What is an internal cardiac defibrillator ( ICD)?
An internal cardiac defibrillator (ICD ) is a special type of pacemaker which can pace the heart if needed but also shock the heart back into normal rhythm for a life-threatening arrhythmia. Because the device requires capacitors as well as a larger battery than a normal pacemaker, it has about 5 times the volume of a pacemaker and is therefore often placed under the muscle layer below the collar bone, rather than above the muscle layer.
How does it work?
An ICD continuously monitors the signal coming from the heart by means of implanted electrodes. There may be 1, 2 or 3 electrodes, depending on the ICD configuration. If the heart beats too slowly, it can pace the heart to keep the rate up, if it goes too fast, with certain characteristics, the device may charge the capacitors and deliver a shock to restore normal rhythm. In many cases patients would die if the ICD was not there to intervene.
The ICD is programmed according to the type of arrhythmia you have and your symptoms. It will be programmed once it has been implanted by the consultant with the use of a computer programme. The consultant can change the programme during the course of your therapy, without needing to perform another surgery.
How is the ICD inserted?
The ICD can be inserted under local or general anaesthetic, your consultant recommending the best option for you. You will need to discuss with your consultant any medication you are taking, and you will be asked to not eat or drink anything six hours before the procedure.
During the procedure you will be connected to an electrocardiogram machine to monitor your heart rhythm. Unless you are under general anaesthesia, a needle will be inserted in your arm to dose the local anaesthetic which will cause a slight discomfort and pain as the needle is inserted.
The ICD is typically inserted in the opposite arm to your dominant side. The consultant will insert wires through your vein that will go to your heart. The number of wires depends on what kind of ICD you need. Once the wires are in position against your heart wall, the consultant will create a small pocket under the skin to place the generator and connect the wires to it.
After everything is set in the place the consultant will test the ICD to check it’s programmed correctly.
Recovering after the procedure
After the procedure you will return to your room where your heart rhythm will be monitored for the following 12 to 24 hours. The team will assist you with anything you may need whilst the sedation wears off.
Before going home, the ICD will be checked again to make sure the defibrillator is working correctly and the device is programmed correctly.
You may feel uncomfortable in the following days whilst your wound heals. You mustn’t lift the arm above the shoulder where the ICD is implanted for the first four weeks. You can move the arm where the ICD is implanted normally to prevent stiffness but avoid heavy lifting, pushing or pulling in the first four weeks.
Your consultant will inform you about the whole recovery period.
What are the benefits of an ICD Implantation?
An ICD is 99.8% likely to detect and treat a life-threatening ventricular arrhythmia. This is why many patients who suffer from arrhythmias will have more peace of mind having an ICD implanted because it can provide instant treatment. Also, some patients notice a decrease in symptoms such as light-headedness, dizziness or fainting when having the ICD.
How safe is the treatment?
This is a safe procedure. However, sometimes patients may receive inappropriate shocks. This happens in about 15% of patients. Your consultant will discuss with you all the risks before giving your consent. Potential risks are:
Allergic reactions to medicine
Severe bruising and swelling where the ICD is inserted
- Pericardial effusion
- Lead displacement
- Blockage in the veins