Efficacy of propranolol versus placebo in long-term treatment in patients with mitral valve prolapse.

In 60 patients with mitral valve prolapse syndrome a randomized controlled interindividual double-blind study of propranolol (p) was performed. Patients received p 80 mg (A), 160 mg (B) and placebo (C) orally for 4 weeks. Prior to and after treatment, heart rate (HR) and blood pressure (RR) as well as systolic time intervals (STI) were measured and corrected for heart rate--electromechanical systole (QS2I), left ventricular ejection time (LVETI), and preejection period (PEPI). The ratio PEP/LVET was calculated. Plasma levels were measured by an optimized fluorimetric method. 1. STI lay in the upper part of the normal range, indicating that some patients had a hyperkinetic cardiac function. 2. P had no influence on QS2I and LVETI in A and B. PEPI was prolonged (A: +13.2 ms, B: +14.2 ms) and PEP/LVET was increased (A: +0.040, B: +0.050). 3. As indicated by the changes in HR, RR, PEPI, and PEP/LVET p showed in B compared to A only minor additional effects. 4. Plasma levels of p were in B three times higher than in A (A: 89.2 +/- 10.0 nmol/l B: 246.7 +/- 30.5 nmol/l). With a dose of 80 mg propranolol a point close to the plateau of maximum efficacy was reached, where a higher dose resulted only in small additional negative inotropic effects.