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Implantable cardioverter-defibrillators (ICDs) improve survival even in the oldest, sickest heart failure patients, but advancing age appears to lessen this survival advantage, researchers reported.

The analysis of pooled data from five clinical trials also showed no evidence of a greater increase in rehospitalizations among elderly ICD recipients, researcher of Duke Clinical Research Institute, and colleagues, noted in the journal published online.

More than 40% of new ICD placements occur in patients , and this percentage is But there has been uncertainly about the efficacy and safety of placing ICDs in very elderly patients, given the under-representation of patients over the age of 70 in clinical trials, Hess and colleagues noted.

"On the one hand, undergoing a potentially hazardous and expensive procedure without realizing a clinical benefit is objectionable," they wrote. "On the other hand, withholding an effective therapy is also undesirable."

23% of ICD Recipients Died

Findings from the pooled analysis should help alleviate concerns that advancing age is a barrier to the placement of ICDs, but the researchers concluded that more study is needed to confirm this since so few trials have included very elderly patients.

Of the 3,530 patients included in the pooled analysis, just 390 (11%) were age 75 or older. The median age of the patients was 62.

Around four out of five patients in all age groups (<55, 55-64, 65-74, ≥75) were male (range 78.1%-81.5%) and compared with younger patients, older patients were more likely to be white, have advanced heart failure, and have comorbidities including atrial fibrillation, hypertension, peripheral vascular disease, and pulmonary disease.

They were also more likely to have been revascularized and have elevated creatinine, left bundle-branch block, and widened QRS.

During a median follow up of 2.6 years, 323 of 1,836 ICD recipients (23%) and 463 of 1,694 nonrecipients (30.6%) died.

Patients who received ICDs were less likely to die than nonrecipients in all age groups.

"Death rates among women receiving usual care were comparable with those of men among patients aged <55 years and lower in older age groups, and among patients receiving ICDs the death rate was comparable between sexes among patients aged <55 years and lower in older age groups," the researchers wrote.

Kaplan-Meier estimates of death as a function of time and corresponding hazard ratios from the stratified Cox-proportional hazards models showed a mortality benefit of ICD therapy in all age groups.

In the total study cohort, 1,045 (71.4%) ICD recipients and 771 (60.2%) nonrecipients were hospitalized one or more times, the researchers wrote.

Among the other major findings:

• Weibull survival regression models that included continuously valued age, ICD therapy, and their interaction, without or with adjustment for baseline characteristics, indicated that point estimates for ICD therapy efficacy compared with usual care were consistent with a survival benefit across the spectrum of age.
• The absence of a survival benefit could not be ruled out above the age of 70, and the impact of ICD therapy on survival appeared to be attenuated with increasing age (two-sided posterior tail probability of no interaction is 0.02 in the unadjusted model and <0.01 in the adjusted model).
• There was no evidence of an interaction between age and ICD treatment with regard to rehospitalizations (two-sided posterior tail probability of no interaction is 0.58 in the unadjusted model and 0.44 in the adjusted model).
• In sensitivity analyses, using a quadratic model on age, there appeared to be an interaction between age with ICD treatment for death but not rehospitalization.

'Studies Should Included More Elderly Patients'

"The current analysis suggests that the survival benefit of ICD therapy exists but diminishes with increasing age," the researchers wrote. "Analyses of ICD effectiveness yielded similar results."

They noted that in their study and others, older age was associated with a reduction in treatment with beta-blockers, ACE inhibitors, and other evidence-based therapies, representing "a potential missed opportunity to improve patient outcomes."

Potential study limitations cited by the researchers included the relatively small number of patients ages 75 and older.

"The power of our study to detect small differences in ICD treatment effect was correspondingly limited, particularly among older groups," they wrote. "Because the treatment benefit of ICD therapy likely increases with time after ICD placement and the follow-up of the current analysis was short compared with some, our ability to discern a survival benefit of ICD therapy may have been correspondingly limited."

From the American Heart Association:

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