A Randomized Study of CRT-D Versus Dual-Chamber ICD in Ischemic Cardiomyopathy With Narrow QRS: The NARROW-CRT Study

Study Questions:

Does cardiac resynchronization therapy (CRT) improve outcomes in patients with a QRS <120 ms and an ischemic etiology for heart failure (HF) who have evidence of dyssynchrony?


The NARROW-CRT study was a multicenter randomized trial for CRT-defibrillator (CRT-D) versus dual-chamber implantable cardioverter-defibrillator (D-ICD) therapy in patients with ischemic HF (left ventricular ejection fraction ≤35%), New York Heart Association (NYHA) II-II symptoms, a QRS ≤120 ms, and mechanical dyssynchrony on echocardiogram (septal-lateral wall delay of ≥60 ms). The primary endpoint of interest was a HF clinical composite score at 12 months, which classified patients as improved (improved NYHA class), worsened (death, HF hospitalization, worsening NYHA class), or unchanged.


Of 1,290 patients referred for ICD implant, 233 patients met baseline criteria and 120 of these had evidence of dyssynchrony and were randomized to CRT-D (n = 60) or D-ICD therapy (n = 60). The mean ± standard deviation QRS duration was 107 ± 14 and 104 ± 14 ms in the CRT-D and D-ICD, respectively. At 1 year, biventricular pacing was 99% in the CRT-D group and right ventricular apical pacing was 1% in the D-ICD group. There were 11 deaths and 16 hospitalizations for HF. In the CRT-D group, 23/56 (41%) had improvement in the HF clinical composite score versus 9/55 (16%) in the D-ICD group (p = 0.004). Survival free of HF hospitalization or death was not significantly higher with CRT-D therapy (p = 0.077), but CRT-D patients had improved survival free of death, HF hospitalization, or ICD shock for ventricular fibrillation (p = 0.028).


The authors concluded that CRT improves clinical status in some patients with ischemic HF and a narrow QRS.


In this small randomized trial, CRT-D appeared to lead to improved clinical outcomes in patients with systolic HF and narrow QRS. This is in contrast to the ECHO-CRT study, which was just halted due to lack of efficacy. In ECHO-CRT, QRS duration was defined as <130 ms with evidence of dyssynchrony on echo. Thus, results are conflicting regarding the benefit for CRT-D in patients with HF and a narrow QRS.

Clinical Topics: Arrhythmias and Clinical EP, Heart Failure and Cardiomyopathies, Noninvasive Imaging, Implantable Devices, SCD/Ventricular Arrhythmias, Acute Heart Failure, Echocardiography/Ultrasound

Keywords: Myocardial Ischemia, Defibrillators, Ventricular Fibrillation, New York, Cardiac Resynchronization Therapy, Heart Diseases, Cardiac Pacing, Artificial, Cardiomyopathies, Cardiology, Heart Failure, Ventricular Function, Echocardiography

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