Glossary of terms to understand how a malfunctioning ICD can be lifethreatening



| Medical Devices | Product Liability

Implantable Cardioverter Defibrillator (ICD)

An implantable cardioverter-defibrillator (ICD) is a small battery-powered device placed in your chest to monitor the heart rhythm and detect irregular heartbeats. An ICD can deliver electric shocks via one or more wires connected to the heart to fix an abnormal Implantable heart rhythm.

An ICD is needed if for a dangerously fast heartbeat (ventricular tachycardia) or a chaotic heartbeat that keeps the heart from supplying enough blood to the rest of the body (ventricular fibrillation). Ventricles are the lower chambers of the heart.  ICDs detect and stop abnormal heartbeats (arrhythmias). The device continuously monitors the heartbeat and delivers electrical pulses to restore a normal heart rhythm when necessary. An ICD differs from a pacemaker — another implantable device used to help control abnormal heart rhythms.

What an ICD Does

TV shows often show hospital workers “shock” an unconscious person out of cardiac arrest with electrified paddles. An ICD does the same thing only internally and automatically when it detects an abnormal heart rhythm.  An ICD is surgically placed under the skin, usually below the left collarbone. One or more flexible, insulated wires (leads) run from the ICD through the veins to the heart.  Because the ICD constantly monitors for abnormal heart rhythms and instantly tries to correct them, it helps when the heart stops beating (cardiac arrest), even when the nearest hospital is located at a distance.

How an ICD works

When a rapid heartbeat occurs, the wires from the heart to the device transmit signals to the ICD, which sends electrical pulses to regulate the heartbeat. Depending on the problem with the heartbeat, the ICD could be programmed for:

  • Low-energy pacing. There may be no feeling or a painless fluttering in the chest when the ICD responds to mild disruptions in the heartbeat.
  • A higher-energy shock. For more-serious heart rhythm problems, the ICD may deliver a higher-energy shock. This shock can be painful, possibly feeling like a kick in the chest. The pain usually lasts only a second, and there should not be discomfort after the shock ends.

Usually, only one shock is needed to restore a normal heartbeat. Sometimes, however, two or more shocks may occur during a 24-hour period.  Having three or more shocks in a short-time period is known as an electrical or arrhythmia storm. If this electrical storm occurs it is important to seek emergency care to check that the ICD is working properly or if there is a conduction problem that is causing an abnormal heartbeat.  If necessary, the ICD can be adjusted to reduce the number and frequency of shocks Additional medications may be needed to make the heartbeat regularly and decrease the chance of an ICD storm.

An ICD can also record the heart’s activity and variations in rhythm. This information helps doctors evaluate the heart rhythm problem and, if necessary, reprogram an ICD.

Subcutaneous implantable cardioverter-defibrillator (S-ICD)

A subcutaneous ICD (S-ICD) is a newer type of ICD available at some surgical centers. An S-ICD is implanted under the skin at the side of the chest below the armpit. It is attached to an electrode that runs along the breastbone.

Candidates for this device may have structural defects in the heart that prevent inserting wires into the heart through your blood vessels, or there may be other reasons for wanting to avoid traditional ICDs. Implanting a subcutaneous ICD is less invasive than an ICD that attaches to the heart, but the device is larger in size than an ICD.

Who needs an ICD

A candidate for an ICD would have had sustained ventricular tachycardia, survived a cardiac arrest, or fainted from a ventricular arrhythmia. Others who benefit from an ICD have:

  • A history of coronary artery disease and heart attack that has weakened the heart.
  • A heart condition that involves abnormal heart muscle, such as enlarged or thickened heart muscle.
  • An inherited heart defect that makes the heartbeat abnormally. These include long QT syndrome, which can cause ventricular fibrillation and death even in young people with no signs or symptoms of heart problems.
  • Other rare conditions that may affect the heart rhythm.

Risks of ICD implantation

Risks associated with ICD implantation are uncommon but may include:

  • Infection at the implant site
  • Allergic reaction to the medications used during the procedure
  • Swelling, bleeding or bruising where the ICD was implanted
  • Damage to the vein where your ICD leads are placed
  • Bleeding around the heart, which can be life-threatening
  • Blood leaking through the heart valve where the ICD lead is placed
  • Collapsed lung (pneumothorax)

To determine whether you need an ICD, a doctor might perform a variety of diagnostic tests, which may include:

  • Electrocardiography (ECG). This noninvasive test uses sensor pads with wires attached (electrodes) placed on the body to measure the heart’s electrical impulses. The heart’s beating pattern offers clues to the type of irregular heartbeat.
  • Echocardiography. This noninvasive test uses harmless sound waves that allow doctors to see the heart without making an incision. During the procedure, a small instrument called a transducer is placed on the chest to collect reflected sound waves (echoes) from the heart and transmit them to a machine that uses the sound wave patterns to compose images of the beating heart on a monitor. These images show how well the heart is functioning and the size and thickness of the heart muscle.
  • Holter monitoring. Also known as an ambulatory electrocardiogram monitor, a Holter monitor records the heart rhythm for 24 hours. Wires from electrodes on the chest go to a battery-operated recording device carried in a pocket or worn on a belt or shoulder strap.

While wearing the monitor, a diary of your activities and symptoms is kept. A doctor will compare the diary with the electrical recordings and try to figure out the cause of the symptoms.

  • Event recorder. A doctor might recommend wearing a pager-sized device that records heart activity for more than 24 hours. Unlike a Holter monitor, it does not operate continuously — it is turned on when an abnormal heartbeat is felt.
  • Electrophysiology study (EPS). Electrodes are guided through blood vessels to the heart and used to test the function of the heart’s electrical system. This can identify whether a heart rhythm problem is suspected, might develop or a heart rhythm problem already exists.

Usually, the procedure to implant an ICD can be performed with numbing medication and a relaxing sedative that allows an awareness of the surroundings. In some cases, general anesthesia may be used that would allow for being unconscious during the procedure. During surgery, one or more flexible, insulated wires (leads) are inserted into veins near the collarbone and guided, with the help of X-ray images, to the heart. The ends of the leads are secured to the heart, while the other ends are attached to the generator, which is usually implanted under the skin beneath the collarbone. The procedure usually takes a few hours.

Once the ICD is in place, a doctor tests it and programs it for a heart rhythm problem. Testing the ICD might require speeding up the heart and then shocking it back into normal rhythm.

Because some defibrillators have leads placed through the veins into the heart, abrupt movements that raise your left arm above shoulder-height need to be avoided for two to three weeks including driving. This is to prevent the leads from moving until the area has had time to heal. If a subcutaneous defibrillator is placed, there are no leads placed through the veins, so there are no restrictions on driving or lifting your arm above your shoulder.

ICDs have become standard treatment for anyone who has survived cardiac arrest, and they are increasingly used in people at high risk of sudden cardiac arrest. An ICD lowers the risk of sudden death from cardiac arrest more than medication alone. Although the electrical shocks can be unsettling, they are a sign that the ICD is effectively treating a heart rhythm problem and protecting from sudden death. After the procedure, precautions need to be taken to avoid injuries and make sure the ICD works properly.

Short-term precautions

For four weeks after surgery, doctors might ask to refrain from:

  • Vigorous above-the-shoulder activities or exercises, including golf, tennis, swimming, bicycling, bowling or vacuuming
  • Lifting anything heavy
  • Strenuous exercise programs

A doctor will probably advise to avoid contact sports indefinitely. Heavy contact may damage the device or dislodge the wires.

Long-term precautions

Problems with an ICD due to electrical interference is rare. It is still important to take precautions with the following:

  • Cellular phones and other mobile devices. It is safe to talk on a cell phone but placing a cell phone within 6 inches (about 15 centimeters) of an ICD implantation site when the phone is turned on should be avoided. Although unlikely, it is possible that an ICD could mistake a cell phone’s signal for a heartbeat and slow a heartbeat, causing symptoms such as sudden fatigue.
  • Security systems.  A card is given to confirm the implantation of an ICD to show to airport personnel because the ICD may set off airport security alarms.

Also, hand-held metal detectors often contain a magnet that can interfere with an ICD. Limit scanning with a hand-held detector to less than 30 seconds over the site of an ICD or make a request for a manual search.

  • Medical equipment. Doctors, medical-technicians and dentists should be informed of the presence of an ICD. Some procedures, such as magnetic resonance imaging (MRI), magnetic resonance angiography (MRA), and radiofrequency or microwave ablation are not recommended if an ICD is present.
  • Power generators. Stand at least 2 feet (0.6 meters) from welding equipment, high-voltage- transformers or motor-generator systems. If working around such equipment, a doctor can arrange a test in the workplace to see if the equipment affects the ICD.
  • Headphones. Headphones may contain a magnetic substance that can interfere with an ICD. Keep headphones at least 6 inches (about 15 centimeters) from an ICD.
  • Magnets. Might affect ICD, so it is a good idea to keep magnets at least 6 inches (15 centimeters) from your ICD site.

Devices that pose little or no risk to an ICD include microwave ovens, televisions and remote controls, AM/FM radios, toasters, electric blankets, electric shavers and electric drills, computers, scanners, printers, and GPS devices.

Driving restrictions

If you have an ICD to treat ventricular arrhythmia, driving a vehicle presents a challenge. The combination of arrhythmia and shocks from an ICD can cause fainting, which would be dangerous while driving.

The American Heart Association’s guidelines discourage driving during the first six months after a procedure if your ICD was implanted due to a previous cardiac arrest or ventricular arrhythmia. If no shocks during this period,  driving again may be allowed. But if a shock was to occur, with or without fainting, a doctor would make proper recommendations for safety. In most cases, driving will be discouraged until shock-free for another six months.

If an ICD has been placed but have no history of life-threatening arrhythmias, driving can usually be resumed within a week after the procedure if no shocks have occurred. Doctors should always be the ones to make this determination. Patients however may not be compliant with driving restrictions. A commercial driver’s license is usually banned if you have an ICD.

Battery life

The lithium battery in the ICD can last up to seven years. The battery should be checked during regular checkups, which should occur about every six months. When the battery is nearly out of power, the old shock generator is replaced with a new one during a minor outpatient procedure.

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