1. No significant difference in overall mortality was found between the implantable cardioverter-defibrillator (ICD) group and the control group.
2. A significant difference in sudden cardiac death was found between the ICD group and the control group.
Evidence Rating Level: 1 (Excellent)
Study Rundown: The benefit of ICDs has been well validated by multiple randomized controlled trials for improving outcomes, such as overall mortality and sudden cardiac death, in patients with heart failure due to ischemic heart disease. Insufficient evidence has been demonstrated to show that the recommendations that results from these studies are sufficiently generalizable to other, non-ischemic causes of heart failure.
This paper reports the findings of the DANISH study, a multicenter, unblinded, randomized, controlled trial to compare outcomes in patients with non-ischemic systolic heart failure who received ICDs to those who did not. The primary outcome was death from any cause. The secondary outcomes were sudden cardiac death, cardiovascular death, resuscitated cardiac arrest or sustained ventricular tachycardia, and change from baseline in quality of life.
For the primary outcome, a significant difference was not observed between the ICD and control groups; however, when these cohorts were stratified by age, patients less than 68 years of age who received ICDs were found to have improved overall survival. The risk of sudden cardiac death was found to be halved by ICD. Despite its unblended design, this study draws strength from its use of unambiguous endpoints – death, cardiovascular death, and sudden cardiac death. However, the generalizability of these findings is limited by their relatively short follow-up period of a median of 67.6 months.
Relevant Reading: Rationale, design, and baseline characteristics of the DANish randomized, controlled, multicenter study to assess the efficacy of Implantable cardioverter defibrillators in patients with non-ischemic Systolic Heart failure on mortality (DANISH)
In-Depth [randomized controlled trial]: In this two-arm multicenter, unblinded, randomized, controlled trial carried out between 2008 and 2014, 556 patients were assigned to the ICD group and 560 patients were assigned to the control group. Baseline characteristics were comparable between the two groups. The hazard ratio for death from any cause in the ICD group, as compared with the control group, was 0.87 (95%CI 0.68 to 1.12; p = 0.28). However, in the subgroup of patients younger than 68 years of age, the rate of death from any cause was significantly lower in the ICD group than in the control group (HR 0.64; 95%CI 0.45 to 0.90; p = 0.01). Sudden cardiac death occurred in 24 patients (4.3%) in the ICD group and in 46 patients (8.2%) in the control group (HR 0.50; 95%CI 0.31 to 0.82; p = 0.005).
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