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We describe an apparent case of atavism involving a 59-year-old man with chest pain whose coronary circulation and myocardial architecture resembled those of the reptilian heart. ...

Coronary angiography showed that our patient had a noncompacted myocardium, along with multiple coronary cameral fistulae that drained blood from the right and left coronary artery systems directly into the LV cavity. Remarkably, the morphology resembled that of the reptilian heart—that is, it featured direct communications to the ventricular cavity and had the sinusoidal characteristics of noncompacted myocardium. To our knowledge, this is only the 2nd reported case involving such morphology, the 1st case having been reported by Osman and associates.2

The basic anatomy and physiology of the mammalian heart is very different from that of the reptilian heart.3 Unlike mammals, reptiles have a single ventricle responsible for distributing mixed blood to both the systemic and pulmonary circulations, which are not completely separate from each other. Hence, the reptilian heart has been called the “transitional heart.” In poikilothermic (“cold-blooded”) reptiles, the heart has a unique adaptive value that enables the conservation of energy during prolonged hibernation.3-6

The mammalian coronary circulation is also distinctly different from that of nonmammalian vertebrates. Not until the appearance of birds and mammals did the coronary arteries develop. In the human heart, the arterial supply of the myocardium is provided by the left and right coronary arteries, and venous drainage occurs via the anterior cardiac veins,7-9 which drain most of the right and left coronary arteries and the coronary sinus.10,11 In reptiles, however, a thin periphery, consisting of about one twelfth of the myocardial mass, is supplied by small, external coronary vessels.