In manifest Wolff-Parkinson-White (WPW) syndrome, antegrade conduction occurs over the accessory pathway. If atrial fibrillation (AF) develops, the normal rate-limiting effects of the atrioventricular (AV) node are bypassed, and the resultant excessive ventricular rates (sometimes 200 to 240 beats/min) may lead to ventricular fibrillation (see Fig. 14: Arrhythmias and Conduction Disorders: Atrial fibrillation in Wolff-Parkinson-White syndrome.) and sudden death. Patients with concealed WPW syndrome are not at risk because in them, antegrade conduction does not occur over the accessory connection.
Atrial fibrillation is a medical emergency in the setting of antegrade conduction over an accessory pathway in Wolff-Parkinson-White syndrome.
The treatment of choice is direct-current cardioversion. The usual rate-slowing drugs used in AF are not effective, and digoxinand the nondihydropyridine Ca channel blockers (eg,erapamil diltiazem) are contraindicated because they may increase the ventricular rate and cause ventricular fibrillation. If cardioversion is impossible, drugs that prolong the refractory period of the accessory connection should be used. IV procainamide or amiodarone is preferred, but any class Ia, class Ic, or class III antiarrhythmic can be used.
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