[Dose-dependent anti-arrhythmia effect of retard metoprolol in coronary disease patients with ventricular arrhythmia].

The antiarrhythmic efficacy of a slow-release form of metoprolol was studied in 13 male coronary patients, mean age 47 years (39-59 years) with frequent and complex ventricular arrhythmias (couplets, salvos). The prospective, single-blind trial was based on 24 h Holter monitoring. In each case, the extent of coronary heart disease and the presence of old myocardial infarction was documented by coronary angiography. Initial treatment with placebo was followed by active treatment with 200 and 400 mg metoprolol per day, respectively, and placebo again during one week each. Thereafter, 200 mg metoprolol/24 h were administered over a period of one month. At the end of each treatment period, metoprolol plasma levels were determined simultaneously with the assessment of cardiac arrhythmias by Holter monitoring. Under a daily dose of 400 mg metoprolol, plasma levels increased from 235 +/- 326 (under 200 mg) to 841 +/- 613 mumol/l (p less than 0.001), and mean heart rate decreased from 75 to 63 bpm (p less than 0.001), the average number of ventricular extrasystoles decreased from 1,722 to 480/24 h (p less than 0.05) and the number of couplets from 38 to 7/24 h (p less than 0.05) when compared to the placebo period. After one month's treatment with 200 mg metoprolol per day, a significant reduction in heart rate from 75 to 67 bpm was observed (p less than 0.05); however, antiarrhythmic efficacy with regard to the number of premature ventricular contractions and couplets was insignificant.(ABSTRACT TRUNCATED AT 250 WORDS)