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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.

Clinical trials have shown that cardiac resynchronization therapy (CRT) improves symptoms and reduces mortality and readmission among selected patients with heart failure and left ventricular systolic dysfunction. Following broad implementation of CRT, it was recognized that one-third to one-half of patients receiving the therapy for heart failure do not improve.¹ Identification of patients likely to benefit from CRT is particularly important, because CRT defibrillator (CRT-D) implantation is expensive, invasive, and associated with important procedural risks.

A primary question regarding optimal patient selection for CRT is whether patients with longer QRS duration or left bundle-branch block (LBBB) morphology derive greater benefit than others. Current guidelines recommend selection of patients primarily on the basis of QRS duration and morphology based predominantly on meta-analyses and subgroup analyses of clinical trials evaluating either QRS duration or morphology. Only 1 study specifically evaluated the combination of QRS duration and morphology but did not assess meaningful patient outcomes.² Thus, the role of QRS duration and morphology in the selection of patients for CRT in contemporary clinical practice remains unclear.

The objectives of this study were to determine the long-term outcomes of unselected patients undergoing CRT-D implantation in real-world settings and associations between combinations of QRS duration and presence of LBBB and longitudinal outcomes, including mortality, readmission, and complications following CRT-D implantation in a large population of Medicare beneficiaries who received CRT-Ds.

SOURCE

http://jama.jamanetwork.com/article.aspx?articleid=1728715&utm_content=sidebar-related&utm_term=alsolike&utm_source=Silverchair%20Information%20Systems&utm_medium=email&utm_campaign=JAMA:OnlineFirst08/30/2015