An implantable cardioverter defibrillator (ICD) is a heart monitoring device. When necessary, it provides an electric shock that corrects an abnormal heart rhythm and prevents sudden cardiac death.

This small, implantable device works by sensing an irregular heartbeat, known as arrhythmia, and shocking the person’s heart into a normal rhythm.

A doctor may recommend an ICD for individuals who have experienced one or more episodes of life threatening cardiac arrhythmias or those who have an increased risk of these rhythm abnormalities.

In this article, we examine ICDs and how they work. We also look at who might need an ICD and the procedure for implanting one.

An implantable cardioverter defibrillator surrounded by waves of electricity.Share on Pinterest
ArjanL/Getty Images

An ICD monitors and regulates heart rate. It is a small battery-powered device that a surgeon places inside the chest and connects to the heart.

If the device detects an irregular heartbeat, it sends electrical impulses through the wires to the heart, correcting the heartbeat.

The heart has two atria, or upper chambers, and two ventricles, or lower chambers. The atria receive oxygenated blood from the lungs, and the left ventricle pumps blood from the heart around the body. The four chambers must contract in a timed sequence or rhythm for the heart to work correctly.

Electrical tissue in the heart controls the heart’s rhythm with an electrical impulse that causes the heart muscles to contract. If this timing is irregular, the heart does not pump efficiently and may stop, which can be fatal without immediate treatment.

An ICD is valuable in preventing heart attacks and sudden death in individuals who have dangerous heart rhythms.

An ICD continuously monitors an individual’s heart rate 24 hours a day. Once it detects an abnormal rhythm or cardiac arrhythmia, it sends a tiny electric shock to restore normal rhythm.

Standard ICDs may also act as a pacemaker and send regular electrical impulses at a slow heart rate. If a person has heart failure, a special ICD called a cardiac resynchronization therapy (CRT) device can help synchronize the heart.

Doctors recommend an ICD for people who have an increased risk of developing a life threatening ventricular arrhythmia, an abnormal heartbeat that begins in the lower heart chambers.

These at-risk individuals include those who have:

  • had a heart attack
  • had ventricular arrhythmia
  • survived sudden cardiac arrest (SCA)
  • a congenital heart condition
  • long QT syndrome, another type of arrhythmia
  • Brugada syndrome, a genetic disorder that causes an irregular heartbeat
  • congestive heart failure with reduced pumping function of the heart

Both ICDs and pacemakers are implantable devices that help regulate the heart. However, there are some differences.

A pacemaker monitors an individual’s heartbeat and delivers low level electrical pulses to maintain the heart’s normal pace. It can speed up a slow heart rhythm and coordinate the heart’s chambers as they beat.

In contrast, an ICD monitors heart rhythm and can deliver both low level and high level electrical pulses, called defibrillation. Therefore, as well as acting as a pacemaker, an ICD can act as a defibrillator to shock the heart with a high level electrical pulse if it detects a life threatening arrhythmia.

A person may need a pacemaker device because their heart’s natural pacemaker slows down as they age. However, doctors may recommend an ICD for people with life threatening arrhythmias that can cause sudden cardiac arrest.

The procedure for implanting an ICD is minimally invasive and relatively short, taking about 90 minutes. People require local anesthesia to numb the area and general sedation to help them relax and feel drowsy.

These are the general steps of the procedure:

  1. A surgeon makes a small incision in the upper left chest, just below the collarbone, and inserts the device.
  2. They then guide one end of the lead or wire through the subclavian vein and position it in the correct area of the heart.
  3. The leads connect to a pulse generator at the other end.
  4. The surgeon then programs the defibrillator settings and tests the device to verify that it functions correctly and meets the individual’s medical needs.
  5. They then place the pulse generator in a pocket under the skin, usually below the left shoulder, and close the chest incision.

Typically, following the procedure, people stay overnight in the hospital. This stay allows doctors to monitor them and then discharge them the next day following a chest X-ray to check that the leads are in the correct place.

A person may experience short-term complications, but this is rare, affecting just 2–3% of individuals. These complications may include bleeding, clots, and collapsed lungs. In some cases, the device can twist, which disrupts its function.

Serious complications, which occur 1–2% of the time, include device-related infection and pulseless electrical activity (PEA). PEA means that even though there is electrical activity, there is no organized pulse.

Recovery looks different for everyone and may take a few days to a few weeks.

A person with an ICD will need to attend regular follow-up appointments with a doctor, who will check the device and evaluate the person’s heart health. Typically, these appointments are every 3–12 months and continue throughout a person’s life.

During a doctor’s visit, people can discuss any symptoms they experience, ask questions, and talk about their concerns.

Follow-up appointments also allow a doctor to look at the device and monitor the condition of the battery. They can also check and adjust the device’s settings to ensure that it meets the individual’s needs.

A doctor uses a small computer called a programmer to retrieve the information that the ICD stores.

A remote monitoring system may replace some of these consultations. Using a home docking station, the ICD can transmit data from the implanted device to the cardiac care team.

People with an ICD may need to make some lifestyle changes. For example, they might need to limit contact sports and be aware of how other electronic devices, such as airport security systems, may affect them.

Depending on their reason for needing an ICD, some individuals will also not be able to drive for several weeks or months after the implantation of the ICD or a generated electric shock to preserve their own safety and that of others. This is because about 14% of people lose consciousness following a shock, which could cause an accident. A person’s doctor will inform them when it is safe for them to drive.

An ICD is a small device that surgeons implant in the chest to monitor heart rhythm. If an individual’s heartbeat becomes dangerous, the ICD delivers a small burst of electrical current to reset the heart’s rhythm.

The procedure to fit the device is relatively minor, and most people can leave the hospital after staying for just 1 night. The recovery is generally straightforward. However, people must attend regular monitoring visits throughout their life to check on their health and the status of the ICD.

An ICD can help control life threatening heart arrhythmias and prevent people from experiencing sudden cardiac arrest.