Heart block

Last updated:

Reviewed by:

Dr Rhianna McClymont

, Lead GP at Livi

Medically reviewed

Heart block is a condition where the heart beats more slowly or with an irregular rhythm, caused by a problem in your heart’s electrical system. Find out about the different types of heart block and how it’s treated.

What is heart block?

Heart block is a problem in your heart’s electrical system. The heart beats more slowly (called bradycardia) or with an irregular rhythm. It’s caused when the electrical impulses that send messages to the bottom chambers of your heart (the ventricles) to beat are prevented or delayed.

There are different heart block types – some won’t cause any symptoms, but more severe heart blocks need medical attention.

Heart block types

There are three main types of heart block, categorised depending on how badly the electrical signals are affected.

First-degree heart block

In first-degree heart block, the electrical impulses still reach the heart but are more delayed than usual. This type doesn’t usually cause any symptoms and is commonly discovered when testing for another condition.

Second-degree heart block

This can be split into two categories – Mobitz Type I and Mobitz Type II:

  • Type I is less severe and means that the electrical signals get progressively slower and eventually cause the heart to skip a beat.

  • In Type II, not all the electrical signals reach the ventricles, and your heartbeat may be slow, irregular or both.

Third-degree heart block

This is the most serious type of heart block, where no electrical signals get through to the ventricles. For this reason, it’s sometimes called ‘complete heart block’. It forces other parts of the heart to create electrical signals, but as these are less efficient, it can make the heartbeat slower.

Symptoms of heart block

First-degree heart block doesn’t usually cause any symptoms. Common symptoms for other types of heart block include:

Second-degree heart block symptoms

Many people with Mobitz Type I don’t experience any symptoms, although they may feel dizzy or lightheaded. Also, people with Mobitz Type II might experience:

  • Chest pain

  • Breathlessness

  • Low blood pressure, which can cause dizziness when you stand up suddenly

Third-degree heart block symptoms

With third-degree heart block you might feel:

  • Faint or dizzy

  • Breathless

  • Extremely tired

  • Chest pain

  • Confused

If these symptoms suddenly come, it’s essential to get immediate medical attention, as third-degree heart block can be severe.

What causes heart block?

Sometimes there’s no cause for heart block, and it can occur in people with a normal heart.

For some people, heart block is a condition they’re born with, called congenital heart block.

But most people develop it later in life, and this can be down to several reasons:

  • Other heart conditions, like coronary heart disease (including heart attack), congenital heart disease and cardiomyopathy

  • Certain prescription medication

  • Other conditions, like Lyme disease

  • Heart surgery

  • Changes to the heart, like thickening of the heart muscle or ageing of electrical pathways

Heart block diagnosis

Heart block is often diagnosed when your doctor takes other routine tests.

If you’re experiencing symptoms, you’ll usually have an electrocardiogram (ECG), which measures the heart’s electrical activity. If your doctor wants to see your heart’s activity over a longer period, you might need to wear a portable ECG.

Treatment for heart block

It’s not usually necessary to treat first-degree heart block unless you’re experiencing symptoms. If you’re taking medication for another type of heart problem, your doctor may adjust this to see if it stops the heart block.

In second-and third-degree heart block, a pacemaker in the most commonly used treatment. This is a small device fitted in your chest and sends electrical pulses to your heart to help keep it beating efficiently and regularly.

Living with heart block

If you have a pacemaker fitted, it shouldn’t affect everyday life too much. But you may need to adjust some of the physical activities you take part in. If you’re unsure, your doctor will be able to advise you on what’s safe to do.

You’ll also need to avoid close contact with magnetic devices and those that send out electrical fields, like security screens at airports. Some medical procedures can clash with pacemakers too, so always tell doctors and dentists that you have one fitted.

Last updated:
Reviewed by:
Lead GP at Livi Dr Rhianna McClymont
Dr Rhianna McClymont, Lead GP at Livi