Implantable Cardioverter Defibrillator

The ICD (pulse generator) contains a microprocessor, battery and electronic circuitry sealed in a titanium case. The battery life is approximately six years depending on the number of treatments it delivers. The ICD is implanted in a pocket of muscle in the upper chest.

The leads are insulated conductors. They monitor the electrical activity of the heart (ie carrying information from the heart to the ICD where relevant data is stored) and deliver therapy to the heart from the ICD when necessary. Depending on the type of ICD there may be one or more leads.

Why Is The ICD Indicated?

1. It is used to terminate life threatening episodes of Ventricular Tachycardia or Ventricular fibrillation.
2. If medication has been unsuccessful in terminating the tachyarrhythmia (fast abnormal rhythm) – or caused side effects. Often a combination of drug therapy and the ICD will be used.
3. If other antiarrhythmic therapies, such as surgery or ablation have been unsuccessful.
4. Following a history of Cardiac Arrest.

Ventricular Tachycardia (V.T.) A heart rhythm characterised by an abnormal fast heart beat that originates in the lower heart chambers (the ventricles). Rapid contractions prevent the heart from filling adequately with blood resulting in poor circulation so that the patient may feel dizzy, faint, breathless, chest discomfort, blurred vision or be rendered unconscious.

VENTRICULAR FIBRILLATION (V.F.) A very fast, chaotic, irregular rhythm arising from many different areas in the ventricles causing a quivering effect on the heart. This prevents the heart from pumping any blood to the body and quickly leads to an unconscious state and may result in Cardiac arrest if left untreated. Ventricular Fibrillation can only be treated with an electric shock - defibrillation.

The ICD is similar to a pacemaker in that it is designed to correct arrhythmias. However the pacemaker is primarily used to correct abnormally slow heart rates (bradycardia) whereas the ICD primarily detects and corrects fast (tachycardia) rhythms but today it can also be used as a back up pacing for slow rhythms (bradycardia).

ICD therapies

Bradycardia Pacing - backup pacing when the heart becomes too slow

Antitachycardia pacing (ATP) - A rapid sequence of small pacing pulses intended to stop/over-ride VT allowing the heart to return to its normal rhythm (Sinus Rhythm). The patient may feel “fluttering” of the heart whilst this treatment is in progress.

Cardioversion If ATP does not resolve the arrhythmia, the ICD will be programmed to deliver a small shock to stop VT. Described as a thump, these shock impulses may progress from low energy to high as needed.

Defibrillation. A high energy shock is delivered to treat VF. It is designed to interrupt the rapid heart rhythm so that a normal rhythm can be restored - it is described as a “kick in the chest.”

Although ICD’s do not cure the underlying disease that causes the arrhythmia, the device will monitor the heart rate, deliver the appropriate treatment and keep a record of the event for evaluation. Initially, apprehension, fear, anxiety and depression are very common emotions for the patient and their families. However, it is important to look upon the device as a “safety net” that will only “kick in” if a rhythm problem arises. In that respect it will hopefully remove the fear of a life threatening event, ultimately giving the patient more confidence to return to their previous activities and resume a “normal” life. In time most people do develop a very positive attitude to the ICD device and enjoy a full and active life after ICD implantation. It is always very important to follow the Doctors advice with regard to resuming normal activities and to attend regular follow up clinics.

The ICD is implanted with a similar concept as Heart Pacemakers.

Getting started with your implantable defibrillator: Of course, while you’re healing, you may experience some discomfort. There may also be some limits on moving your left arm, so you do not dislodge the leads. These limits usually apply for two to six weeks. Your doctor will provide more detailed information on what type of movements and lifting is allowed.

Living successfully: Developing the confidence you need: Your new heart device will keep you feeling safe and secure. It is always on call, continuously monitoring your heart 24 hours day. If your implantable defibrillator detects a rhythm problem, it will send out electrical signals to correct it. You can think of it as an emergency response team that is always with you. And very soon you will feel those positive effects in your everyday life. Keep in mind that you still have to take your medication as directed and have your device monitored periodically by both your cardiologist and electrophysiologist (heart rhythm specialist). Otherwise, your life is your own. So enjoy it. Go ahead and schedule things. Tell people how well you’re doing, what you've accomplished thus far, and what you’re going to be doing soon. Achieving quality of life often means identifying what you enjoy doing and returning to the activity.

What happens after a shock: Making a plan: If your implantable defibrillator detects a problem with your heart rhythm, it may deliver a shock to your heart. People describe the shock as surprising and uncomfortable, and sometimes painful, but it passes quickly. It also means the implantable defibrillator has done its job and that it has probably saved your life. It's helpful to understand that what you were doing at the time of the shock did not cause the shock. Generally you will still be able to do the activities that you enjoy. Although getting a shock may reduce your confidence temporarily, it’s important to return to your everyday activities and focus on enjoying life.

If you receive a shock, do the following:

1. Calm and find a quiet place to sit or lie down, 
2. Take notice of how you feel and tell others. 
3. Ask a family member or friend to stay with you until you feel better. Anyone touching you while the device is delivering a-shock might feel the muscles in your chest and upper arms contract. The shock will not harm the person touching you.
4. Instruct the friend or family member to call for an ambulance if you receive a shock and remain unconscious for more than one minute.
5. If you do not do well after the shock, ask someone to call your doctor and help you get to the nearest emergency room.