Implantation of Automated Implantable Cardioverter-Defibrillator (AICD)

What is Implantation of Automated Implantable Cardioverter-Defibrillator (AICD)?

An automated implantable cardioverter-defibrillator (AICD) is a small electronic device implanted in the chest, just beneath the skin below the collar bone. Its main function is to prevent sudden death from cardiac arrest due to life threatening abnormally fast heart rhythms (tachycardias). The AICD is capable of monitoring the heart rhythm. When the heart is beating normally, the device remains inactive. If the heart develops a life-threatening tachycardia, the ICD delivers an electrical “shock(s)” to the heart to terminate the abnormal rhythm and return the heart rhythm to normal.

An AICD consists of 2 parts: the pulse generator and the wires (also called leads). The leads monitor the heart rhythm, deliver energy to pace or “shock” the heart. The pulse generator houses the battery and a tiny computer. Energy is stored in the battery until it is needed. The computer receives information from the leads to determine what rhythm is occurring. The battery usually lasts 7 to 10 years, after which the entire pulse generator needs to be changed. The wires are inserted into the heart via the veins from one of the arms. The AICD will not improve symptoms as it remains inactive when the heart rhythm is normal. It will however, serve to prevent sudden cardiac death should a life-threatening abnormal heart rhythm develop. Modern AICDs are unobtrusive and do not affect activities of daily living.

How does an AICD work?

The AICD is like a little computer. It monitors the heart rhythm, identifies abnormal heart rhythms, and determines the appropriate therapy to return your heartbeat to a normal heart rhythm. Your doctor programs the AICD to include one or all of the following functions:

  • Anti-tachycardia Pacing (ATP) – When the heart beats too fast, a series of small electrical impulses are delivered to the heart muscle to restore a normal heart rate and rhythm.
  • Cardioversion – A low energy shock is delivered at the same time as your heartbeat to restore a normal heart rhythm.
  • Defibrillation – When the heart is beating dangerously fast, a high-energy shock is delivered to the heart muscle to restore a normal rhythm.
  • Bradycardia pacing – When the heart beats too slow, small electrical impulses are sent to stimulate the heart muscle to maintain a suitable heart rate.

What happens during the AICD implantation?

You will need to be warded for 1 to 2 days for the AICD implantation. The implant procedure usually lasts about one hour and is performed in the Invasive Cardiac Laboratory. You will need to fast for at least 6 to 12 hours before the implantation. Before the procedure, some routine blood tests and electrocardiograms may be performed. A full explanation of the procedure with its attendant risks will be provided and you will be required to sign a consent form after that.

During the procedure, you will lie on a bed. The nurse will connect you to several monitors which allow the doctor and nurse to monitor your condition at all times. As it is very important to keep the area of insertion sterile to prevent infection, your chest will be shaved (if necessary) and cleansed with a special soap. Sterile drapes will be used to cover you from your neck to your feet. A soft strap will be placed across your waist and arms to prevent your hands from coming in contact with the sterile field.

A small plastic cannula will be inserted in one of the veins on your hand to facilitate injection of medication. Just before implantation, you will be given an injection of an antibiotic to prevent wound infections. You will also receive medication through the intravenous cannula to make you drowsy but you may not be fully asleep.

After injection of a numbing medication, a small incision (cut) is made in the upper left chest (if you are right-handed) and a small “pocket” is created under the skin to accommodate the pulse generator. The lead is then inserted through a vein in the upper chest and is positioned under X-ray guidance until its tip lies snugly within the heart. The other end of the lead is then connected to the pulse generator. Your doctor may have to test the AICD by inducing an abnormal heart rhythm in the laboratory and observing if the AICD functions as expected. You will be put to sleep with medication before the test. The incision wound is then stitched up, cleaned and a waterproof dressing applied to the wound.

Upon returning to the ward, you will be required to lie flat in bed until the next day. Your arm on the side of the AICD may be held in a sling to avoid excessive movement. You will be given regular antibiotic injections for a day followed by oral antibiotics for about 5 days. Please inform the attending nurse if you experience pain at the implant site so that painkillers can be prescribed. The following day, you will be sent for a chest X-ray to check the position of the AICD lead and to look for potential complication. The AICD settings will also be checked and programmed by a technologist. Most patients can be discharged one to two days after the implantation.

Upon discharge, you will be given an appointment for follow-up at the Pacemaker Clinic in a week’s time. The waterproof dressing should not be removed until your return for review at the Pacemaker Clinic. The stitches need not be removed as they are absorbable. After your first review, your doctor will arrange a schedule of periodic checks to ensure normal AICD function and to electronically program the AICD settings to suit your heart’s requirements.

What precautions do you need to take after the implantation procedure?

  1. You should watch for fever, excessive pain and inflammation over the wound. Inform your doctor immediately if you have these symptoms.
  2. On the side of the AICD, avoid excessive movement of the arm, lifting the arm above your head and lifting more than 5kg load for 1 week after implantation.
  3. Complete the course of antibiotic medication prescribed on discharge.
  4. Remember to inform all your attending doctors that you have an AICD implanted. Some important reasons for this include:
    • Use of diathermy close to the AICD site during surgery should be avoided
    • You should avoid magnetic resonance imaging, a medical diagnostic imaging technique.
  5. Avoid using mobile phones on the side of the AICD as there is concern that mobile phones may affect the functions of the pacemaker.
  6. You will receive a temporary identification card that indicates what type of AICD and leads you have, the date of implant and the doctor who performed the implant. Carry this card with you at all times in case medical care is needed. Within three months you will receive a permanent card from the AICD company.
  7. Ensure that you return for regular check-up at the appointed dates so that you derive the greatest benefits from the AICD.
  8. Should you feel the AICD shock (feels like you have received a punch in your chest), please contact the Pacemaker clinic for an earlier appointment, failing which, please return to the hospital Emergency department.

If you have any query regarding these instructions, please contact your doctor.

What are the potential risks or complications associated with the implantation?

The procedure is extremely safe, with a low risk of complication. Most complications are minor and easily treated, such as pain, bleeding and bruising at the implant site. An infrequent complication is pneumothorax, a condition when the lung is accidentally punctured during the insertion of the lead. Air then leaks into the chest cavity, causing the lung to collapse. This condition can be treated with insertion of a chest tube to allow the air to escape and the lung to re-expand. A rare but serious complication is infection of the implant site or the pulse generator/lead, requiring antibiotic therapy and even surgical removal of the entire AICD system if severe.