SummaryWe studied the morphology of the aortic valves of 1,036 Syrian hamsters belonging to two families subjected to high endogamous pressure. Most (n=955) specimens were examined using a corrosion-cast technique. In the remaining 81 specimens, valvar morphology was assessed by means of a stereomicroscope, and in 18 of these cases a histologic study was also performed. In one of the families, a high proportion (30.5%) of hamsters had aortic valves with two leaflets, the aortic sinuses being oriented ventrodorsally. The percentage of such anomalous valves was found to be positively correlated with the inbreeding coefficient of specimens. In the other family, the occurrence of an aortic valve with two leaflets was a sporadic event. Stereoscopic and histologic observations demonstrated that, in 52 of 63 aortic valves with three leaflets, the ventral commissure between the right and left leaflets was partially fused, while in 10 other cases this commissure was completely fused. In addition, in nine of 18 aortic valves with two leaflets, there was a more or less well-developed raphe located in the ventral aortic sinus, approximately where the true ventral commissure would have been. Our observations suggest the existence of a continuous spectrum of aortic valvar morphology, ranging from a valve with three leaflets and no fusion of the ventral commissure to an aortic valve with two leaflets devoid of any raphe. This spectrum seems to be the result of the interaction of genetic and intrauterine environmental factors. Results of crosses between both related and unrelated hamsters suggest that the observed morphology in individuals is the result of quantitative inheritance.
Acute Limited Intimal Tear of the Right Aortic Sinus
