Cardiovasc Pathol Vol. 2. No. 1 January-March 1993:35-39 35 Anomalous Origin of the Left Coronary Artery From the Nonfacing Aortic Sinus: A Study in the Syrian Hamster Josep M. Arqu6, MD,* Gaetano Thiene, MD,* Manuel Cardo, BSc,* Diego Franco, BSc,* Ana C. Dur~in, PhD,* and Valentfn Sans-Coma, PhD* From the *Regional ttospital "Carlos Haya", Mdlaga, Spain, ~Institute of Pathological Anatomy, University qf Padova, Padova, ltaly, and *Department of Animal Biology (Zoology), University of Mdlaga, M61aga, Spain ++ A coronary artery that arises from the nonfacing (posterior or dorsal) aortic sinus is re- garded 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. A coronary artery that arises from the nonfacing (pos- terior or dorsal) aortic sinus is regarded as having an anomalous origin (1). In mammals, two coronary ar- teries are normally present; the right and left take rise from the right and left sinuses, respectively. Examples of a coronary artery originating from the nonfacing or dorsal aortic sinus have been found in two nonhuman mammalian species, namely the laboratory mouse (2), and the white-tailed deer (3). However, in both cases this vessel coexisted with the right and left coronary arteries and thus behaved as a third coronary artery. Only a few cases of anomalous origin of the left main coronary artery from the nonfacing aortic sinus have been reported in humans (4-13). The youngest patients suddenly died during or immediately after exercise. Manuscript received August 6, 1992; accepted September 23, 1992. Address for reprints: Prof. Valentin Sans-Coma, PhD, Departa- mento de Biologia Animal (Zoologla), Facultad de Ciencias, Uni- versidad de M~ilaga, E-29071 M~laga, Spain. The lack of animal model is one of the reasons little understanding of the morphogenesis and pathogenesis of coronary artery malformations has been gained (1). To our knowledge, among nonhuman mammals, ana- malous origin of the left main coronary artery from the nonfacing aortic sinus was briefly reported only in the Syrian hamster (14-16). Considering that this rodent species might provide an appropriate animal model for further investigation of the etiology of this rare, clini- cally relevant anomaly, we conducted a morphologic study of 34 affected hamsters from our laboratory. This paper reports our findings. Materials and Methods This study is based on 34 Syrian hamsters (20 males, 14 females) belonging to a single family subjected to high endogamous pressure by mating animals of the same litter or, occasionally, first cousins. As previously reported (14-17), the frequency of coronary artery anomalies as well as bicuspid aortic and pulmonary ©1993 by ElsevierSciencePublishingCo., Inc. 1054-8807/93/$6.00