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Implantable cardioverter-defibrillatorPage Content: ICDInformation An implantable cardioverter-defibrillator (ICD) is a device designed to quickly detect a life-threatening, rapid heartbeat coming from the bottom chamber of the heart. It converts the abnormal rhythm back to normal by delivering an electrical shock to the heart. An ICD can effectively prevent sudden cardiac death. An ICD is a minicomputer that consists of:
All ICDs have a built-in pacemaker. Pacing may be necessary to support the heart in some instances, for example, after a shock, or during a very slow heart beat. The pacemaker also allows the device to correct heartbeats that are too fast. The ICD continously monitors the heartbeats for regularity. It only delivers a shock to the heart when it senses a life-threatening rhythm. During the implantation of a pacemaker-type ICD, electrodes are inserted through the veins into the heart. The pulse generator is surgically buried under the skin of the chest, generally below the left collarbone. Who needs an ICD? In some people, the lower chamber of the heart either suddenly starts beating in a disorganized manner (ventricular fibrillation or VF), or it starts beating very rapidly (ventricular tachycardia or VT). Both VF and VT can make the heart stop pumping blood, leading the person to a sudden loss of consciousness or death. Abnormal rhythms, like VT and VF, require emergency treatment and are best treated in hospital coronary care units. In these units, VT and VF can be converted back to the normal rhythm by an electric shock given across the chest (external defibrillation). Many episodes of VT or VF, however, occur outside hospitals and people without ICDs often die because defibrillation is not immediately available. Candidates for ICDs are people at risk of sudden death, including:
Occasionally, an electrophysiological study (EPS) is required to make the decision about ICD implantation. The EPS is a special test conducted by a cardiologist with a specialization in arrhythmias. The EPS measures how much the heart is at risk for an event that could prove fatal. What to expect after ICD implantation The recovery time after the ICD implantation is quite short. Hospital stays are rarely longer than 1 day; and patients quickly return to prior activity levels. Full recovery of activity can be expected in about 4 to 6 weeks. You will be discharged from the hospital with a wallet card listing the specifications of your ICD and providing contact information for emergencies. This wallet card should always be with you when you go out. You will need to make regular visits to the doctor so the ICD can be monitored. The monitoring shows whether the device is sensing the heartbeat properly, how many shocks have been delivered, and how much power is left in the batteries. The ICD batteries are designed to last 5 to 8 years. When they are about to run down, the ICD generator must be replaced. This requires minor surgery. The ICD generator is metal and will be detected by metal detectors such as those in airports or public places with safety checks. For air travel, public events, and admission to certain areas you will need to show your wallet card to the security personnel to prevent setting off any alarms. People with ICDs still need to follow their doctor's advice about medication, diet, and exercise. Benefits of the ICD Among patients considered good candidates for an ICD, the ICD has shown to prolong life by preventing sudden death. The device provides peace of mind, relieving concerns about fainting spells and risks of death. Most patients adapt to the uncertainty of the shocks. Most patients also can resume driving. Potential risks of the ICD The ICD is implanted through a surgical procedure which in itself might result in death, but this is very rare. The most common problem with the ICD is that it sometimes delivers shocks when you do not need them. Even though a shock lasts a very short time, you can usually feel it. Every shock you feel should be notified to your doctor. Potential ICD malfunctioning can be prevented by the incorporation of audible alerts that can be programmed by your electrophysiologist. If your ICD alert goes off, you should promptly contact your doctor. WARNING: In June 2005, certain ICD models and biventricular pacemaker-defibrillators were recalled by the manufacturer because of a circuitry flaw that prevent the devices from delivering therapeutic electrical shocks when needed. The problem may result in patient death. Two deaths are believed to be associated with the malfunction. Although the U.S. Food and Drug Administration did not make any specific recommendations, the agency encourages patients who may have such a device to ask their health care doctor if they should have it removed or replaced. The devices affected by this recall are:
References US Food and Drug Administration. FDA Issues Nationwide Notification of Recall of Certain Guidant Implantable Defibrillators and Cardiac Resynchronization Therapy Defibrillators. Rockville, MD: National Press Office; June 17, 2005. Paper P05-29. Al-Khatib SM, Anstrom KJ, Eisenstein EL, et al. Clinical and economic implications of the Multicenter Automatic Defibrillator Implantation Trial-II. Ann Intern Med. 2005 Apr 19;142(8):593-600. Goldstein NE, Lampert R, Bradley E, Lynn J, Krumholz HM. Management of implantable cardioverter defibrillators in end-of-life care. Ann Intern Med. 2004 Dec 7;141(11):835-8. Illustrations
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