Facilitating influence of procainamide on conversion of atrial flutter by rapid atrial pacing

In a prospective, double-blind, randomized, placebocontrolledstudy we investigated the facilitating influence of intravenousprocainamide on conversion of atrial flutter by rapid atrialpacing. Fifty consecutive patients with spontaneous sustained atrialflutter were 1:1 randomized into two homogenous groups: groupA received 10 mg. kg^–1 procainamide intravenously, groupB placebo. After infusion there was a significant (P<0·01)lengthening of the flutter cycle with respect to baseline ingroup A, exceeding the flutter cycle length of the control group(P<0·05). The overall success rate of rapid atrialpacing in restoring sinus rhythm was significantly higher afterpre-treatment with procainamide compared to placebo (100% vs76% P<0·05): 20 patients of group A reverted immediatelyafter pacing to sinus rhythm, the remaining five after a briefepisode of atrial fibrillation. In the placebo group, 16 patientsshowed a prompt conversion to sinus rhythm and three after transientatrial fibrillation. In the remaining six patients, due to sustainedpacing-induced atrial fibrillation, direct current cardioversionwas necessary. After administration of procainamide a less aggressivestimulation protocol with significantly (P<0·01) longerpaced cycles to interrupt atrial flutter was achievable. In conclusion, intravenous procainamide augments the efficacyof atrial pacing to convert atrial flutter to sinus rhythm.