In Wolff-Parkinson-White syndrome, antegrade conduction occurs over an accessory pathway. If atrial fibrillation, develops this is a medical emergency as very rapid ventricular rates can develop.
In manifest Wolff-Parkinson-White (WPW) syndrome, antegrade conduction occurs over the accessory pathway. If atrial fibrillation develops, the normal rate-limiting effects of the atrioventricular (AV) node are bypassed, and the resultant excessive ventricular rates (sometimes 200 to 300 beats/minutes) may lead to ventricular fibrillation (see figure 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 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).
Treatment of Atrial Fibrillation and WPW Syndrome
- Direct-current cardioversion
The treatment of choice for Wolff-Parkinson-White syndrome is direct-current cardioversion. The usual rate-slowing drugs used in atrial fibrillation are not effective, and digoxin and the nondihydropyridine calcium channel blockers (eg, verapamil, 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 drug can be used.
Pearls & Pitfalls
Drugs Mentioned In This Article
|Drug Name||Select Trade|
|procainamide||No US brand name|
|diltiazem||CARDIZEM, CARTIA XT, DILACOR XR|