Genetic basis and pathogenesis of Familial WPW Syndrome

The Wolff-Parkinson-White (WPW) syndrome has been a known clinical entity for over fifty years. In 1967 Durrer et al postulated WPW syndrome was due to an accessory pathway, bypassing the AV node, from the atria to the ventricles1. This was later confirmed by epicardial mapping. WPW is the second most common cause of paroxysmal supraventricular tachycardias in the western world and the most common cause in China2. WPW syndrome has a prevalence of 1.5 to 3.1 per 1000 persons in western countries3,4,5 . Patients with the WPW syndrome may present with palpitations, presyncope, syncope, or sudden cardiac death (SCD). In some patients the first and only manifestation of the disease is SCD. This is more likely to occur in the setting of atrial fibrillation with a rapid ventricular response. Electrocardiographic findings of WPW syndrome consist of preexcitation manifested by a shortened PR interval (<120 msec), a widened QRS (>100 msec) a delta wave (abnormal initial QRS vector) and supraventricular tachycardia. The EKG finding of preexcitation is a result of early ventricular depolarization through the accessory pathway. SVT can occur with retrograde or antigrade conduction through the accessory pathway forming the basis of the so-called “macro-reentrant” arrhythmia model6. Rapid conduction through the accessory pathway in the setting of atrial fibrillation markedly increases the risk of SCD7. We recently identified the gene responsible for familial Wolff-ParkinsonWhite8. The gene (PRKAG2) which encodes for a protein AMPK (AMPactivated protein kinase) was identified as the causal gene. Missense (single nucleotide change) mutations in this gene were identified in families with WPW. Six such mutations have been identified. Along with preexcitation the affected families had conduction abnormalities (AV block) and cardiac hypertrophy.