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Implantable defibrillators

What is an implantable defibrillator?

An implantable defibrillator (or ICD for short) is a device used to treat dangerous abnormal heart rhythms (arrhythmias) such as ventricular tachycardia and ventricular fibrillation (see elsewhere in the patient information section for an explanation of these conditions). These arrhythmias can cause a cardiac arrest (a cardiac arrest is a loss of effective heart contraction preventing effective blood flow to vital organs). A cardiac arrest leads to death within a few minutes unless it is treated effectively. An ICD consists of a small metal box (or pulse generator), not much bigger than a match box with between one and three leads (flexible, insulated wires connecting the pulse generator to the heart). The function of an ICD is to detect dangerous abnormal heart rhythms and treat them with either small pulses of electricity (this is called overdrive pacing) or with an electric shock. This will return the heart rhythm to normal within a few seconds.


How is an ICD implanted?

ICDs are usually implanted under general anaesthetic but sometimes sedation and local anaesthetic is used. The doctor makes a small incision under the left collar bone. A lead (or leads – up to 3 might be used) is then inserted into a large vein underneath the collar bone and passed along the vein into the heart. The ICD uses the lead to sense the heart rhythm and to deliver electrical stimuli or electrical shocks to the heart. The lead is then attached to the generator and the wound is closed with sutures. The sutures or stitches are usually absorbed by the body and do not need to be removed.


What are the risks of implanting an ICD?

The risks include: death (less than 1% of cases), infection (less than 1% of cases), bleeding (risk of serious bleeding less than 1%) and pneumothorax or collapsed lung (less than 1% of cases).


How does the ICD function?

The ICD monitors the heart rhythm at all times. If a person develops ventricular tachycardia or fibrillation, it decides whether to treat the rhythm with pacing (small electrical stimuli) or an electric shock. The appropriate treatment is usually delivered within a few seconds returning the heart rhythm to normal.


What is the recovery period after ICD implantation?

Even though the wound is covered with a waterproof dressing, we recommend that the patient does not allow the wound to become wet for seven days. The dressing is usually removed at this time. We also recommend that you do not perform vigorous arm movements or raise the arm on the side of the ICD above the level of the shoulder for 4 weeks after the implant surgery. This is because it takes some time for the ICD lead to become fixed properly in the heart. Excessive arm movement can dislodge the lead. You can move the arm on the opposite side to the implant normally. It is important not to keep the arm rigidly by the side as this may cause the shoulder to become stiff. Your doctor will show you some gentle movements you should use to exercise the arm on the side of the implant. In Australia it is illegal to drive a motor vehicle for 2 weeks after an ICD is implanted.


Will the ICD restrict my activities?

In general, people with ICDs can undertake most activities. However, people with ICDs should not place magnets near the ICD and should not perform electrical welding. In some cases it may be possible to use an electric welder but this should only be done if the welding machine has been tested with a technician present and the results discussed with your electrophysiologist. Driving a motor vehicle may be restricted in patients with ICDs but this is not because of the ICD itself but rather because of the medical condition which caused the need for the ICD.


Can I hold a driver’s licence if I have an ICD?

Most people with ICDs can continue to drive a car but it is essential that you discuss this with your cardiologist before getting back behind the wheel. Restriction from driving is not caused by the ICD itself.  If your doctor thinks that here is a high risk of you losing consciousness from your heart condition, the licensing authorities might not allow you to drive or might place a restriction on your driving (for example, you might restricted to driving short distances)

Will devices apart from welders cause problems with the ICD?

Most devices such as mobile phones, airport metal detectors, electric blankets, microwaves and shop security systems do not usually cause problems with the ICD.


Do ICDs sometime make mistakes?

Occasionally, ICDs will deliver shocks for abnormal heart rhythms that are not dangerous; however, nearly always, your cardiologist can ‘teach’ the ICD not to do this.


How long does the ICD battery last?

The battery usually lasts between 5 and 10 years. The battery itself cannot be changed, but a new pulse generator will be implanted. The device is usually changed well before the battery runs out.

Will I need to see my doctor regularly to have the ICD checked?

Yes. It is very important to visit your electrophysiologist regularly. In most cases the ICD is checked every 6 months but visits will be scheduled more frequently as the time for ICD replacement approaches.


What about remote monitoring?

Some ICDs are capable of being connected to a device which will send a message to your electrophysiologist if a problem develops with the ICD. This is called a remote monitor. These devices are usually placed in your bedroom (for example, under the bed or on a bedside table) and communicate with your ICD on a regular basis. If a problem is detected, a message is sent over the mobile phone network or over a landline. However, these messages are not monitored on a 24/7 basis and it maybe 24-72 hours before the message is received. These devices do not remove the need for regular checks with your electrophysiologist although it may be possible to increase the interval between checks. In addition if a problem is detected by the monitor which requires the ICD to be re-programmed it will be necessary to visit your electrophysiologist since the ICD cannot be reprogrammed using the remote monitor.


Are ICD shocks painful?

ICDs can terminate an abnormal heart rhythm (arrhythmia) with an electric shock or with pacing (see above). Most arrhythmias are terminated with pacing which causes little or no discomfort. However, if the arrhythmia is not terminated by pacing or if the arrhythmia is more serious an electric shock might be required to restore the heart rhythm to normal. ICD shocks are painful but the discomfort lasts only for a moment. Sometimes the abnormal heart rhythm which causes your ICD to discharge causes a loss of unconsciousness and if this occurs the shock will not be felt.


What should I do if I get a shock from my ICD?

If you receive a shock from your ICD, try to remain calm and rest for a few minutes. If you receive a shock this does not mean that your heart is deteriorating. It is not necessary to attend hospital if you receive a single shock. You should contact your doctor but this is not urgent and can wait until the office reopens if the shock occurs out of working hours. However if you feel unwell or receive multiple shocks over a 24 hour period you should contact your doctor immediately or call an ambulance so that the ICD can be checked and your medication can be reviewed.


Can I have an MRI scan if I have a ICD?

Most modern ICDs and leads are “MRI compatible”, in other words it is safe to have an MRI scan if you have one of these ICDs. Older ICDs may not be MRI compatible or may not have been tested for MRI safety. Careful planning is essential before performing a MRI scan since it may be necessary to have technician present during the scan and the ICD’s program will need to be adjusted so that the scan can be performed safely. Lastly, MRI scanning in patients with ICDs is a relatively new procedure and not all MRI centres have developed protocols; these centres may not be prepared to perform the scan.


© Dr Mark McGuire 10/1/2018 (version 1.0)