Left Bundle Branch Block Predicts Better Survival in Women Than Men Receiving Cardiac Resynchronization Therapy: Long-Term Follow-Up of ~145,000 Patients

Study Questions:

What is the impact of left bundle branch block (LBBB) on long-term survival in male versus female cardiac resynchronization therapy defibrillator (CRT-D) patients, after accounting for baseline comorbidities?


The investigators analyzed Medicare records from 144,642 CRT-D recipients between 2002 and 2008, that were followed up for up to 90 months. Medicare billing data were used to determine age, sex, race, and comorbidities. Hazard ratios (HRs) were calculated to assess if conventional LBBB diagnosis had different prognostic significance according to sex.


In univariate analysis, LBBB was associated with a 31% reduction in death in women (HR, 0.69; 95% confidence interval [CI], 0.67-0.71), but only a 16% reduction in death in men (HR, 0.84; 95% CI, 0.82-0.85). In multivariable analyses controlling for comorbidities, LBBB was associated with a 26% reduction in death in women (HR, 0.74; 95% CI, 0.71-0.77) and a 15% reduction in death in men (HR, 0.85; 95% CI, 0.83-0.87). A significant interaction (p < 0.0001) between sex and LBBB was seen.


The authors concluded that LBBB diagnosis is associated with greater survival in women than in men receiving CRT-D.


This study reports that LBBB is associated with significantly greater survival in women than in men receiving CRT-D, and this discrepancy is not explained by differences in comorbidities. Furthermore, a significant interaction between sex and LBBB confirmed that the LBBB diagnosis in and of itself carries a different prognosis for female and male CRT-D recipients. Since developing more patient-specific selection criteria for CRT-D may reduce the risks and costs associated with inappropriate therapy, future studies should investigate appropriate QRS duration thresholds in men and women that identify optimal CRT-D candidates.

Clinical Topics: Arrhythmias and Clinical EP, Heart Failure and Cardiomyopathies, Implantable Devices, EP Basic Science, SCD/Ventricular Arrhythmias

Keywords: Defibrillators, Follow-Up Studies, Bundle-Branch Block, Medicare, United States, Cardiac Resynchronization Therapy

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