High‐Density Epicardial Activation Mapping to Optimize the Site for Video‐Thoracoscopic Left Ventricular Lead Implant

Cardiac resynchronization (CRT) is the established therapy of chronic systolic heart failure in patients with intraventricular conduction delay—wide QRS complex.1,2 Approximately 30% of patients, however, do not respond to this therapy clinically; and in 50% of patients, CRT is not associated with left ventricular (LV) reverse remodeling.3 Left ventricular pacing lead position is closely associated with the response to CRT. Several methods have been advocated for optimization of its position. However, only two of them have been studied more extensively. One comprises echocardiographic local mechanical delay,4–8 while the other consists of time interval between the onset of QRS complex and local LV lead electrogram (EGM) during spontaneous ventricular activation (QLV).9–14 The evidence from observational studies is mounting that more optimal LV lead position (at the site of more delayed contraction and longer QLV) predicts better clinical response and reverses LV remodeling. Inappropriate LV lead position with QLV shorter than one-half of the QRS duration was associated with higher mortality in a small retrospective study.12 Reduced mortality and reduced heart failure hospitalization rate (combined endpoint) were observed in patients randomized to echocardiographically optimized LV lead position in the TARGET trial.4 Unlike transvenous LV lead implantation, which is limited by the anatomy of the coronary sinus and its tributaries, minimally invasive surgical video-thoracoscopic approach has fewer constraints. In such situations, empirical selection of the LV pacing site, which is usually a central lateral segment of the LV according to previous hemodynamic studies,15,16 and endocardial activation mapping in patients with left bundle branch block (LBBB),17 may not be optimal. Therefore, we proposed a new method for fast epicardial mapping of QLV during video-thoracoscopic surgery to optimize the LV lead position. This study was primarily aimed at assessing the feasibility and safety of this approach. In addition, we hypothesized that the benefit of this technique could be indirectly demonstrated.