Symptoms of heart block
Symptoms of heart block may include:
- dizziness
- fainting or feeling like you're about to faint
- chest pain
- tiredness
- shortness of breath
These symptoms can range from mild to severe depending on the type of heart block you have and how it's affecting you.
You may have no symptoms and only find out you have heart block during tests for something else.
Urgent advice: Get help from NHS 111 if:
- you feel dizzy all the time or it keeps coming back
- you've fainted
- you have shortness of breath that gets worse when you've been doing your normal activities, or when you lie down
It's important to get medical advice to make sure it's nothing serious. You are not wasting anyone's time by getting it checked out.
You can call 111 or get help from 111 online.
Immediate action required: Call 999 if:
- you've been diagnosed with heart block and have chest pain
- you have severe difficulty breathing – you're gasping, choking or not able to get words out
- you feel sweaty, sick or lightheaded
- someone faints and they are not breathing or cannot be woken up within 1 minute
Call 999 straight away as you may need immediate treatment in hospital.
Do not drive yourself to A&E.
The person you speak to at 999 will give you advice about what to do.
How heart block is diagnosed
The main test used to diagnose heart block is an electrocardiogram (ECG), which measures the electrical activity of your heart.
It usually only takes a few minutes, but you may be asked to wear a portable ECG for 1 or 2 days to monitor your heart.
Other tests that may be used to help diagnose heart block include:
- an echocardiogram or MRI scan – to get a picture of your heart and the nearby blood vessels
- exercise tests – to check your heart while you use a bike or treadmill
- blood tests
Types of heart block
The most common type of heart block is called AV (atrioventricular) heart block.
AV heart block may be diagnosed as:
- 1st-degree – which does not usually need treatment
- 2nd-degree – which sometimes needs treatment
- 3rd-degree (complete) – which often needs treatment
There are other types of heart block which affect different areas of the heart, but the symptoms are often similar.
Find out more about different types of heart block on the British Heart Foundation website.
Treatments for heart block
The treatment for heart block depends on what's causing it and whether you have any symptoms.
If you have heart block that is not causing any symptoms, you will not usually need any treatment.
If you have severe symptoms, you may need a pacemaker, which keeps your heart beating regularly and not too slowly.
You may need a pacemaker for a short time or permanently, depending on what's causing your heart block.
Causes of heart block
Heart block is most often caused by a heart condition such as coronary heart disease, or a heart attack.
Sometimes babies are born with heart block, known as congenital heart block.
Other possible causes of AV heart block include:
- taking some types of medicine
- infection and inflammation of the heart, caused by another condition
- having heart surgery
Sometimes there's no obvious cause.
Help and support for heart block
If you're diagnosed with heart block, you can get advice and support from your GP or other healthcare professionals.
You can also get information and support from the British Heart Foundation.
The British Heart Foundation
The British Heart Foundation is a charity that provides information and support for anyone living with a heart condition.
Page last reviewed: 10 March 2025
Next review due: 10 March 2028