Anomalous origin and course of the coronary arteries.

In the normal heart, the right and left coronary arteries arise from the aortic valvar sinuses adjacent to the pulmonary trunk. The right coronary artery then directly enters the right atrioventricular groove, whereas the main stem of the left coronary artery runs a short course before dividing to become the anterior interventricular and circumflex arteries. These arteries can have an anomalous origin from either the aorta or pulmonary trunk; their branches can have various anomalous origins relative to arterial pedicles. Other abnormal situations include myocardial bridging, abnormal communications, solitary coronary arteries, and duplicated arteries. Understanding of these variations is key to determining those anomalous patterns associated with sudden cardiac death. In the most common variant of an anomalous origin from the pulmonary trunk, the main stem of the left coronary artery arises from the sinus of the pulmonary trunk adjacent to the anticipated left coronary arterial aortic sinus. The artery can, however, arise from a pulmonary artery, or the right coronary artery can have an anomalous pulmonary origin. The key feature in the anomalous aortic origin is the potential for squeezing of the artery, produced by either the so-called intramural origin from the aorta, or the passage of the abnormal artery between the aortic root and the subpulmonary infundibulum.