Antiarrhythmic agents in facilitating electrical cardioversion of atrial fibrillation and promoting maintenance of sinus rhythm

Atrial fibrillation (AF) is a prevalent arrhythmia associated with signific ant morbidity and mortality. Electrical cardioversion of AF is a potentiall y definitive treatment, but as little as 67% of patients may be successfull y cardioverted and, after normal sinus rhythm (NSR) is achieved, AF often r ecurs. Class IA, IC, and III antiarrhytmic agents are used for both facilit ation of electrical cardioversion and subsequent maintenance of NSR. The me chanisms of these agents may be related to suppressing automaticity, prolon ging the wavelength of reentrant wavelets, and preventing electrical remode ling. The possibility of proarrhythmia and other adverse effects complicate s use of these drugs, and no large trials have been completed to elucidate definite indications. Several factors may predict failure with electrical c ardioversion alone (duration of AF, atrial size, age, underlying disease, a nd factors that affect transthoracic impedance), calling for empiric pharma cotherapy to facilitate cardioversion. For this purpose, class IA agents ho ld some promise, evidence for class IC agents is conflicting, and class III agents are the most effective. Adverse effects are rare given the short co urse before cardioversion, but ibutilide, the most efficacious in this rega rd, may be proarrhythmic after only a single dose. In promoting maintenance of sinus rhythm, antiarrhythmics across the different classes have similar efficacies: NSR may be maintained in similar to 40-65% of patients compare d to similar to 30-35% with placebo at 1 year. Amiodarone is distinct in it s success, with similar to 60-80% of patients remaining in NSR. For all of these agents, long-term therapy may lead to proarrhythmia or other substant ial adverse effects. Finally, a serial antiarrhythmic strategy may be effec tive, with maintenance of NSR and minimal adverse effects ultimately achiev ed by trial and error. Copyright (C) 2001 S. Karger AG, Basel.