An implantable cardioverter defibrillator (called an ICD) is a small device placed in the chest that detects and corrects life-threatening irregular heart rhythms (arrhythmias). An ICD can help the heart maintain a steady, stable rhythm.

Implantable cardioverter defibrillators are critical in preventing cardiac arrest among people who have certain heart-rhythm abnormalities that put them at high risk for it. These conditions include ventricular tachycardia (when the heart’s lower chambers beat too quickly, resulting in poor oxygen distribution in the blood) and ventricular fibrillation (when the heart’s lower chambers beat too quickly and erratically, affecting blood flow throughout the body). An implantable cardioverter defibrillator responds to an irregular heart rhythm with an electrical shock that restores the heartbeat back to a normal, healthy rhythm.

Fortunately, with the aid of an ICD, people with life-threatening heart-rhythm disorders can lead normal lives.

An implantable cardioverter defibrillator is a battery-operated device that helps people with heart rhythm problems avoid life-threatening complications caused by an abnormal (too fast or too slow) heartbeat. The device monitors the heart’s activity and provides shocks or stimulation, as needed, to keep the heart beating steadily. The implanted device, which is about the size of a deck of cards, is attached to the heart with wires.

Some people who need ICDs have had or are at risk for developing life-threatening conditions, such as ventricular tachycardia or ventricular fibrillation; the device helps prevent these life-threatening heart-rhythm abnormalities from becoming fatal.

Many ICDs are also used to help the heart pump blood more effectively among people with heart failure and specific electrical heart abnormalities. This treatment is known as cardiac resynchronization therapy.

ICDs have a lifespan of between eight and twelve years. Doctors regularly monitor the device to ensure that it functions well. When battery life runs low, a new ICD can be implanted in a minor procedure.

In most cases, the ICD is implanted beneath the skin or beneath the skin and muscle in a patient's chest, often near the left collarbone. Less frequently, for instance in infants or in people who have conditions that affect the blood vessels around their heart, the device is implanted in the abdomen.

Wires, known as electrodes, connect the ICD implanted in the chest or abdomen to the heart. To reach the heart, doctors thread these electrodes through a blood vessel near the collarbone. Two or three electrodes are then placed inside the heart and attached to its ventricles (lower) and/or upper (atrial) chambers. The doctors then attach the electrodes (which track the heart’s activity and provide shocks as needed) to the device, which contains the battery that powers any necessary therapy to the heart. ICDs that are implanted using this technique are known as transvenous ICDs.

Less commonly, doctors will implant the ICD in the abdomen or upper chest and attach the leads to the epicardium, the heart’s outermost layer, rather than guiding them through blood vessels. This kind of epicardial implantation may be used in children or adults with congenital heart disease, endocarditis, or other conditions that affect the blood vessels, making them unsuitable for transvenous ICD implantation, or increase the risk for infection.

For some patients, doctors may implant a newer type of device known as a subcutaneous ICD (S-ICD). An S-ICD is inserted under the skin along the ribs on the left side of the body. Instead of connecting a lead to the heart, with an S-ICD the lead is placed under the skin along the left side of the breastbone.

Children or adults may need an ICD if they have a life-threatening arrhythmia caused by an abnormality in the heart’s lower chambers, specifically ventricular tachycardia or ventricular fibrillation. An ICD can’t prevent an arrhythmia from occurring. Instead, it is designed to stop an arrhythmia in its tracks, potentially saving a person’s life.

People who are at risk for life-threatening heart-rhythm problems may have:

• A prior heart attack
• Heart failure
• Prior sudden cardiac arrest
• Cardiomyopathy
• Long QT syndrome
• Brugada syndrome
• Cardiac sarcoidosis
• Congenital heart disease
• Other conditions that put them at risk for sudden cardiac arrest
  

Research has shown that implantable cardioverter defibrillators significantly reduce the risk of recurrence of life-threatening ventricular tachycardia or ventricular fibrillation among those who have already experienced these arrhythmias. For this reason, ICDs rather than medications are the treatment of choice for these patients.

Although ICD implantation is a safe procedure, there are risks with any medical procedure. There’s a small risk that the wires used to connect the ICD to the heart may puncture a lung, vein, or even the heart. After the procedure, although rare, it is possible to develop an infection or have bleeding.

In addition, there are extremely rare instances in which an ICD can malfunction and deliver unnecessary shocks. Repeated inappropriate shocks may reduce a patient’s quality of life. Therefore, patients should report all unnecessary shocks to their doctor.

Objects with strong magnetic fields may interfere with your implantable cardioverter defibrillator. In some cases, they may cause the ICD to malfunction.

A patient with an ICD can have all forms of advanced imaging, including CT scans, PET scans, and MRIs. It may be necessary to coordinate with your provider prior to undergoing imaging to ensure that the tests are performed safely.

Cell phones may cause problems with implantable cardioverter defibrillators. You may be instructed to avoid placing your phone in a left shirt pocket.

When possible, you should avoid:

• Welding
• High-voltage power lines
• Handheld security wands in the airport; request to be hand-searched instead
• Metal detectors
• Magnetic resonance imaging (MRI) machines
• Magnetic therapy massagers, pillows, or other devices

Certain medical treatments can damage your ICD. Talk to your doctor before having:

• Radiation therapy for cancer treatment
• Shortwave or microwave diathermy, which may treat pain or muscle spasms

If you have a medical emergency, it’s crucial for emergency responders and emergency physicians to know about your implantable cardioverter defibrillator. For this reason, you should wear a medical ID bracelet or carry a card in your wallet, which can list details about your ICD. You should also inform your doctors and dentist that you have an implantable cardioverter defibrillator.

“Yale is at the cutting-edge of defibrillator implant and managing technology,” says Eric Bader, MD, a Yale Medicine cardiologist who specializes in electrophysiology, the treatment of complex heart arrhythmias. “We utilize the latest implant techniques to ensure the best possible outcomes for our patients. Our excellence in care does not stop with device implantation. We have one of the largest and most comprehensive remote monitoring networks in the country, leveraging the latest in digital technology and artificial intelligence to monitor thousands of implanted defibrillators all around the world. Additionally, in the rare event that a device malfunctions, we have one of the highest volume management centers for troubleshooting and lead/device extraction.”