Implantable cardioverter-defibrillators: indications and unresolved issues.

Since the implantable cardioverter-defibrillator was first used clinically in 1980, several large randomized controlled trials have shown that therapy with this device can be beneficial in various patient populations. Evidence suggests that this therapy is useful in the secondary prevention of sudden cardiac death among patients who have survived arrhythmic events. Several trials have also shown the usefulness of implantable cardioverter-defibrillator therapy in the primary prevention of sudden cardiac death in patients with coronary artery disease and nonischemic cardiomyopathy. Other data support the use of this device for various infiltrative and inherited conditions. When used with cardiac resynchronization therapy, implantable cardioverter-defibrillators have improved survival rates and quality of life in patients with severe heart failure. Further research is needed to examine the potential benefits of implantable cardioverter-defibrillators in elderly, female, and hemodialysis-dependent patients, and to determine the optimal waiting period for implantation after myocardial infarction, coronary revascularization, and initial heart-failure diagnosis.