When you have heart failure, the lower chambers of your heart (the ventricles) aren't able to pump as much oxygen-rich blood as the body needs. Some people who have heart failure also may have abnormal heart rhythms that can cause sudden death.

The heart may beat so fast that the ventricles don't have time to fill with blood. This type of abnormal rhythm is called ventricular tachycardia (say "ven-TRICK-yuh-ler tack-ih-KAR-dee-uh"). Some types of ventricular tachycardia may lead to ventricular fibrillation (say "ven-TRICK-yuh-ler fib-ruh-LAY-shun"). With ventricular fibrillation, the heart quivers, or flutters, and stops pumping blood. Then, if the heart stops beating, this is called cardiac arrest. Cardiac arrest causes sudden death.

An ICD is a battery-powered device that can fix an abnormal heart rhythm and prevent sudden death.

An ICD is always checking your heart rate and rhythm. If the ICD detects a life-threatening rapid heart rhythm, it may try to slow the rhythm back to normal using electrical pulses. If the dangerous rhythm does not stop, the ICD sends an electric shock to the heart to restore a normal rhythm. The device then goes back to its watchful mode.

Some ICDs also can fix a heart rate that is too slow without using a shock. The ICD can send out electrical pulses to speed up a heart rate that is too slow.

Whether you get pulses or a shock depends on the type of ICD, the type of heart problem that you have, and the way the doctor programs the ICD to respond to it.

In some people who have heart failure, the ventricles don't beat at the same time. If these people also have a risk for abnormal heart rhythms, they may get a device that combines an ICD and a biventricular (say "by-ven-TRICK-yuh-ler") pacemaker. This pacemaker is also called cardiac resynchronization therapy (CRT). This type of pacemaker uses electrical pulses to make the ventricles pump at the same time. The ICD part of the device can give a shock to fix an abnormal heart rhythm.

Your doctor will put the ICD in your chest during minor surgery. You will not have open-chest surgery. You probably will have local anesthesia. This means that you will be awake but feel no pain. You also will likely have medicine to make you feel relaxed and sleepy.

The doctor will make an incision (cut) in the skin just below your collarbone or at the side of your chest. The doctor will put the ICD leads (wires) through the cut. For one type of ICD, your doctor puts one or two leads in a large blood vessel and threads them into the heart. For another type, the lead may be placed under the skin through a small cut in the middle of your chest. Then your doctor connects the leads to the ICD. Your doctor puts the ICD under the skin of your chest and closes the cut. Your doctor also programs the ICD.

Most people spend the night in the hospital, just to make sure that the device is working and that there are no problems from the surgery.

You may be able to see a little bump under the skin where the ICD is placed.

The shock from an ICD hurts briefly. It's been described as feeling like a punch in the chest. But the shock is a sign that the ICD is doing its job to keep your heart beating. You won't feel any pain if the ICD uses electrical pulses to fix a heart rate that is too fast or too slow.

There's no way to know how often a shock might occur. It might never happen.

It's possible that the ICD could shock your heart when it shouldn't. If that were to happen, you would have pain. The shock could make you fall out of bed, and that could injure you. You also might be afraid or worried about when the ICD might shock you again.

In rare cases, the shock could cause ventricular fibrillation. If this happened, the ICD would shock your heart again to stop the abnormal rhythm.

Many people say that they have a good quality of life with an ICD. But shocks—and the fear of shocks—can make some people worry too much. They may be afraid all the time that the ICD might shock them. This worry can reduce a person's quality of life.

An ICD often is placed in people with heart failure who have survived a dangerous abnormal rhythm. The ICD would protect them if they get another abnormal heart rhythm.

But it also may be offered to people with heart failure who haven't had an abnormal heart rhythm but are at risk for one.

You will have tests to see whether you are at risk for abnormal heart rhythms. These may include an electrocardiogram (EKG, ECG), an echocardiogram, or an electrophysiology study.

Your doctor will use these test results and your medical history to figure out if an ICD could help you. Your doctor also will rely on guidelines that help find out who might benefit from an ICD.^{footnote 1} You and your doctor can work together to decide whether you want to get an ICD.

Your personal feelings are just as important as the medical facts. Talk with your doctor about what matters most to you.

Your doctor may talk with you about a few things. These include whether:

• You're taking medicine to treat heart failure and to prevent abnormal heart rhythms.
• You're expected to live more than 1 year.
• Your ejection fraction is lower than normal.
• You have had a heart attack.

An ICD can prevent sudden death from an abnormal heart rhythm. ICDs may also help certain people who have heart failure live longer. How much an ICD might help you depends on a few things, including your overall health. Your doctor can help you understand how well an ICD might help you.

There are several risks to getting an ICD. But the risks are different for each person. The risks also depend on the type of ICD that you get. Your doctor can help you understand what your risks are from an ICD.

During the procedure. Problems can happen during or soon after the procedure to implant an ICD. Here are some examples.

• You may have pain or bruising.
• Serious bleeding could occur after placement of the ICD.
• A lung could collapse (pneumothorax) from a buildup of air in the space between the lung and the chest wall.

After the procedure. Problems can also happen months or years after the ICD is implanted. These problems are related to the device or the leads.

• The leads that attach to the heart may break or stop working right. If a lead does break or does not work anymore, you would need surgery. The surgery would be more complex than that needed to replace an ICD battery.
• You could get an infection where the ICD is placed.
• The ICD could shock the heart when it shouldn't. There is no way to know if or when this could happen. It might never happen. Your doctor will program your ICD to lower the risk of one of these shocks.
• There also is a chance that a manufacturer may recall an ICD for a problem. If this were to happen, you might need surgery to take out the ICD and leads.
• The idea of living with an ICD and getting shocked worries some people. For some people, getting a shock can cause anxiety and depression.

Talk with your doctor about the possibility of turning off the ICD at the end of life. Many people consider turning off the ICD when their health goals change from living longer to getting the most comfort possible at the end of life. Turning off your ICD is legal. It isn't considered suicide. The decision to leave on or turn off your ICD is a medical decision that you make based on your values.