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418 An Australian Experience Of Starting A Program To Use Computed Tomography Assessment Of The Left Atrial Appendage To Avoid Trans-oesophageal Echocardiography In The Covid-19 Pandemic

      Introduction: Trans-oesophageal echocardiography (TOE) has long been the gold standard for assessment of the left atrial appendage (LAA). In the COVID-19 pandemic Australian and international guidelines recommend avoiding aerosol generating procedures (AGP). Computed tomography left atrial appendage (CTLAA) is not an AGP and has a negative predictive value for LAA thrombus of 99% in meta-analyses. CTLAA has been endorsed by the Society of Cardiac Computed Tomography to exclude LAA thrombus but is not used widely in Australia outside of pulmonary vein isolation and LAA occlusion device insertion planning. We seek to present our experience for other sites to encourage uptake of CTLAA imaging.
      Methods: A retrospective audit of all patients undergoing CTLAA or TOE at our institution between September 2020 and August 2021 was performed. CTLAA protocol had a single contrast bolus with arterial and delayed phase imaging acquisition.
      Results: 12 CTLAA procedures were performed. Indications included exclusion of thrombus in atrial fibrillation (8), reassessment of known thrombus (2), assessment of filling defect on CTCA (1) and review of atrial appendage occlusion post-surgical ligation (1). LAA thrombus was identified in 2 studies. TOE was required for 1 patient with indeterminant CTLAA findings. 134 TOE procedures were performed during the same period. A primary indication of excluding LAA thrombus was most frequent (40), a single TOE was done for review of LAA occlusion device (1), other indications (93) included investigation of suspected endocarditis, mitral valve pathology and patent foramen ovale which are not indications for CTLAA. Ultra-fast, low-dose high pitch image acquisition was associated with lower radiation doses (118-255mGy*cm). Radiation doses were higher in the 2 patients requiring helical acquisition (1450 and 2978mGy*cm). There were no contrast related complications.
      Conclusions: CTLAA is a safe alternative to TOE avoiding TOE in 11 out of 12 cases. At our centre CTLAA uptake was not universal. The factors behind this require further study. Given the existing expertise with assessment of the LAA for PVI and occlusion planning we suggest expanding this should not be burdensome and should be considered given the ongoing surges of infections in the COVID-19 pandemic.