Comparison of Implantable Cardioverter Defibrillator Therapy and Medical Therapy in Individuals Aged 75 and Older

To the Editor: Implantable cardioverter defibrillator (ICD) therapy has been shown to reduce mortality in high-risk individuals for primary and secondary prevention of sudden cardiac death (SCD),1-3 but the benefit and safety of the ICD in elderly adults is unclear because of controversial results obtained in observational studies and the lack of randomized trials in individuals in this age group.4-6 Of all individuals consecutively referred to the echocardiography laboratory for a transthoracic echocardiogram between January 2008 and April 2012, 607 aged 75 and older with left ventricular ejection fraction of 35% or less were identified, and all with a potential indication for ICD according to Class I or IIa recommendations of the 2008 guidelines of the American Heart Association/American College of Cardiology were selected. Subjects were divided into two groups: those in whom an ICD device had been implanted (ICD group) and those with a potential indication for ICD but who did not receive the device because of the decision of the individuals or the advice of the physician in charge (non-ICD group). The primary endpoint was a composite of death from any cause and unplanned hospitalization for heart failure or ventricular tachycardia (cardiovascular events), whichever occurred first. A multivariate Cox regression analysis was performed to identify significant predictors of cardiovascular events and mortality. Two hundred eighty-six individuals with a mean age 82 ± 5 of were included. During follow-up, an ICD was implanted in 76. Individuals with an ICD were younger (79 vs 83) and more likely to be male (90% vs 65%); be in New York Heart Association (NYHA) functional Class III (33% vs 11%); and use beta-blockers (89% vs 71%), angiotensin-converting enzyme inhibitors or angiotensin receptor blockers (90% vs 79%), and anti-aldosterone drugs (71% vs 47%). During the follow-up of 25 ± 15 months, total mortality was 42% and cardiovascular events occurred in 62% of subjects. After a multivariate analysis, only beta-blocker therapy was shown to be an independent protective variable against total mortality (hazard ratio (HR) = 0.4, 95% confidence interval (CI) = 0.3–0.7). ICD therapy did not reduce overall mortality or cardiovascular event rate (Figure 1). Data regarding the benefit of ICD in elderly adults are limited and controversial.4-6 Combined data from five randomized controlled trials on ICD implantation for primary prevention suggest that ICD reduces all-cause mortality in individuals aged 75 and older (HR = 0.73, 95% = CI 0.51–0.97).7 In contrast, a subgroup analysis of the Sudden Cardiac Death in Heart Failure Trial found that ICD therapy did not reduce mortality in individuals aged 65 and older.3 Moreover, in a meta-analysis of three secondary prevention ICD trials (Antiarrhythmics vs Implantable Defibrillator study, Cardiac Arrest Study Hamburg, Canadian Implantable Defibrillator Study), 252 subjects aged 75 and older did not experience any significant reduction in total or arrhythmic mortality.8 Other studies have concluded that, although older ICD recipients have arrhythmic events and SCD rate similar to those of their younger counterparts, all-cause and noncardiac mortality tend to be significantly higher in elderly adults, probably because of their frailty.9, 10 The current study assessed the benefit of ICD and the prognostic factors related to cardiovascular events in an elderly population with a potential indication for ICD implantation. Because the study was not randomized, there were some differences in baseline characteristics and medical therapy between the two study groups. To avoid possible biases, these variables (NYHA class, pharmacological treatment, comorbidities) were included in the multivariate analysis. Beta-blocker therapy was the only independent variable that was protective (odds ratio = 0.43, 95% CI = 0.27–0.70) against mortality. The study population did not benefit from ICD in terms of primary endpoint-free survival or lower mortality. This may be because older adults are usually frail and have more comorbidities and at more-advanced stages. These factors increase mortality in the elderly population and dilute the clinical benefit of ICD therapy. Furthermore, consistent with the current results, individuals with appropriate ICD shocks had higher mortality than those without ICD shocks (64% vs 24%), suggesting that having an ICD indicates poor prognosis because of unfavorable clinical status and does not necessarily save lives. Better adjustment of medical treatment to current clinical recommendations would have a greater clinical effect. Nevertheless, well-designed randomized controlled studies to ascertain the value of ICD in older adults are needed. Conflict of Interest: The editor in chief has reviewed the conflict of interest checklist provided by the authors and has determined that the authors have no financial or any other kind of personal conflicts with this paper. Author Contributions: Cortés: study design, data interpretation, statistics, drafting the article. Farré, Palfy: data interpretation, critical revision of article. García, Martín, Hernández, Romero, López: collected data. Briongos, Benezet, Franco, Rubio: study design, data interpretation. All the authors have read and approved the manuscript. Sponsor's Role: None.

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