Long-Term Effect of ICDs in Nonischemic Heart Failure With Reduced Ejection Fraction: Extended Follow-Up Analysis of DANISH

Background: The most common causes of death may change over time in heart failure with reduced ejection fraction (HFrEF). These shifts can influence the risk-benefit balance of interventions such as implantable cardioverter-defibrillators (ICDs), which are designed to prevent sudden cardiac death. Long-term follow-up is therefore essential to determine whether early benefits are sustained, attenuated, or lost over time. Objectives: This study sought to examine the long-term effect of primary prevention ICD implantation, compared with usual clinical care, in patients with nonischemic HFrEF enrolled in the DANISH (Danish Study To Assess the Efficacy of ICDs in Patients With Nonischemic Systolic Heart Failure on Mortality) trial. Methods: The DANISH trial enrolled 1,116 patients with nonischemic HFrEF, left ventricular ejection fraction ≤35%, NYHA functional class II-III (class IV if cardiac resynchronization therapy was planned), and elevated natriuretic peptide levels. The primary outcome was all-cause death, and secondary outcomes were cardiovascular death and sudden cardiovascular death. In this study with extended follow-up, patients were followed until death or January 31, 2024, whichever came first. Results: During a median follow-up of 13.2 years (Q1-Q3: 11.6-14.6 years), 294 patients (52.9%) in the ICD group and 299 (53.4%) in the control group died. Compared with usual clinical care, ICD implantation did not significantly reduce the long-term rate of all-cause death (HR: 0.96; 95% CI: 0.82-1.13), but it did reduce the long-term rate of sudden cardiovascular death (HR: 0.54; 95% CI: 0.36-0.80). The effect of ICD implantation on all-cause death was consistent regardless of age (P _interaction = 0.89). However, age significantly modified the effect of ICD implantation on sudden cardiovascular death, such that ICD implantation reduced the rate of this outcome in patients ≤70 years (HR: 0.38; 95% CI: 0.23-0.62), but not in those >70 years (HR: 1.27; 95% CI: 0.56-2.89; P _interaction = 0.01). Similar trends were observed when age was analyzed as a continuous variable. The effect of ICD implantation was generally consistent across other key subgroups, including cardiac resynchronization therapy use at baseline. Conclusions: In patients with nonischemic HFrEF, during a median follow-up of 13.2 years, primary prevention ICD implantation did not reduce all-cause death, but it did reduce sudden cardiovascular death, and younger individuals appeared to derive a greater benefit.