Background

Pre-excitation syndrome, bundle of Kent from atrium through to ventricular myocytes
This pre-excitation leads to delta wave and short PR interval, and abnormal repolarization (T wave abnormalities)

EKG Features

Resting EKG

Short PR

Symptomatic EKG

AVRT (narrow or wide complex depending on direction of reentrant loop)
Wide complex irregular tachycardia (AF with pre-excitation) --> high risk of degeneration into VF

The 12-lead ECG shows the typical features of Wolff-Parkinson-White; the PR interval is short and the QRS duration prolonged as a result of a delta wave, indicating ventricular preexcitation.

Management of WPW

Acute WPW

Institute ACLS algorithm. Patient should be treated as undifferentiated wide complex tachycardia if there is diagnostic uncertainty.

For orthodromic AVRT, consider AV nodal blocking agents such as adenosine, verapamil, beta-blockers. Procainamide would be a second line therapy.

For antidromic AVRT, procainamide is preferred. Avoid AVN blocking agents unless the tachycardia is definitely known to be antidromic AVRT.

For atrial fibrillation with pre-excitation, AV nodal blocking drugs should be avoidedas they increase the risk of degeneration to ventricular fibrillation due to rapid accessory pathway conduction. If the patient is unstable then they should be electrically cardioverted. Otherwise, consider procainamide or ibutilide.

Prevention of Recurrent Arrhythmia

Ablation is recommended for nearly all patients who have been stabilized after an acute episode of symptomatic tachyarrhythmia.

Pharmacologic therapy such as flecainide, propafenone are preferred for those were not surgical candidates. Beta-blockers could be used as second line therapy for lower risk patients. Verapamil or digoxin should be avoided. Amiodarone is effective but has significant long-term toxicity.