Implantable cardiac arrhythmia devices--Part II: implantable cardioverter defibrillators and implantable loop recorders.

Implantable cardiac devices have become firmly entrenched as important therapeutic tools for a variety of cardiac conditions. The second part of this two-part review discusses the contemporary use and follow-up of implantable cardioverter defibrillators (ICD) and the implantable loop recorder. The ICD has become the standard therapy for protecting patients against sudden cardiac death. Two recent trials, the Multicenter Automatic Defibrillator Trial II (MADIT II) and the Sudden Cardiac Death Heart Failure Trial (SCD-HEFT), demonstrated that the ICD is associated with a significant survival benefit for patients with reduced ejection fraction (< 0.30-0.35), particularly if heart failure symptoms are present. The ICD has an important role in the management of other conditions associated with a high risk for sudden death, such as hypertrophic cardiomyopathy, long QT syndrome, and Brugada syndrome. The implantable loop recorder has become an important diagnostic tool for the patient with unexplained syncope.