Atrial fibrillation: What are the effects of drug therapy on the effectiveness and complications of electrical cardioversion?

Aerial fibrillation is the most common cardiac rhythm disorder associated w ith hospitalization. Two therapeutic options have been available: antiarrhy thmic drug therapy, and external or internal electrical cardioversion. Elec trical cardioversion of atrial fibrillation remains one of the most widely used and effective treatments fur the restoration of normal sinus rhythm. H owever, many patients continue to receive an antiarrythmic drug before and after cardioversion in an attempt either to cardiovert the arrhythmia chemi cally or to maintain sinus rhythm after successful cardioversion. Because s ome pharmacological agents can affect the cardioversion procedure for aeria l fibrillation or flutter, and because many patients with such arrhythmias may require electrical cardioversion when they are taking antiarrhythmic dr ugs, the question of a possible effect of drug therapy on the efficacy and safety of electrical cardioversion of aerial fibrillation arises. Early rep orts of direct current cardioversion provoking potentially lethal ventricul ar arrhythmias raised suspecions of an arrhythmogenic role for digoxin anti arrhythmic therapy, and it is customary to withhold these drugs for 24 to 4 8 h before cardioversion is attempted. However, this complication is likely to arise only in patients who are close to, or actually manifesting, signs of drug toxicity. On the other hand, treatment with therapeutic concentrat ions of antiarrhythmic drugs before cardioversion may in some cases be asso ciated with a significant reduction in the number of shocks and decreased e nergy required to restore synus rhythm, a lower incidence of postshock arrh ythmias and a reduced risk of early recurrence of atrial fibrillation.