Strauss-Defined LBBB Identifies Patients With Improved Outcomes After CRT-D: A Comparative Cohort Study

Left bundle branch block (LBBB) is a well-established predictor of response to cardiac resynchronization therapy (CRT) in heart failure with reduced ejection fraction. However, several electrocardiographic definitions are used, and their relative significance remains unclear.

Stricter electrocardiographic definitions of LBBB are associated with improved response to CRT and more favorable clinical outcomes.

We conducted a retrospective single-center cohort study including 109 patients who underwent CRT-defibrillator implantation. Baseline electrocardiograms were classified according to six commonly used LBBB definitions. The primary endpoint was echocardiographic response at 6 months, defined as a ≥ 10% absolute increase in left ventricular ejection fraction or a ≥ 15% reduction in left ventricular end-systolic volume. Secondary endpoints included heart failure hospitalization and all-cause mortality. Multivariable logistic, Cox, and negative binomial regression models were used, with odds ratios (OR), hazard ratios (HR), incidence rate ratios (IRR), and 95% confidence intervals (CI).

Strauss-defined LBBB was independently associated with echocardiographic response (adjusted OR, 7.47; 95% CI, 2.52-25.0; p < 0.001) and showed the highest discriminative performance (area under the curve, 0.728; 95% CI, 0.643-0.814). Strauss was also associated with lower heart failure hospitalization rates (adjusted IRR, 0.30; 95% CI, 0.13-0.64; p = 0.002) and reduced mortality (adjusted HR, 0.14; 95% CI, 0.02-0.99; p = 0.049). Median follow-up was 30 months (IQR 14-60).

Different LBBB definitions are associated with differences in CRT response and outcomes. Stricter criteria appear to better identify patients more likely to respond, with more favorable outcomes. These findings may help refine patient selection for CRT.