What is an implantable cardioverter-defibrillator?
An implantable cardioverter-defibrillator (often called an ICD) is a device that is capable of sending an electric current through the heart. It is "implanted," or 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 then sends an electric current from the pulse generator back to your heart.
Why might I need an ICD?
Normally, your heart has a natural “pacemaker” (called the sinoatrial node, which helps your heart beat steadily) and its own electrical system. If your heart is working properly, an electrical current starts in one of the upper rooms or chambers of the heart (called the atria). The signal travels through the heart to the bottom chambers (called the ventricles). The different chambers work together to produce a regular heartbeat.
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.
What is ventricular tachycardia?
When the heart beats too fast, it's called tachycardia (say tack-ee-card-ee-ya). If the problem begins in the bottom chambers of the heart known as the ventricles, it's called ventricular tachycardia. When your heart goes into ventricular tachycardia, it doesn't pump blood very well. As a result, not enough blood is pumped to your body and your brain. You may feel your heart pounding, or you may feel dizzy or faint. If ventricular tachycardia isn't treated properly, it can be life-threatening.
What is ventricular fibrillation?
Ventricular fibrillation is when the heart’s normal electrical system becomes unsteady and causes the heart to beat very fast and unevenly within the ventricles. The heart just quivers, and little or no blood is pumped to the body or the brain. A person who is having ventricular fibrillation usually passes out very quickly. Unless treatment is given within 5 to 10 minutes, ventricular fibrillation causes death.
In people who don't have an ICD, ventricular fibrillation is treated with an external defibrillator. Paddles are placed on the outside of the chest, and an electrical shock is given through the paddles. This shock goes through the heart and stops the irregular beat. The heart then goes back to a more regular rhythm.
Unfortunately, ventricular fibrillation can occur without warning, so treatment often can't be given in time. An ICD may be recommended for you because your doctor thinks you're at high risk for having ventricular fibrillation. The ICD can quickly recognize and stop ventricular fibrillation.
How does the ICD work?
The ICD constantly keeps track of your heart rhythm. If your heart is beating too fast, it 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 only a second. Although you may feel upset for a short time after a defibrillator shock, it is good to know that the ICD is treating the heart rhythm problem.
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 can 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 be protected from 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