Abstract 4357805: Guideline-directed medical therapy's effect on systolic function in patients with heart failure and left bundle branch block

Background: The current guidelines recommend at least 3 months of optimal guideline-directed medical therapy (GDMT) for patients with heart failure and left bundle branch block (LBBB) before implantation of the beneficial biventricular pacemaker and cardiac resynchronisation therapy (CRT). Research Question: This study evaluated the impact of GDMT and CRT on ventricular function and volumes in patients with heart failure and LBBB, and whether this effect is dependent on mechanical dyssynchrony. Methods: This retrospective cohort study included all patients from the North Denmark Region with a diagnosis of heart failure between January 1 st , 2015, and December 31 st, 2021, and selected patients with LBBB using the validated Marquette 12SL algorithm. Salient exclusion criteria included prior cardiac device, valve disease, and cardiac revascularization without a post-procedural echocardiogram. Patients were grouped based on whether they displayed a typical two-dimensional strain pattern by echocardiogram, indicating a specific dyssynchrony pattern. The typical pattern mandates early activation of a mid-ventricular or basal segment of the septal or anteroseptal wall with peak shortening before 70% of the ejection phase and early stretching of opposing wall segments with peak contraction after the aortic valve closes. Patients without this pattern were in the non-typical pattern group. Results: A total of 381 patients were included. Baseline left ventricular ejection fraction (LVEF) was 26 [IQR 21-31] and 28 [IQR 25-33] in the typical and non-typical pattern groups, respectively. The typical pattern group improved LVEF by 3.5% points (95%CI, 2.6-4.4) versus 11.3% points (95%CI, 9.6-13.0) in the non-typical pattern group during the median titration time of 160 days. In total 24/284 (8.5%) of patients with a typical pattern recovered LVEF > 35% after titration of GDMT, compared to 68/97 (70.1%) in the non-typical pattern group. A total of 175 patients in the typical pattern group had CRT. Resynchronization improved LVEF by 17.3% (CI 95%, 16.2-18.6) and significantly reduced LVEDV by 46.2mL (±50.4) and LVESV by 56.2mL (±43.4), resulting in 136/168 (81.0%) recovering LVEF > 35%. Conclusion: Patients with heart failure, left bundle branch block, and a typical pattern show clinically insignificant improvements in LVEF by GDMT. However, these patients had a five-fold increase in LVEF after CRT. These patients may benefit from early treatment with CRT.