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

I DIOPATHIC hypertrophic subaortic stenosis, in contrast to valvular, supravalvular, or discrete subaortic stenosis, is characterized by obstruction to left ventricular ejection, which may vary from moment to moment. Since the obstruction results from the contraction of the hypertrophied muscle in the left ventricular outflow tract during systole, it was anticipated that influences that tend to augment the force of left ventricular contraction would increase the severity of obstruction. This hypothesis was confirmed by the demonstration that in patients with idiopathic hypertrophic subaortic stenosis the obstruction becomes more severe after the administration of drugs that augment myocardial contractility, such as digitalis glycosides ` and isoproterenol.2 1Similarly, the stimulation of the myocardium, which occurs during muscular exercise, also narrows the left ventricular outflow tract' ,' and the administratioin of nethalide, a beta-adrenergic receptor blocking agent, prevents the augmentation of obstruction produced by exercise and by isoproterenol.5 The purpose of the present investigation was to study the effects of nitroglycerin and of the Valsalva maneuver in patients with idiopathic hypertrophic subaortic stenosis and to compare the responses in these patients with those observed in patients with valvular aortic stenosis. The differences in the responses of these