septal defect

a hole in the partition (septum) between the left and right halves of the heart. This abnormal communication is congenital due to an abnormality of heart development in the fetus. It may be found between the two atria (see atrial septal defect) or between the ventricles (see ventricular septal defect). A septal defect permits abnormal circulation of blood from the left side of the heart, where pressures are higher, to the right. This abnormal circulation is called a shunt and results in excessive blood flow through the lungs. pulmonary hypertension develops and heart failure may occur with large shunts. A heart murmur is normally present. Large defects are closed surgically but small defects do not require treatment.

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a defect in one of the cardiac septa, resulting in an abnormal communication between the opposite chambers of the heart. See atrial septal d's and ventricular septal d.