What is an implantable cardioverter-defibrillator?
An implantable cardioverter-defibrillator (often called an ICD) is a device that keeps track of your heartbeat and, if necessary, sends an electric current through the heart.
An ICD is "implanted" in your body, meaning it is put in your body surgically. It is not much bigger than a cell phone, and has two main parts: a pulse generator and one or more leads. The pulse generator constantly keeps track of your heartbeat. It’s like a small computer that runs on a battery. The lead (say: "leed") is a wire from the pulse generator to the inside of your heart. The lead sends signals from your heart to the ICD and, if necessary, sends an electric current from the pulse generator back to your heart.
Why might I need an ICD?
Sometimes, your heartbeat may become irregular. A heartbeat that is not regular is called arrhythmia (say: “ah-rith-mee-ya”). There are many different types of arrhythmias. Treatment for arrhythmia depends on what kind of arrhythmia you have. You may need an ICD if you have had or are at high risk of having certain life-threatening arrhythmias, including ventricular tachycardia and ventricular fibrillation.
Ventricular tachycardia (say: “tack-ee-card-ee-ya”) is when the bottom chambers of your heart (the ventricles) beat too fast (called tachycardia). When this happens, your heart doesn’t pump blood very well. As a result, your body and brain don’t get enough blood. If it isn’t treated properly, this type of arrhythmia can be life threatening.
Ventricular fibrillation is when the bottom chambers of your heart (the ventricles) beat very fast and unevenly (called fibrillation). The heart just quivers, and little or no blood is pumped to the body and brain. A person who is having this type of arrhythmia usually passes out. To prevent death, a person having ventricular fibrillation needs treatment as soon as possible, within a few minutes.
Your doctor may recommend an ICD for you if you have chronic (long-term) ventricular tachycardia, or if you are at high risk for having ventricular fibrillation. The ICD can quickly recognize and stop these problems.
How does the ICD work?
The ICD constantly keeps track of your heart rhythm. If your heart beat becomes life-threatening, the ICD delivers the treatment programmed by your doctor. The ICD can do several things:
- Pacing: If you have ventricular tachycardia that isn't too severe, the ICD can deliver several pacing signals in a row. When those signals stop, the heart may go back to a normal rhythm.
- Cardioversion: If the pacing doesn't work, cardioversion can be used. In cardioversion, a mild shock is sent to the heart to stop the fast heartbeat.
- Defibrillation: If ventricular fibrillation is detected, a stronger shock is sent. This stronger shock can stop the fast rhythm and help the heartbeat go back to normal.
- Pacemaker: The ICD can also detect when your heart beats too slowly. It can act like a pacemaker and bring your heart rate up to normal.
What does treatment with an ICD feel like?
When the ICD delivers pacing therapy, you may not feel anything. Some people feel a fluttering in their chest. They usually say that it doesn't feel uncomfortable or painful.
Cardioversion is stronger than a pacing pulse. It feels like being thumped in the chest.
The defibrillator shock is the strongest treatment. Many people say it feels like being kicked in the chest. It usually comes suddenly and lasts less than a second. Although you may feel upset for a short time after a defibrillator shock, it is good to know that the ICD probably saved your life.
Pacing a slow heart rate uses very little energy. You may not feel it at all.
How is an ICD implanted?
The ICD is usually implanted during a minor surgical procedure. The pulse generator may be implanted either under your collarbone on the left or right side of your chest, or in your abdomen (stomach area). In any of these places, the generator may be put in a "pocket" the doctor makes under your skin or, sometimes, in a muscle. One end of the lead wire is put into a vein that goes to your heart. The wire is moved through the vein until it reaches the heart. The other end of the wire is attached to the pulse generator.
Once it is implanted, the ICD is programmed and tested by the doctor to treat your specific heart rhythm problem. This usually requires a short hospital stay. The generator battery should be tested during your regular check-ups and can last up to seven years. It can be replaced in outpatient surgery.
How will an ICD affect my lifestyle?
So that you can heal well, your doctor will want you to limit your activities for the first few weeks after you get the ICD. Then you can slowly go back to a normal lifestyle. Depending on your condition and your local laws, your doctor will tell you when it's safe for you to drive a car. In general, you can expect to be back to normal after a month.
You'll need to stay away from machines that could interfere with your ICD. You shouldn't work near strong magnetic fields or strong electrical fields. The ICD is built to work around most home power tools and electric appliances, including microwave ovens. However, you need to be certain that all electric items are properly grounded and in good repair. Your doctor will help you understand what to avoid when you have an ICD.
Written by familydoctor.org editorial staff