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Coronary venous anatomy can be divided into the greater cardiac venous system and the lesser cardiac venous system. With protocol optimization, including appropriate contrast bolus timing, coronary veins can be depicted with excellent detail on CT. Knowledge of variant coronary venous anatomy can sometimes play a role in pre-procedural planning. Analysis of the coronary venous anatomy on CT can detect coronary venous anomalies that cause right to left shunts with risk of stroke, left to right shunts, and arrhythmias.
With protocol optimization including appropriate contrast bolus timing, ECG gated multidetector computed tomography (CT) can noninvasively show coronary venous anatomy with excellent detail. This can be useful for pre-procedural planning of some cardiac interventions. Adequate depiction of the coronary venous system can be achieved by modifying the CT coronary angiography technique such that data acquisition occurs 2–3 s later than normal. Magnetic resonance imaging has also been advocated as a tool for evaluating coronary venous anatomy but remains inferior to CT regarding image quality and resolution.
In this article, we review both normal and variant coronary venous anatomy.
2. Coronary venous system: anatomy overview
The coronary venous system can be divided into two groups of veins: the greater cardiac venous system and the lesser cardiac venous system.
2.1 Greater cardiac venous system
Coronary sinus and tributary veins
Great cardiac vein
Anterior interventricular vein
Left marginal vein
Left posterior veins
Oblique vein of Marshall
Posterior interventricular vein
Small cardiac vein
Ventricular septal veins
Veins draining the right ventricle
Right marginal vein
Anterior cardiac veins
Vein of Zuckerkandl
Vein of Cruveilhier
Veins draining the atria
2.2 Lesser cardiac venous system
Small vascular channels
While the greater cardiac venous system is much larger than the lesser cardiac venous system, both play an important role in the venous drainage of the heart. The greater cardiac venous system is illustrated in Fig. 1.
The coronary sinus (CS) is a tubular venous structure sitting in the inferior portion of the left atrioventricular groove that receives blood from many tributary veins before emptying into the posteromedial right atrium (Fig. 2). It is the largest cardiac venous structure, with a diameter measuring up to 12 mm and length ranging from 30 to 63 mm. A CS length of 20 mm or less is considered a short CS.
A muscular sleeve surrounding the CS has been associated with arrhythmias, however this is not well visualized on CT. The muscular sleeve of the CS is contiguous with the muscle of the right and left atria and the muscular sleeve around the oblique vein of Marshall.
The Thebesian valve, present up to 86% of the time, is located at the junction of the coronary sinus and the right atrium. It is visualized on CT in approximately 72% of individuals as a thin, hypodense linear structure at the junction of the CS and the right atrium. Image noise and heart failure can make it difficult to visualize the Thebesian valve the remainder of the time.
In approximately 16% of people the Thebesian valve has features that make cannulation of the CS during cardiac procedures difficult. These features include: fibromuscular or muscular composition, covering over 75% of the ostium, and lack of fenestrations. Of these features, CT can detect when the Thebesian valve covers more than 75% of the CS ostium.
Anomalies of the CS are uncommon and include enlargement, hypoplasia, and absence of the CS. A persistent left superior vena cava is an uncommon anomaly occurring in 0.3–0.5% of individuals and can result in enlargement of the coronary sinus (Fig. 3). A persistent left superior vena cava results from failure of the left common and left anterior cardinal veins to regress. The persistent left superior vena cava forms from the confluence of the left internal jugular and left subclavian veins and courses caudally, draining into the CS.
Enlargement of the CS can also occur secondary to an unroofed CS, another rare anomaly. An unroofed CS consists of communication between the superior portion of the CS and the left atrium, resulting in a left to right shunt or sometimes a bidirectional shunt placing the individual at risk for cerebral embolus (Fig. 4).
Additional rare causes of CS enlargement include coronary artery fistulae, partial and total anomalous pulmonary venous return (PAPVR and TAPVR), and interrupted inferior vena cava. Fistulae between the coronary arteries and the CS are usually congenital and result in enlargement of both the coronary artery and the CS (Fig. 5).
Interruption of the inferior vena cava with drainage of the hepatic veins directly to the CS as well as hemiazygous continuation of a left inferior vena cava with drainage into the CS via a persistent left superior vena cava can also lead to CS dilation.
A rare condition associated with absence of the CS is Raghib syndrome. In Raghib syndrome, the CS is absent and a persistent left superior vena cava drains directly into the left atrium resulting in a right to left shunt (Fig. 6). An atrial septal defect is commonly although not invariably present in the posterior/inferior portion of the interatrial septum. Patients may present with paradoxical stroke. Veins that would normally empty into the CS may drain into the superior vena cava or left atrium.
The CS receives bloodflow from many coronary veins. Some veins drain directly into the CS while others contribute to the venous return to the CS indirectly by draining into other coronary veins that drain into the coronary sinus. Coronary veins that directly or indirectly contribute to the venous return of the CS are commonly referred to collectively as CS tributary veins and include: the great cardiac vein, the anterior interventricular vein, the left marginal vein, left posterior veins, oblique vein of Marshall, posterior interventricular vein, small cardiac vein, and ventricular septal veins.
3.2.1 Great cardiac vein and anterior interventricular vein
The anterior interventricular vein travels in the anterior interventricular groove with the left anterior descending coronary artery (LAD) (Fig. 7). It typically arises at the left ventricular apex, but occasionally in the mid portion of the anterior interventricular groove.
Its relationship to the LAD is variable as it can be located right, left, superficial, or deep relative to the LAD. Crossing into the left antrioventricular groove, it creates a characteristic triangle with the left anterior descending and left circumflex coronary arteries known as the trigone of Brocq and Mouchet.
The great cardiac vein continues within the left atrioventricular groove alongside the left circumflex artery, empyting into the CS. Similar to the anterior interventricular vein, the relationship of the great cardiac vein to the left circumflex artery is highly variable. It may be located left, right, superficial, or deep to the left circumflex coronary artery.
Anomalies of these two cardiac veins are uncommon and include myocardial bridging of the anterior interventricular vein, anomalous course through the transverse sinus empyting into the superior vena cava or right atrium (Fig. 9), and aneurysmal dilation of the great cardiac vein.
The left marginal vein, also known as the left obtuse marginal vein, travels alongside the lateral border of the left ventricle with one of the obtuse marginal arterial branches of the left circumflex artery and drains the lateral wall of the left ventricle (Fig. 10). It is present in up to 85% of individuals and usually drains into the great cardiac vein. Approximately 20% of the time it drains into the CS.
The left posterior veins, also known as the posterolateral veins, range from one to three in number, course along the lateral and inferior walls of the left ventricle, and typically drain into the CS (Fig. 11).
Approximately 15% of the time they drain into the great cardiac vein. Approximately 5% of the time, there is no left posterior vein and the left marginal vein drains the left ventricular posterolateral wall by itself.
The oblique vein of Marshall, also known as the oblique vein of the left atrium, is present in up to 95% of individuals and is a remnant of the left superior vena cava. It is a short vein of approximately 2–3 cm that courses between the left atrial appendage and left pulmonary veins to join the CS at its junction with the valve of Vieussens (Fig. 2B). It can be completely fibrotic with only a ligament of Marshall remaining. The ligament of Marshall appears as a thin band of soft tissue on CT.
The oblique vein of Marshall is surrounded by a muscular sleeve called the Marshall bundle. The Marshall bundle connects to the musculature surrounding the pulmonary veins and the coronary sinus. The Marshall bundle is associated with various arrhythmias.
The posterior interventricular vein is also known as the inferior interventricular vein and the middle cardiac vein. The posterior interventricular vein arises at the left ventricular apex and travels in the posterior interventricular groove with the posterior descending artery and drains into the coronary sinus (Fig. 12).
It drains a portion of the apex, the posterior interventricular septum, and the posterior walls of the ventricles. The posterior interventricular vein can become aneurysmal or have a diverticulum at its junction with the CS, both of which have been associated with cardiac arrhythmias.
The small cardiac vein, sometimes referred to as the right coronary vein in older literature, travels in the right atrioventricular groove with the right coronary artery and usually empties into the CS (Fig. 13). Less commonly it may empty into the posterior interventricular vein or occasionally into the right atrium. It drains the inferior wall of the right ventricle and is present in approximately 50% of people.
The veins draining the right ventricle consist of the right marginal vein, the anterior cardiac veins, and the infundibular veins. The right marginal vein travels along the lateral wall of the right ventricle alongside the right marginal artery and drains directly into the right atrium (Fig. 15). Approximately one-third of the time, the right marginal vein drains into the small cardiac vein.
The left atrium is drained by many small caliber coronary veins that empty into a variety of structures depending on their proximity: coronary sinus, great cardiac vein, superior pulmonary vein, mediastinal veins, and right atrium.
The thebesian vessels are a complex network of small vascular channels and sinusoids that drain the inner third of the myocardium. They empty directly into the four cardiac chambers, and are most prevalent in the right atrium and right ventricle.
Coronary venous anatomy can be depicted with excellent detail using CT. Knowledge of coronary venous anatomy and anomalies can play a part in the planning various procedures such as left ventricular pacing. Analysis of the coronary venous anatomy on CT can detect coronary venous anomalies causing right to left shunts with risk of stroke, left to right shunts, and arrhythmias.
Funding and conflicts of interest
This work was supported by the Intramural Research Program of the National Heart, Lung, and Blood Institute , National Institutes of Health, USA . Andrew E. Arai is a principal investigator on a US government Cooperative Research and Development Agreement (CRADA) with Siemens Healthineers, Bayer Healthcare Pharmaceuticals, and Circle Cardiovascular imaging. Marcus Y. Chen has a research agreement with Canon Medical Systems. Other coauthors have no conflicts of interest relevant to this publication to declare.
Imaging of the coronary sinus: normal anatomy and congenital abnormalities.