Implantable cardioverter defibrillator therapy: the sickest patients benefit the most.

At times, our clinical intuition may lead us down the wrong path, but the scientific method helps direct us back to the proper course. In 1970, Mirowski et al1 published their first experience with the standby automatic defibrillator in animals, but their innovative approach to prevent sudden cardiac death was not initially accepted by the cardiac community. Concerns about the practicality of the implanted defibrillator to save lives stimulated Mirowski and colleagues to perform additional investigations; this culminated in their 1980 publication documenting life-saving internal defibrillation with an implantable device in 3 patients.2 The era of the clinical use of the implantable cardioverter defibrillator (ICD) therapy began just 20 years ago, and progress in the field since that time has been astounding. A series of randomized ICD trials began in the early 1990s. When my colleagues and I were designing the Multicenter Automatic Defibrillator Implantation Trial (MADIT), the general attitude was that the ICD might prolong life for only a short time in patients with advanced coronary disease. Although the ICD had already been shown to be effective in terminating acute ventricular fibrillation, it was assumed that defibrillation in patients with chronic coronary disease would only be a temporizing measure, with early occurrence of death due to heart failure. This was not the case. The results of MADIT were published in 1996,3 and those of the Multicenter UnSustained Tachycardia Trial (MUSTT) in 1999.4 These 2 primary prevention trials substantiated improved survival with ICD therapy in coronary patients with nonsustained ventricular tachycardia. Two secondary prevention trials that focused on patients with aborted cardiac arrest or life-threatening cardiac arrhythmias have also been completed; these are the Antiarrhythmics Versus Implantable Defibrillators (AVID) study5 and the Canadian Implantable …