First Aid

Advice for First Aiders, lifeguards, friends, family and colleagues of anyone who has an Implanted Defibrillator and whose machine starts firing.

What is an internal defibrillator?

It is a “built-in” Heart Start machine and works exactly like the external defibrillator machine you see on TV being used to resuscitate someone who has had a cardiac arrest.  It has a computer which monitors the heart and fires the machine if the patient’s heart goes wonky.

What is wrong with the people who have these machines?

They may have one of several different heart problems but they all get periods when their heart starts going very fast (more than 180 beats in a minute).  This speed makes the heart very inefficient and if it is not slowed down they will die.  The shock the machine gives usually settles the heart rate.

How will I know if their heart is going too fast?

The patient is faint, or has passed out.  Usually their pulse cannot be felt, but it may be very faint and too fast to count.

How will I know if the person’s defibrillator has fired?

Two things may happen:-
  1. They faint and fall down and then twitch quite violently once or up to five times with intervals of about 30 seconds between.  The twitching is not continuous, as it would be with epilepsy. 
  2. They remain conscious and tell you that the machine has fired.  During the firing they may twitch strongly enough to fall down and they may make a loud sound.  They may be able to tell you that the machine is about to fire again.

If the defibrillator fires will it harm anyone touching the patient?

No.  It is not like in “Casualty” with everyone having to stand back whilst the person is zapped.  The internal defibrillator uses a much lower charge.  If you are in contact when it fires, you may feel a slight tingle or nothing at all.

What should be done if you come across someone whose machine has fired?

  1. Don’t panic.
  2. If they are still conscious help them to a seat or to lie down and get them to safety if they are anywhere that might be dangerous – but do ask them what help they want.
  3. If they are unconscious, follow the usual First Aid procedures and put them in the recovery position.  Keep feeling their pulse to see if it is going at an ordinary rate or of it is too fast.
  4. Once the episode is over, ask the person if they want to go to hospital.  If they do and there has been one firing only, then they could go by car, but otherwise they should go by ambulance (tell Ambulance Control that a Coronary Care Ambulance is needed).

What if the machine does not settle the heart down?

The machine gives up if the rhythm does not settle after five firings.  If that happens then you must start Cardio-Pulmonary Resuscitation (heart massage and mouth-to-mouth breathing) until the patient recovers or the paramedics arrive.  Get someone to call an ambulance while you are doing this.


1.   Don’t panic – Remember your First Aid.

2.   Get the patient to safety.

3.   If unconscious, put the patient in the recovery position.

4.   Monitor their pulse.

5.   If the pulse remains absent or very fast after the machine has fired – start CPR.

6.   Summon help.

Whilst the Sutton ICD Support Group makes every effort to ensure accurate information,
we disclaim any legal responsibility for actions as a result of the contents of this page.