The implantable cardioverter defibrillator (ICD) is a small, lightweight electronic device that is placed inside your body. When you have an arrhythmia, the ICD helps your heart return to its normal rhythm. This rhythm is set by signals from the heart's electrical system. A problem with these signals can cause your heart to beat too quickly, too slowly, or irregularly. This is called an arrhythmia.

A heart rhythm problem can stop the heart from pumping blood. This is called cardiac arrest and can be life threatening. (Note: cardiac arrest is not the same as a heart attack. A heart attack is when a blood vessel to the heart muscle is blocked.) Some symptoms of a fast heart rhythm may include:

• Palpitations, (a fluttering, fast heartbeat), dizziness or lightheadedness
• Fainting spells
• Weakness
• Warm, flushed feeling

You may be given an ICD if you have had a cardiac arrest or if you have a fast heart rhythm problem that could lead to cardiac arrest. The ICD is not a cure for your heart rhythm problem, but it can save your life by quickly bringing a dangerously fast heart rhythm under control. You will need an ICD for the rest of your life, so having one implanted means a lifelong commitment.

Problems with electrical signals can cause very fast heart rhythms. Two common types of heart rhythms are ventricular tachycardia (V-Tach) and ventricular fibrillation (V-Fib). Both can lead to cardiac arrest, so an ICD is usually needed.

With ventricular tachycardia, a ventricle contains a group of abnormal electrical cells called a circuit. The circuit sometimes sends out signals that make the lower chambers beat very fast. The chambers don't have time to fill with blood before the next beat, so the heart pumps less blood than the body needs, causing your symptoms. V-Tach can progress to a more serious arrhythmia called ventricular fibrillation.

With ventricular fibrillation, abnormal circuits in the ventricles sometimes send signals quickly and irregularly. The heartbeat can be so fast and uneven that the heart muscle quivers rather than pumps. A quivering heart is in cardiac arrest and can lead to death.

An ICD can do one or more of the following:

• Antitachycardia pacing (ATP): The ICD can send out a series of pulses to override a fast rhythm. This may feel like fluttering in your chest, or may not be felt at all.
• Cardioversion: If ATP doesn't slow a fast rhythm, the ICD can give the heart one or more small shocks. These break up the fast rhythm and may feel like thumps in your chest.
• Defibrillation: If the ICD senses a very fast, irregular rhythm, it quickly sends a strong shock to the heart to override the fast rhythm. You may feel this as a strong kick in your chest.
• Bradycardia Pacing: If you have a second heart rhythm problem that causes a slow heartbeat, or your heart beats too slowly after an ICD shock, your device can send pulses to get a slow heartbeat back to the right speed.

Inserting the ICD into your body is called implantation and is a minor procedure done in an operating room or cardiac catheterization lab. The ICD can be inserted near the right or left shoulder. If you prefer to have it implanted on a particular side, discuss your preference with your physician.

Before the procedure begins, you may be given some medication to help you relax. This medication will help you "sleep" through part or all of the procedure, so you won't feel pain. An incision is made in your skin below your collarbone. For an abdominal implant, a second incision is also made below your ribcage. A small pocket is made under your skin or muscle for the ICD generator to sit in. For the abdominal implant, the pocket is made near the incision below the rib cage.

The lead for the ICD is threaded through the incision into a vein in your upper chest. The lead is then guided into your heart's chambers using x-ray monitors. Electrical measurements are taken to determine a good position for the lead in the heart. For an abdominal implant, the other end of the lead is threaded under the skin from the chest to the abdomen.

The ICD generator is attached to the lead. Then, the generator is placed in the pocket under your skin. The ICD's settings are programmed to treat your heart rhythm problem. The incision is then closed and covered with a sterile dressing. (Note: A patch electrode is sometimes also used to help the ICD do its job. If one is needed, your physician will make another incision to place the patch under the skin or muscle near your heart. A lead connects the patch to the generator.)

After your ICD is implanted, you'll probably stay in the hospital for a day or two. Before you go home, you will be told how to take care of your incisions. You may have some tests to make sure the ICD is working correctly. You'll also have some follow-up visits scheduled. During these visits, the ICD's record is checked and the settings can be changed, if necessary. Your ICD's battery will also be checked. ICD batteries last three to seven years and your physician will know well in advance when the battery needs to be replaced.

When you have an event, you may feel your usual symptoms of a fast heart rhythm. If you do, find a place to sit or lie down. Put your feet up. If possible, have someone stay with you for about 15 minutes. You won't always feel the ICD working.

When you first get your ICD, you'll be given an ID card to carry. This ID card contains important information about your ICD and tells others what to do in an emergency. Show it to any physician, dentist, or other medical professional you visit. Also, because pacemakers tend to set off security devices like those found in airports and libraries, you may need to show your card to security personnel.

ICD's are well protected from outside signals, so there are very few things that can interfere with your pacemaker. But if you ever feel symptoms that make you think a device is disrupting your ICD's signals, turn the device off or move away from it. Your symptoms should stop and your ICD shouldn't be damaged. To be safe, check with your physician.

Appliances which should be safe to use include:

• Microwave ovens and other appliances in good repair
• Computers
• Hair dryers
• Power tools
• TV's and Radios
• Stereos
• Electric blankets and heating pads
• Vacuum cleaners

There are a few things to avoid that might interfere with your ICD including: very strong magnets, (like those used for an MRI or in hand-held security wands), radio transmitting tours, ham radios, certain surgical instruments and cell phones. When using a cell phone, hold it on the ear farthest away from your pacemaker. Don't carry it in your breast pocket, even when it's turned off. Also, a running car engine generates an electrical field, so avoid leaning directly over the open hood of a running car.

An ICD won't keep you from living an active life. You can usually do almost everything you did before you got your ICD. Talk to your physician about exercise and ask whether there are any activities you should avoid.