Abstract 2163: Single-site Left Ventricular Apex And Left Ventricular Septal Pacing For Long Term Maintenance Of Cardiac Contractility

Abstract

Objective: Conventional right ventricular (RV) apex pacing is associated with asynchronous activation and reduced left ventricular (LV) pump function. Previous studies have shown acute hemodynamic benefits over RV apex pacing by LV septal or LV apex pacing. We investigated whether this improvement translates into a long-term benefit and how acute LV function during single site LV pacing compares to biventricular pacing. Methods: After AV-nodal ablation, mongrel dogs were randomized to receive 16 weeks of VDD pacing at the RV apex (n = 7), LV apex (n = 7), or LV mid-septum (n = 8; trans-ventricular septal approach). LV contractility (dP/dt max /P instantaneous ) was measured during normal ventricular conduction from atrial pacing (AP) and during ventricular pacing 1–3 hours and 16 weeks after implant. At 16 weeks, contractility was also measured after an acute switch from the implant site (IS) to the non-implanted apex (both for LV septal group) and to RV apex + LV lateral (BiV) pacing. Results: While acute and chronic RV apex pacing significantly reduced contractility (Figure a ; mean ± SD, *p<0.05 contrasted to 1), LV pacing maintained contractility near AP levels. After 16 weeks of RV apex pacing, switching to LV apex pacing (but not BiV pacing) increased contractility (Figure b ). After 16 weeks of LV pacing, switching to RV apex pacing decreased contractility. Collectively, acute LV apex pacing enhanced contractility over acute BiV (p<.001). Conclusions: Chronic LV apex and LV mid-septal pacing maintain contractility near normal levels, and at a higher level than RV apex pacing. Acutely, LV apex pacing improves contractility compared to BiV pacing.