Abstract 13142: Implantable Cardioverter Defibrillators Continue to Offer Mortality Benefit After Improvement in Ejection Fraction to Above 35%: Results From the Sudden Cardiac Death in Heart Failure Trial

Abstract

Introduction: Patients (pts) discovered to have low ejection fraction (EF ≤ 35%) frequently show increase in EF to > 35% over time. The efficacy of implantable cardioverter defibrillators (ICD) to improve survival is unknown in these pts. Hypothesis: Mortality benefit with ICD therapy is less in pts whose EF improves to > 35% than those whose EF remains ≤ 35%. Methods: A total of 1875 (74%) participants of the Sudden Cardiac Death in Heart Failure Trial (SCD-HeFT) had a repeat assessment of EF 13.5 ± 6 months after randomization. We stratified them by EF ≤ 35% and > 35% based on the 1 st repeat EF after randomization and compared all-cause mortality of 649 pts randomized to placebo vs. 624 pts randomized to ICD (602 pts randomized to amiodarone were not analyzed). Follow-up started at the time of 1 st repeat EF assessment. Results: Repeat EF was > 35% in 186 (30%) pts in the ICD group and 185 (29%) pts in the placebo group (mean EF increased from 26±7% to 46±8%). The all-cause mortality rate was lower in the ICD group vs. placebo group, both in pts whose EF remained ≤ 35% and in those whose EF improved to > 35% (Table). Compared to placebo, the unadjusted hazard ratio for ICD effect on mortality was 0.72 (95% CI 0.55-0.95) in pts with repeat EF ≤ 35% and 0.58 (95% CI 0.29-1.17) in those with repeat EF > 35%. After adjustment for potential confounders, the estimated effect of ICD was 0.64 (95% CI 0.48-0.85) and 0.62 (95% CI 0.29-1.30) in patients with repeat EF ≤ 35% or > 35%, respectively (Table). We found no evidence of an interaction between treatment assignment and repeat EF for prediction of mortality (p=0.93), suggesting that the ICD effect was similar in patients with EF ≤ 35% or > 35%. Conclusions: Pts with an improvement in EF to > 35% accrued a similar relative reduction in mortality with ICD therapy as those whose EF remained ≤ 35%. However, the absolute benefit of ICD therapy was less in pts with repeat EF > 35% due to the lower mortality risk in this group.