Correct answer is C, the location of the coronary sinus found in the atrioventricular sulcus. The sinus is at risk of injury during an atrio-septal defect repair in the exceptionally rare cases when a persistent left vena cava exists. The latter will drain into the sinus and can lead to a thrombus in the coronary sinus after the septal defect repair.
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Answer to this question is based on material presented in lectures 11 of the Thorax Lecture Series.
= Location of r. coronary a.
= Location of Great cardiac vein
= Atrioventricular sulcus
= Superior vena cava
= Inferior vena cava