syndrome of the week

Wolff-Parkinson-White syndrome (WPW) is a syndrome of pre-excitation of the ventricles of the heart due to an accessory pathway known as the bundle of Kent. This accessory pathway is an abnormal electrical communication from the atria to the ventricles.

The incidence of WPW syndrome is between 0.1 and 3% of the general population.
While the vast majority of individuals with a bundle of Kent remain asymptomatic throughout their entire lives, there is a risk of sudden death associated with the syndrome. Sudden death due to WPW syndrome is rare (incidence of less than 0.6%), and is due to the effect of the accessory pathway on tachyarrhythmias in these individuals.

Acutely, people with WPW who are experiencing a tachydysrhythmia may require electrical cardioversion if their condition is critical, or, if more stable, medical treatment may be used. Patients with atrial fibrillation and rapid ventricular response are often treated with amiodarone or procainamide to stabilize their heart rate.

Adenosine and other AV node blockers should be avoided in atrial fibrillation and atrial flutter with WPW or history of it; this inlcudes adenosine, diltiazem, verapamil, other calcium channel blockers and beta-blockers. Patients with a rapid heart beat with narrow QRS complexes (circus movement tachycardias) may also be cardioverted, alternatively, adenosine may be administered if equipment for cardioversion is immediately available as a backup.

The definitive treatment of WPW syndrome is a destruction of the abnormal electrical pathway by radiofrequency catheter ablation. This procedure is performed almost exclusively by cardiac electrophysiologists. Radiofrequency catheter ablation is not performed in all individuals with WPW syndrome because there are inherent risks involved in the procedure.

When performed by an experienced electrophysiologist, radiofrequency ablation has a high success rate. If radiofrequency catheter ablation is successfully performed, the patient is generally considered cured. Recurrence rates are typically less than 5% after a successful ablation. The one caveat is that individuals with underlying Ebstein's anomaly may develop additional accessory pathways during progression of their disease.