A cardioverter-defibrillator (ICD) is a type of medical implant device. It tracks and treats an irregular heartbeat. It sends an electric current through your heart when needed.

The ICD is smaller than a mobile phone. It has two main parts: a pulse generator and a lead. The pulse generator monitors your heartbeat. It is like a small computer that runs on a battery. The lead is a wire from the pulse generator to the inside of your heart. It sends signals and electric currents between your heart and the pulse generator. Some people need multiple leads with their ICD.


Your doctor may recommend an ICD to treat your irregular heartbeat (arrhythmia). There are many different types of arrhythmias. Treatment depends on what kind you have. An ICD is only one form of treatment. You may need an ICD if you have or are at high risk of a life-threatening ventricular arrhythmia. Examples include ventricular tachycardia and ventricular fibrillation. Having a previous heart attack, heart disease, or cardiac arrest are other reasons you may need an ICD.

Ventricular tachycardia is when the bottom chambers of your heart (the ventricles) beat too fast. When this happens, your heart has a hard time pumping blood. As a result, your body and brain don’t get enough blood. This is life-threatening.

Ventricular fibrillation is when the bottom chambers of your heart (the ventricles) beat too fast and unevenly. The heart flutters and little or no blood is pumped to your body and brain. Someone who has this type of arrhythmia is at risk of passing out. Treatment is required within minutes in order to prevent death.


A doctor or surgeon implants an ICD during minor surgery. The pulse generator is placed under your collarbone on the left or right side of your chest, or in your abdomen (stomach area). It can go in a “pocket” under your skin or in a muscle. The doctor inserts one end of the lead (wire) into a vein that goes to your heart. They move the wire through the vein until it reaches the heart. The other end of the wire gets attached to the pulse generator.

Once it is implanted, the doctor programs and tests the ICD to treat your heart rhythm problem. The process requires a short hospital stay.

How does an ICD work?

The ICD’s job is to quickly recognize and stop problems. It does this by keeping track of your heart rhythm at all times. If your heartbeat becomes irregular, the ICD delivers the treatment. Your doctor can program the ICD to do several things.

  • Pacing: For mild ventricular tachycardia, the ICD can deliver several pacing signals in a row. These signals cause your heart to return to a normal rhythm.
  • CardioversionThis is used if pacing doesn’t work. Cardioversion sends a mild shock to your heart to stop the fast heartbeat.
  • DefibrillationFor ventricular fibrillation, the ICD sends a stronger shock. This can stop the fast rhythm and help the heartbeat go back to normal.
  • Pacemaker: The ICD can detect when your heart beats too slow. It can act like a pacemaker and bring your heart rate up to normal.


When the ICD delivers pacing or acts as a pacemaker, you may not feel anything. This is because little energy is used. Some people feel fluttering in their chest. However, there is no pain or discomfort. Cardioversion is stronger. It can feel like a thump in your chest.

Defibrillation is the strongest. Most people say it feels like being kicked in the chest. It often happens all of a sudden. It lasts less than a second. It can make you upset or anxious afterwards. However, it’s important to remember that it probably saved your life.

Things to consider

An ICD does not cure arrhythmia or heart disease. It manages your condition(s) and helps prevent cardiac arrest and death. In addition to ICD, your doctor may prescribe medicine. Follow all instructions and tell your doctor what other medicines you take.

Ask your doctor for an ICD wallet ID card. It is important that you carry this at all times. You will need this when you travel and in case of an emergency.

How will an ICD affect my lifestyle?

After you get an ICD, you will need to limit activity. This allows your body to adjust and heal properly. You can slowly go back to your regular lifestyle. Ask your doctor when it is safe to drive a car again. It will vary based on your condition and the local laws. You can expect to be back to normal after a month.

You need to stay away from machines that could interfere with your ICD. Do not work near strong magnetic or electrical fields. The ICD is safe around most home power tools and electric appliances, including microwave ovens. However, make sure that all electric items are properly grounded and in good repair. Your doctor can help you understand what to avoid when you have an ICD. Machines, devices, or procedures that may cause interference, include:

  • Security metal detectors.
  • Magnets.
  • Power-generating equipment.
  • Some power tools and electronic devices.
  • Electric fences and transformer boxes.
  • Electronic mattresses or pillows.
  • Anti-theft systems.
  • Cell phones.
  • Magnetic resonance imaging (MRI).
  • Therapeutic radiation.
  • Electrolysis (electric hair removal).

When to see a doctor

Your doctor should test your ICD at regular checkups. Its generator battery can last 5 to 7 years. It can be replaced in outpatient surgery.

Getting an ICD may cause new emotions or depression. Talk to your family and a doctor if this happens to you. The doctor can recommend counselling or a support group.

Questions to ask your doctor

  • Once I have an ICD will I always need it?
  • How do I care for my wound after ICD surgery?
  • How long after getting an ICD can I return to my normal activities?
  • Can I have drive?
  • Can I have sex?
  • Can I play video games and use electronics?
  • Will I know when a shock is coming?
  • How do I know if my ICD is working or not?
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