Characteristics of Cardiomyopathy in Patients With Chronic Left Bundle Branch Block Undergoing Right Ventricular Pacing.

Background: Left bundle branch block (LBBB) and right ventricular pacing (RVP) are associated with abnormal myocardial mechanics and cardiomyopathy. Consequently, chronic LBBB may increase the risk of heart failure and mortality in patients undergoing RVP.

Methods: Using the TriNetX Analytics Network database, we identified patients who underwent pacemaker implantation between January 1, 2014 and January 1, 2024. Exclusion criteria included a history of heart failure, previous cardiac devices, cardiac resynchronization therapy (CRT) during the index hospitalization, or a left ventricular ejection fraction (LVEF) of less than 50%. The primary outcome incident systolic heart failure and all-cause mortality occurring from the index hospitalization through November 2024.

Results: Among 70,526 patients undergoing RVP implantation, 3916 (5.6%) had chronic LBBB prior to the procedure, with a median age of 75 ± 15 years. Over a median follow-up of 2.5 years, 5356 (7.6%) developed incident systolic heart failure, and 9714 (13.7%) experienced all-cause mortality. After propensity score matching, chronic LBBB was associated with a higher risk of systolic heart failure (HR: 1.39; 95% CI: 1.20-1.62) but not all-cause mortality (HR: 0.93; 95% CI: 0.83-1.06). Patients with chronic LBBB who developed systolic heart failure were more likely to present with moderately depressed LVEF and require CRT upgrades during follow-up compared to those without chronic LBBB.

Conclusion: Chronic LBBB was associated with a higher risk of systolic heart failure, worse left ventricular function, and greater likelihood of CRT upgrade among patients undergoing RVP.