Effect of propranolol on left ventricular relaxation in hypertrophic cardiomyopathy: an echographic study.

Many authors have shown that hypertrophic cardiomyopathy (HCM) is often associated with diastolic abnormalities. The purpose of this study was to determine the effect of propranolol on left ventricular isovolumic relaxation time (IVRT) measured by echocardiography in 20 patients with hypertrophic cardiomyopathy under basal conditions and under increasing doses of propranolol (160 mg, 320 mg, and 480 mg per day) and in two control groups, 10 patients with aortic stenosis, and 10 normal subjects. IVRT was less than 50 msec in all normal subjects, while it was always above this limit in aortic stenosis (77 msec +/- 8, p less than 0.001), and in hypertrophic cardiomyopathy (94 msec +/- 19, p less than 0.001), with also a significant difference between these two last groups (p less than 0.01). Under increasing doses of propranolol, relaxation time often shortens gradually until 50 msec or less. These results show an improvement in left ventricular relaxation dependent on the propranolol dosage and often a normalization at high dosages.