Amiodarone or Procainamide for the Termination of Sustained Stable Ventricular Tachycardia: An Historical Multicenter Comparison

OBJECTIVES: The objective was to compare the effectiveness of intravenous (IV) procainamide and amiodarone for the termination of spontaneous stable sustained ventricular tachycardia (VT). METHODS: A historical cohort study of consecutive adult patients with stable sustained VT treated with IV amiodarone or procainamide was performed at four urban hospitals. Patients were identified for enrollment by admissions for VT and treatment with the study agents in the emergency department (ED) from 1993 to 2008. The primary measured outcome was VT termination within 20 minutes of onset of study medicine infusion. A secondary effectiveness outcome was the ultimate need for electrical therapy to terminate the VT episode. Major adverse effects were tabulated, and blood pressure responses to medication infusions were compared. RESULTS: There were 97 infusions of amiodarone or procainamide in 90 patients with VT, but the primary outcome was unknown after 14 infusions due to administration of another antidysrhythmic during the 20-minute observation period. The rates of VT termination were 25% (13/53) and 30% (9/30) for amiodarone and procainamide, respectively. The adjusted odds of termination with procainamide compared to amiodarone was 1.2 (95% confidence interval [CI]=0.4 to 3.9). Ultimately, 35/66 amiodarone patients (53%, 95% CI=40 to 65%) and 13/31 procainamide patients (42%, 95% CI=25 to 61%) required electrical therapy for VT termination. Hypotension led to cessation of medicine infusion or immediate direct current cardioversion (DCCV) in 4/66 (6%, 95% CI=2 to 15%) and 6/31 (19%, 95% CI=7 to 37%) patients who received amiodarone and procainamide, respectively. CONCLUSIONS: Procainamide was not more effective than amiodarone for the termination of sustained VT, but the ability to detect a significant difference was limited by the study design and potential confounding. As used in practice, both agents were relatively ineffective and associated with clinically important proportions of patients with decreased blood pressure.