What is an implantable cardioverter defibrillator?

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 healthcare provider 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.

Why might I need an ICD?

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 that results in low heart function. The most common cause of cardiomyopathy is heart artery disease.

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

What are the risks of 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 the leads.

• 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 could be, or are currently breastfeeding, tell your healthcare provider. 

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

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 healthcare provider before the procedure.

How do I get ready for an ICD?

• Your healthcare provider 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 test. Read the form carefully and ask questions if something is not clear.

• Tell your healthcare provider 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 healthcare provider will tell you how long to fast, usually overnight.

• If you are pregnant or think that you could be, tell your healthcare provider.

• Tell your healthcare provider of all medicines you take. This includes prescription and over-the-counter medicines, and herbal or other supplements.

• Tell your healthcare provider if you have heart valve disease. You may need to take an antibiotic before the procedure.

• Tell your healthcare provider 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 healthcare provider 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 healthcare provider may ask you to do other things to get ready.

How is an ICD implanted?

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 healthcare provider’s practices.

Generally, a transvenous ICD insertion follows this process:

1. You will be asked to remove any jewelry or other objects that may interfere with the procedure.

2. You will be asked to remove your clothing and will be given a gown to wear.

3. You will be asked to empty your bladder before the procedure.

4. An IV (intravenous) line will be started in your hand or arm for injection of medicine and fluids

5. You will be placed on your back on the procedure table.

6. You will 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 kept track of 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 will get medicine (sedative) in your IV before the procedure to help you relax.

10. The healthcare 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 healthcare provider will make a small cut (incision) at the insertion site.

14. The healthcare provider 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 that the catheter does not move out of place. It helps prevent damage to the insertion site.

16. The healthcare provider 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 healthcare provider may insert 1, 2, or 3 leads, depending on the type of device your healthcare provider has chosen for your condition. The healthcare provider 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 healthcare provider 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 healthcare provider 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.

What happens after an ICD is implanted?

Next steps

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