Some physiologic and hemodynamic observations in ventricular septal defect

Abstract The hemodynamic data of eighty-two patients with ventricular septal defect are presented. A drop in systolic pressure between the right ventricle and pulmonary artery trunk was present in sixty-four patients. The largest gradient found was 25 mm. Hg. We believe this gradient does not represent an associated pulmonary stenosis but is due rather to functional effects. Analysis of the hemodymanic data suggests that the size of the ventricular septal defect is the principal factor determining the various changes. In smaller septal defects, the magnitude of the left-to-right shunt is a function of the size of the hole. Pulmonary resistance determines the magnitude of the left-to-right shunt in larger defects. The presence or absence of a right-to-left shunt depends on right ventricular pressure. The mechanism by which changes in the pulmonary resistance occur remains unknown.