An implantable cardioverter defibrillator (ICD) is a small, electronic device that's implanted inside the body. It is used to correct dangerously rapid heart rhythms by delivering pulses or shocks to the heart.

The ICD has two parts: a pulse generator and one or more leads.

The pulse generator continuously checks the heart's electrical signals, and stores retrievable information for follow-up visits. If it senses a life-threatening rapid rhythm, it delivers electrical energy to return the heart to a more normal rhythm.

The leads are insulated, flexible wires that are placed in the heart. They carry electrical energy from the pulse generator to the heart. They also help the ICD keep track of the heart's activity by carrying signals from the heart to the pulse generator.

During the procedure, a local anesthetic is given by injection to numb the area where the ICD will be inserted. Then an incision is made below the collarbone to create a small pocket. For an abdominal implant, the pocket is made below the rib cage. The lead is threaded through the incision through a vein, then positioned into the heart's chambers using x-ray monitors. The lead is then tested, to be sure it's working properly. The incision is then closed and covered with a sterile dressing.

The ICD implantation usually takes between one and two hours. Generator batteries usually last five to eight years before needing replacement. Because the battery is sealed inside the generator, this involves replacing the generator itself. The generator replacement is generally simpler and shorter than the initial implantation.

To replace the generator, the ICD pocket is opened, the old generator is detached from the leads, the new generator is attached to the leads and placed in the pocket and the pocket is closed. Occasionally the lead wears out and a lead replacement is required.

ICD recipients are given an ID card to carry. This should be shown to doctors, dentists and other medical professionals. Because ICDs can set off security devices in place like airports and libraries, the card may also need to be shown to security personnel.

An ICD is not a cure for a heart rhythm problem. However, it can save a life by quickly bringing a dangerous rapid heart rhythm under control. It may provide the extra help a heart needs to relieve symptoms and allow the recipient to be active and enjoy the activities they love.