Life versus death.

Randomized clinical trials have clearly shown that the implanted cardiac defibrillator (ICD) saves lives1–3 and that cardiac resynchronization therapy (CRT) and combined ICD and CRT devices reduce both heart failure and mortality.4–6 However, during long-term follow-up of patients with these implanted devices, only a minority will use appropriate ICD therapy for life-threatening ventricular tachyarrhythmic events. For example, in the Multicenter Automatic Defibrillator Implantation Trial II (MADIT-II), only 35% of the patients in the ICD arm received appropriate ICD therapy (shock or antitachycardia pacing) during 3-year follow-up.7 The challenge facing the medical profession is how to better identify and select patients who will benefit from implanted ICD or combined ICD and CRT devices so as to achieve greater therapeutic efficacy without losing patients. During recent years, several noninvasive and invasive electrophysiological tests have been evaluated, including signal-averaged ECG, heart rate variability, heart rate turbulence, T-wave alternans, and programmed electrophysiological testing, but the risk-stratification results from these tests have not been very encouraging. Recently, Goldenberg et al demonstrated that the ICD:conventional therapy hazard ratio in patients with advanced renal disease (blood urea nitrogen 50 mg/ dL) and in good-risk patients without adverse clinical factors such as heart failure, atrial fibrillation, older age, and wide QRS complex, renal dysfunction was close to 1.0 in 35% of the ICD-treated patients, with no evident benefit from the ICD.8 The remaining 65% of the at-risk ICD-treated patients received considerably enhanced benefit from the ICD, with a 50% or greater reduction in mortality. These findings are encouraging, but we should be able to do better.