Indications for Implantable Cardioverter Defibrillators

Sudden death caused by cardiac arrest due to ventricular tachycardia or ventricular fibrillation remains a serious health problem worldwide. In the United States alone, cardiovascular disease accounts for over 900,000 deaths annually (1). Of these deaths, 350,000 are due to out-of-hospital cardiac arrest (2), two-thirds of which occur without prior recognition of cardiac disease (1). In the United States, 15–20% of all fatalities and 50% of all cardiac fatalities are sudden. Although sudden death caused by asystole or pulseless electrical activity is not preventable, sudden death caused by a ventricular arrhythmia can be. Prompt treatment to stop the ventricular arrhythmia before it causes death is possible. Most individuals who die suddenly from a cardiac cause have no warning and are not even diagnosed with a cardiac condition (1). The challenge is to identify the high-risk individuals for whom sudden death due to ventricular fibrillation is likely and for whom a defibrillation shock could be life saving. Although ventricular tachycardia and ventricular fibrillation can also simply represent the last cardiac rhythm in a cascade of comorbid events, a large body of data now suggests that life can be restored, meaningful life can be extended, and the risk for sudden death can be reduced by use of implantable cardioverter defibrillators (ICDs) to correct ventricular tachyarrhythmias. This chapter addresses the role of and indications for ICD therapy to treat patients with cardiovascular disease at risk for sudden cardiac death (SCD) caused by ventricular arrhythmias. Important clinical trials are reviewed that contrast medical therapies with the ICD in specific high-risk patient populations. The benefits, technological advances, and emerging areas in ICD therapy are considered in light of practical patient applications and recent clinical guidelines.