title: Left bundle branch block predicts better survival in women than men receiving cardiac resynchronization therapy: long-term follow-up of ∼ 145,000 patients.
abstract: OBJECTIVE
  The goal of this study was to test the hypothesis that in recipients of cardiac resynchronization therapy defibrillators (CRT-D), conventional left bundle branch block (LBBB) diagnosis predicts better survival in women than in men.
  
  
  BACKGROUND
  New York Heart Association class I and II patients without LBBB do not benefit from CRT-D, and women have better survival after CRT-D than men. Separate analysis suggests that QRS duration thresholds for LBBB diagnosis differ according to sex, and conventional LBBB electrocardiographic criteria are falsely positive in men more frequently than in women.
  
  
  METHODS
  We 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.
  
  
  RESULTS
  In univariate analysis, LBBB was associated with a 31% reduction in death in women (HR: 0.69 [95% confidence interval (CI): 0.67 to 0.71]) but only a 16% reduction in death in men (HR: 0.84 [95% CI: 0.82 to 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 to 0.77]) and a 15% reduction in death in men (HR: 0.85 [95% CI: 0.83 to 0.87]). A significant interaction (p < 0.0001) between sex and LBBB was seen.
  
  
  CONCLUSIONS
  LBBB diagnosis is associated with greater survival in women than in men receiving CRT-D, and this discrepancy is not explained by differences in measured comorbidities. Possible explanations for this difference include that LBBB may have different prognostic significance according to sex or that LBBB diagnosis is more often false-positive in men compared with women.
authors.affiliation: Center for Devices and Radiological Health, US Food and Drug Administration, Silver Spring, Maryland; Duke University School of Medicine, Durham, North Carolina.
authors.forename: Zak
authors.initials: Z
authors.lastname: Loring
authors.affiliation: Center for Devices and Radiological Health, US Food and Drug Administration, Silver Spring, Maryland.
authors.forename: Daniel A
authors.initials: DA
authors.lastname: Caños
authors.affiliation: Center for Devices and Radiological Health, US Food and Drug Administration, Silver Spring, Maryland; Division of Cardiology, Department of Internal Medicine, University of Utah School of Medicine, Salt Lake City, Utah.
authors.forename: Kimberly
authors.initials: K
authors.lastname: Selzman
authors.affiliation: Center for Devices and Radiological Health, US Food and Drug Administration, Silver Spring, Maryland.
authors.forename: Naomi D
authors.initials: ND
authors.lastname: Herz
authors.affiliation: Acumen, LLC, SafeRx, Burlingame, California.
authors.forename: Henry
authors.initials: H
authors.lastname: Silverman
authors.affiliation: Acumen, LLC, SafeRx, Burlingame, California.
authors.forename: Thomas E
authors.initials: TE
authors.lastname: MaCurdy
authors.affiliation: Centers for Medicare & Medicaid Services, Baltimore, Maryland.
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Worrall
authors.affiliation: Centers for Medicare & Medicaid Services, Baltimore, Maryland.
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Kelman
authors.affiliation: Center for Devices and Radiological Health, US Food and Drug Administration, Silver Spring, Maryland.
authors.forename: Mary E
authors.initials: ME
authors.lastname: Ritchey
authors.affiliation: Center for Devices and Radiological Health, US Food and Drug Administration, Silver Spring, Maryland; Division of Cardiology, Albert Einstein College of Medicine, Bronx, New York.
authors.forename: Ileana L
authors.initials: IL
authors.lastname: Piña
authors.affiliation: Center for Devices and Radiological Health, US Food and Drug Administration, Silver Spring, Maryland. Electronic address: david.strauss@fda.hhs.gov.
authors.forename: David G
authors.initials: DG
authors.lastname: Strauss
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002037:Bundle-Branch Block / Q000401:mortality* / Q000628:therapy*; D058406:Cardiac Resynchronization Therapy; D017147:Defibrillators, Implantable; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D012737:Sex Factors; D013997:Time Factors
keywords: cardiac resynchronization therapy; left bundle branch block; sex