[Left ventricular function at rest and during exercise and the effects of propranolol in patients with hypertrophic cardiomyopathy].

To determine left ventricular function during the stress of exercise and to evaluate the effects of propranolol on it in patients with hypertrophic cardiomyopathy (HCM), the ECG-multigated blood pool cardiac scintigraphy was performed in 12 without (HNCM) and 10 with (HOCM) left ventricular outflow obstruction at rest and during bicycle ergometer loading. The results were compared to those in 13 normal subjects. 1. Control measurements: Resting and exercise heart rates and blood pressures did not significantly differ between patients with hypertrophic cardiomyopathy and normal subjects. Ejection fraction (EF) was normal or higher in HCM than in normal subjects at rest, but during exercise it failed to increase normally. The increment in cardiac output was half of the normal value. Responses of count-derived end-diastolic volume (EDV) and stroke volume (SV) were different between HOCM and HNCM. They were unchanged during exercise in HNCM and declined in HOCM. End-systolic volume (ESV) was unchanged in HNCM and slightly decreased in HOCM. Responses of the peak ejection rate (PER) and time to the peak ejection rate (TPE) were not significantly different from normal subjects. Left ventricular (LV) ejection time (ET) and TPE/ET were not different from normal subjects. The peak filling rate (PFR) was significantly higher than normal in HOCM at rest and during exercise. The time to peak filling rate was prolonged at rest in HOCM, but not during exercise. 2. Effects of propranolol: Heart rates significantly decreased especially after intravenous propranolol administration. Cardiac output (CO) and SV were unchanged. EDV and ESV increased significantly. The PER was unchanged. The PFR decreased, but not significantly. TPE, time to the PFR (TPF) and ET were prolonged. The ratio of TPE/ET decreased initially, but abruptly increased later. In conclusion, in the control state of HCM patients, the responses of LVEF, EDV and ESV to exercise were abnormal and CO remained half of the normal. There was no difference between patients with and without obstruction. The effect of propranolol on left ventricular function was more obvious in patients with obstruction than without obstruction, especially in ESV, EDV, PFR and TPF. Propranolol did not improve LV systolic and diastolic functions, but the double product decreased depending on the decrease of heart rate maintaining CO by Frank-Starling mechanism due to increased EDV, which may play a part in improving subjective complaints.