We retrospectively studied 28 patients with 38 episodes of newly occurring ventricular fibrillation during antiarrhythmic drug therapy. Twenty-six of these patients, who had ventricular fibrillation during single-drug therapy with quinidine, procainamide, or disopyramide, were compared with a control group of 62 patients who had been treated similarly for ventricular arrhythmias but did not have ventricular fibrillation during treatment. The median duration of therapy before ventricular fibrillation was three days. The left ventricular ejection fraction of the study group was lower than that of the control group (0.29 vs. 0.43; P < 0.0001), and concomitant treatment with digitalis and diuretic agents was more common in the study group. The base-line QT interval (corrected for heart rate) was slightly longer in the study group than in the controls (0.47 vs. 0.44; P < 0.005), although both groups had similar degrees of QT prolongation during drug therapy. Four of 13 patients (31 percent) who underwent multiple trials of antiarrhythmic drugs had recurrent episodes of ventricular fibrillation. Six patients died suddenly after a mean follow-up of 18 months - four who were receiving antiarrhythmic therapy and two who were not. We conclude that drug-associated ventricular fibrillation is an early event, that there may be an increased risk of its recurrence with subsequent trials of antiarrhythmic drugs, and that left ventricular dysfunction and concomitant therapy with digitalis and diuretic agents may predispose patients to this complication.
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