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DictionarySeeICDEncyclopediaSeedefibrillatorimplantable cardioverter-defibrillator
Implantable Cardioverter-Defibrillator DefinitionThe implantable cardioverter-defibrillator is an electronic device to treat life-threatening heartbeat irregularities. It is surgically implanted.PurposeThe implantable cardioverter-defibrillator is used to detect and stop serious ventricular arrhythmias and restore a normal heartbeat in people who are at high risk of sudden death. The American Heart Association recommends that implantable cardioverter-defibrillators only be considered for patients who have a life-threatening arrhythmia. A recent study by the National Heart, Lung, and Blood Institute demonstrated that implantable cardioverter-defibrillators are the treatment of choice instead of drug therapy for patients who have had a cardiac arrest or heart attack and are at risk for developing ventricular tachycardia, which is a very rapid heartbeat, or ventricular fibrillation, which is an ineffective, irregular heart activity. Other studies suggest that 20% of these high risk patients would die within two years without an implantable cardioverter-defibrillator. With the device, the five-year risk of sudden death drops to five percent.PrecautionsThe implantable cardioverter-defibrillator should not be used on patients who faint from causes other than a known life-threatening ventricular arrhythmia, to treat slow heart rates, or during an emergency.DescriptionAccording to the American College of Cardiology, more than 80,000 Americans currently have an implantable cardioverter-defibrillator; 17,000 of these were implanted in 1995 alone. The battery-powered device rescues the patient from a life-threatening arrhythmia by rapid pacing and/or delivering electrical shock(s) to suspend heart activity and then allow it to initiate a normal rhythm. Before the development of the implantable cardioverter-defibrillator, most people who experienced ventricular fibrillation and were not near a hospital with a well equipped emergency team died within minutes.The implantable cardioverter-defibrillator is like a mini computer connected to the patient's heart. Newer models weigh less than 10 ounces and can be implanted beneath the skin of the chest in the pectoral region, without major surgery. A lead from the device is then inserted into the heart through a vein. The procedure is performed in an operating room under general anesthesia. Earlier versions of implantable cardioverter-defibrillators were implanted in the abdomen and required open-chest surgery to connect the electrodes to the left and right ventricles.The implantable cardioverter-defibrillator is set above the patient's exercise heart rate. Once the device is in place, many tests will be conducted to ensure that the device is sensing and defibrillating properly. The newer implantable cardioverter-defibrillators last seven or eight years. Technology and procedures continue to evolve.PreparationBefore the procedure, a complete medical history and physical exam will be done. Electrocardiography, special electrophysiologic testing, chest x ray, urinalysis, and a blood test are usually also required.AftercareThe patient is monitored for arrhythmias and to ensure that the implantable cardioverter-defibrillator is working properly. The physician also watches for signs of infection. Before the patient leaves the hospital, the device is tested again. Anti-arrhythmia drug therapy is necessary in more than half of all patients with implantable cardioverter-defibrillators, but the number of drugs and the dosages are usually reduced. Any time a significant change in anti-arrhythmia medication is made, the device will be tested again.The patient is taught how the device works, and that the shock it delivers will feel like a punch or kick in the chest. The patient is told to notify his/her physician when the implantable cardioverter-defibrillator delivers a shock, and to go to the emergency room if multiple shocks are sent within a short period of time.Although most patients with implantable cardioverter-defibrillators are glad that they have the device and feel that it has extended their lives, they do experience fear and anxiety. This stems from the sensation of the shock(s), the unpredictable circumstances under which shock(s) occurs, and unknown outcomes.RisksThere can be serious complications to the implantation of a cardioverter-defibrillator. These include inflammation of the pericardium, the sac that surrounds the heart; heart attack; congestive heart failure; and post-operative stroke. Serious infections can develop in the area around the device while the patient is initially hospitalized or up to several months later. Death due to the device's failure while being tested during surgery is an uncommon risk. The risk of death from the implantation procedure is about the same as that for a pacemaker, less than one percent. There are also potentially serious risks associated with the device's improper functioning once it is in place.ResourcesOrganizationsAmerican Heart Association. 7320 Greenville Ave. Dallas, TX 75231. (214) 373-6300. http://www.americanheart.org.Texas Heart Institute. Heart Information Service. PO Box 20345, Houston, TX 77225-0345. http://www.tmc.edu/thi.Key termsArrhythmia — A variation of the normal rhythm of the heartbeat.Cardioverter — A device to apply electric shock to the chest to convert an abnormal heartbeat into a normal heartbeat.Defibrillation — An electronic process which helps re-establish a normal heart rhythm.Ventricles — The two large lower chambers of the heart which pump blood to the lungs and the rest of the human body.Ventricular fibrillation — An arrhythmia in which the heart beats very fast but blood is not pumped out to the body. Ventricular fibrillation can quickly become fatal if not corrected.Ventricular tachycardia — An arrhythmia in which the heart rate is more than 100 beats per minute.cardioverter [kahr´de-o-ver″ter] an energy-storage capacitor-discharge type of condenser that is discharged with an inductance; it delivers a direct-current shock which restores normal rhythm of the heart.automatic implantable cardioverter-defibrillator (implantable cardioverter-defibrillator) see under defibrillator" >defibrillator.
defibrillator [de-fib´rĭ-la″ter] an apparatus used to produce defibrillation by application of brief electroshock to the heart, directly or through electrodes placed on the chest wall.automatic external defibrillator (AED) a portable defibrillator designed to be automated such that it can be used by persons without substantial medical training who are responding to a cardiac emergency.automatic implantable cardioverter-defibrillator (AICD) (implantable cardioverter-defibrillator (ICD)) an implantable device that detects tachycardia" >sustained ventricular tachycardia or fibrillation and terminates it by a shock or shocks delivered directly to the myocardium, thus preventing sudden cardiac death. Three different types of electrodes may be used: a superior vena cava spring lead, a transvenous bipolar electrode, and a ventricular patch lead. One third of the patients who have had this device implanted have received spontaneous device countershocks. Other reported side effects are similar to those of pacemakers.implantable cardioverter-defibrillator Cardiology A device implanted subcutaneously–anterior chest wall, which provides automatic electrical impulses in Pts with severe–life-threatening or treatment refractory ventricular tachycardia or fibrillation. Cf Ablation therapy. im·plant·a·ble car·di·o·ver·ter-de·fib·ril·la·tor (im-plantă-bĕl kahrdē-ō-vĕr-tĕr-dē-fibyū-lā-tŏr) A device surgically inserted into the thoracic area that monitors cardiac activity and is capable of adjusting current flow to deal with arrythmias. |