Using the right drug. A treatment algorithm for atrial fibrillation

Atrial fibrillation is the commonest sustained cardiac arrhythmia. Its incidence increases with age and in association with organic heart disease, in particular valvular heart disease, left ventricular dysfunction and in association with thyrotoxicosis and alcohol excess. Atrial fibrillation may present as paroxysms of self-terminating arrhythmia or as a sustained arrhythmia. In the former instance, management is directed towards suppression of paroxysms and will commonly involve class 1C, class 2 or class 3 agents. If atrial fibrillation is sustained, a decision as to the desirability of cardioversion must be made. If this can be achieved successfully, particularly if the episode was of brief duration and associated with a reversible cause, sinus rhythm may be preserved without further antiarrhythmic therapy. Otherwise prophylactic therapy as used for paroxysmal atrial fibrillation is appropriate. In patients who fail to respond to cardioversion, or in those with advanced organic heart disease, long-standing atrial fibrillation or marked dilatation of the left atrium in which case cardioversion is unlikely to be successful, the principal therapeutic strategy is to control ventricular rate. Classically, digoxin is used for this purpose. Additional agents which will slow the ventricular rates, such as beta-blockers, amiodarone or calcium channel antagonists (verapamil or diltiazem), may be necessary if the ventricular rate remains uncontrolled and continues to produce severe symptoms. In the event of failure of medical therapy to control ventricular rate, atrioventricular nodal modification or ablation may be appropriate.