CORRESPONDENCE: LETTER TO THE EDITOR
On Being Critical of Implantable Cardioverter-Defibrillator Therapy
Nicholas J. Stamato, MD*
* SUNY-Upstate Medical University, 30 Harrison Street, Suite 250, Johnson City, New York 13790-2143 (Email: nstamato{at}binghamton.edu).
Tung et al. (1) are to be congratulated for their insightful and meticulous analysis of the literature of randomized trials of implantable cardioverter-defibrillator (ICD) therapy. There are 2 additional points that deserve amplification and to be made regarding the use of ICDs in clinical practice. First, a material weakness that cannot be minimized is that beta-blocker therapy was applied unequally in some of the ICD trials. For example, the 5% absolute improvement in survival that Epstein (2) points to as clinically important is almost matched (4.6%) by the beta-blocker carvedilol (3). This does not negate the conclusion that ICD therapy may prolong life (as Epstein points out), but it does cast some doubt on this conclusion.
This doubt, combined with other factors, has contributed to the use of the ICD in fewer than the predicted numbers of patients (4,5). Perhaps the most significant other factor limiting the use of ICDs is the presence of comorbid conditions in patients in the general population at a higher rate than the carefully selected patients in the randomized trial. Studies such as that of Hernandez et al. (5) exaggerate this underutilization of ICD therapy by applying findings from randomized trials to patients who were dissimilar (nearly 10 years older) to patients enrolled in trials and to patients who would have been excluded from such trials, for example, because of azotemia (4–6).
Difficulty in applying ICD therapy comes not only from concern about an overestimate of ICD benefit in appropriate patients, but also from the application of randomized trial data to the universe of patients, in whom the presence of multiple medical conditions would have led to their exclusion from such trials. In these patients, with other medical conditions competing as causes of death, the benefit of ICD therapy will likely be less and the potential for ICD harm may be greater (6).
The findings of underutilization of ICD therapy may well be the manifestation of the medical community agreeing with Tung et al. (1) in their assessment of the benefit of ICD therapy (7,8).
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1. Tung R, Zimetbaum P, Josephson ME. A critical appraisal of implantable cardioverter-defibrillator therapy for the prevention of sudden cardiac death J Am Coll Cardiol 2008;52:1111-1121.[Abstract/Free Full Text]2. Epstein AE. Benefits of the implantable cardioverter-defibrillator J Am Coll Cardiol 2008;52:1122-1127.[Abstract/Free Full Text] 3. Packer M, Bristow MR, Cohn JN, et al. The effect of carvedilol on morbidity and mortality in patients with chronic heart failure N Engl J Med 1996;334:1349-1355.[Abstract/Free Full Text] 4. Ruskin JN, Camm AJ, Zipes DP, et al. Implantable cardioverter defibrillator utilization based on discharge diagnosis from Medicare and managed care patients J Cardiovasc Electrophysiol 2002;13:38-43.[CrossRef][Web of Science][Medline] 5. Hernandez AF, Fonarow GC, Liang L, et al. Sex and racial differences in the use of implantable cardioverter-defibrillators among patients hospitalized with heart failure JAMA 2007;298:1525-1532.[Abstract/Free Full Text] 6. Stamato NJ. Implantable cardioverter-defibrillators, heart failure, and patient characteristics JAMA 2008;299:285-286.[Free Full Text] 7. Levy R, DellaValle A, Atav S, et al. The relationship between glomerular filtration rate and survival in patients treated with an implantable cardioverter defibrillator Clin Cardiol 2008;31:265-269.[CrossRef][Web of Science][Medline] 8. Surowiecki J. The Wisdom of Crowds: Why the Many Are Smarter Than the Few and How Collective Wisdom Shapes Business, Economies, Societies and NationsNew York, NY: Doubleday; 2004.[CrossRef][Medline]
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