Atrial fibrillation (AF) is a medical emergency when rapid antegrade conduction over an accessory pathway occurs in Wolff-Parkinson-White (WPW) syndrome.

In manifest WPW syndrome, antegrade conduction occurs over the accessory pathway. If 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. 15: 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.

Fig. 15
Atrial fibrillation in Wolff-Parkinson-White syndrome. Ventricular response is very fast (RR intervals minimum of 160 msec). Shortly thereafter, ventricular fibrillation develops (lead II continuous rhythm strip at bottom).

Pearls & Pitfalls Do not give digoxinSome Trade Names DIGITEK LANOXIN Click for Drug Monograph or nondihydropyridine Ca channel blockers (eg, verapamilSome Trade Names CALAN ISOPTIN Click for Drug Monograph , diltiazemSome Trade Names CARDIZEM CARTIA DILACOR Click for Drug Monograph ) to patients with atrial fibrillation and WPW because these drugs may trigger ventricular fibrillation.

The treatment of choice is direct-current cardioversion. The usual rate-slowing drugs used in AF are not effective, and digoxinSome Trade Names
DIGITEK
LANOXIN
Click for Drug Monograph
and the nondihydropyridine Ca channel blockers (eg, verapamilSome Trade Names
CALAN
ISOPTIN
Click for Drug Monograph
, diltiazemSome Trade Names
CARDIZEM
CARTIA
DILACOR
Click for Drug Monograph
) 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 procainamideSome Trade Names
PROCAN SR
PRONESTYL
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or amiodaroneSome Trade Names
CORDARONE
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is preferred, but any class Ia, class Ic, or class III antiarrhythmic can be used.

Last full review/revision July 2012 by L. Brent Mitchell, MD

Content last modified November 2012