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 < 0.05) and from 0.7 ± 0.7 to 0.3 ± 0.5 episodes per day by Holter monitor (p < 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 diary, 67 ± 111 by Holter; verapamil, 3 ± 3 by diary, 1 ± 2 by Holter (p < 0.05). Five patients required a total of 35 pharmacologic cardioversions for sustained tachycardia: two during verapamil and 33 during placebo (p < 0.001). No verapamil treatment period was shortened due to unacceptable paroxysmal supraventricular tachycardia, but five of 22 placebo treatment periods were shortened (p = 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.