Muscular Subaortic Stenosis

Left ventricular ejection time was correlated with the intraventricular pressure gradient in 35 cases of muscular subaortic stenosis in which simultaneous aortic and left ventricular pressure recordings were available. Ejection times were corrected for heart rate by dividing them by the square root of the cycle length. There was a direct relation between the degree of prolongation of the ejection time and the magnitude of the pressure gradient whether the latter varied spontaneously or followed surgical or pharmacological intervention. The only exceptions occurred in three of nine cases during stimulation of the gradient with isoproterenol. In contrast, when an intraventricular pressure difference resulted from catheter entrapment in left ventricular myocardium in patients with nonobstructive cardiomyopathy, there was an inverse relation between ejection time and pressure difference, whether the latter varied spontaneously or following pharmacological intervention. These studies provide further evidence that (1) two types of intraventricular pressure difference may be encountered within the left ventricle of man, and (2) the pressure difference in muscular subaortic stenosis results from obstruction to the left ventricular outflow.