Mechanistic insights into the benefits of multisite pacing in cardiac resynchronization therapy: The importance of electrical substrate and rate of left ventricular activation

BACKGROUND Multisite pacing (MSP) of the left ventricle is proposed as an alternative to conventional single-site LV pacing in cardiac resynchronization therapy (CRT). Reports on the benefits of MSP have been conflicting. A paradigm whereby not all patients derive benefit from MSP is emerging. OBJECTIVE We sought to compare the hemodynamic and electrical effects of MSP with the aim of identifying a subgroup of patients more likely to derive benefit from MSP. METHODS Sixteen patients with implanted CRT systems incorporating a quadripolar LV pacing lead were studied. Invasive hemodynamic and electroanatomic assessment was performed during the following rhythms: baseline (non-CRT); biventricular (BIV) pacing delivered via the implanted CRT system (BIVimplanted); BIV pacing delivered via an alternative temporary LV lead (BIValternative); dual-vein MSP delivered via 2 LV leads; MultiPoint Pacing delivered via 2 vectors of the quadripolar LV lead. RESULTS Seven patients had an acute hemodynamic response (AHR) o