Wolff‒Parkinson‒White (WPW) syndrome is characterized by an anomalous accessory pathway (AP) connecting the atrium and ventricle, leading to abnormal myocardial excitation and cardiac arrhythmias. The effective refractory period (ERP) of the AP is crucial for risk stratification. Building on previous research indicating the significance of the source‒sink mismatch mechanism in AP conduction, this study explored the hypothesis that the ERP of the AP involves such a source‒sink relationship. To investigate this, computer simulations of antegrade and retrograde AP conduction were conducted using simplified models, focusing on the presence or absence of asymmetrical junctions in AP conduction among patients with WPW syndrome. Analysis revealed that morphological features at the AP junction significantly altered the source‒sink relationship, consequently affecting the ERP of the AP. Thus, the asymmetrical shape primarily determines the ERP in both antegrade and retrograde AP conduction. This study provides novel insights into the ERP of the AP in WPW syndrome.