Why pacemakers are used 

Pacemakers are sometimes recommended for people with conditions that cause the heart to beat abnormally.

When the heart beats, the heart muscle contracts (pulls inwards) in preparation for pumping blood around the body. The contractions are triggered by electrical pulses. These are generated by a group of specialised cells known as the sinoatrial node (SA node).

The SA node is often referred to as a natural pacemaker because it generates a series of electrical pulses at regular intervals.

The pulse is then sent to a group of cells known as the atrioventricular node (AV node). The AV node relays the pulse to the two lower chambers of the heart (the ventricles).

A pacemaker or implantable cardioverter defibrillator (ICD) is required when something disrupts this process and causes an abnormal heartbeat.

Having an abnormal heartbeat is called arrhythmia. Some of the most common causes of arrhythmias are described below.

Sick sinus syndrome

In sick sinus syndrome, the SA node no longer works as it should. This can lead to an abnormally slow heartbeat (bradycardia), an abnormally fast heartbeat (supraventricular tachycardia) or a combination of both.

Symptoms of sick sinus syndrome can include:

  • feeling tired all the time
  • fainting
  • a dull, heavy or tight pain in the chest that is usually triggered by physical activity or stress (the medical term for this sort of pain is angina)

It is thought that most cases of sick sinus syndrome are related to age. Over time, the tissue that makes up the SA node can become hardened and scarred. This can disrupt the normal pattern of electrical pulses released by the SA nodes.

Some types of medication can also trigger sick sinus syndrome as a side effect. These include calcium-channel blockers and beta-blockers.

Atrial fibrillation

Atrial fibrillation is a condition in which the heart beats abnormally fast. This is usually defined as 140 beats or more a minute.

Most cases of atrial fibrillation can be treated with medication, but a small number of cases do not respond to treatment. In these cases, a pacemaker may be recommended.

Heart block

heart block is where the pulse that needs to be sent from the SA node to the AV node is either delayed or absent.

Heart block can be caused by damage to the heart (known as acquired heart block). Alternatively, it can occur if a baby is born with one or more defects that affect their heart (known as congenital heart block).

If you have heart block and it's causing symptoms that trouble you, having a pacemaker implanted is usually recommended.

Cardiac arrest

A similar device to a pacemaker, called an implantable cardioverter defibrillator (ICD), is mainly used to prevent cardiac arrest.

A cardiac arrest is a potentially fatal condition where the electrical activity that controls the heart becomes so disrupted that the heart stops beating. Unless it is treated quickly, a cardiac arrest will be fatal. 

An ICD is designed to detect abnormal electrical signals that could suggest that a cardiac arrest is about to happen.

If it detects these types of signal, it sends a powerful electrical shock to the heart. This basically "reboots" the heart. After the shock, the heart should start beating again normally.

You may be recommended to have an ICD implanted if you have previously had a cardiac arrest or if it's thought that you have a significant risk of having one in the future.

Factors that increase the risk of a cardiac arrest include:

Pacemakers can be used to correct an abormal heartbeat 

Types of pacemaker

There are several different types of pacemaker.

The main types of pacemaker are:

  • single-chamber pacemakers – this has one wire, which is connected to either the right atrium (upper heart chamber) or right ventricle (lower heart chamber)
  • dual-chamber pacemakers – this has two wires, which are connected to the right atrium and right ventricle
  • biventricular pacemakers – this has three wires, which are connected to the right atrium, right ventricle and left ventricle

The type of pacemaker you need depends on your heart problem.

Page last reviewed: 04/12/2013

Next review due: 04/12/2015