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Randomized clinical trials have shown that implantable cardioverter-defibrillators (ICDs) can substantially reduce mortality from sudden cardiac death by treating ventricular arrhythmias in certain patients with cardiovascular disease. Over the past 25 years the use of ICDs has increased immensely, and the number of patients with these devices continues to rise.To review the literature on ICDs, including data on the prevention of excessive or inappropriate shocks, and the management of patients who have experienced ICD discharge.The authors searched the PubMed and MEDLINE databases for articles published in English between January 1990 and September 2006. The guidelines of the ACC, AHA, and Heart Rhythm Society were also searched. A combination of keywords were used to perform the search, including "defibrillators", "implantable", "electric counter-shock", "tachycardia therapy", "ventricular tachycardia", "supraventricular tachycardia", "antiarrhythmic agents", and "quality of life". Emphasis was placed on randomized controlled trials, but prospective cohort studies were also included. Case studies were omitted from the search.A total of 72 trials, cohort studies, scientific statements, and guidelines were included in the review. Two trials found that 13% and 22% of patients with ICDs received inappropriate shocks owing to a variety of causes, which included atrial arrhythmias or other supra-ventricular tachycardias, lead failure, electromagnetic interference, and oversensing of T waves or diaphragmatic myopotentials. Four studies demonstrated that ICD shocks adversely affected patient quality of life. Effects included the following: feelings of poor health; low psychological, physical, and emotional wellbeing; depression; anxiety; panic attacks; and agoraphobia. Several studies reported that antitachycardia pacing, ICD programing with a sudden-onset algorithm or ventricular rate stability criteria, or the use of a dual-chamber ICD incorporating atrial-sensing capabilities, reduced the rate of ICD shocks (both appropriate and inappropriate) and, therefore, helped to improve patient quality of life. Antiarrhythmic medication, while not indicated as a replacement for ICD therapy, was reported to reduce the rate of shocks in seven separate studies. Medications trialed included racemic sotalol, azimilide (an investigational class III antiarrhythmic drug), β-blockers (with and without amiodarone), and statins. Gehi et al. recommend that, in the event of an ICD shock preceded by shortness of breath, syncope, chest pain, or palpitations, the patient should be assessed by a physician who specializes in emergency medicine, and an electrophysiologist. This assessment will help to determine the appropriateness of the shock, and whether the shock was triggered by a change in the patient's clinical status (e.g. heart failure, active coronary disease, or electrolyte imbalance).The occurrence of excessive ICD shocks can be controlled with effective programing of the device and the use of antiarrhythmic medication. These measures can improve the patient's quality of life while preserving the efficacy of the ICD.