VENTRICULAR TACHYCARDIA Amiodarone versus amiodarone and a type IA agent for treatment of patients with rapid ventricular tachycardia

Induction of rapid ventricular tachycardia or fibrillation during therapy with amiodarone is associated with an increased risk of sudden death. To determine whether the addition of a type IA antiarrhythmic agent to therapy would improve outcome, 37 patients in whom ventricular tachyarrhythmia of a cycle length less than 350 msec was induced after 14 + 2 days of amiodarone were randomly assigned to therapy with amiodarone alone (group 1, 20 patients) or amiodarone plus type IA agent (group 2, 17 patients). Type IA therapy consisted of procainamide in 13 patients and quinidine in four procainamide-intolerant patients. To assess the short-term effects of a type IA agent on inducibility of ventricular tachyarrhythmia, cycle length, and hemodynamic tolerance, 16 of 20 patients in group 1 and all patients in group 2 underwent repeat programmed stimulation after the intravenous administration of procainamide during amiodarone therapy (mean procainamide serum concentration 7.2 + 2.0 1ag/ml). Procainamide prevented induction of sustained arrhythmia in only two of 33 patients. Procainamide increased the cycle length of induced ventricular tachycardia from 283 30 to 352 46 msec (p < .001). After the addition of procainamide, 16 of 31 patients vs 10 of 37 patients on amiodarone alone had an induced arrhythmia that was tolerated hemodynamically (p < .05). There were no differences between groups 1 and 2 with respect to patient or arrhythmia characteristics, response to short-term procainamide, or duration of follow-up. The mean follow-up for all patients was 14 + 10 months. By life table analysis, outcome did not differ between group 1 and group 2 patients with respect to either development of sudden death or syncope (four patients in group 1 vs five patients in group 2) or the development of any arrhythmia event or side effect that required withdrawal of antiarrhythmic therapy (nine patients in group 1 patients vs 12 patients in group 2). Forty percent of group 2 patients developed adverse effects necessitating withdrawal of drug. We conclude in patients in whom rapid ventricular tachycardia is induced on amiodarone (1) type IA agents increase the cycle length and result in improved hemodynamic tolerance but rarely prevent induction of ventricular tachycardia, and (2) outcome is not improved by the addition of a type IA agent to therapy. Circulation 74, No. 5, 1037-1043, 1986. INDUCTION of a rapid, poorly tolerated ventricular arrhythmias during amiodarone therapy has been associated with a poor prognosis. Horowitz et al.' reported a 50% incidence of sudden death in this patient populaFrom the Clinical Electrophysiology Laboratory, Hospital of the University of Pennsylvania, and the Cardiovascular Section, Department of Medicine, University of Pennsylvania School of Medicine, Philadelphia. Supported in part by grants from the American Heart Association, Southeastern Pennsylvania Chapter, Philadelphia; grants HL24278, HL28093, and HL07346 from the National Heart, Lung, and Blood Institute, Bethesda; and a grant from the McCabe Fund. Address for correspondence: Francis E. Marchlinski, M.D., Hospital of the University of Pennsylvania, Ravdin Bldg., Room 656B, 3400 Spruce St., Philadelphia, PA 19104. Received Jan. 28, 1986; revision accepted Aug. 7, 1986. Drs. Marchlinski and Buxton are supported by the Department of Medicine Measey Foundation. Dr. Josephson is the Robinette Foundation Professor of Medicine (Cardiovascular Disease). tion during continued amiodarone therapy, with a mean follow-up of 1 year. The effect of the addition of a type IA agent on inducibility of tachycardia and clinical outcome has not been evaluated previously. The present study was undertaken to (1) determine the effect of procainamide on inducibility and rate/hemodynamic tolerance of rapid ventricular arrhythmias induced during amiodarone therapy, and (2) to determine whether the addition of a type IA agent (procainamide or quinidine) to amiodarone therapy results in a better clinical outcome.