Propafenone: Noninvasive evaluation of efficacy

Abstract

Propafenone, a new antiarrhythmic drug, was administered to 60 patients with a history of refractory ventricular tachyarrhythmias, including ventricular fibrillation in 16 and ventricular tachycardia (VT) in 44. A noninvasive protocol was followed utilizing ambulatory monitoring and exercise testing for evaluation of drug effect. The protocol involved acute drug testing with 450 mg of propafenone followed by maintenance therapy with 150 to 300 mg t.i.d. for 4 days. The protocol was completed by 57 patients; in 3 patients side effects developed that necessitated discontinuation of the drug before evaluation. When evaluated by monitoring, 34 patients (60%) responded to the drug, with total elimination of runs of VT, a greater than 90% reduction in couplets and a greater than 50% decrease in the frequency of ventricular premature beats. Based on exercise testing, 36 patients (63%) were deemed responders. When both exercise and monitoring were considered, 30 of 57 patients (53%) responded to propafenone. The acute drug test predicted the response to maintenance therapy in 84% of patients. Propafenone did not change left ventricular function in patients with normal ejection fractions (greater than 50%). However, in those with an ejection fraction less than 50%, propafenone significantly reduced this value (34% vs 29%, p less than 0.01). Side effects occurred in 20 patients (33%) and included nausea, congestive heart failure, aggravation of arrhythmia and conduction abnormalities. Eleven patients have continued on propafenone for an average of 16 months with continued efficacy and freedom from side effects.