Flecainide versus quinidine for treatment of chronic ventricular arrhythmias. A multicenter clinical trial.

The antiarrhythmic efficacy and safety of oral flecainide acetate and quinidine sulfate were compared in a double-blind, 16-center parallel trial involving 280 patients with chronic premature ventricular complexes (PVCs). Eighty-five percent of the flecainide patients had at least 80% suppression of PVCs, vs 57% of the quinidine patients (p less than 0.0001). Sixty-eight percent of the flecainide patients met the above criterion and also had complete suppression of couplets and beats of ventricular tachycardia, vs 33% of the quinidine patients (p less than 0.0001). PR and QRS intervals were prolonged by flecainide without clinical consequence, but they were not substantially affected by quinidine (p less than 0.0001). Quinidine prolonged JT (QT minus QRS) intervals significantly more than flecainide (p less than 0.05). Nineteen of 141 flecainide patients and 21 of 139 quinidine patients discontinued therapy because of side effects (p greater than 0.50). Flecainide side effects included dizziness, blurred vision, headache and nausea. Quinidine side effects included diarrhea, nausea, headache and dizziness. Flecainide was more effective than quinidine in suppressing chronic ventricular arrhythmias (especially complex forms), and thus is an important new antiarrhythmic agent.