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Implantable Cardioverter Defibrillation (ICD)

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An implantable cardioverter defibrillator (ICD) is a miniaturized computer that monitors the heart’s rhythm for very fast and potentially dangerous rhythm disorders, and it delivers therapy when a dangerously fast heart rhythm is detected. Yet today's ICDs are small enough to fit easily in the palm of your hand.


While the device is helping your heart maintain its rhythm, it is also storing information that can be used by your doctor to program the ICD.

How It Works

The device is implanted under the skin and attached to one or more leads, which are thin wires. The leads are inserted through a vein to the heart. One end of the lead is placed in or on the heart muscle and the other end is connected to the ICD system. The leads pick up your heart rhythm and transmit this information to the ICD, which adapts its response to your needs. As soon as an abnormal heart rhythm occurs, the ICD can send a shock to the heart muscle to defibrillate it or stop the cycle of rapid twitching.

Some patients are not even aware of the shock when it occurs. Others say it feels like being kicked in the chest. While it may be uncomfortable to receive a shock, it means your ICD responded to a very dangerous rhythm disorder.

ICDs can provide lower- and higher-energy therapy to treat rhythm disorders.

Photo of an ICD: ICDs treat dangerously fast rhythm disorders. 

Implanting the ICD

Usually, the procedure for an implanted cardiac device involves medication to help you relax, but you will still be aware of your surroundings and will be able to hear and even talk with the medical team as the procedure is being conducted. Numbing medication will be given where the incision is to be made. You may, however, feel some pressure while the device is being implanted.

The procedure to place an ICD typically follows these steps:

  • Your doctor makes a small cut in the upper chest and locates a vein
  • A small puncture is made in the vein and the leads are guided down the vein to the heart
  • The surgical team monitors the progress of the leads using a large overhead monitor called a fluoroscope
  • Once they are in place, your doctor tests the leads to make sure they are in the best position to deliver energy to the heart
  • Your doctor plugs the leads into the ICD
  • Your doctor makes a pocket by separating the skin and underlying tissue from the muscle beneath the tissue and places the ICD in the pocket
  • The incision is closed

The length of the surgery depends on what kind of device you are getting, as well as your specific anatomy and the time it takes to locate a good position for the lead. Implanting an ICD can take a number of hours.

Benefits and Risks

Your ICD has the potential to sense and treat a dangerously fast or quivering heartbeat in the lower half of your heart so you can live a longer, more productive and healthier life. With your ICD, you may be able to do all of the things you used to do—and possibly more.

As with any surgery, there are risks involved with having an ICD implanted. Your doctor is the best source of information about risks. A small percentage of patients may develop complications from the implant surgery including infection, a reaction to a drug used during surgery or the device itself, blood loss or damage to a blood vessel, the heart wall or other organ. Individual risks are best evaluated by your doctor. Generally, risks depend on age, general health, specific medical condition and heart function. Talk to your doctor to better understand your potential benefits and risks.

See Important Safety Information for additional information.

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Last Reviewed: March 11, 2010 900245