Dr. MJ Bazos MD, Patient Handout
Implantable Cardioverter-Defibrillator

What is an implantable cardioverter-defibrillator?

An implantable cardioverter-defibrillator (often called an ICD) is a device that briefly passes an electric current through the heart. It is "implanted", or put in your body surgically. It includes a pulse generator and one or more leads. The pulse generator constantly watches your heartbeat. It is 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 takes signals from your heart to the ICD and then takes an electric current from the pulse generator to your heart.

Why might I need an ICD?

Normally, your heart has a natural pacemaker that helps your heart beat steadily. An electrical current starts in one of the upper chambers (called the atria) of the heart and goes through the heart to the bottom chambers (called the ventricles). You may need an ICD if you have had, or are at high risk of having, certain heart rhythm problems (ventricular tachycardia or ventricular fibrillation).

What is ventricular tachycardia?

When the heart beats too fast, it's called tachycardia. When the problem begins in the bottom chambers of the heart, it's called ventricular tachycardia. When your heart goes into ventricular tachycardia, it doesn't pump blood as well. As a result, less 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?

When a ventricular arrhythmia (irregular heartbeat) becomes very fast and irregular, it's called ventricular fibrillation. The heart just quivers, and no blood is pumped to the body or the brain. A person with ventricular fibrillation usually passes out very quickly. Unless treatment is given in 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 put 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 - often, treatment 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 watches your heart rhythm. If it sees that your heart is beating fast, it delivers the treatment programmed by your doctor. The ICD can do several things:

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 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 either place, 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 doctor will program the ICD to treat your specific heart rhythm problem.

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 your 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 electric fields. The ICD is built to be protected from most home shop 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.