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CRT Outcomes With Very Wide QRS Duration
Study Questions:
What are the outcomes in patients receiving cardiac resynchronization therapy defibrillators (CRT-Ds) who have a very wide (≥180 ms) QRS complex duration?
Methods:
Medicare patients from the Implantable Cardioverter Defibrillator (ICD) Registry with a CRT-D and confirmed Class I or IIa guideline indications for CRT-D were matched to ICD patients without CRT despite having Class I or IIa indications for CRT. Mortality and heart failure (HF) hospitalizations over 4 years with CRT-D versus standard ICDs based on QRS complex duration (QRSD) and morphology were analyzed.
Results:
A total of 24,960 patients were included. Among those with left bundle branch block (LBBB), patients with QRSD >180 ms had a greater adjusted survival benefit with CRT-D versus standard ICD (hazard ratio [HR] for death, 0.65; 95% confidence interval [CI], 0.59-0.72) compared with those having QRSD 120-149 ms (HR, 0.85; 95% CI, 0.80-0.92) and 150-179 ms (HR, 0.87; 95% CI, 0.81-0.93). CRT-D versus ICD was associated with an improvement in survival in those with LBBB and QRSD ≥180 ms (adjusted HR for death, 0.78; 95% CI, 0.68-0.91), but not in those with LBBB and QRSD 150-179 ms (adjusted HR for death, 1.06; 95% CI, 0.95-1.19).
Conclusions:
Improvements in both survival and HF hospitalization with CRT-D were greatest in patients with QRSD ≥180 ms with or without LBBB.
Perspective:
Despite the fact that most CRT clinical trials required QRSD of ≥130 msec at enrollment, most enrolled patients had QRS duration between 150 and 180 msec. About one third of patients receiving CRT therapy are nonresponders. In the current American College of Cardiology Foundation/American Heart Association/Heart Rhythm Society guidelines, patients with LBBB and a QRSD ≥150 ms have a stronger indication for CRT-D (Class I) than patients without LBBB and a QRSD ≥150 ms (Class IIa). The authors of the present manuscript demonstrated that in patients without LBBB and QRSD ≥180 ms, there was an improvement in both overall survival and survival free of HF hospitalizations with CRT-D versus matched standard ICD patients. This is consistent with a prior patient-level meta-analysis by Cleland et al. (Eur Heart J 2013;34:3547–56). Unfortunately, there has never been a published randomized controlled trial specifically addressing non-LBBB patients. It would be beneficial for such a trial to take place. The strength of recommendations for patients with non-LBBB pattern and QRS ≥180 ms may have to be reconsidered.
Keywords: Arrhythmias, Cardiac, Bundle-Branch Block, Cardiac Resynchronization Therapy, Defibrillators, Implantable, Geriatrics, Heart Failure, Medicare, Secondary Prevention, Survival, Treatment Outcome
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