An Individual Patient Meta-Analysis of Five Randomized Trials Assessing the Effects of Cardiac Resynchronization Therapy on Morbidity and Mortality in Patients With Symptomatic Heart Failure

Study Questions:

What variables prior to device implantation predict the response to cardiac resynchronization therapy (CRT)?


A meta-analysis of five randomized trials (MIRACLE, MIRACLE ICD, CARE-HF, REVERSE, RAFT) was conducted comparing CRT with no CRT with more than 6 months of follow-up. The two outcomes were all-cause mortality and first hospitalization for heart failure or death. A total of 4,317 patients were studied comparing CRT with no active control or CRT-D with implantable cardioverter-defibrillator (ICD). Patients with New York Heart Association (NYHA) functional class I and not in sinus rhythm or with a pre-existing pacemaker were excluded from the trial.


A total of 3,782 patients were analyzed. The median age was 66 (58-73) years, QRS duration was 160 (146-176) ms, left ventricular (LV) ejection fraction was 24% (20-28%), and 78% had a left bundle branch block (LBBB); 22% of patients were women. A significant interaction between CRT and QRS duration was observed for both the composite outcome (p < 0.0001) and all-cause mortality alone (p = 0.0013), suggesting that a longer QRS may receive greater benefit from CRT. After adjusting for QRS duration, LBBB on electrocardiogram was not a significant predictor of CRT responder.


In those patients in sinus rhythm, QRS is a predictor of the effects of CRT on morbidity and mortality with symptomatic heart failure and LV dysfunction.


This meta-analysis confirms that patients with a QRS >140 ms with >NYHA class II heart failure symptoms and moderate to severe LV dysfunction in sinus rhythm will benefit from CRT therapy.

Clinical Topics: Arrhythmias and Clinical EP, Heart Failure and Cardiomyopathies, Implantable Devices, EP Basic Science, SCD/Ventricular Arrhythmias, Acute Heart Failure

Keywords: Heart Diseases, Defibrillators, Follow-Up Studies, Cardiac Pacing, Artificial, Heart Failure, Bundle-Branch Block, Ventricular Function, Pacemaker, Artificial, Electrocardiography, New York, Cardiac Resynchronization Therapy

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