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CLINICAL RESEARCH: HEART RHYTHM DISORDER

Risk Stratification for Primary Implantation of a Cardioverter-Defibrillator in Patients With Ischemic Left Ventricular Dysfunction

Ilan Goldenberg, MD^_*,1,_*, Anant K. Vyas, MD, MPH^,1, W. Jackson Hall, PhD^,1, Arthur J. Moss, MD^_*, Hongyue Wang, PhD, Hua He, MA, Wojciech Zareba, MD, PhD^_*, Scott McNitt, MS^_*, Mark L. Andrews, BBA^_* for the MADIT-II Investigators

^_* Cardiology Unit of the Department of Medicine, University of Rochester Medical Center, Rochester, New York
Department of Biostatistics and Computational Biology, University of Rochester Medical Center, Rochester, New York
Cardiovascular Division of the Department of Medicine, University of Buffalo, Buffalo, New York.

Manuscript received May 31, 2007; revised manuscript received July 27, 2007, accepted August 20, 2007.

^_* Reprint requests and correspondence: Dr. Ilan Goldenberg, Heart Research Follow-up Program, Box 653, University of Rochester Medical Center, Rochester, New York 14642. (Email: Ilan.Goldenberg{at}heart.rochester.edu).

Objectives: The study was designed to develop a simple risk stratification score for primary therapy with an implantable cardioverter-defibrillator (ICD).

Background: Current guidelines recommend primary ICD therapy in patients with a low ejection fraction (EF). However, the benefit of the ICD in the low EF population may not be uniform.

Methods: Best-subset proportional-hazards regression analysis was used to develop a simple clinical risk score for the end point of all-cause mortality in patients allocated to the conventional therapy arm of MADIT (Multicenter Automatic Defibrillator Implantation Trial)-II after excluding a pre-specified subgroup of very high-risk (VHR) patients (defined by blood urea nitrogen [BUN] 50 mg/dl and/or serum creatinine 2.5 mg/dl). The benefit of the ICD was then assessed within risk score categories and separately in VHR patients.

Results: The selected risk score model comprised 5 clinical factors (New York Heart Association functional class >II, age >70 years, BUN >26 mg/dl, QRS duration >0.12 s, and atrial fibrillation). Crude mortality rates in the conventional group were 8% and 28% in patients with 0 and 1 risk factors, respectively, and 43% in VHR patients. Defibrillator therapy was associated with a 49% reduction in the risk of death (p < 0.001) among patients with 1 risk factors (n = 786), whereas no ICD benefit was identified in patients with 0 risk factors (n = 345; hazard ratio 0.96; p = 0.91) and in VHR patients (n = 60; hazard ratio 1.00; p > 0.99).

Conclusions: Our data suggest a U-shaped pattern for ICD efficacy in the low-EF population, with pronounced benefit in intermediate-risk patients and attenuated efficacy in lower- and higher-risk subsets.

Abbreviations and Acronyms   BUN = blood urea nitrogen   EF = ejection fraction   ICD = implantable cardioverter-defibrillator   LBBB = left bundle branch block   MI = myocardial infarction   NYHA = New York Heart Association   VHR = very high risk

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