PRENATAL CLOSURE OF THE INTERATRIAL FORAMEN

Abstract

THE ABSENCE of an interatrial communication before birth causes distortions in cardiac development which render the heart incapable of proper function after birth. Patten¹ has called attention to the fact that the foramen ovale normally transmits at least half of the blood that enters the left side of the fetal heart. Premature closure of the foramen, therefore, deprives the left atrium and ventricle of all blood from the systemic and placental circulations. Only the pulmonary circulation, which in the fetus is of relatively small quantity, empties into the left atrium. Since this is not sufficient to bring about normal expansion and muscular development of the left-sided chambers, they become hypoplastic, whereas the right-sided chambers tend to become distended and hypertrophied. The right ventricle during fetal life must assume the entire burden of pumping blood through the systemic circulation by way of the ductus arteriosus. These conditions may be tolerated