CORRESPONDENCE: LETTER TO THE EDITOR
Time Dependence of Defibrillator Benefit Postcoronary Revascularization
Patrizio Pascale, MD* and
Martin Fromer, MD
* Division of Cardiology, University Hospital, 1011 Lausanne, Switzerland (Email: Patrizio.Pascale{at}chuv.ch).
In a recent issue of the Journal, Goldenberg et al. (1), in a subgroup analysis of MADIT-II (Multicenter Automatic Defibrillator Implantation Trial) (2), showed that in patients with ischemic left ventricular dysfunction who underwent coronary revascularization (CR), the efficacy of implantable cardioverter-defibrillator (ICD) therapy was not apparent when the device was implanted 6 months or less following CR. The authors concluded a time dependence of the ICD therapy efficacy and raised the question of the optimal timing of device implantation following CR. In our opinion, the issues raised by the study should instead focus on the reasons why the ICD benefit was only apparent when implanted after long time frames following revascularization.
In view of the elapsed time following CR by the time of patient enrollment, we can assume that the distinguishing feature between patients enrolled early and those enrolled late after CR resides in the probability of recurrent ischemia. This was moreover the rationale of the selected time frames based on the probability of coronary artery disease progression. Because several observations suggest a role for silent (or overt) ischemia as at least a contributing factor to sudden death (3,4), the lack of survival benefit of ICD therapy in the group characterized by a lower probability of ischemia may therefore be attributed to the prevention of recurrent ischemia by revascularization. This hypothesis is further substantiated by the CABG (Coronary Artery Bypass Graft)-Patch trial (5) where no survival benefit was conferred by prophylactic ICD in patients undergoing CABG with depressed left ventricular function.
Accordingly, this subgroup analysis (1) further confirms the importance of revascularization to lower the risk of sudden cardiac death. As it is reasonable to first treat the contributing factors rather than the consequences, a systematic evaluation of the coronary artery status with CR if required prior to prophylactic ICD implantation should be the conclusion to draw from this subset of the MADIT-II study. The investigators raised the question of the optimal timing of device implantation. However, considering time frames from up to and more than 5 years following CR, the "timing" for a significant life-saving benefit of ICD to become apparent also coincides with an increasing probability of progression of coronary artery lesions. We may then assume that a substantial proportion of patients in these time frames would actually have qualified for a coronary evaluation prior to ICD implantation.
The recruitment of patients with remote myocardial infarction and depressed left ventricular function without systematic coronary artery status evaluation was precisely one of the limitations raised by the MADIT-II study (6). Is it then appropriate to implement the MADIT-II in patients considered for prophylactic ICD after a coronary evaluation has been performed as warranted in clinical practice in light of the present observations? Indeed, Goldenberg et al. (1) observe that those patients who qualify for a revascularization procedure subsequently performed will not enjoy a significant survival benefit due to the ICD. Similarly, for those whom a revascularization procedure is not needed, hence without an ischemic substrate, the corollary of the study suggests that their risk of sudden death might be lower than expected and hence limit the detectable benefit of ICD.
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1. Goldenberg I, Moss AJ, McNitt S, et al. MADIT-II Investigators Time dependence of defibrillator benefit after coronary revascularization in the Multicenter Automatic Defibrillator Implantation Trial (MADIT)-II J Am Coll Cardiol 2006;47:1811-1817.[Abstract/Free Full Text]2. Moss AJ, Zareba W, Hall WJ, et al. Multicenter Automatic Defibrillator Implantation Trial II Investigators Prophylactic implantation of a defibrillator in patients with myocardial infarction and reduced ejection fraction N Engl J Med 2002;346:877-883.[Abstract/Free Full Text] 3. Passamani E, Davis KB, Gillespie MJ, Killip T. A randomized trial of coronary bypass surgerySurvival of patients with a low ejection fraction. N Engl J Med 1985;312:1665-1671.[Abstract] 4. Wiesfeld ACP, Crijns HJGM, Hillege HL, Tuininga YS, Lie KI. The clinical significance of coronary anatomy in post-infarct patients with late sustained ventricular tachycardia or ventricular fibrillation Eur Heart J 1995;16:818-824.[Abstract/Free Full Text] 5. Bigger JT, Coronary Artery Bypass Graft (CABG) Patch Trial Investigators Prophylactic use of implantable cardiac defibrillators in patients at high risk for ventricular arrhythmias after coronary-artery bypass graft surgery N Engl J Med 1997;337:1569-1575.[Abstract/Free Full Text] 6. Pascale P, Taffe P, Regamey C, Kappenberger L, Fromer M. Reduced ejection fraction after myocardial infarction: is it sufficient to justify implantation of a defibrillator? Chest 2005;128:2626-2632.
Related Article
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- Ilan Goldenberg and Arthur J. Moss
J. Am. Coll. Cardiol. 2007 49: 125.
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