Oral verapamil for paroxysmal supraventricular tachycardia: a long-term, double-blind randomized trial.

The effectiveness and safety of orally administered verapamil was tested in 11 patients with frequent paroxysmal supraventricular tachycardia. In a 4-month randomized, double-blind, placebo-controlled trial, the frequency of paroxysmal supraventricular tachycardia fell from 0.3 +/- 0.3 (mean +/- SD) to 0.1 +/- 0.1 episodes per day by patient diary (p less than 0.05) and from 0.7 +/- 0.7 to 0.3 +/- 0.5 episodes per day by Holter monitor (p less than 0.05) for placebo and verapamil treatment periods, respectively. Verapamil caused a decrease in the duration of paroxysmal supraventricular tachycardia (in minutes per day): placebo 27 +/- 51 by dairy, 67 +/- 111 by Holter; verapamil, 3 +/- 3 by diary, 1 +/- 2 by Holter (p less than 0.05). Five patients required a total of 35 pharmacologic cardioversions for sustained tachycardia: two during verapamil and 33 during placebo (p less than 0.001). No verapamil treatment period was shortened due to unacceptable paroxysmal supraventricular tachycardia, but five of 22 placebo treatment periods were shortened (p equal to 0.02). Verapamil was well-tolerated, causing mild constipation in five patients and headache in one. Oral verapamil is both safe and effective in the long-term treatment of patients with paroxysmal supraventricular tachycardia.