Anomalous origin of the left main coronary artery from the right anterior aortic sinus: angiographic definition of anomalous course.

Five cases of anomalous origin of the left main (LM) coronary artery from the right anterior aortic sinus are presented. In 4 patients the anomalous artery ran a septal course through the floor of the right ventricular infundibulum and in 1 an interarterial course between the aorta and pulmonary trunk. The cineangiographic features of these courses are contrasted with arteries running anterior free wall and retro-aortic courses. A caudal anterior loop of the anomalous LM coronary artery indicates a septal course, a cranial posterior loop an interarterial course, a cranial anterior loop an anterior free wall course and a caudal posterior loop a retro-aortic course. Review of previously documented cases shows that the septal course is relatively common, although previously not recognized.