Implantable Cardioverter Defibrillator (ICD)

An ICD is meant to prevent sudden death. The expected lifespan will be determined by the severity of the underlying heart disease and not the ICD.

Definition of implantable cardioverter defibrillator (ICD)

An implantable cardioverter defibrillator (ICD) is a small battery powered device that is placed under the skin of the chest wall and connected by insulated wires (leads) threaded through blood vessels into the heart. Its purpose is to monitor the heart’s rate and rhythm. If it senses an abnormal, potentially fatal heart rhythm such as ventricular fibrillation, the ICD will deliver a shock to the heart, and restore a normal heartbeat preventing sudden death.

There are four different types of ICDs that can help restore heart rhythms if needed. The first three also have heart pacemaker capabilities.

• Single chamber ICD – This device has a single lead that attaches to the right ventricle of the heart. When the energy is delivered to the heart, the ventricle is stimulated to contract.
• Dual chamber ICD – There are two leads that attach to the heart, one to the right atrium and one to the right ventricle. The atrium contraction comes first, pushing blood into the ventricle, followed by the ventricle contraction to pump blood to the body.
• Biventricular ICD – Three electrodes are involved, one each attached in the right atrium, right ventricle, and the left ventricle. This ICD is used in cardiac resynchronization therapy to treat patients with significant heart failure, where medications don’t work.
• Subcutaneous ICD – This type of ICD has its wires placed under the skin near the heart instead of being threaded into the heart itself. It is a much larger device, but its benefit is that wires do not need to enter the blood stream or attach directly to the heart. But while it can shock a heart back into a safe rhythm, it cannot pace a heart that is beating too slowly.

Implantable cardioverter defibrillator vs. pacemaker

The electrical system of the heart helps coordinate the timing related to the filling of the heart and then contracting. The heart’s natural pacemaker is located in the right atrium and generates a new impulse 60-100 times a minute.

The electrical grid in the heart takes that impulse and spreads it to every muscle cell in the heart, first to the atria and then to the ventricles. This allows a coordinated contraction of the heart muscle to make a heartbeat.

There is a “junction box” between the atria and the ventricles parts of the heart (the AV node) where the electrical signal is delayed for a split second. This allows the blood that is pumped from the atrium to fill the ventricle before it is pumped out to the body.

An artificial pacemaker is implanted to generate a heartbeat when the natural pacemaker fails or when a heart block happens in the electrical grid that prevents electrical impulses from reaching the ventricle.

An ICD is activated when the electrical activity of the ventricle becomes chaotic and the muscle cells cannot coordinate their contractions to pump blood. The ICD may shock the heart and restore normal electrical activity within the ventricle.

Sudden cardiac death kills more than 430,00 people in the United States every year. Most of these deaths are due to ventricular fibrillation, an abnormal heart rhythm that cannot generate a heartbeat. It is a complication of atherosclerotic heart disease, a narrowing of the heart arteries that is the cause of heart attacks. Patients at risk for sudden death include those with cardiomyopathies and abnormal heart muscle function.

Implantable cardioverter defibrillators have a few potential functions:

• The defibrillator function is used to shock ventricular fibrillation back into a regular rhythm.
• The cardioverter can sense another potentially fatal rhythm, ventricular tachycardia, and use a different wave form of electric shock to convert the tachycardia to a regular rhythm.
• Newer ICDs also have a pacemaker function that can sense and treat a too slow heartbeat.

Is a defibrillator implant a surgery?

Implanting an ICD is a significant procedure and requires the technical skill of a cardiologist. It does not require general anesthesia, but it does have potential risks and complications. Sedation is usually provided to the patient as well as local anesthesia at the incision area.

An incision is made in the chest wall below the collarbone and a small pocket of tissue is formed to hold the ICD. Lead wires (there may be more than one) are threaded through one of the large veins located nearby in the chest and attached to the heart. Finally, the cardiologist runs tests to make certain that the ICD works and then programs it to meet the specific needs of the patient’s situation.

*Subcutaneous ICDs do not use wires that are inserted into the heart.

Are you awake during ICD surgery?

During the ICD placement, the patient may be awake or may be sedated with intravenous medication. Most often, the level of sedation is such that the patient continues to breath on their own and does not need intubation or a ventilator (general anesthesia).

After the ICD placement, patients are usually kept in the hospital for heart monitoring for 24 hours.

The skin incision where the ICD pocket was made will take 1-2 weeks to heal, just like any other skin laceration. There is always the risk of bleeding or infection and during that time, the area will need to be watched. Signs of infection include warmth, redness, swelling, and tenderness at the incision site, plus general fever, chills, and malaise.

Sutures are usually removed in about a week, but it may take longer for the area to heal completely.

While the goal is to return the patient to their normal pre-ICD level of function, in the first 4 weeks there may be limitations on driving, lifting, sports, or other strenuous activities.

To allow complete healing, it is recommended to avoid lifting the arm on the side of the incision above shoulder height for eight weeks.

Contact sports are also not recommended because of the risk of damage to the ICD or the potential for dislodging or damaging the leads.

The ICD will be monitored and checked routinely. This can be done remotely or in the office. If needed, the ICD can have its programming adjusted using a specialized magnet.

The battery life of an ICD is usually about 7-10 years. Its lifespan depends on whether it fires to deliver a shock to the heart and how often that happens.

There is a success rate of ICD placement in preventing sudden death. Studies have found survival rates of 98% at one year, and 80% at five years. The ICD function to deliver appropriate shocks was the same regardless of the age of the patient.

Electrical interference with implantable cardioverter defibrillator

An ICD can be affected by electrical fields or magnets. However, routine household and workplace exposures cause no problems. Microwave ovens, TV remote controls, computers, GPS devices and home power tools, like electric drills are all safe.

Cellphones are safe to use but it should not be kept within 6 inches of the ICD (like in a shirt pocket). The ICD could mistake the cellphone signal for a heart rhythm.

Headphones and wireless chargers should be kept at least 6 inches away from the ICD.

Power generators like transformers, motor generators, and welding machines can affect ICD function.

The ICD could set off airport security alarms, and patients will receive a card to advise the need for alternative screening. Handheld security wands may not be safe and could affect the ICD. Manual searches should be requested.

Theft detectors at stores are safe to walk through quickly, but the patient should not spend time standing near them.

• An MRI uses a magnet to generate images. Some ICDs are safe for MRI imaging, some are not. The healthcare provider ordering the test will need to determine whether the test can be safely done. The technologist will also check its safety before allowing the patient into the area near the MRI machine.

Local complications may occur at the insertion site of the ICD.  These include pain, swelling, bleeding, and risk of infection. More serious complications are uncommon and are related to the insertion of the lead wires into the veins leading to, and into, the heart. These may include pneumothorax (collapsed lung), deep vein thrombosis (clot in vein), perforation of the heart muscle, heart rhythm disturbances, stroke or heart attack. The need for emergency surgery is rare.

Lifespan after ICD implant

An ICD is meant to prevent sudden death. The expected lifespan will be determined by the severity of the underlying heart disease and not the ICD. Life expectancy was lower in patients with advanced heart failure.