Medical management of atrial fibrillation: Future directions

Atrial fibrillation is the most common arrhythmia that requires treatment, and although ablation is appropriate in many cases, antiarrythmic drug therapy remains the first and most appropriate therapy in most patients. Currently available antiarrhythmic drugs are limited by modest efficacy and significant toxicity. Cardiac toxicity realtes to effects on the ventricle, especially in prolonging the QT interval and causing torsades de pointes. Amiodarone, an agent with multiple antiarrhythmic effects, is unique in its relative lack of proarrhythmia, although its non-cardiac toxicities limit its use. Some investigational agents are directed at multiple ion channels, or are designed to be analogs of amiodarone. The other line of investigation focuses on the antiarrhythmic action of agents that affect novel ion channel targets. Basic and early clinical studies show promise for drugs that provide atrial antiarrhythmic effects without ventricular proarrhythmia by affecting the atrium preferentially or selectively (inhibiting the ITO and IKur currents, respectively). Future drugs may possess preferential effects on the remodeled atrium (and as such would be selective for patients with atrial fibrillation). It is hoped that efforts to develop new drugs, including those with preferential effects on the atrium, will provide therapy with greater efficacy and safety.