Noninvasive evaluation of indecainide for serious ventricular tachyarrhythmia

Indecainide, a new class 1C agent, was administered to 16 patients with a history of ventricular fibrillation or ventricular tachycardia. Evaluation of drug effect consisted of acute testing with 125 mg followed by a period of maintenance therapy. Efficacy, as evaluated with both ambulatory monitoring and exercise testing, was defined as total elimination of runs of ventricular tachycardia, greater than 90% reduction in couplets and greater than 50% decrease in ventricular premature complex. During acute drug testing 9 of the 16 patients responded to the drug. Four patients did not receive maintenance therapy with indecainide, because of toxic side effects. Of the remaining 12 patients, 7 responded to indecainide based on monitoring, 5 responded judged by exercise testing and 4 when both monitoring and exercise testing were considered. There was no correlation between dose, blood level of drug and effect on arrhythmia. In this small group acute drug testing did not appear to predict the response to the drug during maintenance therapy. Neurologic side effects were reported by 5 patients. Aggravation of arrhythmia occurred in 5 patients, 3 of whom had this complication during acute drug testing and 2 during maintenance therapy. Left ventricular ejection fraction, measured before and during therapy, decreased from an average of 43% to 35% (p less than 0.005). A reduction was observed irrespective of baseline left ventricular function. Indecainide is an effective antiarrhythmic agent in a small number of highly selected patients with serious ventricular arrhythmia, but potentially serious side effects limit its usefulness.