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April 22, 2021  
EDUCATION CENTER: Heart Procedures
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  • Implantable Cardioverter Defibrillator (ICD)


    An implantable cardioverter defibrillator is an instrument that operates by using electric currents to maintain the viability and functioning of the heart.
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    Click here to learn more about ICDs
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    Video courtesy of Guidant Corp.
    Patients who have had or who are at high risk of having heart rhythm problems, such as ventricular tachycardia (when the heart beats too fast and does not pump blood as effectively) or ventricular fibrillation (when an irregular heartbeat becomes very fast and irregular to prevent the heart from pumping any blood to the body or brain) may be recommended to receive an ICD. The device is surgically implanted in the patient’s body.
    ICD implantation is relatively simple procedure, and is only slightly more complicated than surgically inserting a pacemaker. When implanting an ICD, the surgeon may insert the pulse generator under the collarbone on the left or right side of the chest, or in the abdomen (stomach area). The generator is typically placed just the skin. Once the doctor implants the device, he or she will program the ICD to treat the specific heart rhythm problem.

    Detailed Description

    Copyright 2007 David DiAngelis

    The ICD constantly watches and monitors a patient’s heart rhythm. It runs like a small computer on a battery. The device includes a pulse generator and several leads. The lead is a wire that originates at the pulse generator and connects to the inside of the heart. If the ICD determines the heart is beating too fast, an electric current is sent from the from the pulse generator to the heart. The shock, which can be mildly jarring to the patient, helps maintain a steady and strong heartbeat. The ICD can perform several functions:

  • Pacing: If the heart suffers from ventricular tachycardia, the ICD can deliver several pacing signals in a row to the heart muscle. When those signals cease, the heart may go back to a normal rhythm.

  • Cardioversion: If pacing proves to be ineffective, the device may revert to cardioversion. In cardioversion, a mild shock is sent to the heart to stop fast heartbeats.

  • Defibrillation: If the pulse generator detects ventricular fibrillation, a stronger electrical current is sent to the heart. This stronger shock can stop the fast rhythm and help the heartbeat resume a normal pace.

  • Slow Pacing: The ICD can also see when the heart beats too slowly. The device can act like a pacemaker and bring the heart rate up to normal.

    Recovery time

    Most patients can be discharged to go home 24 to 48 hours after the implantation, following post-surgery device function checks. Patients are usually followed up 4 to 6 weeks later, then at intervals every 3 to 6 months. At each follow up visit, the device and its memory are checked, and standard pacing and sensing tests are performed. If necessary, appropriate programming changes can be made, or the patient's medication can be altered.

    Frequently asked questions

    Is the shocking sensation painful?

    When an ICD delivers pacing therapy, one may not feel the electric currents. Some people may feel a fluttering in their chest. However, patients do not usually complain that the device is uncomfortable or painful. Cardioversion is stronger than a pacing pulse. It feels like being thumped in the chest. The defibrillation shock is the strongest of the treatments delivered by an ICD. Many people say the shock feels like being kicked in the chest. It usually comes suddenly and lasts only a second. Pacing a slow heart rate uses very little energy, and the effects are usually not felt at all.

    How will an ICD affect my lifestyle?

    After receiving an ICD, one’s activities will be limited for the first couple of weeks, so that the body can become accustomed to the changes to the heart’s more regulated rhythms. In general, patients can expect to resume a normal daily lifestyle after a month. Doctors recommend that patients stay away from machines that could interfere with the functioning of the ICD device. Strong magnetic fields or strong electric fields are highly discouraged. The ICD is built to be protected from most home shop tools and electric appliances, including microwave ovens.

    How long do ICD devices last?

    ICDs have a battery-life of approximately five to seven years, which is monitored closely during routine visits with your doctor. When the battery is nearing depletion, the pulse generator will need to be replaced.

    Last updated: 14-Aug-07

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