Side effects of antiarrhythmic drug (AAD) therapy -- not inefficacy -- are responsible for the inability of rhythm control to maintain long-term sinus rhythm, according to an analysis from the Rate Control vs. Electrical Cardioversion (RACE) study.1 Presenting the data at the European Society of Cardiology 2003 Congress (Vienna, Austria), Eduard H. Hoekstra, MD, University Hospital (Groningen, The Netherlands) on behalf of the RACE investigators reported that long-term maintenance of sinus rhythm was significantly reduced by the side effects of sotalol and amiodarone and the discontinuation amiodarone, but not by clinical characteristics. They suggested that the high incidence of side effects from the drugs is responsible for the failure of rhythm control to show superiority over rate control for the treatment of atrial fibrillation (AF), as reported in several large randomized trials. The current analysis was designed to determine the actual number of AAD side effects, their clinical characteristics, and relation of the side-effects to the failure of long-term maintenance of sinus rhythm in the 266 patients with AF (</= 6 months) randomized to the rhythm control arm of the RACE study. Patients enrolled in the study had persistent AF despite previous electrical cardioversion. Baseline clinical characteristics were "typical" of a patient population with persistent AF; 91% of rhythm patients presented with >/= 1 risk factor for stroke.