Is It Time to Tell the Emperor He Has No Clothes?

Abstract

In this issue of the Journal , Chang et al1 present a thought-provoking, single-center retrospective analysis of 37 patients receiving either procainamide or IV amiodarone for refractory supraventricular arrhythmias (SVA), excluding junctional ectopic tachycardia (JET). They compare the relative efficacy of the drugs, finding procainamide to be fully successful in 50% of cases, whereas amiodarone was only successful for 15%, a statistically significant difference. Adverse effects were similar between the drugs. They conclude that procainamide may be a more effective treatment option and more importantly challenge the “perceived superiority and safety of amiodarone.” Article see p 134 The findings are indeed intriguing, but before drawing too strong a conclusion, it is critical to review a few important limitations of the study. The retrospective nature of the study along with small group sizes and diverse clinical situations led to considerable differences between the patients treated with amiodarone and those treated with procainamide. Those treated with amiodarone were more likely to have congenital heart disease and to have a postoperative arrhythmia. The mechanisms of the tachycardias differed as well, with the procainamide group having more patients with ectopic atrial tachycardia. Thus, the inferiority of amiodarone may reflect a patient population with intrinsically more difficult-to-treat arrhythmias. Further, the initial loading and maintenance doses of amiodarone (median, 2.5 mg/kg and ≈7 mg/kg/d, respectively) were considerably lower than the doses reported to be effective in previous retrospective studies2 and a prospective randomized trial,3 in which loading doses are typically 5 mg/kg and maintenance 10 mg/kg/d. However, the doses of procainamide used (median, 10 mg/kg load and 20 μg/kg/min maintenance) were comparable to those reported in the literature for acute management of tachyarrhythmias.4 This difference was probably a reflection of the authors’ observation that an arrhythmia specialist was more likely to be …