Ventricular septal defect and subaortic stenosis: an analysis of 41 patients.

Forty-one patients with subaortic stenosis (SAS) and ventricular septal defect (VSD) were identified from the cardiac records of the Hospital for Sick Children, Toronto, Ontario. The diagnosis of an associated SAS was made clinically in only 1 patient, who had findings of left ventricular (LV) hypertrophy with strain on the electrocardiogram. There was a delay of 3.1 years between initial presentation and detection of SAS. The SAS was not diagnosed at initial catheterization in 17 patients and was confirmed at subsequent catheter studies in 8 patients, surgery in 5 and autopsy in 4. Associated defects included coarctation of the aorta in 12 patients, mitral valve abnormalities in 4, and right-sided obstructions, including anomalous right ventricular muscle bundles in 6 patients, tetralogy in 4 and pulmonic stenosis in 1 patient. The mean gradient across the LV outflow tract was 25 mm Hg. Nineteen patients had serial catheters without intervening surgery, and the outflow gradient increased from a mean of 9 to 36 mm Hg. The mechanism of SAS consisted of fibrous diaphragm and fibromuscular obstruction in 31 cases, muscular narrowing in 4, protruding tricuspid valve leaflet in 2, hypertrophic cardiomyopathy in 2, anterolateral twist in 1 patient and redundant tissue tag in 1. Thirty-eight patients had a perimembranous VSD, 19 of whom had an associated so-called aneurysm of the membranous septum; 2 had an infundibular VSD and 1 patient had a central muscular defect. Although the SAS was located below the VSD in 30 cases, the associated heart failure and reduced cardiac output can mask the presence or severity of associated SAS.(ABSTRACT TRUNCATED AT 250 WORDS)