How does a pacemaker work?

Most people are aware that pacemakers help to regulate your heartbeat, but how much do you actually know about how they work?

We take a look under the lid of this matchbox-sized device to discover the extraordinary technology involved.

We take a look inside a pacemaker

1. Leads

There are two leads connected to most pacemakers. In some atrial fibrillation patients we only insert one lead.
These leads are very thin, flexible, electrically insulated wires that are inserted into the vein at the top of the shoulder and travel inside it to go into chambers on the right side of the heart. 

2. Pacemaker box

The leads are attached to a pacemaker box/generator that contains a battery and a small computer with some memory in it to record any heart rhythm abnormalities. The box sits in the upper left chest, below the collarbone. A pacemaker senses through its wires what the heart is doing. If it senses that the heart has slowed down or missed a beat, then it will send an electrical impulse to stimulate the heart to restore it to its normal rate.

3. Battery

The average lifespan of a pacemaker battery is about 6–7 years. There is plenty of warning before the battery runs out and patients are regularly checked towards the end of the battery life.
The procedure for changing the battery is much simpler than when pacemakers are put in. The wound is reopened and the pacemaker box is removed, but the leads stay in place. Most people go home the same day. 

Inside a pacemaker

4. Electrodes

At the tip of each wire are electrodes. These are the contact points between the pacemaker and the heart – where the electrical signal is delivered from the pacemaker to your heart, and where the information about your heart’s signalling action is received and carried back to the pacemaker. 

5. Barbs or screws

The leads are attached to the heart muscle by a tiny barb or small screw mechanism. Traditionally there will be one in the right ventricle and one in the right atrium.
  • Read the inspiring stories of two people who have had pacemakers fitted.
  • Have more questions about pacemakers? We cover your frequently asked questions.


Which device?

Pacemaker closeupThere are several types depending on your needs:

A standard pacemaker

This has one or two leads and is used to treat conditions such as heart block or slow heart rate.

Cardiac resynchronisation therapy (CRT)

This is a more sophisticated pacemaker with three leads used to improve the pumping efficiency of the heart muscle in heart failure patients, when the main pumping chambers beat out of time with each other. Some CRT devices also have an Implantable Cardioverter Defibrillator (ICD) function (see below).

Implantable cardioverter defibrillators (ICDs)

These deliver an electric shock to kickstart the heart. They're used for people at risk of a life-threatening heart rhythm disturbance such as ventricular tachycardia or ventricular fibrillation. Some also have a pacing function as part of the device.

Find out more

Read more about pacemaker do's and don'ts.

If you're concerned about interference from any equipment at home or at work, call your pacing clinic or the Medicines Healthcare Regulatory Agency on 020 3080 6000.

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