent to the clinical needs of the ACP patient. The presentation with a potentially life-threatening syndrome requires expedited completion of the acquisition, reconstruction, interpretation and reporting of studies in these patients, and therefore these should be given priority over non-acute cases. Any potentially life-threatening findings should be communicated urgently and directly to ED staff. This includes emergent non-cardiac findings such as aortic dissection and acute pulmonary emboli.
      All segments of the coronary tree should be analyzed using the 18-segment SCCT model.
      • Raff G.L.
      • Abidov A.
      • Achenbach S.
      • et al.
      SCCT guidelines for the interpretation and reporting of coronary computed tomographic angiography.
      Lesions should be characterized by segment, and all segments should be analyzed. The final impression should include statements on (1) the presence or absence of obstructive CAD, (2) the presence or absence of high risk plaque, and (3) a semi-quantitative or quantitative measure of total plaque burden
      • Kitagawa T.
      • Yamamoto H.
      • Horiguchi J.
      • et al.
      Characterization of noncalcified coronary plaques and identification of culprit lesions in patients with acute coronary syndrome by 64-slice computed tomography.
      Stenosis severity should be expressed as maximal percent diameter stenosis following SCCT Guidelines.
      • Leipsic J.
      • Abbara S.
      • Achenbach S.
      • et al.
      SCCT guidelines for the interpretation and reporting of coronary CT angiography: a report of the Society of Cardiovascular Computed Tomography Guidelines Committee.
      Coronary diameter stenosis should be graded into the following categories: minimal (1–24% narrowing), mild (25–49%), moderate (50–69%), severe (70–99%), and occluded (100%). For the left main coronary artery, >50% narrowing represents severe stenosis.
      Plaque morphology should also be evaluated for all coronary lesions. Plaque should be characterized as calcified, noncalcified, predominant calcified, predominant non-calcified, mixed calcified/noncalcified. In addition, plaque with high-risk features (HRP) should be identified. HRP is defined as plaque with two or more high-risk features: positive remodeling, low attenuation (<30 Hounsfield Units), napkin ring sign, and spotty calcification.
      • Cury R.C.
      • Abbara S.
      • Achenbach S.
      • et al.
      CAD-RADS(TM) coronary artery disease - reporting and data system. An expert consensus document of the society of cardiovascular computed tomography (SCCT), the American College of Radiology (ACR) and the north American society for cardiovascular imaging (NASCI). Endorsed by the American College of Cardiology.
      Reporting the presence of HRP improves risk stratification and helps guide clinical management, as it is independently associated with ACS and future MACE events beyond stenosis severity.
      • Motoyama S.
      • Ito H.
      • Sarai M.
      • et al.
      Plaque characterization by coronary computed tomography angiography and the likelihood of acute coronary events in mid-term follow-up.
      ,
      • Taron J.
      • Foldyna B.
      • Mayrhofer T.
      • et al.
      Risk stratification with the use of coronary computed tomographic angiography in patients with nonobstructive coronary artery disease.
      • Williams M.C.
      • Moss A.J.
      • Dweck M.
      • et al.
      Coronary artery plaque characteristics associated with adverse outcomes in the SCOT-heart study.
      • Shaw L.J.
      • Blankstein R.
      • Bax J.J.
      • et al.
      Society of cardiovascular computed tomography/north American society of cardiovascular imaging – expert consensus document on coronary CT imaging of atherosclerotic plaque.
      • Chang H.J.
      • Lin F.Y.
      • Lee S.E.
      • et al.
      Coronary atherosclerotic precursors of acute coronary syndromes.
      The final impression should include a statement on the total coronary plaque burden. This can be based on semi-quantitative measurement of CAC, segment involvement score (SIS) or quantitative measurement of total plaque volume or burden.
      • Hecht H.S.
      • Blaha M.J.
      • Kazerooni E.A.
      • et al.
      CAC-DRS: coronary artery calcium data and reporting system. An expert consensus document of the society of cardiovascular computed tomography (SCCT).
      In patients undergoing CAC scoring, it is recommended to report the total CAC score and the risk category of 0, 1–99 (mild burden), 100–200 (moderate burden), and ≥300 (severe burden).
      • Hecht H.S.
      • Blaha M.J.
      • Kazerooni E.A.
      • et al.
      CAC-DRS: coronary artery calcium data and reporting system. An expert consensus document of the society of cardiovascular computed tomography (SCCT).
      ,
      • Williams M.C.
      • Moss A.
      • Dweck M.
      • et al.
      Standardized reporting systems for computed tomography coronary angiography and calcium scoring: a real-world validation of CAD-RADS and CAC-DRS in patients with stable chest pain.
      Alternatively, SIS can be assessed by counting the number of coronary segments on the coronary CTA scan in which plaque is present.
      • Shaw L.J.
      • Blankstein R.
      • Bax J.J.
      • et al.
      Society of cardiovascular computed tomography/north American society of cardiovascular imaging – expert consensus document on coronary CT imaging of atherosclerotic plaque.
      Quantitative evaluation of coronary plaque volume and burden is gradually becoming feasible, and plaque software that are validated against invasive techniques, such as quantitative coronary angiography, intravascular ultrasound and optical coherence tomography are preferred. While an estimate of total plaque burden within the coronary tree is recommended on all coronary CTA reports for post-acute risk stratification,
      • Shaw L.J.
      • Blankstein R.
      • Bax J.J.
      • et al.
      Society of cardiovascular computed tomography/north American society of cardiovascular imaging – expert consensus document on coronary CT imaging of atherosclerotic plaque.
      plaque burden has a limited role in the early triage of acute chest pain.
      Extra-coronary cardiac evaluation should include examination of cardiac morphology and the pericardium. Interpretation of the LV myocardium should include evaluation of myocardial hypertrophy, thinning and/or enhancement. The identification of regional subendocardial or transmural hypoattenuation of the myocardium is suspicious for ischemia or infarction
      • Nakauchi Y.
      • Iwanaga Y.
      • Ikuta S.
      • et al.
      Quantitative myocardial perfusion analysis using multi-row detector CT in acute myocardial infarction.
      and should warrant further investigation even in the absence of an identifiable critical coronary stenosis. Aortic evaluation is usually possible within the extent of the typical cardiac field-of-view (generally mid-pulmonary artery to diaphragm). This scan length generally includes the aortic root, most of the ascending aorta and dorsal thoracic aorta, but not the transverse aorta. Within these limitations the presence of any pathology should be reported. In the case of triple-rule-out or coronary bypass full thorax acquisitions, the entire thoracic aorta should be reported. Pulmonary artery pathology should be reported within the constraints of the acquisition protocol. In standard coronary CTA, the contrast administration protocol and the scanned volume used for coronary imaging will be suboptimal for evaluation of the pulmonary vasculature and hence the detection of pulmonary embolism. Nevertheless, large proximal pulmonary emboli may still be detectable as contrast filling defects. Disproportionate enlargement of the right ventricular chamber should raise the suspicion for pulmonary emboli. In patients undergoing triple-rule-out procedures, contrast enhancement and field-of-view should be sufficient to permit review of all pulmonary arterial pathology.

      7.1 CAD-RADS

      The CAD-RADS lexicon should be incorporated into the report, with a numeric CAD-RADS assessment category and CAD-RADS modifiers to follow the final impression. CAD-RADS is a standardized reporting system for patients undergoing coronary CTA that links imaging findings with patient management recommendations.
      • Cury R.C.
      • Abbara S.
      • Achenbach S.
      • et al.
      CAD-RADS(TM) coronary artery disease - reporting and data system. An expert consensus document of the society of cardiovascular computed tomography (SCCT), the American College of Radiology (ACR) and the north American society for cardiovascular imaging (NASCI). Endorsed by the American College of Cardiology.
      The primary goal of CAD-RADS is to improve patient care by facilitating communication of scan results to referring physicians. It also provides a framework that may benefit education, research, peer-review, and quality assurance. The classification is applied on a per-patient basis for the clinically most relevant stenosis. Assessment categories range from CAD-RADS 0 (denoting complete absence of coronary plaque and stenosis) to CAD-RADS 5 (denoting the presence of at least one totally occluded coronary artery). Associated with each assessment category are specific management recommendations to guide next steps in the care pathway. CAD-RADS modifiers denote the presence of absence of high-risk plaque (modifier “HRP”), coronary stent(s) (modifier “S”), bypass graft(s) (modifier “G”), and one or more non-diagnostic coronary segments (modifier “N”).
      An updated CAD-RADS 2.0 classification (JCCT 2022, in review) was published in 2022 and provides an expanded framework for coronary reporting, including a description of coronary plaque burden in addition to stenosis severity. The updated CAD-RADS classification will follow an established framework of stenosis, plaque burden, and modifiers, which will include assessment of lesion-specific ischemia using CT fractional-flow-reserve (CT-FFR) or myocardial CT perfusion (CTP), when performed. Plaque burden is categorized as mild, P1 (CAC 1–100, or SIS ≤2); moderate, P2 (CAC 101–300, or SIS 3–4); severe, P3 (CAC 301–999, or SIS 5–7); or extensive, P4 (CAC >1000, or SIS ≥8). Thus, a coronary CTA exam with mild plaque burden (e.g., total CAC score 32), and mild stenosis of the proximal LAD (e.g., estimated 30–40%), but no significant stenosis elsewhere in the coronary tree, would be classified “CADRADS 2 P1.”
      CAD-RADS 2.0 also allows the option to include ischemia evaluation by FFR-CT or stress myocardial CTP, designated by the modifier “I”. Abnormal ischemia evaluation, designated “I+“, includes an abnormal FFR-CT ≤0.75 or the presence of a stress myocardial perfusion defect on CTP that resolves on resting perfusion images. Ischemia testing with FFR-CT or stress myocardial CTP should be considered with coronary stenoses ranging from 50 to 90% to better define if a stenosis is hemodynamically significant.

      7.2 Recommendations

      • Interpretation and reporting should be consistent with SCCT Guidelines.
      • Coronary CTA scans should be reviewed for stenosis severity, plaque morphology, and an estimate of total coronary plaque burden.
      • The CAD-RADS 2.0 lexicon should be incorporated into the report, with a final assessment category, modifiers, and management recommendations.
      • Ordering clinicians should be notified immediately of abnormal coronary CTA scans with severe stenosis.
      • All coronary CTA scans from the ED should be evaluated and reported in a timely manner per local institutional policy.
      • Non-coronary findings should be included in the body of the report, and clinically significant findings (i.e. pulmonary embolism, aortic dissection) should be communicated directly to the ordering clinician.

      8. Future developments

      As the evidence base for FFR-CT and CTP continues to evolve, increased clinical adoption of these strategies in the ED setting is anticipated. This will facilitate efficient, comprehensive anatomic and functional coronary evaluation to improve accuracy for ACS and optimize management. Considering the need for rapid decision-making in the ED, FFR-CT calculations will require rapid turn-around-time, and ideally on-site evaluation. In addition, standardized CTP protocols will allow for easier implementation in ED pathways.
      • Patel A.R.
      • Bamberg F.
      • Branch K.
      • et al.
      Society of cardiovascular computed tomography expert consensus document on myocardial computed tomography perfusion imaging.
      Recognizing most ACS events occur in patients with non-obstructive coronary lesions, increased attention to high-risk plaque features on coronary CTA will provide additional biomarkers for risk assessment. Radiomics, which includes the extraction and mining of a large number of quantitative features from imaging, may facilitate this process with the aid of artificial intelligence. Quantitative plaque analysis tools are also emerging, which may enable faster post-processing and detailed evaluation of plaque progression and regression to direct optimal medical therapy.
      Finally, techniques for visualizing and quantifying inflammation around the coronary arteries may provide additional biomarkers help guide early targeted primary prevention. Changes in CT attenuation related to inflammation-induced lipolysis within the epicardial adipose tissue are described with the perivascular adipose tissue attenuation.
      • Klüner L.V.
      • Oikonomou E.K.
      • Antoniades C.
      Assessing cardiovascular risk by using the fat attenuation index in coronary CT angiography.
      In the CRISP-CT trial,
      • Oikonomou E.K.
      • Marwan M.
      • Desai M.Y.
      • et al.
      Non-invasive detection of coronary inflammation using computed tomography and prediction of residual cardiovascular risk (the CRISP CT study): a post-hoc analysis of prospective outcome data.
      high perivascular adipose tissue attenuation was an indicator of increased cardiac mortality. A link between pericoronary adipose tissue attenuation on coronary CTA and culprit lesions has been suggested,
      • Goeller M.
      • Achenbach S.
      • Cadet S.
      • et al.
      Pericoronary adipose tissue computed tomography attenuation and high-risk plaque characteristics in acute coronary syndrome compared with stable coronary artery disease.
      with higher pericoronary adipose tissue attenuation around low attenuation, noncalcified plaques. Further research and clinical trials are needed to assess its value in ACP populations.

      9. Conclusion

      Coronary CTA has established itself as the preferred first-line test for ACP triage in select patients, and is now recognized as a Class I indication by multiple international professional societies, including the American College of Cardiology, the American College of Radiology, and the European Society of Cardiology. Appropriate patient selection and utilization of coronary CTA in the ED is essential for extracting its potential clinical and economic value, which includes improving patient outcomes, lowering healthcare costs, and preventing unnecessary diagnostic procedures. These recommendations were produced as an educational tool for practitioners evaluating ACP in the ED in the interest of developing systematic standards for coronary CTA based on clinical evidence and expert consensus. As CT technology rapidly expands in the era of artificial intelligence, promising new diagnostic and prognostic CT strategies are likely to further impact clinical management and risk stratification.

      Declaration of Competing Interest

      The Society of Cardiovascular Computed Tomography Guidelines Committee makes every effort to avoid any actual or potential conflicts of interest that might arise as a result of an outside relationship or a personal interest of a member of the Guidelines Committee or its Writing Groups. Specifically, all members of the Guidelines Committee and of both Writing Committees are asked to provide disclosure statements of all such relationships that might be perceived as real or potential conflicts of interest relevant to the document topic. The relationships with industry information for Writing Group and Committee members are available in the Acknowledgments section of this document. These are reviewed by the Guidelines Committee and will be updated as changes occur.

      Appendix A. Supplementary data

      The following are the Supplementary data to this article:

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