Coronary sinus and great cardiac vein electroanatomic mapping predicts the activation delay of the coronary sinus branches

Background: Implantation of left ventricular (LV) lead in segments with delayed electrical activation may improve response to cardiac resynchronization therapy (CRT). The search for the latest LV electrical delay (LVED) site can be time-consuming. Objective: To assess if electrical mapping of coronary sinus (CS) and magna cardiac vein can help to identify the latest activated CS branch. Methods: We retrospectively evaluated 48 consecutive patients who underwent electroanatomic mapping system-guided (EAMS)-CRT device implantation with ≥2 mapped CS branches. The activation mapping of the CS and relative branches were performed using an insulated guide wire. LVED was defined as the interval between the beginning of the QRS complex on the surface electrocardiogram and the local electrogram and expressed in milliseconds (ms). Results: Thirty-two (67%) patients showed left bundle branch block (LBBB) and 16 (33%) non-LBBB electrocardiographic patterns. A total of 116 CS branches (mean, 2.4/patient; range, 2-5) were mapped. In the left oblique view, most patients (N = 39, 81%) showed the latest CS-LVED in lateral segments while nine (19%) showed the latest CS-LVED in anterior or posterior segments. Specifically, 94% of patients with LBBB showed the latest CS-LVED in lateral segments while CS activation among non-LBBB patients was heterogeneous. In all patients, the CS branch that demonstrated the highest LVED originated from the latest activated segment of the CS. Conclusion: Electrical mapping of CS allows identifying the latest activated branches. This finding may contribute to simplify CRT device implantation compared to activation mapping of all the branches.