Abstract
Clinical, echocardiographic, hemodynamic, and angiographic features of 7 patients with midventricular obstruction, aged 12-51 years, are described. All had cardiac catheterization and left ventricular cineangiography with special care to eliminate catheter entrapment. Simultaneous biventricular cineangiography was performed in 2 subjects and autopsy in another. Carotid upstroke was brisk in all but 1. Echocardiogram, available in 6 patients, showed septal thickness in all, however systolic anterior motion of the mitral valve was absent in 5 individuals. A resting gradient ranging from 58 to 185mmHg (mean 117mmHg) was detected across the midventricular narrowing in 6 patients. In 1 patient with no resting gradient, 40mmHg pressure difference was provoked between the apex and inflow tract following intravenous administration of isoproterenol. Midventricular obstruction, distinctly different from subaortic narrowing observed in hypertrophic obstructive cardiomyopathy (HOCM) was present in cineangiogram. Midbiventricular bulging of the septum was present in 2 patients with simultaneous biventricular cineangiogram and another at autopsy.Disappearance of gradient following intravenous administration of propranolol and its return after sublingual administration of nitroglycerine favor the dynamic nature of the obstruction. Midventricular obstruction must be distinguished from HOCM by its characteristic hemodynamic and angiographic features for proper surgical approach, consisting of midventricular myectomy with or without papillary muscle resection and mitral valve replacement.
