Your Questions Answered: Pacemaker or Implantable Defibrillator?


Have you ever heard of implantable cardioverter defibrillators (ICDs) or pacemakers? Admittedly, they’re not really topics which come into every day conversation.

Depending upon diagnosis and the different cardiac conditions which can occur, one of these devices may be required to prevent the patient from experiencing a dangerous cardiac event in the future or be fitted as a preventative measure.

It’s quite common for these two devices to be mixed up, but we’re here to clear up the differences on these small, but powerful devices that both have the power and technology to save a life.


A pacemaker is a small device – about the size of a matchbox – that is surgically implanted into a patient’s chest or abdomen and weighs around 20-50g.

The pacemaker consists of a pulse generator – which includes a battery and a small computer circuit and either one or more wires which attach to your heart, these wires are known as pacing leads.

The generator sends electrical impulses through the wires to the heart; the rate at which the impulses are sent out are called the pacing rate.

Almost all modern pacemakers will work on demand. If the device senses that your heart is beating too slow, signals will be sent which will assist with steadying and regulating the rhythm. If it senses that your heart is beating regularly of its own accord, no signals will be sent out.

Pacemakers can be required for many reasons. A few of them are:

  • Abnormally slow heartbeat (Bradycardia)
  • Abnormally fast heartbeat (Tachycardia)
  • Cardiac arrest – where a problem with the electrical signals cause your heart to stop beating altogether and quiver
  • Heart block – where your heart beats irregularly because the electrical signals are not being transmitted properly

Implantable Defibrillators

An Implantable Cardioverter Defibrillator (ICD) is a small device that is again placed under the skin of either your chest or abdomen and is usually fitted if you have an irregular heartbeat or are at risk of suffering a cardiac arrest.

Even though these two devices are very similar, ICDs send a bigger shock to the heart that will ‘reboot’ it to get it pumping and beating in a regular rhythm again. Some devices contain both an ICD and a pacemaker.

ICDs are usually used as a preventative measure for people thought to be at risk of sudden cardiac arrest at some point in the near future.

If the fitted ICD senses the heart is beating at a potentially dangerous abnormal rate, it will deliver an electrical shock to the heart. This shock will often help the heart and return it back to a normal rhythm.

Now You Know

So, there you have it. Now you know the difference between these small but powerful, life-saving devices.

Maybe you’re one step ahead of us and already knew the difference between these two devices – which if you did is great! If this is you, then we’d love to hear how you already knew the differences!

Leave us a comment below or if commenting isn’t your thing, head on over to social media and Tweet us @defibshop with how you knew the difference.

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