Ablation of a Para-Hisian Accessory Pathway from the Non-coronary Cusp: A Case Report

Para-Hisian accessory pathways (PHAPs) remain among the most challenging substrates for catheter ablation because of their close anatomical relationship to the atrioventricular (AV) conduction system and the consequent risk of iatrogenic AV block. The non-coronary cusp (NCC) has emerged as a valuable alternative when right-sided ablation is ineffective or associated with an unacceptable risk of injury to the His bundle. We report the case of a 23-year-old man who presented with pre-excited atrial fibrillation. Electrophysiological study localized an anteroseptal/para-Hisian accessory pathway. Electroanatomical mapping identified the earliest ventricular activation at the para-Hisian region; however, multiple irrigated radiofrequency applications from the right atrial septum failed to eliminate pre-excitation because of the close proximity to the His bundle. A retrograde aortic approach to the NCC was subsequently undertaken using three-dimensional electroanatomical mapping integrated with intracardiac echocardiography. Mapping within the NCC demonstrated an accessory pathway potential with atrioventricular fusion and ventricular activation preceding delta-wave onset by 20 ms. Radiofrequency delivery at this site resulted in elimination of pre-excitation within 3 s while preserving normal AV conduction. No recurrence of pre-excitation or impairment of AV nodal conduction was observed during post-ablation assessment. This case supports the NCC as a safe and effective alternative target when conventional right-sided ablation is unsuccessful or poses a significant risk of AV conduction injury.