Heart block

A condition that causes a slower than normal heartbeat

Heart block is an abnormal heart rhythm caused by a problem with the electrical process that tells your heart when to beat

What is heart block?

Heart block is a condition which affects the flow of electricity in the heart. The most common type is atrioventricular (AV) heart block, which is sometimes called congenital heart block.

AV heart block is when electrical signals between the top chambers of the heart (atria) and the bottom chambers (ventricles) are slowed down or blocked. This causes your heart to beat more slowly than normal (known as bradycardia), or with an abnormal rhythm (cardiac arrhythmia).

Heart blocks are not always serious, and some people do not notice any symptoms. 

Some people with heart block will require treatment to prevent the condition from worsening. If your heart block is severe, then you may need a pacemaker to regulate your heart rhythm and reduce symptoms.

Causes of heart block

Sometimes babies are born with heart block (this is known as congenital heart block), but in most cases it develops later in life (this is known as acquired heart block). 

In some cases illness, surgery or medication you are taking for another condition can affect the electrical signals which control your heartbeat, resulting in heart block.

Causes of heart block can include:

  • Heart attack
  • Other heart conditions such coronary artery disease, heart valve disease, an overactive vagus nerve (which causes the heart to slow down), rheumatic heart disease, sarcoidosis or a congenital heart defect
  • Previous heart surgery
  • Some medications such as beta blockers and calcium channel blockers
  • Different types of heart block have different causes. However, in some cases heart block occurs in healthy people who have no other heart problems.

Types of heart block

The three main types of heart block are:

1. AV (atrioventricular) heart blocks
2. Bundle branch blocks
3. Tachy-brady syndrome

AV (atrioventricular) heart blocks

Also known as congenital heart block, this is categorised as first degree, second degree and third degree, according to severity. Third degree heart block is the most severe, and can lead to a cardiac arrest if it is not treated.

Bundle branch blocks

This type of heart block is caused by electrical impulses travelling slower than normal through the ventricles (the lower chambers of the heart). 
There are two types of bundle branch blocks:

Left bundle branch block: this is usually a sign of heart disease
Right bundle branch block: this can occur in otherwise healthy people, however, sometimes is a sign of an underlying heart problem

Most people with bundle branch blocks don’t notice any symptoms. However, if your heart isn’t pumping enough blood around your body then you may feel light-headed or even pass out. 

Bundle branch blocks can be caused by an underlying heart problem which requires treatment, so it’s important to see a cardiologist for a proper diagnosis.

Tachy-brady syndrome

Sometimes referred to as sick sinus syndrome, tachy-brady syndrome is caused by a problem in the sinus node of the heart. The sinus node is the heart’s natural pacemaker and tells the heart when to beat. In tachy-brady syndrome, the sinus node isn’t working properly, so heartbeats can alternate between too fast (atrial flutter) and too slow (bradycardia), or pause suddenly. These sudden pauses can make you feel dizzy.

Symptoms of tachy-brady syndrome include light-headedness, palpitations and fainting (syncopy).

Diagnosing heart block

Heart block may be diagnosed during routine tests for other conditions. The main test used to diagnose heart block is an electrocardiogram (ECG), which measures the electrical activity of your heart.

Other diagnostic tests include a wearable monitors, where you'll wear an ECG device continuously over a period of time to track your heart's rhythm and an implantable loop recorder, which is a small device that's placed underneath the skin in your chest and records your heart rhythm for up to three years.

Complete Heart Block Treatment

Some types of heart block do not require any treatment. Your treatment options will depend on the level of heart block you have, your symptoms and the underlying cause of your condition. 

Pacemakers
If you are diagnosed with second or third degree heart block, you may need to have a pacemaker fitted.

A pacemaker is a small device which is implanted under your skin just below your collarbone. The procedure is carried out under local anaesthetic, which means you will be awake throughout, but you won’t feel any pain.

A pacemaker is attached to tiny wires (known as pacing leads), which are guided into your heart through a vein. It sends electrical impulses to your heart, to regulate your heartbeat. Pacemakers are responsive, which means that they react to different activity levels and sense when your heart is beating normally on its own.


Although most people don’t experience complications after having a pacemaker fitted, there are some risks associated with the procedure. These include:

  • Blood clots: these can form in a vein of the left arm, although they usually disappear on their own or with anticoagulant medication 
  • Infection: if you have a high temperature or swelling, pain or redness at the site of the pacemaker, it may be infected. Speak to your GP or cardiologist as soon as possible, as you may need antibiotics and a replacement pacemaker
  • Punctured lung: in rare cases, a lung can be punctured when a pacemaker is fitted, causing a small air leak. This usually heals on its own, but you may need treatment to drain the air out
  • Pacemaker malfunction: sometimes, pacemakers fail to work properly or become damaged. If you notice symptoms including dizziness, rapid (or very slow) heartbeat, hiccups, swollen feet or fainting then contact your GP or cardiologist immediately.  If your pacemaker cannot be repaired, then you will need a replacement.

If you have a pacemaker fitted, you will be given a card with details of the type of pacemaker it is. Carry it with you and always tell doctors, dentists and other healthcare providers that you have a pacemaker. 

Medication
Your cardiologist may also make changes to medicines that you're taking for another condition. This is because certain medicines can make heart block worse. They include:

  • Digoxin
  • Calcium-channel blockers
  • Beta blockers
  • Tricyclic antidepressants  
  • Clonidine

You should not stop taking any medications suddenly, as this can have adverse side effects. Your GP or cardiologist will be able to advise you.

Lifestyle changes
Although heart block cannot always be prevented, your cardiologist may recommend certain lifestyle changes to improve the overall health of your heart. These may include:

  • Eating a diet which is high in fibre, fruit and vegetables and low in fat and sugar
  • Giving up smoking
  • Reducing your alcohol intake
  • Maintaining a healthy weight
  • Exercising regularly

Making healthy choices will help keep your heart stronger and reduce the symptoms of heart block.

Our locations

From complex cardiothoracic surgery to tests and diagnostic procedures, we provide exceptional cardiac care across our network of hospitals, outpatient centres and specialist clinics.

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020 7079 4344
This content is intended for general information only and does not replace the need for personal advice from a qualified health professional.
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