When is an ICD shock an emergency?

Call 995 if a shock is followed by feeling unwell (chest pain, breathlessness, dizziness, fainting or continuing palpitations), or if you receive more than one shock in a short time (often described as within about a day), whether you feel well or not. Take your device card to hospital.

Is it safe to touch someone while their ICD fires?

Yes, completely. If a person with an ICD collapses and is unresponsive, start CPR and call 995, and use a public AED if available (pads clear of the device bump). If the device fires while you touch them, you may feel a harmless small tingle, which must not stop you helping.

What are two or more shocks a sign of?

Multiple shocks in a short time can mean the heart keeps returning to a dangerous rhythm (an electrical storm), which needs urgent hospital assessment. Do not wait to see if it settles: call 995 or go straight to A&E, whether you feel well or not.

What is a shock plan?

A written plan agreed with your team before you need it, setting out exactly what to do after a shock and who to call, which your family also know. Keep your device card, medicines list and clinic number accessible. The device records each shock so the clinic can review it.

What to Do if Your ICD Delivers a Shock

Q: I had one ICD shock and feel fine. What should I do?

Sit or lie down somewhere safe, as a shock can leave you light-headed, then contact your ICD or device clinic to report it and arrange follow-up. This is usually not an emergency but must be reported. Some teams advise seeking help for a first-ever shock, so follow your own plan.

Written & reviewed by the BestDoctors.sg editorial team · Last updated 28 Aug 2026 · General information, not medical advice

An ICD shock can be frightening, but knowing in advance exactly what to do makes it manageable and can be life-saving. The response depends on a few simple questions: was it one shock or more, and do you feel well or unwell afterwards. This guide sets out the clear rules, taught by device teams, so you and your family know what to do. Always follow your own team’s written shock plan, as plans can differ.

Chest pain, palpitations or breathlessness on your mind?

Message our care team on WhatsApp. Tell us what’s going on and we’ll help you find the right cardiologist — free, with no obligation.

Chat with our care team on WhatsApp

Not sure who to see? Find the right specialist →

In a medical emergency, or for severe or sudden symptoms such as breathing difficulty, chest pain, fainting or stroke signs, call 995 immediately.

Call 995 immediately if a shock is followed by feeling unwell (chest pain, breathlessness, dizziness or fainting), if you receive more than one shock in a short time, or if someone with a device collapses. It is safe to touch a person while their ICD fires: start CPR and call 995. After a single shock while feeling well, contact your device clinic to report it.

What a shock feels like

An ICD only acts on a dangerous fast rhythm, and it may first try painless rapid pacing, which some people feel as a brief flutter and should not mistake for a shock. If a shock is needed, it feels like a sudden heavy thump or kick in the chest or back. It is startling, and you may jump or call out, and those nearby may be alarmed too. A shock can also leave you briefly light-headed, so the first thing to do is get yourself safe, sitting or lying down before you do anything else.

One shock, and you feel well

If you receive a single shock and feel well afterwards, sit or lie down somewhere safe, because a shock can leave you light-headed for a moment. Then contact your ICD or device clinic to report it and arrange follow-up. This is usually not an emergency, but it must be reported, so the clinic can read what the device recorded and check everything is working as it should. Some teams advise seeking help for a first-ever shock, so follow your own written plan.

A shock, and you feel unwell

If a shock is followed by feeling unwell, this is an emergency. Warning signs include chest pain or pressure, breathlessness, continuing palpitations or a racing heartbeat, dizziness, confusion, feeling faint, or simply feeling very unwell. In this situation, call 995 or go to A&E without delay. The shock means the device has detected and treated a dangerous rhythm, and feeling unwell afterwards can mean the problem is ongoing and needs urgent care.

Two or more shocks in a short time

Receiving two or more shocks within a short period, which guidance often describes as within about a day, is an emergency whether you feel well or not. Multiple shocks can mean the heart keeps going back into a dangerous rhythm, sometimes called an electrical storm, and this needs urgent hospital assessment. Do not wait to see if it settles. Call 995 or go straight to A&E, and take your device identification card with you.

If someone with an ICD collapses

This is vital for families to know. If a person with an ICD collapses and is unresponsive and not breathing normally, treat it as you would any cardiac arrest: start CPR (chest compressions) straight away and call 995, and send someone for a public defibrillator (AED) if one is nearby. It is completely safe to touch and do CPR on someone with an ICD. If the device fires while you are touching them, you may feel a harmless small tingle, which must not stop you helping. A public AED can still be used, with the pads placed clear of the device bump.

Your shock plan and the device record

Prepare a written shock plan with your team before you ever need it, setting out exactly what to do and who to call, and make sure your family know it and know the clinic number. Keep your device identification card, a list of your medicines and the clinic contact accessible. The device stores exactly what happened, so after a shock the clinic can read the event, at the clinic or through a home monitor upload, and adjust settings if needed. Knowing these few rules in advance, and sharing them with your family, turns a frightening moment into something you can handle calmly. It is worth going over the plan more than once with the people you live with, so that everyone knows what to do and who to call if the moment ever comes, which makes it far less frightening for them as well as for you. In Singapore, 995 is the emergency number, and your device clinic is your first contact to report a shock and arrange review.

Sources

Sudden Cardiac Arrest UK – How to respond to an ICD shock: suddencardiacarrestuk.org
Sudden Cardiac Arrest UK – ICD shocks: what they feel like: suddencardiacarrestuk.org
Liverpool Heart and Chest Hospital NHS – ICD shock plan: lhch.nhs.uk
Resuscitation Council UK – How we save lives: resus.org.uk

General information only. This guide supports, but does not replace, the advice of your cardiology team, who fit and program your device and tailor your care. Always carry your device identification card, and tell any doctor, dentist, surgeon or radiographer that you have a cardiac device before any procedure or scan. Never assume an MRI is safe. Call 995 if an ICD delivers a shock and you feel unwell (chest pain, breathlessness, dizziness or fainting), if you receive more than one shock in a short time, or if someone with a device collapses: start CPR and call 995, as it is safe to touch them. Do not drive until your cardiologist and the traffic authority have cleared you. If you are struggling emotionally, you are not alone: the Samaritans of Singapore (SOS) are on 1767 and mindline.sg on 1771.

What to Do if Your ICD Delivers a Shock (Singapore)