Atrial fibrillation and flutter. Immediate control and conversion with intravenously administered verapamil

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Abstract
The safety efficacy of the i.v. Ca channel blocker, verapamil, in controlling the ventricular response or converting to sinus rhythm patients with atrial flutter or atrial fibrillation were assessed. Seventeen patients (9 with atrial flutter and 8 with atrial fibrillation) with these arrhythmias that were difficult to control pharmacologically were chosen for the study. All patients at the time of study were receiving digoxin. Either verapamil or placebo was chosen randomly and a bolus of 0.075 mg/kg (up to 5 mg) was administered. Twelve patients had a marked reduction in their ventricular response after i.v. administration of verapamil (7 with atrial flutter and 5 with atrial fibrillation). None of these 12 patients converted (nonconverters). The average minimum of 83 .+-. 13 beats min within 20 min after drug administration. Verapamil converted 5 patients with atrial arrhythmias to sinus rhythm (2 with atrial flutter and 3 with atrial fibrillation) (converters). In addition, 3 patients with atrial arrhythmias of < 1 mo. who did not convert with parenteral drug therapy converted within 24 h while receiving the oral drug. Converters had their supraventricular arrhythmias of significantly shorter duration (median, 3 h vs. 30 days) and tended to have smaller left atrial size (3.8 .+-. 0.7 vs. 4.3 .+-. 1.3 cm) than did the nonconverters. Apparently, verapamil is safe and effective when administered i.v. to patients with atrial flutter and fibrillation for control of ventricular response. In short duration atrial arrhythmias, conversion to sinus rhythm is likely once the ventricular response is controlled.