Acquired subvalvular right ventricular outflow obstruction in patients with ventricular septal defect

Abstract

In patients with ventricular septal defect, the development of right ventricular outflow obstruction has been suspected clinically but infrequently has been documented by serial cardiac catheterizations. In this study six patients, including five girls, with ventricular septal defect were catheterized both before and after the development of obstruction to right ventricular outflow. Initially, at ages six months to four years, all six patients had large left to right shunts, and five of the six had pulmonary hypertension. Two of the patients had no gradient across the right ventricular outflow tract, and in the remainder the gradients ranged from 6 to 22 mm Hg. When the patients were restudied 1.7 to 5.8 years later, obstruction to right ventricular outflow had appeared or progressed in each of them, and the right ventricular to pulmonary artery systolic pressure gradient averaged 56 mm Hg. The left to right shunt had decreased in every patient, and in one the shunt was right to left. Pulmonary arterial pressure had become normal in five patients. Right ventricular angiography may predict the development of outflow obstruction. Even when a gradient was absent at the time of the initial study, abnormally hypertrophied cristal bands sometimes were identified. Although physiologically similar to patients with Fallot's tetralogy, these patients with acquired obstruction to right ventricular outflow were not a homogeneous group anatomically. In all patients the obstruction was subvalvular, but in two subendocardial fibrous tissue contributed significantly. One patient had a small right ventricle despite systemic pressure in the right ventricle. One had double outlet right ventricle, and another had an atrial septal defect. All six had infracristal ventricular septal defects, but one also had a supracristal defect. In patients with acquired right ventricular outflow obstruction the defect should be easier to correct surgically than in patients with tetralogy of Fallot since the pulmonary artery and right ventricular outflow tract are not underdeveloped.