Fig. 1.

(A) Twelve-lead ECG strip showing overt pre-excitation; (B) Mapping in sinus rhythm (antegrade conduction) showing the earliest ventricular activity at the RCC (ABL d) in relation to the right para-Hisian area (HIS d). Catheter manipulation within the RCC led to mechanical block of the AP and revealed the His-bundle deflection in the right side (arrow in the HIS d recordings); (C) RF energy delivery led to permanent loss of pre-excitation. At the successful ablation site, the ventricular electrogram is significantly larger than the atrial electrogram confirming the RCC position; (D) Aortography in LAO projection showing the anatomical relationships of the RCC, the LCC, and the para-Hisian area (HIS catheter); (E) Fluoroscopic image in LAO projection showing the position of the ablation catheter within the RCC; (F) Electroanatomic activation mapping during sinus rhythm showing the earliest ventricular activation sites in the RCC and the right para-Hisian area (red color). ECG: electrocardiogram; LAO: left anterior oblique; LCC: left coronary cusp; NCC: non-coronary cusp; RCC: right coronary cusp; RF: radiofrequency; SVC: superior vena cava.