An implantable cardioverter defibrillator, or ICD, is an electronic device that treats your arrhythmia and prevents your heart from beating too fast (tachyarrhythmia) or too slow (bradycardia).
An ICD consists of a pulse generator, or defibrillator, and leads. The defibrillator is like a small computer that runs on a battery. The battery and circuitry are sealed inside a titanium case. The leads are insulated wires that connect the defibrillator to your heart.
The defibrillator continually monitors your heart rhythm and has been programmed by your cardiologist to respond in specific ways to treat your arrhythmia. There are three ways the ICD may respond: pacing, cardioversion and defibrillation.
This may be used to treat slow or fast rhythms. If your heart beats too slowly or (below a limit set by your cardiologist), your ICD will detect this and will deliver pacing impulses to stimulate your heart. It will continue to do this until your heart starts to beat at a normal rate on its own.
Your cardiologist may also program your ICD to deliver a sequence of pacing impulses as the first step in the treatment of a rapid heart rhythm. One particular form of rapid heart rhythm that is treated this way is called ventricular tachycardia (VT). If normal rhythm is restored no further treatment is delivered.
If pacing does not stop the arrhythmia, the ICD will deliver the next therapy – cardioversion. This involves delivering stronger electrical impulses to the heart muscle. Cardioversion shocks may progress from low energy to high energy as needed.
This is similar to cardioversion, but delivers a stronger high energy shock to your heart. This is used when pacing and cardioversion have not been successful in treating VT. It is also always used first to treat a different form of rapid heart rhythm, ventricular fibrillation (VF). VF is where several areas of the heart muscle are contracting in a disorganised and erratic manner. If this happens the heart muscle quivers and the heart no longer pumps any blood at all. The body quickly becomes starved of oxygen and you would usually pass out within a few seconds. This situation is called cardiac arrest.
The electrical current from the ICD during defibrillation passes through the heart, shocking your heart out of VT or VF and stopping the erratic electrical activity allowing the heart to return to a more regular rhythm within those first crucial seconds.
A programmer is a machine that is kept by your cardiologist and used to communicate with your ICD via radiofrequency waves. It is used to program the settings of your ICD so that it is fine-tuned to your specific needs. The programmer also reads information contained in the ICD.
Detailed data, including date and time, is provided by the ICD regarding any rapid or slow rhythms you may have had and how they were treated by your device.
What do the treatments feel like?
Most people do not feel these impulses and may not be aware that pacing is occurring. If the pacing is to stop VT, you may feel a slight fluttering sensation in your heart. Clinical data suggests that around 90% of VTs are stopped by pacing.
Most people say this is mildly uncomfortable and describe it as a sharp thump to the chest.
Often the person has lost consciousness when this therapy is delivered, so they are not aware of it occurring. People who have experienced a defibrillation shock whilst conscious describe it feeling like a "kick to the chest". They say it startles them and is distressing but only lasts for a second.
Your preparation may include tests to gather information about your heart rhythms. You may have already had these prior to admission. These tests may include: a blood test, a 12 lead Electrocardiograph (ECG), or a Cardiac Electrophysiology Study (EPS).
Your doctor will advise you if any medication needs to be ceased prior to the procedure. You will be required to fast for 6 hours prior to the procedure. Male patients will be required to have their chest shaved. You will have a cannula inserted and connected to a drip. Before the procedure, you will be given a sedative to help you relax.
The procedure will be performed in the cardiac catheter theatre and should take approximately 2 hours. It will be performed under a local anaesthetic.
The ICD leads will be implanted transvenously, meaning they will be inserted through a vein, in the left upper chest region. The lead is then threaded through the vein to the appropriate chamber in the heart.
After the leads are in position, they are secured and connected to the pulse generator which is positioned on the left side of your upper chest.
During the procedure, the ICD may be tested to ensure it can detect and successfully treat VF. During this time you will be given a light anaesthetic.
Following your procedure, you will return to the ward and be monitored overnight.
Your ICD will be checked the following morning by your doctor or pacemaker technician. The monitoring leads will be removed once your device has been checked. It is normal to still experience some pain at the insertion site. This should be eased by taking paracetamol.
You will have a dressing over your wound site and will be advised on how to care for this by the nursing staff. The dressing will be removed 3 days after you are discharged, then the site will be left uncovered. You do not need to have any stitches removed as they are dissolvable.
Most people will be discharged from hospital the following day. Your doctor will advise you on your follow up appointments prior to discharge.
It is quite normal to leave hospital feeling emotionally and physically drained and perhaps a little depressed. This will improve as you recover. Most people adapt very well to their ICD and return to most of their previous activities.
How will the ICD affect my life?
Your doctor will advise you on what you should and should not do when you return home. Once you have fully recovered, you should be able to confidently resume all your normal activities.
You can safely use all common household appliances including microwaves, televisions, computers etc.
Depending on your condition, your doctor may advise you to avoid activities during which a few seconds of unconsciousness may be dangerous to you or others. These may include driving, climbing a ladder or boating alone.
You will receive an ID card prior to discharge. We advise you to carry your ID card at all times to alert medical and security personnel that you have an implanted device.
Avoid the following probable sources of electrical interference
- Mobile phones and handheld devices (iPad etc.)
- Studies have indicated that there may be some potential interaction between mobile phones, handheld devices and ICDs. The effect is temporary and may include preventing pacing when the phone is within close proximity (15cms). You can use your mobile phone and device safely by doing the following:
- Maintain a minimum distance of 15cms between your ICD and mobile phone/device.
- Hold the phone / device to the ear opposite your ICD.
- Don't carry your phone in your breast pocket.
- MRI Scanners.
- TENS machines used by physiotherapists.
- Electrical arc welding equipment.
- Dielectric heaters – used in industry to bend plastic.
- Electric steel furnaces.
- CB radio antennas.
- Some battery powered tools.
Airport screening devices may detect the ICD's metal case. It will be necessary to present your pacemaker identification card to obtain clearance.
Always tell any health professional that you have an ICD and show your ID card. Most medical procedures are unlikely to interfere with your pacemaker, except MRI scanners.
Follow Up Appointments
An important feature of your ICD is the information that it stores about your heart function that is accessed by your cardiologist to assist with your ongoing treatment. This takes place at regular routine check-ups either in the QCG's rooms or via our Remote Home Monitoring service (see below) that your doctor will schedule; the first after 3 months, and at least every 12 months thereafter. At these appointments, your doctor will also ensure that your ICD is functioning correctly. A typical follow up appointment in the rooms will last about 20 minutes, during which time your doctor will assess how your device has performed since your last visit, any irregular heart rhythms or events that have occurred and remaining battery life (which will be replaced well before the battery is flat).
Remote Monitoring Service
QCG offers a remote monitoring service that enables 'virtual check-ups' for your implanted device. This allows you to directly and securely transmit data from your device to your cardiologist from the comfort of your own home. This enables us to detect significant events such as an abnormal heart rhythm, monitor the performance of your device such as battery life, and optimise your care through device programming or medication change.
Your participation in remote monitoring allows us to follow your device function between visits, and in some situations, it may replace office visits. This means less time spent at the doctor’s office for regular checks, faster time to treatment if your cardiologist detects a medical problem and faster troubleshooting if a problem is detected with your device. Research evidence has shown that early detection of issues through remote monitoring leads to improved health outcomes and a reduced risk of hospital admission. It also allows you to monitor your own heart rhythm and quickly detect any irregularities or arrhythmias.
For more information go to Remote Monitoring Service.