Posterior coronary vein as the substrate for an epicardial accessory pathway.

Catheter ablation of Wolff-Parkinson-White syndrome is associated with up to 5% of failure. Coronary sinus (CS) abnormalities or connections between CS myocardial coat and left ventricular epicardium are associated with posteroseptal and left posterior accessory pathways (AP). A 41-year-old patient with WPW syndrome was referred to our hospital after three unsuccessful ablations. The 12-lead ECG suggested a left posteroseptal AP. CT imaging and electro-anatomic mapping showed a relationship between AP electrical course and CS posterior branch. This finding supports the hypothesis CSAPs lie in the myocardial coat around CS and represent an extensive connection between atrial and ventricular epicardial surface.