Diseases & Conditions A - Z
powered by Talix

Implantable Cardioverter Defibrillator (ICD)

What is an implantable cardioverter defibrillator?

An implantable cardioverter defibrillator (ICD) is a small device that your doctor can put into your chest to help regulate an irregular heart rhythm, or an arrhythmia.

Although it’s smaller than a deck of cards, the ICD contains a battery and a small computer that monitors your heart rate. The computer delivers small electrical shocks to your heart at certain moments. This helps control your heart rate.

Doctors most commonly implant ICDs in people who have life-threatening arrhythmias and who are at risk for sudden cardiac arrest, which is a condition in which the heart stops beating. Arrhythmias can be congenital, which means something you were born with, or a symptom of heart disease.

ICDs are also known as cardiac implantable devices or defibrillators.

Why do I need an implantable cardioverter defibrillator?

Your heart has two atria, or upper chambers, and two ventricles, or lower chambers. Your ventricles pump blood from your heart to the rest of your body. These four chambers of your heart contract in a timed sequence to pump blood throughout your body. This is called a rhythm.

Two nodes in your heart control your heart’s rhythm. Each node sends out an electrical impulse in a timed sequence. This impulse causes your heart muscles to contract. First the atria contract, and then the ventricles contract. This creates a pump. When the timing of these impulses is off, your heart doesn’t pump blood very efficiently. Heart rhythm problems in your ventricles are very dangerous because your heart can stop pumping. This can be fatal if you don’t receive treatment immediately.

You might benefit from an ICD if you have:

  • a very fast and dangerous heart rhythm called ventricular tachycardia
  • erratic pumping, which is referred to as quivering or ventricular fibrillation
  • a heart weakened by a history of heart disease or a previous heart attack
  • an enlarged or thickened heart muscle, which is called dilated, or hypertrophic, cardiomyopathy
  • congenital heart defects, such as long QT syndrome, which causes heart quivering
  • heart failure

How does an implantable cardioverter defibrillator work?

An ICD is a small device implanted in your chest. The main part, which is called a pulse generator, holds a battery and tiny computer that monitors your heart rhythms. If your heart beats too fast or irregularly, the computer delivers an electric pulse to correct the problem.

Wires called leads run from the pulse generator into specific areas of your heart. These leads deliver the electric impulses sent by the pulse generator.

Depending on your diagnosis, your doctor may recommend one of the following types of ICDs:

  • A single-chamber ICD sends electrical signals to the right ventricle.
  • A dual-chamber ICD sends electrical signals to the right atrium and right ventricle.
  • A biventricular device sends electrical signals to the right atrium and both ventricles. Doctors use it for people who have heart failure.

An ICD can also deliver up to four different types of electrical signals to your heart.


Cardioversion gives a stronger electrical signal that can feel like a thump to your chest. It resets heart rhythms to normal when it detects a very fast heart rate.


Defibrillation sends a very strong electrical signal that restarts your heart. The sensation is painful and can knock you off your feet, but lasts only a second.


Antitachycardia pacing provides a low-energy pulse meant to reset a rapid heartbeat. Typically, you feel nothing when the pulse occurs. However, you may sense a small flutter in your chest.


Bradycardia pacing restores a heartbeat that’s too slow to normal speed. In this situation, the ICD works like a pacemaker. People with ICDs usually have hearts that beat too fast. However, defibrillation can sometimes cause the heart to slow down to a dangerous level. Bradycardia pacing returns the rhythm to normal.

How do I prepare for the procedure?

You shouldn’t eat or drink anything after midnight on the day before your procedure. Your doctor may also ask you to stop taking certain medicines, such as aspirin or those that cause blood clotting. Be sure to tell your doctor about the medications, over-the-counter drugs, and supplements you take before the procedure. You should never stop taking a medication without talking to your doctor first.

What happens during the procedure?

An ICD implant procedure is minimally invasive. An electrophysiologist usually implants the device in an electrophysiology laboratory. In most cases, you’ll be awake during the procedure. However, you’ll receive a sedative to make you drowsy and a local anesthetic to numb your chest area.

After making small incisions, the doctor will guide the leads through a vein and attach them to the specific muscles of your heart. An X-ray monitoring tool called a fluoroscope may help guide your doctor to your heart.

They’ll then attach the other end of the leads to the pulse generator. The doctor will make a small incision and place the device in a pocket of skin on your chest, most often under your left shoulder.

The procedure typically takes between one and three hours. Afterward, you’ll stay in the hospital for at least 24 hours for recovery and monitoring. You should feel fully recovered within four to six weeks.

A doctor can also implant an ICD surgically under general anesthesia. In this case, your hospital recovery time can last up to five days.

What are the risks associated with the procedure?

As with any surgery, an ICD implant procedure may cause bleeding, pain, and infection at the incision site. It’s also possible to have an allergic reaction to the medications you receive during the procedure.

More serious problems specific to this procedure are rare. However, they can include:

  • blood clots
  • damage to your heart, valves, or arteries
  • fluid buildup around the heart
  • a heart attack
  • a collapsed lung

It’s also possible that your device will occasionally shock your heart unnecessarily. Although these shocks are brief and not harmful, it’s likely you’ll feel them. If there’s a problem with the ICD, your electrophysiologist may need to reprogram it.

What happens after the procedure?

Depending on your situation, recovery can take anywhere from a few days to a few weeks. You should avoid high-impact activities and heavy lifting for at least a month after your procedure.

The American Heart Association discourages driving for at least six months after an ICD implant procedure. This gives you a chance to assess whether a shock to your heart will cause you to faint.

What is the long-term outlook?

Having an ICD is a lifelong commitment.

After you recover, your doctor will meet with you to program your device. You should continue to meet with your doctor about every three to six months. Be sure to take any prescribed medications and adopt the lifestyle and diet changes your doctor recommends.

The batteries in the device last for five to seven years. You’ll need another procedure to replace the batteries. However, this procedure is slightly less complicated than the first one.

Certain objects can interfere with your device’s performance, so you’ll need to avoid them. These include security systems and certain medical equipment, like MRIs and power generators.

You may want to carry a card in your wallet or wear a medical identification bracelet that states the type of ICD you have. You should also try to keep cell phones and other mobile devices at least 6 inches away from your ICD.

Tell your doctor if you’re experiencing any problems with your device, and call your doctor immediately if your defibrillator delivers a shock to restart your heart.

Content licensed from:

Written by: Danielle Moores
Medically reviewed on: Mar 31, 2016: Debra Sullivan, PhD, MSN, RN, CNE, COI

This feature is for informational purposes only and should not be used to replace the care and information received from your health care provider. Please consult a health care professional with any health concerns you may have.
Symptom Search
Enter your symptoms in our Symptom Checker to find out possible causes of your symptoms. Go.
Drug Interaction Checker
Enter any list of prescription drugs and see how they interact with each other and with other substances. Go.
Pill Identifier
Enter its color and shape information, and this tool helps you identify it. Go.
Drugs A-Z
Find information on drug interactions, side effects, and more. Go.