MITRAL REGURGITATION IN MUSCULAR SUBAORTIC STENOSIS

Mitral regurgitation was assessed in 34 patients with muscular subaortic stenosis by indicator-dilution studies. All patients with obstruction to left ventricular outflow at rest had evidence of mitral regurgitation. Infusion of angiotensin resulted in amelioration or abolition of both outflow tract obstruction and mitral regurgitation in 11 of 15 patients. In 4 patients abolition by angiotensin of the outflow tract obstruction produced no change in the degree of mitral regurgitation. One of these patients was demonstrated to have an abnormality of the mitral valve. Abolition of the outflow tract obstruction by ventriculomyotomy either abolished the mitral regurgitation or reduced it to a trivial degree if there was no additional abnormality of the mitral valve. Pharmacologic intensification of the obstruction by administration of isoproterenol or amyl nitrite increased the degree of mitral regurgitation in 15 of 18 studies. These pharmacodynamic studies provided evidence that, in the majority of patients with muscular subaortic stenosis and a normal mitral valve mechanism, the degree of mitral regurgitation varied directly with the severity of the outflow tract obstruction and was secondary to the obstruction. © 1969.