Conduction block and the impact of multipoint pacing with fusion optimization in cardiac resynchronization therapy, an electrocardiographic imaging mapping insight

Background: MultiPoint Pacing (MPP) CRT may improve electrical resynchronization of the left ventricle (LV). Optimization with SyncAV dynamically combines intrinsic atrioventricular (AV) conduction and pacing. Objective: To assess regions of fixed and functional conduction block in patients with LBBB and the impact of MPP & SyncAV, evaluated by electrocardiographic imaging (ECGi). Methods: Patients in sinus rhythm with LBBB, having CRT implantation (MPP CRT, quadripolar LV lead) underwent ECGi mapping; during intrinsic rhythm, nominal AV delay and optimized SyncAV (offset minimizing QRS duration) during biventricular (BiV), MultiPoint pacing (MPP) and LV only MPP (LVMPP). Activation times (AT) were calculated. Sites with conduction block were defined as difference in AT >50ms over 10mm. Results: ECGi was completed in 10 patients (80% male, mean age 66±16 years, 60% ischemic, LVEF 30±6%, QRSd 167±15ms). Latest activating LV segments during intrinsic rhythm were heterogenous: basal-anterior 20%, anterolateral 30%, lateral 10%, inferolateral 30%, inferior 10%. LV lead positions were concordant to the latest activating segment in 50%; adjacent 20% and remote (≥2 LV segments) 30%. Two or more lines of block of varying distribution were present in all cases. Leads were concordant with lines of block in 0%, adjacent 60% and remote 40%. Area of block was reduced by LVMPP SyncAV from intrinsic (p