Accessory Pathway Antegrade Effective Refractory Period Among Wolff Parkinson White Patients: the Risk in Relation to the Location

The Wolf-Parkinson-White (WPW) syndrome is a clinical entity characterized by the presence of ≥1 accessory pathways between the atria and the ventricles pre-disposing patients to arrhythmias. Anterograde conduction through the accessory pathway leads to preexcitation of the ventricles and a delta wave in the ECG. The prevalence of preexcitation in the general population has been estimated to be 1 to 3 in 1000 individuals. Although most asymptomatic patients with pre-excitation have a good prognosis, there is also a lifetime risk of malignant arrhythmias and SCD, estimated to be 0.1 % per patient year.

• More worrisome is the fact that this event can be the first manifestation of the disease in up to 53 % of patients.
• Atrial fibrillation (AF) can be a life-threatening arrhythmia in the WPW syndrome if the AV AP has a short anterograde refractory period (RP), allowing too many atrial impulses to be conducted to the ventricle.
• This will result in very high ventricular rates with possible deterioration into ventricular fibrillation (VF) and sudden death.
• Parameters proved to indicate high risk AP include AP effective refractory period <240 ms, shortest preexcited RR interval <250 ms
• Certain Locations were thought to be associated with higher risk of the accessory pathway like Septal localization which was significantly more frequent in patients with VF when compared with individuals with no VF but the overall number of patients is limited . .

These debatable relations between AP location and its risk stratification was not extensively studied in larger scale studies....