Electrocardiographic Predictors of Arrhythmic Death

Sudden Cardiac Death (SCD) refers to death that occurs within 1 hour of the onset of symptoms.Because the majority of SCD occurs as an unwitnessed out-of-hospital event, data on the exact mechanisms are limited.However, in small series of patients who experienced SCD while wearing an ambulatory monitor 1,2 more than 80% of SCD episodes were noted to be due to ventricular tachyarrhythmias; therefore, SCD usually implies arrhythmic death and the terms are often used synonymously.SCD is among the leading causes of death in the developed world, including 350,000-400,000 cases annually in the United States. 3,4Prevention efforts are limited by the unpredictable onset of lethal arrhythmias and the rapid progression to death.Arrhythmia suppression with antiarrhythmic medications has proven ineffective and, in some cases, hazardous. 5Thus, current management strategies have two major components: aggressive treatment of the risk factors and cardiovascular conditions that predispose to SCD (e.g., hypertension, coronary heart disease, and heart failure); and in patients at high risk for arrhythmic death, the increasing use of implantable cardioverter defibrillators (ICDs).Although ICDs have proven to be powerful tools in both the primary 6-10 and secondary prevention of SCD, 11,12 identifying the patients who should receive an ICD remains a challenge.Current guidelines for ICD implantation include patients at the highest risk of SCD, but this represents only a minority of those who will have an event. 13Paradoxically, many of the patients who are covered by these guidelines will never experience SCD.This paradox is a reflection of the manner in which ICD indications have evolved.ICD indications are derived from randomized trials that,