A randomized, double-blind, placebo-controlled study of verapamil and metoprolol in treatment of multifocal atrial tachycardia

Abstract

Purpose: Multifocal atrial tachycardia is a difficult arrhythmia to treat. Patients not showing a response to the correction of predisposing conditions present a therapeutic dilemma. To assess the efficacy of two agents reported to be effective in this condition, verapamil, metoprolol, or placebo was given intravenously in a randomized, double-blind trial.

Patients and methods: Thirteen patients meeting inclusionary criteria were enrolled. Therapeutic response was defined as conversion to sinus rhythm, a decline in the ventricular rate of 15 percent or more [corrected], or a ventricular rate of less than 100 beats/minute. Four male and nine female patients having a mean age (+/- SD) of 81.9 +/- 14.2 years were enrolled. Automated serum chemistries, complete blood cell count with differential, arterial blood gas values, and serum digoxin and theophylline levels were determined and a 12-lead electrocardiogram was obtained at the start of the trial. Following the completion of each phase of the study, a repeat physical examination was performed, and arterial blood gas values and an electrocardiogram were obtained. The trial was designed to run for two days.

Results: Two of 10 (20 percent), four of nine (44 percent), and eight of nine (89 percent) showed a response to placebo, verapamil, or metoprolol, respectively. Mean slowing of ventricular rate was 3.4, 7.3, and 24.5 percent for placebo, verapamil, and metoprolol, respectively (p less than 0.01 for metoprolol versus placebo). Five patients who showed a response to metoprolol had failed to have a response to verapamil.

Conclusion: We conclude that metoprolol appears to be more effective than verapamil in treating multifocal atrial tachycardia. However, careful patient selection is necessary in its use.