Effects of propranolol on patients with complete heart block and implanted pacemakers.

The effects of beta-adrenergic blockade with propranolol were studied in 10 patients with complete heart block and fixed rate internal pacemakers. The patients were grouped according to the absence or presence of premature systoles before propranolol was given. In the patients with premature systoles propranolol was uniformly effective in abolishing the premature systoles. Propranolol was found to increase the systemic venous pressure, to decrease the cardiac output, and to lower myocardial contractility both at rest and during exercise in both groups. Since the heart rate was fixed, it was concluded that beta-adrenergic blockade has a significant negative inotropic effect, in addition to the chronotropic effect.