Left Bundle Branch Block Linked to Increased Risk for Heart Failure

Left bundle branch block (LBBB) may have a causative role in patients’ progression to heart failure, new findings suggest, and may serve as a marker for early preventive interventions.1

These findings were the conclusions of an analysis authored by such investigators as Anna-Sophie Thein, MD, MS, from the Division of Cardiology at the University of California, San Francisco Department of Medicine. Thein and coauthors noted in their summary that despite limited research, prior data suggested a potential causative role of LBBB in the progression to heart failure via mechanical dyssynchrony.2

They highlighted that the study would, therefore, be conducted to assess the link between LBBB in community-dwelling adults with heart failure development and mortality.

“Because there are no current recommendations for further testing or treating patients with asymptomatic LBBB, improving our understanding of these associations may help inform guidelines, identify individuals at high risk of progression to HF, and, ultimately, help uncover novel effective interventions,” Thein and colleagues wrote.1

Trial Design Details

The investigative team described the Cardiovascular Health Study (CHS) as a prospective, population-based cohort that was initiated across 4 sites between 1989 - 1990 in the US, with follow-up extending through 2013. In their present analysis, Thein et al focused on adults aged 65 years and older who demonstrated normal left ventricular ejection fraction (LVEF). The adults they evaluated also had no prior history of heart failure at entry to the study.

The investigative team's data analysis was conducted in the period between February 2018 - October 2024. Those included as participants in this evaluation underwent baseline echocardiography at the time of their enrollment, specifically between 1989 - 1990. If any of these patients lacked evidence of heart failure at their entry to the analysis, were missing baseline electrocardiogram (ECG) data, or borderline/abnormal LVEF values.

Thein and coauthors determined baseline LBBB through the use of 12-lead resting ECGs. These were performed on all of the study's participants using a MAC PC-DT ECG recorder. Any associations identified in the study between LBBB and clinical outcomes were estimated via multivariable Cox proportional hazards models. Such outcomes included heart failure-related hospitalization instances, new-onset heart failure, decline in LVEF over 5 years, and mortality.

Study Findings

Among 4,541 individuals, the mean age was determined to be 72.6 years. 2,697 of these subjects were women (59.4%), and 44 (1.0%) presented with LBBB at the time of baseline. Thein et al found that over a median follow-up of 14.6 years (IQR, 8.4–18.3), 29.1% developed heart failure. In their adjusted analyses, a link between baseline LBBB was identified to a substantially higher incident heart failure risk (hazard ratio [HR], 4.98; 95% CI, 2.18–11.39; P < .001).

Baseline LBBB was also linked to an increase in patients' likelihood of experiencing a 5-year decline in LVEF (odds ratio [OR], 4.73; 95% CI, 1.70–13.70; P = .003). However, Thein and coauthors found that the association between LBBB and overall rates of mortality did not attain statistical significance (HR, 1.39; 95% CI, 0.99–1.94; P = .05).

Overall, their data indicate that even in those with structurally normal hearts, LBBB is linked to a rise in the risk of heart failure and measurable deterioration in cardiac function.

“These findings suggest that identifying LBBB could be important for identifying high-risk individuals and opens up questions regarding optimal surveillance and potential preventive measures,” the investigators wrote.1 “Furthermore, improving our understanding of the underlying mechanisms might advance future strategies for both the prevention and treatment of HF.”

References

1. Thein A, Dixit S, Soliman EZ, et al. Left Bundle Branch Block as a Risk Factor for Heart Failure. JAMA Netw Open. 2025;8(8):e2525801. doi:10.1001/jamanetworkopen.2025.25801.

2. Vernooy K, Verbeek XAAM, Peschar M, et al. Left bundle branch block induces ventricular remodelling and functional septal hypoperfusion. Eur Heart J. 2005;26(1):91-98. doi:10.1093/eurheartj/ehi008.