Anomalous origin of the left coronary artery from the nonfacing aortic sinus: A study in the Syrian hamster.

A coronary artery that arises from the nonfacing (posterior or dorsal) aortic sinus is regarded as having an anomalous origin. We studied 34 Syrian hamsters in which the left coronary artery originated from the nonfacing aortic sinus. All hamsters belonged to a single family subjected to high endogamous pressure in our laboratory. Twenty-four specimens were examined using a corrosion-cast technique and scanning electron microscopy, whereas the remaining 10 were studied histologically. The aortic valve was normal in 15 cases, whereas it was bicuspid in the other 19 cases. In each specimen of our series, the left coronary artery arose with an acute angle with respect to the aortic valve. Moreover, when the coronary ostium was located in the center of the nonfacing aortic sinus, the proximal coronary artery had an intramural aortic course. These left coronary artery arrangements might underlie an unfavorable coronary circulation physiology. Our morphologic findings agree with the morphogenetic hypothesis that each aortic sinus has the potential to develop coronary artery buds, which hollow out from the aorta to become coronary artery trunks.