Created in partnership with

Content created in partnership with British Heart Foundation

Some of the links on this page will go to the British Heart Foundation (BHF) website.

The heart and how it works

The heart is a large muscle that pumps blood around the body. The blood delivers oxygen and nutrients around the body and takes away carbon dioxide and waste products.

The heart is divided into 4 main areas, called chambers – 2 on the right and 2 on the left:

  • The 2 smaller, upper chambers collect blood going into the heart. These chambers are called the right atrium and the left atrium.
  • The 2 larger, lower chambers pump blood out of the heart. These chambers are called the right ventricle and the left ventricle.

The inside of the heart

A diagram showing the inside of the heart. It shows the left atrium and right atrium, left ventricle and right ventricle, valves and sinus node. There are arrows showing the direction of blood flow.
Image: The illustration shows a cross-section of the heart from the front. It shows where tubes (blood vessels) join the heart. Arrows indicate the direction blood flows through these blood vessels, into, through and out of the heart. Four different chambers are shown inside the heart. The two at the top of the heart are called the right atrium and left atrium. The two lower and larger chambers are called the right ventricle and left ventricle. The arrows show that blood travels into each atrium, then through flaps (called valves) and into each ventricle. The arrows then show that blood leaves the ventricles through another set of valves and away from the heart through another set of blood vessels.

There are 4 valves inside the heart. They open and close as the heart pumps blood. The valves keep the blood flowing in one direction through the heart.

Blood travels around the body through tubes called blood vessels. The blood going to the heart is low in oxygen. It travels through the heart and is pumped out to the lungs.

In the lungs, the blood picks up oxygen and gets rid of carbon dioxide, which is then breathed out. The blood carrying oxygen travels back through the heart and is pumped out to the body again.

Outside of the heart

A diagram showing the outside of the heart. Arrows show the direction blood flows through the blood vessels to enter and leave the heart. Some arrows are red to show blood that has oxygen. Some arrows are blue to show blood that needs oxygen.
Image: The illustration shows the front of the heart and where tubes (blood vessels) join the heart. Arrows indicate the direction blood flows through these blood vessels to enter and leave the heart. Some arrows are red to show blood that has oxygen. Some arrows are blue to show blood that needs oxygen. Above the heart is labelled upper body. Below the heart is labelled lower body. Either side of the heart is labelled lungs. Blue arrows (blood that needs oxygen) enter the heart through blood vessels from the upper and lower body. Red arrows (blood that has oxygen) leave the heart through different blood vessels to the upper and lower body. Blue arrows leave the heart through blood vessels to each lung. Red arrows enter the heart through blood vessels from each lung. The main part of the heart is labelled heart muscle. A network of thin lines is shown on the surface of the heart muscle. These are called coronary arteries.

Like the rest of the body, the heart needs its own blood supply to bring it oxygen. Small blood vessels on the outside of the heart carry blood and oxygen to the heart muscle. These blood vessels are called coronary arteries.

The heart has its own electrical system that tells it when to beat and pump blood around the body. A group of cells called the sinus node sends an electrical signal through the heart to start each beat. This happens about 60 to 100 times a minute. The sinus node is also called the heart’s natural pacemaker.

Heart problems

When parts of the heart become diseased or damaged, this can stop it from working properly. Heart problems can be caused by many things, including:

  • narrow or blocked blood vessels
  • damage to the heart muscle
  • damaged heart valves
  • damage to the heart’s electrical system.

Different heart conditions can cause different symptoms. The British Heart Foundation have more information about heart conditions.

If you already have a heart problem

Not all cancer treatments are suitable for people with heart problems. But this can depend on the type of heart problem and how well controlled it is. Your cancer doctor or specialist nurse will talk to you about this. If a cancer treatment is likely to cause serious problems, they may suggest a different type of treatment.

Planning your cancer treatment

If you are having a cancer treatment that might make a heart problem worse, you may need:

You might need to go to extra appointments before cancer treatment starts. Your cancer doctor may arrange for you to see your cardiologist (heart doctor) for specialist advice about the heart problem. If this delays your cancer treatment, you may feel frustrated or worried. But it is important to get the right information, treatment and advice. This way, you can have the cancer treatment as safely as possible.

You may find it helpful to:

  • know who to contact if you have a question about your cancer treatment, heart problems or test results
  • check what will happen next at the end of each appointment
  • speak to your specialist doctors, GP, nurse or other health professionals in your cancer team about any worries you have – they should have access to your test results and medical notes.

If you have a cardiac implantable electronic device

Some people have an electrical device placed under the skin near the heart. It is used to treat abnormal heart rhythms. There are 2 types of this device:

  • pacemakers
  • implantable cardioverter defibrillators (ICDs).

Radiotherapy and some types of scan can affect how these devices work. So it is important to tell your cancer team if you have one. Take any written information or guidance about your device to your radiotherapy pre-treatment appointments and your first radiotherapy treatment appointment. This will help your cancer team to plan any scans and treatment so it does not affect your device. They will also arrange any extra monitoring you need to check your device or change its settings.

If new problems develop during treatment

Sometimes cancer treatment can cause new heart problems. These may develop during or soon after cancer treatment. Some problems may develop many years later.

We have information about heart health and cancer that explains how new problems may be managed.

About this information

Our information about heart health and cancer was developed in partnership with the British Heart Foundation.

If you have questions about your heart health, call the Heart Helpline for free on 0808 8021234, Monday to Friday, 9am to 5pm, or visit bhf.org.uk.

The language we use

We want everyone affected by cancer to feel our information is written for them.

We want our information to be as clear as possible. To do this, we try to:

  • use plain English
  • explain medical words
  • use short sentences
  • use illustrations to explain text
  • structure the information clearly
  • make sure important points are clear.

We use gender-inclusive language and talk to our readers as ‘you’ so that everyone feels included. Where clinically necessary we use the terms ‘men’ and ‘women’ or ‘male’ and ‘female’. For example, we do so when talking about parts of the body or mentioning statistics or research about who is affected.

You can read more about how we produce our information here.

Date reviewed

Reviewed: 01 January 2024
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Next review: 01 January 2027
Trusted Information Creator - Patient Information Forum
Trusted Information Creator - Patient Information Forum

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