Echocardiographic diagnosis of coronary artery fistula in both dizygotic twin brothers: environmental mechanism?

A congenital coronary artery fistula (CAF) is a rare form of heart disease in which a coronary artery and a cardiac chamber or another vascular structure communicate. CAF could worsen ventricular perfusion and function, favoring ventricular ischemia and arrhythmias. To our knowledge, this is the first report of CAF, draining in the pulmonary artery, in two asymptomatic dizygotic twin brothers, diagnosed by echocardiography. Dizygotic twins are siblings with different genes exposed to the same environmental experience during the pregnancy. The occurrence of CAF (with similar instrumental findings) in both twin brothers could depend on a poorly identified environmental factor during pregnancy.