Heart block is a condition where the heart beats more slowly or with an abnormal rhythm. It's caused by a problem with the electrical pulses that control the rhythm and rate of the heart.  

Symptoms depend on which type of heart block you have. First-degree heart block, the least serious type, may not cause any noticeable symptoms.

Second-degree heart block sometimes causes troublesome symptoms that need treatment, and third-degree heart block – the most serious type – can sometimes be a medical emergency.

Symptoms of heart block

First-degree heart block

First-degree heart block doesn't usually cause any noticeable symptoms. Most people only find out they have it when they're tested for an unrelated medical condition.

Second-degree heart block

Most people with the less serious type of second-degree heart block, known as Mobitz type 1, won't experience any symptoms.

But some people may experience:

• mild light-headedness or dizziness
• fainting

People with the more serious type of second-degree heart block, known as Mobitz type 2 heart block, are more likely to experience the above symptoms.

They may also experience:

• chest pain
• shortness of breath
• feeling very dizzy suddenly when standing up from a lying or sitting position – this is caused by having low blood pressure (hypotension)

Third-degree heart block

Symptoms of third-degree or complete heart block include:

• fainting – this can cause someone to collapse 
• breathlessness
• extreme tiredness (fatigue), sometimes with confusion
• chest pain
• having a slow heart beat (bradycardia), or feeling a skipping, fluttering or pounding in your chest (palpitations)

If you experience severe symptoms or ones that come on very quickly, dial 999 to request an ambulance. These symptoms can be life threatening.

All types of heart block can increase your risk of developing other types of heart rhythm problems, such as atrial fibrillation (an irregular and abnormally fast heart rate).

Causes of heart block

Some people are born with heart block – known as congenital heart block.

But more commonly, heart block develops later in life. This is known as acquired heart block and can be caused by:

• other heart conditions, such as a heart attack 
• taking certain medicines
• other diseases, such as Lyme disease
• having heart surgery

Read more about the causes of heart block and who's at risk.

Treatment of heart block

Heart block normally only needs to be treated if it's causing symptoms.

Your heart may need to be stabilised using a method called transcutaneous pacing (TCP), where pads are attached to your chest and electrical pulses are delivered through them to help restore your heart rate to normal.

This procedure can be uncomfortable, so you may be given a sedative. This medication will make you feel drowsy, so you have little or no awareness of what's going on around you.

Once your heartbeat has been stabilised, a permanent pacemaker may need to be fitted. A pacemaker is a small battery-operated device inserted under the skin of your chest. It sends frequent electrical pulses to keep your heart beating regularly.

Read more about how a pacemaker is fitted.

Treatment for heart block usually works well. Deaths caused by heart block are rare.

Diagnosing heart block

Unless you're experiencing symptoms, heart block is often diagnosed during routine tests for other conditions.

An electrocardiogram (ECG) is the main test used to diagnose heart block. It measures the electrical activity of your heart.

An ECG can be carried out at rest or while you're exercising. Your doctor may ask you to wear a portable ECG monitor to get a reading over time. It provides a useful overall assessment of how well your heart is working.

The results of an ECG can also sometimes indicate the type of heart block you have.

Further information and support

There are a number of organisations that provide information and support for people living with a heart condition like heart block.

You may find the following sites useful:

• British Heart Foundation – charity that provides support and information for people living with any kind of heart condition, including information on dealing with abnormal heart rhythms
  Helpline number: 0300 330 3311
• Arrhythmia Alliance – charity that provides information and support for people living with abnormal heart rhythms
  Helpline number: 01789 867 501
• Cardiac Matters – provides information, stories from affected people, and an Ask the Expert service for a range of heart conditions, including heart block
• HealthUnlocked – a social network forum for different health conditions, including heart block
• National Heart, Lung and Blood Institute – provides information for people affected by heart, lung or blood disorders