Patients with ventricular preexcitation related to an atrioventricular accessory pathway may experience both benign and malignant arrhythmias, a condition known as the Wolff-Parkinson-White syndrome (WPW). In this setting, malignant arrhythmias may lead to sudden cardiac death (SCD) and its mechanism has been clearly elucidated. The "primum movens" is generally a reciprocating atrioventricular reentrant tachycardia (AVRT), which, as shown in Fig. 1, triggers atrial fibrillation (AF). in the presence of an accessory pathway with very short anterograde effective refractory period and therefore capable of very fast anterograde conduction, AF may be conducted to ventricles at a very high rate triggering ventricular fibrillation (VF), as shown in Fig. 2, even in subjects without structural heart disease. In rare cases, AF spontaneously occurs, which may degenerate into ventricular fibrillation with the mechanism described before. In this article, only the risk of SCD related to the presence of an accessory pathway is discussed, not considering the possible adjunctive risk related to the presence of a concomitant structural heart disease.
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