Ejection fraction improvement in left ventricular-only pacing vs. BiVentricular pacing in patients with heart failure

Objective: Left ventricular (LV) pacing with resynchronization therapy improves ventricular synchrony in patients with decreased LV function and Left Bundle Branch Bock (LBBB). Ventricular activation in these cases may be obtained by recruiting the intrinsic atrioventricular (AV) conduction, over the right bundle branch that causes a multisite activation and a synchronized activity of the right ventricle and part of the septum. Fusion pacing between intrinsic AV conduction and LV capture initiates right ventricular (RV) activation and compensates for LV electrical delay. The goal of this study is to show that LV-only pacing is superior to BiVentricular (BiV) pacing in patients with LV systolic dysfunction and LBBB. Methods: This is a retrospective study of 2 different hospitals' registries in Lebanon. 121 consecutive patients were identified between January 2014 and December 2019. Patients with left ventricular ejection fraction (LVEF) ≤ 35%, a QRS interval ≥130 msec, and an LBBB pattern on full medical therapy were included in this study and divided in 2 groups: LV pacing and BiV pacing. All patients had echocardiograms before and 3 to 6 months post-device implantation. The primary endpoint was the change in ejection fraction, and the secondary endpoints were a decrease in systolic pulmonary artery pressure (SPAP), a decrease in LV end-diastolic diameter (LVEDD), and a decrease in LV end-systolic diameter (LVESD). Statistical analysis was done with SPSS software, and a p-value <0.05 was considered significant. Results: The study population was mostly males (69.4%) (mean LVEF of 26.5%, mean age of 67 years old), with 74 (61.2%) ischemic cardiomyopathy patients and 47 (38.8%) non-ischemic cardiomyopathy patients. Fifty (41.3%) patients were programmed as LV-only pacing. A statistically significant difference in improvement in ejection fraction (EF) was seen between the LV-only pacing arm (9.2%) and the BiV pacing arm (5.5%) (p=0.043, 95% CI (0.12-7.11)). Similarly, we noticed a significant decrease in the LVEDD (p=0.007, 95% CI (0.15-1.4)) and LVESD (p=0.03, 95% CI (0.13-1.8)) in the LV pacing compared to the BiV pacing group. There was a trend in favor of more SPAP improvement in the LV pacing group that did not reach statistical significance. Conclusion: This study demonstrates that LV-only pacing mode significantly improves EF and LV size compared to BiV pacing mode.