Risk identification for sudden cardiac death—Implications for implantable cardioverter-defibrillator use

In the decade following the first human implantation of an automatic defibrillator in 1980 by Mirowski et al,’ the use of the automatic implantable cardioverter-defibrillator (ICD) in patients at risk of sudden cardiac death has increased dramatically. By early 1992 over 26,000 devices had been implanted worldwide (Cardiac Pacemakers, Inc, data on file; courtesy of M. O-Neal).” Large published series of ICD recipients have demonstrated sudden deathfree survival rates of approximately 95% over periods of up to 5 years. 4-11 A sudden death rate of 1% per year in patients receiving an ICD has recently been reported over a lo-year period.” The ICD is thus highly efficacious at preventing sudden death in high-risk patients. This review will address methods of identifying risk of sudden cardiac death and subsequent patient selection for ICD therapy in cardiac arrest survivors and in patients with sustained and nonsustained ventricular tachycardia (VT), unexplained syncope, and following myocardial infarction (MI). It will also examine the problems of risk stratification for sudden cardiac death in substrates other than coronary artery disease, such as hypertrophic cardiomyopathy (HCM). idiopathic dilated cardiomyopathy (IDM). and long QT syndrome (LQTS).