Implantable cardioverter defibrillator and cardiac resynchronisation therapy

An implantable cardioverter defibrillator (ICD) is a small device fitted under the skin near your collarbone that watches your heart’s rhythm and delivers a shock or pacing pulse if it turns dangerous. Cardiac resynchronisation therapy (CRT) uses a similar device with an extra wire to help the two pumping chambers of your heart beat together, easing the symptoms of heart failure.

What conditions does it treat?

Your cardiologist (heart specialist) may recommend an ICD if you're at risk of a dangerous heart rhythm, or a CRT device if you have heart failure that hasn't responded well enough to medicines alone. Sudden cardiac death affects an estimated 50,000 to 70,000 people in the UK each year, which is why spotting who's at risk matters so much.

• You've survived a cardiac arrest caused by a dangerous heart rhythm known as ventricular tachycardia or ventricular fibrillation
• You've had a fast heart rhythm that made you faint or feel very unwell, even without a full cardiac arrest
• Your heart's main pumping chamber is working at 35% or less of its normal capacity, alongside heart failure symptoms that are no worse than moderate
• You have an inherited heart condition with a high risk of sudden death, such as long QT syndrome, hypertrophic cardiomyopathy, Brugada syndrome or arrhythmogenic right ventricular dysplasia
• You have heart failure alongside a delay in your heart's electrical signal, shown as a widened pattern on a heart tracing (ECG), which CRT is designed to correct.

What are the benefits of an ICD or CRT device?

Clinical trials have shown these devices can meaningfully improve how long you live and how well you feel.

• ICDs have been shown to reduce the risk of dying, compared with medicines alone, by between 23% and 55%, depending on your individual risk.
• In one major trial, CRT-P reduced the combined risk of death or emergency hospital admission by 37%, and cut deaths from any cause by 36%, an effect still seen after 36 months of follow-up.
• CRT can improve your symptoms, quality of life and how far you can walk without becoming breathless.
• Both devices act immediately: they recognise a dangerous rhythm as it happens and deliver treatment, such as painless pacing or a shock, straight away.

Are there different types of device?

There are a few versions of these devices, and your cardiologist will recommend the one that suits your heart condition.

• ICD, single chamber: one wire, placed in the right ventricle (the heart's main pumping chamber).
• ICD, dual chamber: two wires, one in the right ventricle and one in the right atrium (the chamber above it), which can also treat slow heart rhythms like a standard pacemaker.
• CRT-P (cardiac resynchronisation therapy with pacing, also called biventricular pacing): three wires, helping both lower chambers of the heart beat together.
• CRT-D: combines CRT-P with a defibrillator, so it can also deliver a shock if a dangerous rhythm develops.

What happens before the procedure?

Before deciding whether an ICD or CRT device is right for you, your cardiology team will run tests to check your heart's structure and electrical activity. These may include:

• Echocardiogram (an ultrasound scan of the heart), to measure how well your heart pumps and check for any mistiming between its chambers.
• Coronary angiography (a dye test to look at the blood vessels supplying your heart), if needed.
• Cardiac MRI (a detailed scan of your heart), if needed.
• Electrophysiology study (a test that maps your heart's electrical activity), if you've had a dangerous rhythm or cardiac arrest.
• An assessment by an anaesthetist, since your procedure involves sedation or, occasionally, a general anaesthetic.

What happens during the procedure?

1. The procedure is carried out by a cardiologist, usually under local anaesthetic and light sedation, in sterile surgical conditions.
2. A cut around 4–5cm long is made in your chest wall, about 1cm below your collarbone.
3. Your cardiologist accesses a vein close to this point, known as the subclavian, axillary or cephalic vein.
4. Using X-ray guidance, the wires (leads) are carefully threaded through the vein into the right side of your heart, and into the coronary sinus vein too if you're having CRT.
5. The wires are connected to the ICD or CRT device, which is then placed under the skin below your collarbone.

What does recovery look like?

In hospital

Most people stay in hospital overnight after having an ICD or CRT device fitted. Before you go home, you'll have a chest X-ray, a check of your new device, and a review of your wound to make sure everything is settling well.

At home

Heart rhythm devices need regular, long-term follow-up, usually for the rest of your life. Your first check-up is normally within 2 months of your procedure, then at least once every 6 months after that.

• Wound checks and a review of any new symptoms.
• Device checks, including battery level, how well the wires (leads) are working, and how the device is set up.
• Access to a heart failure team, arrhythmia nurses, or a clinical psychologist if you need extra support.
• A 24-hour service if you experience repeated shocks or another device-related problem.
• The device battery typically lasts up to 6 years before it needs replacing.

What are the risks and complications?

As with any procedure that involves fitting a device inside your body, there are some risks to be aware of.

• Damage to the vein used to place the wires, including tearing or a small perforation.
• The wire moving out of position after the procedure, known as lead dislodgement.
• Infection around the wound or device.
• Very rarely, death.
• If you have a defibrillator (ICD or CRT-D) and experience a shock, this can sometimes cause anxiety or other emotional after-effects.