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?

Methods:

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.

Results:

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).

Conclusions:

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

Perspective:

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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