[JNUS]

WPW syndrome and Lown-Ganong-Levine (LGL) syndrome are 2 major variants of preexcitation, having an estimated prevalence of 0.1-0.3% in the general population. LGL syndrome is similar to WPW syndrome in that preexcitation is secondary to an accessory pathway (the James fibers) that directly connects the atria to the His bundle. In LGL syndrome, the ECG demonstrates a short PR interval (usually less than 0.12 s), without a delta wave and with a normal QRS complex. Both of these syndromes predispose patients to paroxysmal tachydysrhythmia (especially paroxysmal supraventricular tachycardia and atrial fibrillation). Related aberrant conduction, as in this case, can result in rapid ventricular rates of up to 300 bpm (which may be symptomatic and even lethal).

As many as 80% of patients with WPW syndrome have reentrant tachycardia, whereas 15-30% have atrial fibrillation and 5% have atrial flutter. Ventricular tachycardia is uncommon with WPW syndrome, though rapid atrial fibrillation with aberrant conduction can appear as ventricular tachycardia (as seen in Figure 1) and, because of excessive stimulation of the ventricles, can lead to ventricular fibrillation.

Initial treatment for acute tachydysrhythmia is as described in the American Heart Association’s Advanced Cardiac Life Support (ACLS) protocol. Synchronized cardioversion was performed because of the patient’s unstable condition. In general, if patients are stable and have narrow-complex tachydysrhythmia, adenosine can be tried first; however, adenosine can theoretically be harmful to those with antidromic reentrant conduction. Medications such as calcium channel blockers (eg, diltiazem, verapamil) and beta blockers (eg, metoprolol, esmolol, propranolol) should be avoided in this situation. Stable patients may be treated with intravenous procainamide; unstable patients may be treated with direct cardioversion. Medications that have variable effects on accessory conduction (eg, phenytoin, esmolol, propranolol, verapamil) should be avoided. Digoxin is absolutely contraindicated because it may shorten the refractory period and enhance conduction over the bypass tract, thus causing an even faster tachydysrhythmia or deterioration into ventricular fibrillation.

Some patients with WPW syndrome are at risk for sudden death, especially those with excessive unstable rhythms with short refractory periods, as in this case. In these patients, electrophysiologic cardiac studies and radiofrequency catheter ablation may be definitive and curative. Catheter ablation can also be used in patients with symptomatic supraventricular tachycardia. Some patients may refuse this somewhat invasive therapy and choose to undergo long-term antiarrhythmic therapy with drugs such as amiodarone, quinidine, or sotalol. Others without worrisome symptoms (ie, syncope, symptomatic tachyarrhythmias, wide-complex tachycardia of uncertain cause, associated structural heart disease, WPW syndrome with a family history of sudden death, recurrent trial fibrillation or atrial flutter) may be treated symptomatically.