The Clinical Course in Muscular Subaortic Stenosis

Abstract

A retrospective and prospective analysis of the clinical course of 60 hemodynamically proved cases of muscular subaortic stenosis showed that in 41 (68%) the murmur was the first evidence of the disease. Fifty-six of the 60 patients (93%) developed symptoms (Class II, New York Heart Association) an average of 10 years after the murmur was first heard, and 40 (66%) deteriorated to Class III-IV an average of 5 years after the onset of symptoms. Of 28 untreated or propranolol-treated patients, 4 (14%) died of the disease. This experience indicates that muscular subaortic stenosis is a progressive disease once symptoms start. Most patients experienced symptomatic improvement with propranolol therapy. However, only 25% of Class III-IV patients with left ventricular outflow tract obstruction at rest maintained this improvement into the second year of therapy, whereas 75% of patients in Class III-IV who underwent ventriculomyotomy have had sustained symptomatic improvement.