Evaluation of metoprolol in suppressing complex ventricular arrhythmias
Echocardiography, Doppler, Color
Heart Valve Diseases
This study documents the extent of suppression of premature ventricular beats which can be achieved with metoprolol, a semiselective beta-adrenergic blocking agent, at doses of 100 to 200 mg daily, utilizing a single-blind placebo-controlled 10-day protocol with continuous ambulatory electrocardiographic recording of 20 patients with cardiac disease and complex ventricular arrhythmias. Metoprolol (200 mg/day) resulted in suppression of 60% of total premature ventricular beats, with couplets (pairs) and ventricular tachycardia decreased 84% and 94%, respectively (all p less than 0.01). Exercise-induced premature ventricular beats, especially ventricular tachycardia, were effectively suppressed. The peak plasma metoprolol level to achieve these results was 72 +/- 34 ng/ml (mean +/- 1 standard deviation). At this plasma concentration, the mean 24-hour heart rate during normal activity was reduced from 78 +/- 8 beats/min (placebo) to 62 +/- 4 (metoprolol 200 mg/day) (p less than 0.001). Beta blockade also was demonstrated by a 20% reduction in heart rate during maximal Bruce exercise testing with metoprolol 200 mg/day. Although resting left ventricular function was not affected by metoprolol, pulmonary function tests show a statistically significant decrease in forced vital capacity, forced expiratory volume in 1 second, and forced expiratory flow rates (25-75) reversible with a beta-2 agonist.