Catheter ablation of a difficult accessory pathway guided by coronary sinus venography and 3D electroanatomical mapping.

A 38-year-old man with history of unsuccessful catheter ablation of paraseptal accessory pathway (AP) and cardiac arrest was referred for reablation. Coronary sinus (CS) venography and detailed three-dimensional electroanatomical mapping demonstrated a large diverticulum near the CS ostium. A single radiofrequency ablation at the neck of the diverticulum eliminated conduction in the AP completely.