Safety considerations in the pharmacological management of atrial fibrillation

The pharmacological management of atrial fibrillation (AF) requires careful consideration from a safety perspective. This article focuses primarily on maintenance therapy using antiarrhythmic drugs (AADs). The foremost safety issue for AADs is the propensity of class IA and III agents to cause torsade de pointes arrhythmias. Class IA drugs, particularly quinidine, can induce torsade de pointes at low or subtherapeutic doses, but higher doses are not necessarily associated with an increased incidence. ‘Pure’ class III drugs such as dofetilide induce torsade de pointes in a dose-related manner, but some class III agents with more complex actions such as amiodarone have a markedly lower potential to cause this arrhythmia. The risk of torsade de pointes precludes the use of class IA and ‘pure’ class III agents in patients with left ventricular hypertrophy and bradycardia. Class IC agents may cause sustained monomorphic ventricular tachycardias and are generally precluded in ischaemic and structural heart disease. Advanced heart failure patients may be treated with amiodarone or dofetilide, but most other AADs are unsuitable. The most important extracardiac toxicities occurring with AADs are those of amiodarone. Drug interactions are a significant safety issue in the management of AF, including pharmacokinetic interactions in which plasma levels of the AAD are raised — increasing the risk of proarrhythmia — and concomitant use of drugs that prolong the QT interval. Notwithstanding these considerations, most patients with AF can be considered for rhythm control, provided there is adequate pre-treatment assessment and protocols for initiation, dosing and monitoring are followed with care.