Author + information
- Nicholas J. Stamato, MD* ()
- ↵*SUNY-Upstate Medical University, 30 Harrison Street, Suite 250, Johnson City, New York 13790-2143
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).
- American College of Cardiology Foundation
- Tung R.,
- Zimetbaum P.,
- Josephson M.E.
- Epstein A.E.
- Surowiecki J.