Indecainide compared with quinidine for chronic stable ventricular arrhythmias secondary to coronary artery disease or to cardiomyopathy

Abstract

Indecainide, a new type Ic antiarrhythmic agent, and quinidine sulfate were compared in a randomized double-blind parallel study. Cardiac patients with ≥30 ventricular premature complexes per hour hour received indecainide, 50 mg, or quinidine, 200 mg every 6 hours, and the doses were increased until more than 80% suppression was noted, adverse effects occurred or a maximal dose of 100 mg of indecainide or 400 mg of quinidine given every 6 hours. Efficacy was achieved in 8 of 10 taking indecainide (p < 0.05) and 7 of 9 taking quinidine (p < 0.05). At least 90% of episodes of ventricular tachycardia were suppressed in 4 of 7 patients taking indecainide and 1 of 4 taking quinidine. No adverse effects were observed in the 7 patients who responded to indecainide and the 4 who responded quinidine, resulting in short-term efficacy without adverse effects in 7 patients (70%) taking indecainide and 4 (44%) taking quinidine. The effective or maximal mean daily indecainide and quinidine doses were 190 ± 32 mg and 1,022 ± 291 mg, respectively; mean trough indecainide and quinidine concentrations were 617 ± 247 ng/ml and 3.3 ± 1.4 μg/ml, respectively. Indecainide prolonged mean PR and QRS intervals (p < 0.05), but not QT and QTc intervals. Quinidine did not change PR or QRS intervals but prolonged QTc interval (p < 0.05). During dosing, 1 patient discontinued indecainide treatment because of nausea; 3 discontinued quinidine because of gastrointestinal complaints. One patient taking indecainide had proarrhythmic effects and died suddenly. Indecainide is an effective antiarrhythmic agent that is well tolerated systemically; however, the incidence of proarrhythmic effects must be explored.