Various algorithms have been established for localizing the accessory pathways based on the surface ECG. The most widely studied and well-established Arruda algorithm1 suggested the presence of a posteroseptal accessory pathway in this patient.
Risk stratification of accessory pathways depends on the identification of markers for sudden cardiac death. These include smaller APERP (less than 250 milliseconds), shortest preexcited R-R intervals of less than 250 milliseconds during atrial fibrillation, presence of multiple accessory pathways, Ebstein anomaly, and familial Wolff-Parkinson-White (WPW) syndrome. On the other hand, abrupt loss of preexcitation during treadmill testing and intermittent preexcitation on the surface ECG imply the presence of bypass tracts with longer refractory periods.2 The coronary sinus pathway is associated with coronary sinus aneurysm, which is found to have a rapid conduction time and thereby high risk of fast ventricular rate and sudden cardiac death during atrial fibrillation episodes.3