Implantable cardioverter defibrillator (ICD)

What is an ICD?

An implantable cardioverter defibrillator (ICD) is a small device, implanted like a pacemaker below the collarbone, that continuously monitors every heartbeat. If it detects a dangerously fast rhythm from the pumping chambers, ventricular tachycardia or ventricular fibrillation, it treats it within seconds, first with rapid painless pacing that can terminate many episodes silently and, if needed, with a shock that restores normal rhythm. An ICD is the most effective protection that exists against sudden cardiac death, and every modern ICD also contains a full pacemaker.

Who should consider an ICD?

ICDs are recommended in two broad situations:

• Secondary prevention, for people who have already survived a cardiac arrest or a dangerous ventricular rhythm, where the case for protection is clear.
• Primary prevention, for people at elevated risk who have not yet had an event: significantly weakened heart muscle after a heart attack or in heart failure, inherited conditions such as certain cardiomyopathies, or other high-risk findings on specialist assessment.

The primary-prevention decision is a careful, personal one. It rests on accurate measurement of heart function with an echocardiogram and often a cardiac MRI, on rhythm assessment, and on an honest conversation about your individual risk, your values and the realities of living with a device. Guidelines set the framework; good judgement fits it to you.

Types of device

Beyond the standard transvenous ICD, a subcutaneous ICD (S-ICD) sits entirely under the skin with no leads inside the heart, attractive for some younger patients. Where heart failure also causes the chambers to beat out of step, a combined resynchronisation defibrillator (CRT-D) treats both problems at once; see our pacemaker and CRT page. We will recommend the device that fits your heart, your risk and your life.

What happens during implantation?

Implantation mirrors a pacemaker procedure: local anaesthetic with sedation, a small incision below the collarbone, lead placement under X-ray guidance, and device testing before you leave. Most procedures take around an hour, with same-day or next-morning discharge and simple wound care for two weeks.

Living with an ICD

Most people return to work, exercise and travel confidently; indeed, confidence is one of the device's greatest gifts. Your ICD is followed by remote monitoring from home, with clinic checks to fine-tune settings and track battery life, typically eight to twelve years between generator changes. Driving is regulated after ICD implantation and after any shock, and we will guide you through the DVLA rules for your circumstances clearly and pragmatically.

If you ever receive a shock, it means the device has done its job. One shock with rapid recovery warrants a prompt device check; multiple shocks are an emergency. Modern programming, and where needed medication or VT ablation, keeps therapies to a minimum.

Device removal and extraction

Occasionally a device or lead must be removed, most commonly for infection or lead failure. Cardiac device extraction is a specialised procedure performed in high-volume London centres with surgical backup, and where it is needed we will coordinate your care with the country's most experienced extraction teams.

Benefits and risks

The benefit is unmatched protection against sudden death, with survival gains proven in large trials for well-selected patients. The considerations are real but manageable: implant risks similar to a pacemaker (bruising, infection, lead issues), the possibility of inappropriate shocks, now much rarer with modern programming, and the practical and emotional aspects of carrying a device, which deserve honest discussion, not a leaflet.

Frequently asked questions

What does an ICD shock feel like?

Patients describe it as a sudden, startling thump in the chest, over in an instant. Many episodes are actually terminated silently by rapid pacing before a shock is ever needed, and some shocks occur during blackouts and are not felt at all. It is worth remembering what a shock represents: a potentially fatal rhythm, treated within seconds.

How is an ICD different from a pacemaker?

A pacemaker treats slow rhythms by adding beats; an ICD protects against dangerously fast rhythms and contains a full pacemaker as well. The implant procedure and daily life with the two devices are very similar.

Can I drive with an ICD?

Usually yes, after a defined interval. For a private licence, UK rules typically require one month off driving after a primary-prevention implant and longer after a shock or a secondary-prevention implant; professional drivers face stricter rules. We will set out your exact DVLA position in writing and keep it under review.

Can I exercise and travel with an ICD?

Yes. Once healed, gym training, swimming, golf and international travel are all realistic, and we will tailor advice for contact sports or strenuous overhead activity. Airport security is straightforward: walk through at normal pace and carry your device card.

What happens when the battery runs down?

Remote monitoring tracks battery life continuously, so a generator change, a short day-case procedure through the original incision, is planned well in advance. The leads usually remain in place for the new device.

Can an ICD be switched off?

Yes. Therapies can be reprogrammed or deactivated painlessly whenever that is the right decision for you, for example ahead of certain operations, or as part of sensitive end-of-life care planning, always under specialist guidance and with your wishes at the centre.

Why choose Dr Assomull?

Dr Assomull provides rigorous, unhurried risk assessment, imaging-led and personal, arranges implantation with London's experienced device electrophysiologists when protection is genuinely warranted, and remains your cardiologist throughout: optimising the medication and lifestyle factors that lower your arrhythmic risk, and looking after you and your device for the long term at 68 Harley Street.

If you have been told you may need an ICD, or you want a definitive assessment of your risk, book a consultation, usually available within one working day.