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.