(see also Ablation; Lown-Ganong-Levine Syndrome)

The WPW syndrome is a ventricular “preexcitation” syndrome in which an impulse “sneaks” down a shorter path (via the Kent's bundle or the Mahaim fibers), bypassing the AV node, while, at the same time, another impulse from the normal bundle of His pathway is conducted. As a result, the ventricle is stimulated from two directions. This sets up recurrent bouts of supraventricular tachyarrhythmias. Two types of WPW have been identified: type A on the left side of the heart and type B on the right side of the heart. The hallmarks of the syndrome are twofold:

• A shortened PR interval (usually <0.12 seconds) because the impulse takes a “shortcut” from the SA to the AV node
• An initial slurring on the upstroke of the QRS (delta wave), reflecting the ventricular activation outside the normal conduction system

Figure 2.80

This syndrome is seen most often in young adults and rarely in the elderly. The patient can go in and out of this rhythm, exhibiting entire runs of supraventricular tachyarrhythmias or just experiencing an occasional beat or two. The syndrome may require no treatment if the occurrences are rare. However, recurrent bouts of tachyarrhythmias must be treated as appropriate with vagal maneuvers and, if they are unsuccessful, with vagotonic drugs. Surgical intervention to sever the Kent's bundle or Mahaim fibers bypass tract is often used for those patients who experience frequent, disabling tachyarrhythmias.