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Original Investigation
August 14, 2013

QRS Duration, Bundle-Branch Block Morphology, and Outcomes Among Older Patients With Heart Failure Receiving Cardiac Resynchronization Therapy

Author Affiliations
  • 1Denver Health Medical Center, Denver, Colorado
  • 2University of Colorado Denver Anschutz Medical Campus, Aurora
  • 3Institute for Health Research, Kaiser Permanente Colorado, Denver
  • 4Duke Clinical Research Institute, Durham, North Carolina
  • 5Department of Medicine, Duke University School of Medicine, Durham
  • 6Department of Medicine, Yale University School of Medicine, New Haven, Connecticut
  • 7Department of Medicine, Ahmanson-UCLA Cardiomyopathy Center, University of California, Los Angeles
  • 8Division of Cardiovascular Disease, Mayo Clinic, Rochester, Minnesota
  • 9VA Palo Alto Healthcare System, Palo Alto, California
JAMA. 2013;310(6):617-626. doi:10.1001/jama.2013.8641
Abstract

Importance  The benefits of cardiac resynchronization therapy (CRT) in clinical trials were greater among patients with left bundle-branch block (LBBB) or longer QRS duration.

Objective  To measure associations between QRS duration and morphology and outcomes among patients receiving a CRT defibrillator (CRT-D) in clinical practice.

Design, Setting, and Participants  Retrospective cohort study of Medicare beneficiaries in the National Cardiovascular Data Registry’s ICD Registry between 2006 and 2009 who underwent CRT-D implantation. Patients were stratified according to whether they were admitted for CRT-D implantation or for another reason, then categorized as having either LBBB or no LBBB and QRS duration of either 150 ms or greater or 120 to 149 ms.

Main Outcomes and Measures  All-cause mortality; all-cause, cardiovascular, and heart failure readmission; and complications. Patients underwent follow-up for up to 3 years, with follow-up through December 2011.

Results  Among 24 169 patients admitted for CRT-D implantation, 1-year and 3-year mortality rates were 9.2% and 25.9%, respectively. All-cause readmission rates were 10.2% at 30 days and 43.3% at 1 year. Both the unadjusted rate and adjusted risk of 3-year mortality were lowest among patients with LBBB and QRS duration of 150 ms or greater (20.9%), compared with LBBB and QRS duration of 120 to 149 ms (26.5%; adjusted hazard ratio [HR], 1.30 [99% CI, 1.18-1.42]), no LBBB and QRS duration of 150 ms or greater (30.7%; HR, 1.34 [99% CI, 1.20-1.49]), and no LBBB and QRS duration of 120 to 149 ms (32.3%; HR, 1.52 [99% CI, 1.38-1.67]). The unadjusted rate and adjusted risk of 1-year all-cause readmission were also lowest among patients with LBBB and QRS duration of 150 ms or greater (38.6%), compared with LBBB and QRS duration of 120 to 149 ms (44.8%; adjusted HR, 1.18 [99% CI, 1.10-1.26]), no LBBB and QRS duration of 150 ms or greater (45.7%; HR, 1.16 [99% CI, 1.08-1.26]), and no LBBB and QRS duration of 120 to 149 ms (49.6%; HR, 1.31 [99% CI, 1.23-1.40]). There were no observed associations with complications.

Conclusions and Relevance  Among fee-for-service Medicare beneficiaries undergoing CRT-D implantation in clinical practice, LBBB and QRS duration of 150 ms or greater, compared with LBBB and QRS duration less than 150 ms or no LBBB regardless of QRS duration, was associated with lower risk of all-cause mortality and of all-cause, cardiovascular, and heart failure readmissions.

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