ANOMALOUS ORIGIN OF THE LEFT CORONARY-ARTERY FROM THE DORSAL AORTIC SINUS AND ITS RELATIONSHIP WITH AORTIC-VALVE MORPHOLOGY IN SYRIAN HARNSTERS

The condition of the aortic valve and the origin of the coronary arter ies were examined in 2413 Syrian hamsters aged between 1 and 823 days, belonging to nine inbred laboratory families. The specimens were stud ied with either a stereomicroscope, a corrosion-cast technique, or his tological techniques (light microscopy). The aortic valve was tricuspi d in 1823 (75 . 5%) cases, and bicuspid in the remaining 590 (24 . 5%) . In all bicuspid aortic valves there were two aortic sinuses, a ventr al and a dorsal, each supporting one cusp. The left coronary artery ar ose from the dorsal aortic sinus in 71 (2 . 9%) hamsters, eight of whi ch died unexpectedly between ages 1 and 622 days. In 29 (40 . 8%) of t he 71 cases, the aortic valve was tricuspid and the right coronary art ery originated from the right aortic sinus. In the remaining 42 (59 . 2%) cases, the aortic valve was bicuspid and the right coronary artery arose from the right side of the ventral aortic sinus. Results of a c hi(2) contingency test demonstrated that the frequency of left coronar y artery arising from the dorsal aortic sinus significantly increased when the aortic valve was bicuspid. This fact, together with previousl y reported data on coronary artery anomalies in the Syrian hamster, su ggests that the left coronary artery arising from the dorsal aortic si nus may be an expression of a single morphogenetic defect which is exp ressed as bicuspid aortic valve in some cases, anomalous origin of the left coronary artery in others, or in the simultaneous occurrence of these two cardiac abnormalities.