Age differences in primary prevention implantable cardioverter-defibrillator use in U.S. individuals.

Objectives: To estimate the potentially inappropriate use of implantable cardioverter-defibrillator ICDs in older U.S. adults.

Design: Retrospective study.

Setting: The National Cardiovascular Data ICD Registry.

Participants: Forty-four thousand eight hundred five individuals in the National Cardiovascular Data's ICD Registry(™) who had received ICDs for primary prevention from January 2006 to December 2008. Individuals with a prior myocardial infarction and ejection fraction less than 30% were included.

Measurements: Mortality risk was categorized using the Multicenter Automatic Defibrillator Implantation (MADIT) II risk-stratification system. Low-risk and very-high-risk individuals were considered potentially inappropriate recipients.

Results: Of 44,805 individuals, 67% (n = 29,893) were aged 65 and older, of whom 51% were aged 75 and older. A significant proportion of ICD recipients had a low risk of death (16%, n = 6,969) or very high risk of nonarrhythmic death (8%, n = 3,693). Potentially inappropriate ICD use was 10% in those aged 75 and older, much less than in younger groups (40%, <65; 21%, 65-74, P < .001). Although age was associated with a high risk of nonarrhythmic death, its influence was markedly attenuated after adjusting for comorbidities and timing of ICD implantation (odds ratio = 1.02, 95% confidence interval = 1.02-1.03, P < .001).

Conclusion: Potentially inappropriate ICD use appears significantly less--and at modest rates--in older Americans than in younger age groups. Overall, almost one-quarter of individuals may have received ICDs inappropriately based on their risk of death. Physicians appear to be conservatively referring older adults and wisely deferring those with high comorbid burden.