The Circulatory Response of Patients with Idiopathic Hypertrophic Subaortic Stenosis to Nitroglycerin and to the Valsalva Maneuver

Abstract

The circulatory responses to nitroglycerin and to the Valsalva maneuver were studied in seven patients with idiopathic hypertrophic subaortic stenosis, in five patients with valvular aortic stenosis, and in three patients without obstruction to left ventricular outflow. In contrast to the patients with valvular stenosis who showed no changes or decreases in their aortic valvular pressure gradients, in all the patients with idiopathic hypertrophic subaortic stenosis an increased pressure gradient was observed following nitroglycerin administration. Similar effects on the pressure gradients were observed during the Valsalva maneuver, an augmentation occurring in patients with hypertrophic obstruction, and a fall being noted in patients with valvular stenosis. In one patient with idiopathic hypertrophic subaortic stenosis, the gradients across the right ventricular outflow tract were increased by nitroglycerin and the Valsalva maneuver. It is postulated that this increase in obstruction resulted primarily from a decrease in ventricular size secondary to the reduction in venous return induced by these interventions. It is proposed that reduction in the size of the left ventricle in patients with idiopathic hypertrophic subaortic stenosis, whether induced by changes in venous return, a decrease in arterial pressure, or by agents having a positive inotropic action, reduces the effective size of the outflow orifice. The administration of nitroglycerin and the performance of the Valsalva maneuver in the course of left heart catheterization provide simple methods for detecting the presence of latent obstruction in patients with idiopathic left ventricular hypertrophy and for differentiating idiopathic hypertrophic subaortic stenosis from other forms of obstruction to left ventricular outflow.