An implantable cardioverter defibrillator (ICD) is a small electronic device connected to the heart. It's used to continuously keep track of and help control fast and sometimes life-threatening electrical problems with the heart.

The ICD is about the size of a stopwatch. It's often implanted under the skin just below the collarbone. It has a pulse generator and wires (leads). The pulse generator has a battery and a tiny computer. One or more leads connect the pulse generator to specific places in the heart. This is called a transvenous ICD. A newer type of defibrillator is implanted several inches below your armpit. The lead for this defibrillator is put underneath the skin over the heart and the breastbone. This is called a subcutaneous ICD.

The ICD responds to fast life-threatening heart rhythms from the lower chambers of the heart. Sometimes the ICD restores normal heart rhythm by briefly sending out a controlled burst of impulses (called "overdrive" pacing). Other times a brief shock (defibrillation) resets the heart rhythm if needed to prevent sudden cardiac arrest. An ICD also records and stores information about your heart rhythm and treatments delivered by the ICD for your doctor to review.

Most people are unaware when the ICD is pacing the heart. But a defibrillation shock is often described as feeling like a "kick in the chest."

The ICD with a wire inside the heart can also be made to work as a basic pacemaker as needed. Sometimes, after a shock is delivered, the heart may beat too slowly. The ICD has a "backup" pacemaker. This can stimulate the heart to beat faster until the normal heart rhythm returns. The ICD can act as a pacemaker any time the heart rate drops below a certain rate. The newer type of defibrillator that has the wire only under the skin can't function as a long-term pacemaker.

You may need an ICD if you have survived sudden cardiac arrest because of ventricular fibrillation. Or you may need one if you have fainted from ventricular arrhythmia, if you have certain inherited heart conditions, or you are at high risk for cardiac arrest. Most often, ICDs are recommended for people who have cardiomyopathy, a heart muscle problem that results in low heart function. The most common cause of cardiomyopathy is heart artery disease.

There may be other reasons for your doctor to advise an ICD.

Possible risks of ICD insertion include:

• Reaction to the medicine (anesthesia or sedative) used during the procedure.
• Swelling or bruising in the upper chest area where the ICD device is placed.
• Bleeding from the wound site.
• Damage to the blood vessel at the wire insertion site.
• Infection.
• Collapsed lung.
• Dislodging of the leads. This needs another procedure to reposition them.
• Mechanical problems with the ICD device.
• ICD shocks for other fast-abnormal heart rhythms that are not life-threatening, or ICD shocks triggered by electromagnetic interference in your surroundings.
• Very rarely, death.

If you are pregnant or think that you might be, or are currently breastfeeding, tell your doctor.

If you are allergic to or sensitive to any medicines or latex, tell your doctor.

Lying still on the procedure table for the length of the procedure may cause some discomfort or pain.

There may be other risks depending on your specific health condition. Be sure to discuss any concerns with your doctor before the procedure.

• Your doctor will explain the procedure and ask if you have any questions.
• You will be asked to sign a consent form that gives your permission to do the procedure. Read the form carefully and ask questions if something is not clear.
• Tell your doctor if you are sensitive to or are allergic to any medicines, iodine, latex, tape, or anesthesia medicines (local and general).
• You will need to fast for a certain period before the procedure. Your doctor will tell you how long to fast, usually overnight.
• If you are pregnant or think that you could be, tell your doctor.
• Tell your doctor of all medicines you take. This includes prescription and over-the-counter medicines, and herbal or other supplements.
• Tell your doctor if you have heart valve disease. You may need to take an antibiotic before the procedure.
• Tell your doctor if you have a history of bleeding disorders or if you are taking any blood-thinning medicines (anticoagulants), aspirin, or other medicine that affect blood clotting. You may be told to stop some of these medicines before the procedure.
• Your doctor may ask for a blood test before the procedure to see how long it takes your blood to clot. You may need other blood tests and a chest X-ray.
• You may get medicine (sedative) before the procedure to help you relax.
• Based on your health condition, your doctor may ask you to do other things to get ready.

You may have an ICD implanted as an outpatient or as part of your stay in a hospital. Procedures may vary depending on your condition and your doctor's practices.

Generally, a transvenous ICD insertion follows this process:

1. You'll be asked to remove any jewelry or other objects that may interfere with the procedure.
2. You'll be asked to remove your clothing and will be given a gown to wear.
3. You'll be asked to empty your bladder before the procedure.
4. An I.V. (intravenous) line will be started in your hand or arm for injection of medicine and fluids.
5. You'll be placed on your back on the procedure table.
6. You'll be connected to an electrocardiogram (ECG) monitor that records the electrical activity of the heart during the procedure. Your heart rate, blood pressure, breathing rate, oxygenation level, and other vital signs will be watched during the procedure.
7. Hair may be shaved or clipped around the area where the ICD will be inserted.
8. Large electrode pads will be placed on the front and back of the chest.
9. You'll get medicine (sedative) in your I.V. before the procedure to help you relax.
10. The health care staff will clean the ICD insertion site with antiseptic soap.
11. Sterile towels and a sheet will be placed around this area.
12. The staff will inject a local anesthesia into the skin at the insertion site.
13. Once the anesthesia takes effect, the doctor will make a small cut (incision) at the insertion site.
14. The doctor will put a sheath (introducer) into a blood vessel, usually under the collarbone. The sheath is a plastic tube through which the ICD lead will be inserted into the blood vessel and advanced into the heart.
15. It will be very important for you to remain still during the procedure. This is so the catheter doesn't move out of place. It helps prevent damage to the insertion site.
16. The doctor will put the lead through the introducer into the blood vessel. They will advance the lead wire through the blood vessel into the heart.
17. Once the lead wire is inside the heart, it will be tested to make sure that it is in the correct place and that it works. The doctor may insert 1, 2, or 3 leads, depending on the type of device your doctor has chosen for your condition. The doctor will use fluoroscopy to put the lead in the correct spot. Fluoroscopy is a special type of X-ray that will be displayed on a TV monitor.
18. The doctor will slip the ICD generator under the skin through the incision just below the collarbone after the lead is attached to the generator. Generally, if you are right-handed, the device will be placed in your upper left chest. If you are left-handed, the device may be placed in your upper right chest.
19. The doctor will watch the ECG to keep track of how well the ICD is working. They may do certain tests to assess the device function. The tests will also make sure there are no complications after the procedure.
20. The skin incision will be closed with stitches, adhesive strips, or special glue.
21. A sterile bandage or dressing will be applied.

For the ICD that uses a wire only underneath the skin, the generator will be placed in the left armpit area with the wire tunneled to the mid chest and then over the breastbone. A second smaller incision is made just beneath the breastbone to secure the wire to the body.

After the procedure, you may be taken to the recovery room for observation, or you may go to your hospital room. A nurse will watch your vital signs.

Tell your nurse right away if you feel any chest pain or tightness, trouble breathing, or any other pain at the incision site.

After a period of bed rest, you may get out of bed with help. The nurse will help you the first time you get up. The nurse will check your blood pressure while you are lying in bed, sitting, and standing. Move slowly when getting up from the bed so you won't have any dizziness from the period of bed rest. You'll be able to eat or drink once you're completely awake. Your arm may be in a sling for a day or so. How long you will need to wear a sling will depend on your doctor. Some people are asked to wear it at night while they sleep after the first couple of days but can take it off during the day.

The insertion site may be sore or painful. You may get pain medicine, if needed. After the procedure, you may have a chest X-ray to check the lung and make sure the systems are stable.

Your doctor will visit with you in your room while you are recovering. The doctor or health care team will give you specific instructions and answer any questions you may have.

If the procedure is done as an outpatient, you may be able to leave after you have completed the recovery process. But it's common to spend at least one night in the hospital after ICD implantation for observation.

Arrange to have someone drive you home from the hospital after your release.

You should be able to return to your daily routine in a few days. Your doctor will tell you if you need to take more time in returning to your normal activities. You may be told to limit movement of the arm on the side that the ICD was placed, based on your healthcare provider's preferences.

You will most likely be able to resume your normal diet, unless your doctor tells you differently.

Keep the insertion site clean and dry. You'll be given instructions about bathing and showering. Your doctor will give you specific instructions about driving. You won't be able to drive until your doctor says it's OK. These limitations will be explained to you, if they apply to you.

You'll get specific instructions about what to do the first time your ICD delivers a shock. For instance, you may be told to dial 911 or go to the nearest emergency room in the event of a shock from the ICD. Calming yourself with slow deep breaths can be helpful if you are anxious after a shock.

Ask your health care team when you will be able to return to work. The nature of your job, your overall health, and your progress will determine how soon you may return to work.

After implantation, your ICD will need regular evaluation (interrogation). This is done to assess its function and battery status. It is also to check for any significant events stored by the device. Your doctor will tell you when and how this is done. A home monitor may be provided to you that can communicate with your ICD wirelessly. Information about ICD function can then be relayed to your doctor over the internet.

Call 911, or get immediate medical care at the nearest Emergency Department if:

• You have severe or unusual chest pain or pressure.
• You have trouble breathing or shortness of breath.
• You feel dizzy, lightheaded, or faint.
• You have uncontrolled or heavy bleeding from the insertion site.
• You have unusual or profuse sweating.
• You receive more than one shock, lose consciousness with the shock, or have symptoms as above before or after the shock.

Contact your doctor right away if:

• You have fever or chills.
• You have increased pain, redness, swelling, or bleeding or other drainage from the insertion site.
• You have chest pain or pressure that is not typical for you.
• You have nausea or vomiting.
• You have palpitations.
• You had a single ICD shock, and you had no noticeable symptoms before or after the shock, and did not lose consciousness.
• Your device generator feels loose or like it is wiggling in the pocket under the skin.

Your doctor may give you other instructions after the procedure, depending on your situation.

Take the following precautions when you have an ICD implanted. Discuss the following in detail with your doctor, or call the company that made your device:

• Always carry an ID card that states you have an ICD. In addition, you may want to wear a medical ID bracelet showing that you have an ICD.
• If you travel by air, tell security screeners that you have an ICD before going through the metal detector. (It may help to say you have a pacemaker. This is true because pacemaker functions are built into most ICDs. Security may not know what an ICD is.) In general, airport security detectors are safe for pacemakers and ICDs, but the small amount of metal in the device and leads may set off the alarm. If you are selected for additional screening, politely remind the screener that the security wand contains a magnet. The magnet may interfere with the programming or function of the ICD (pacemaker) if it's held over the device for more than a few seconds.
• Anti-theft systems or electronic article surveillance used in department stores may interact with an ICD. Don't lean on or stand in this equipment. But it's OK to pass quickly through the detection system.
• Stay away from large magnetic fields, such as power generation sites and industrial sites, such as automobile junkyards, that use large magnets.
• If an MRI has been advised for you, contact your doctor. Newer ICDs are compatible with MRI scanners with some restrictions.
• Don't use diathermy. This is the use of heat in physical therapy to treat muscles. Don't use a heating pad directly over your ICD.
• Don't have transcutaneous electrical nerve stimulation (TENS) therapy. Talk with your doctor if you're considering this treatment.
• Turn off large motors, such as cars or boats, when working on them. They may create a magnetic field.
• Stay away from high-voltage and radar machinery. This includes radio and TV transmitters, electric arc welders, high-tension wires, radar installations, and smelting furnaces.
• If you are scheduled for surgery, let the surgeon know well ahead of the operation that you have an ICD. Also talk with your cardiologist before the procedure to find out if you need any special safety measures.
• When involved in a physical, recreational, or sporting activity, protect yourself from injury to the ICD. A blow to the chest near the ICD can affect its functioning. If you are hit in that area, you may want to see your doctor.
• Always see your doctor when you feel ill after an activity, or when you have questions about beginning a new activity.
• Always talk with your doctor if you have any questions about using equipment near your ICD.
• Your doctor may give you a list of other devices and procedures to stay away from.

Be careful when you use a cell phone or other electronic devices. Follow these tips:

• Keep them at least 6 inches away from your ICD.
• It's safest to hold all cell phones to the ear farthest from your ICD or use the speaker mode setting.
• Don't carry your phone or electronic device in your chest pocket, over the ICD. Instead, carry your cell phone or other electronics in a pocket or bag below your waist.

Most cell phones and electronic devices don't interfere with ICDs. But some cell phones and electronic devices, such as smart watches, use powerful magnets for wireless charging. This may interfere with the normal function of your ICD.

The charging device itself and other magnet accessories can also interfere with the normal function of your ICD. Store these devices at least 15 inches away from your ICD.

Follow any other instructions given to you by your doctor or from the manufacturer of your ICD.

Before you agree to the test or procedure make sure you know:

• The name of the test or procedure.
• The reason you are having the test or procedure.
• What results to expect and what they mean.
• The risks and benefits of the test or procedure.
• What the possible side effects or complications are.
• When and where you are to have the test or procedure.
• Who will do the test or procedure and what that person's qualifications are.
• What would happen if you did not have the test or procedure.
• Any alternative tests or procedures to think about.
• When and how will you get the results.
• Who to call after the test or procedure if you have questions or problems.
• How much you will have to pay for the test or procedure.