Corrected Transposition of the Great Vessels with Ebstein Malformation of the Left Atrioventricular Valve

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Abstract
Two autopsy proven cases of corrected transposition with an Ebstein-type malformation of the left atrioventricular valve are presented. Case 1 had no other defects but the valvular malformation was so severe as to cause death in intractable left heart failure at 17 months. Case 2 had in addition coarctation of the aorta, a large patent ductus, and a ventricular septal defect: the pulmonary artery overrode the septal defect arising chiefly from the left-sided or anatomic "right" ventricle. Despite these multiple defects he survived to 9 years of age. Embryo-logically, the defect is thought to be due to a rightward outgrowth of the caudal part of the ventricular loop, leading to a heart tube bent with its convexity toward the left instead of the right. The anatomic left ventricle thus occupied the right part of the pericardial cavity, and, consequently, the anatomic right ventricle was displaced to the left. The cranial part of the ventricular loop, in its descent, caused an abnormal counterclockwise rotation of the truncus in that the aorta came to lie on the left and anteriorly ("corrected transposition"). In both cases also the left atrioventricular valve, (which had to take part in the migration characteristic of the right atrioventricular valve in a normal heart) became displaced in an Ebstein-type malformation.