Age and Outcomes of Primary Prevention Implantable Cardioverter Defibrillators in Patients with Non-Ischemic Systolic Heart Failure
Background—The Danish Study to Assess the Efficacy of Implantable Cardioverter Defibrillators (ICD) in Patients with Non-ischemic Systolic Heart Failure on Mortality (DANISH) did not demonstrate an overall effect on all-cause mortality with ICD implantation. However, the pre-specified subgroup analysis suggested a possible age-dependent association between the ICD and mortality with survival benefit seen only in the youngest patients. The nature of this relationship between age and outcome of a primary prevention ICD in patients with non-ischemic systolic heart failure warrants further investigation.
Methods—All 1116 patients from the DANISH study were included in this pre-specified subgroup analysis. We assessed the relationship between the ICD and mortality by age, and an optimal age cut-off was estimated non-parametrically using selection impact curves. Modes of death were divided into sudden cardiac death (SCD) and non-sudden death and compared between patients younger and older than this age cut-off, respectively, with the use of Chi2-analysis.
Results—Median age of the study population was 63 years (range 21 - 84 years). There was a linearly decreasing relationship between the ICD and mortality with age, HR 1.03 (95% CI 1.003 - 1.06), p=0.03. An optimal age cut-off for ICD implantation was present at ≤70 years. There was an association between reduced all-cause mortality and the ICD in patients ≤70 years, HR 0.70 (0.51 - 0.96), p=0.03, but not in patients >70 years, HR 1.05 (0.68 - 1.62), p=0.84. For patients ≤70 years, SCD rate was 1.8 (1.3 - 2.5) and non-sudden death rate was 2.7 (2.1 - 3.5) events/100 patient years, whereas for patients older than 70 years SCD rate was 1.6 (0.8 - 3.2) and non-sudden death rate was 5.4 (3.7 - 7.8) events/100 patient years. This difference in modes of death between the two age groups was statistically significant (p=0.01).
Conclusions—In patients with systolic heart failure not caused by ischemic heart disease, the association between the ICD and survival decreased linearly with increasing age. In this study population, an age cut-off for ICD implantation at ≤70 years yielded the highest survival for the population as a whole.
- Received April 7, 2017.
- Revision received August 1, 2017.
- Accepted August 19, 2017.