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

Study Questions:

Do patients with a longer QRS duration or left bundle branch block (LBBB) have greater benefit and outcomes from a cardiac resynchronization therapy defibrillator (CRT-D)?


This was a retrospective cohort study of Medicare beneficiaries found in the National Cardiovascular Data Registry’s (NCDR)implantable cardioverter-defibrillator (ICD) Registry who had undergone implantation of a CRT-D device. The patients were subcategorized into admission for implantation of CRT-D or other, and as LBBB or no LBBB and QRS duration ≥150 or 120-149 ms. The primary outcome was all-cause mortality, readmission, and complications following CRT-D implantation.


Of the 96,380 Medicare beneficiaries 65 years and older who were admitted for CRT-D implantation between April 2006 and December 2009, 24,169 were admitted for CRT-D implantation. The mean age was 75 years, 68% were men, 90% were white, 67% had an LBBB, and 55% had a QRS of 150 ms or greater. One- and 3-year mortality rates were 9.2% and 25.9%. All-cause readmission rates were 10.2% at 30 days and 43.3% at 1 year. The 1-year cumulative incidence of mortality and readmission with CRT-D admission was lowest in patients with LBBB and QRS of 150 ms or greater (6.5% for mortality and 38.6% for readmission). The adjusted 3-year mortality was lowest among patients with LBBB and QRS of 150 ms or greater (20.9%) compared with LBBB and QRS 120-149 ms (26.5%; hazard ratio, 1.30; 99% confidence interval, 1.18-142).


Patients in this registry who underwent CRT-D implantation with an LBBB and QRS ≥150 ms had a lower risk of all-cause mortality and readmissions compared with patients with an LBBB and QRS 120-149 ms.


CRT should continue to be considered in clinical practice in those patients with New York Heart Association class II-IV symptoms, LBBB, and QRS ≥150 ms to lower risk of mortality and improve all-cause readmissions.

Keywords: Defibrillators, Heart Failure, Bundle-Branch Block, Cardiac Resynchronization Therapy

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