How does it work?
The ICD has two parts:
- Leads – monitors the heart rhythm, delivers energy used for pacing, cardioversion and/or defibrillation.
- 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.
There are different types of ICDs:
- Single Chamber – a lead is attached in the right ventricle. If needed, energy is delivered to the ventricle to help it contract normally.
- Dual Chamber – leads are attached in the right atrium and the right ventricle. Energy is delivered first to the right atrium and then to the left ventricle, helping your heart to beat in a normal sequence.
- Biventricular ICD – leads are attached in the right atrium, the right ventricle and the left ventricle. This technique helps the heart beat in a more balanced way and is specifically used for patients with heart failure
The ICD computer 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 ICD 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 should I expect?
You will lie on a bed and the nurse will start an intravenous line (IV) in your arm or hand. This is so you may receive medications and fluids during the procedure. You will be given an antibiotic to prevent infection and a medication through your IV to relax you and make you drowsy, but it will not put you to sleep.
The nurse will connect you to several monitors. The monitors allow the doctor and nurse to check your heart rhythm, blood pressure and other measurements during the pacemaker implant.
Your chest will be shaved and cleansed with a special soap. Sterile drapes are used to cover you from your neck to your feet. A strap will be placed across your waist and arms to prevent your hands from coming in contact with the sterile field.
The ICD may be implanted in three ways:
- Endocardial (transvenous) – A small incision is made under the collar bone. The lead is placed into a vein and guided inside your heart chamber. The generator is placed under skin in the upper chest and attached to the lead(s). Following insertion, the skin is closed with sutures or staples.
- Epicardial (outside your heart) – This requires open heart surgery. Instead of placing the lead through a vein and guiding it to the heart, it is sewn onto the heart. Your doctor will decide if this approach is necessary for you.
- Subcutaneous – The incision is made in the left chest below the armpit and a smaller one to the left of the breast bone. The device is placed in the side, with a wire going under the skin to sit to the left of the breast bone.
The ICD implant takes about one to two hours to perform. Most ICD’s are done as an outpatient.