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

Background —Current recommendations require a QRS duration of ≥120ms as a condition for prescribing cardiac resynchronization therapy (CRT). This study was designed to test the hypothesis that patients with heart failure (HF) of ischemic origin, current indications for defibrillator implantation and QRS <120ms may benefit from CRT in the presence of marked mechanical dyssynchrony. Methods and Results —Patients with intraventricular dyssynchrony on echocardiography were randomly assigned to CRT or dual-chamber defibrillator implantation (CRT-D and D-ICD arm, respectively). The primary endpoint was the HF clinical composite response, which scores patients as improved, unchanged, or worsened. The secondary endpoint was the cumulative survival from HF hospitalization and HF death. An additional secondary endpoint was the composite of HF hospitalization, HF death and spontaneous ventricular fibrillation. Twenty-three of 56 CRT-D patients showed an improvement in their clinical composite response at 1 year, compared with 9 of 55 D-ICD patients (41% versus 16%, p=0.004). After a median follow-up of 16 months, the CRT-D arm showed a non-significant higher survival from HF hospitalization and HF death (p=0.077), and a significantly higher survival from the combined endpoint of HF hospitalization, HF death and spontaneous ventricular fibrillation (p=0.028). Conclusions —In this comparison of CRT-D and D-ICD, CRT improved clinical status in some patients with ischemic cardiomyopathy, mild-to-moderate symptoms, narrow QRS duration, and mechanical dyssynchrony on echocardiography. Clinical Trial Registration —URL: http://clinicaltrials.gov; Identifier: [NCT01577446][1]. [1]: /lookup/external-ref?link_type=CLINTRIALGOV&access_num=NCT01577446&atom=%2Fcircae%2Fearly%2F2013%2F04%2F16%2FCIRCEP.113.000135.atom