Endocarditis is a rare and potentially fatal infection of the inner lining of the heart (the endocardium). It's most commonly caused by bacteria entering the blood and travelling to the heart.

Although the heart is usually well protected against infection, it may be easier for bacteria to bypass the immune system in people who have:

  • an artificial (prosthetic) heart valve - valve replacement surgery is increasingly being used when people experience narrowing of one of their heart valves
  • congenital heart disease - where a person is born with heart defects
  • hypertrophic cardiomyopathy - where the heart muscle cells have enlarged and the walls of the heart chambers thicken
  • damaged heart valves - because of infection or heart disease

People who inject drugs are also more likely to develop endocarditis.

Symptoms of endocarditis

The initial symptoms of endocarditis are similar to the flu and include:

  • a high temperature
  • chills
  • headache
  • joint and muscle pain

Without treatment, the infection damages the heart valves and disrupts the normal flow of blood through the heart.

This triggers a range of life-threatening complications, such as:

  • heart failure – where the heart is unable to pump enough blood around the body to properly meet the body’s demands
  • stroke – where the supply of blood to the brain becomes disrupted

Treating endocarditis

Endocarditis is treated with a course of antibiotics given via a drip. You'll need to be admitted to hospital for this.

Some people also need surgery to repair or replace a damaged heart valve or drain away any abscesses that develop.

Endocarditis is a serious illness, especially if complications develop. Early diagnosis and treatment is vital to improve the outlook for the condition.

Who's affected

Endocarditis is a rare condition in Wales, even in those with a higher risk. 

It's more common in older people.

But cases of endocarditis have been recorded in children, particularly those born with congenital heart disease.

Twice as many men are affected as women.

Although it may sound strange, rates of endocarditis are increasing because of advances in medical care.

This is because there's an increasing number of people being treated with valve replacement surgery or surgery to repair congenital heart disease.


The symptoms of endocarditis can develop rapidly over the course of a few days (acute endocarditis), or slowly over the course of a few weeks or possibly months (subacute endocarditis).

Subacute endocarditis is more common in people with congenital heart disease.

Symptoms of endocarditis

The most common symptoms of endocarditis include:

  • a high temperature
  • chills
  • night sweats
  • headaches
  • shortness of breath, especially during physical activity
  • cough
  • tiredness (fatigue)
  • muscle and joint pain

Other symptoms can include:

  • small red or purple spots on the skin (petechiae); these may be harder to see on brown and black skin
  • narrow, reddish-brown lines of blood that run underneath the nails
  • painful red lumps in the pads of the fingers and toes
  • painful red spots on the palms and soles
  • confusion
  • loss of appetitite
  • unexpected weight loss

When to seek medical advice

Contact your GP as soon as possible if you develop any symptoms of endocarditis, particularly if you're at a higher risk of developing it, such as if you have a history of heart disease.

When to seek emergency medical advice

stroke is one of the most serious complications that can develop from endocarditis.

If you suspect a stroke, dial 999 immediately to request an ambulance.

The most effective way to identify the symptoms of a stroke is to remember the word FAST, which stands for:

  • Face - the face may have dropped on 1 side, the person may be unable to smile, or their mouth or eye may have dropped
  • Arms - the person with suspected stroke may not be able to lift both arms and keep them there because of weakness or numbness in 1 arm
  • Speech - their speech may be slurred or garbled, or the person may not be able to talk at all despite appearing to be awake; they may also have problems understanding what you're saying to them
  • Time - it's time to dial 999 immediately if you see any of these signs or symptoms.

Who can get it

Endocarditis is caused by bacteria in the bloodstream multiplying and spreading across the inner lining of your heart (endocardium). The endocardium becomes inflamed, causing damage to your heart valves.

Your heart is usually well protected against infection so bacteria can pass harmlessly by.

But if your heart valves are damaged or you have an artificial valve, it's easier for bacteria to take root and bypass your normal immune response to infection.

Small clumps of bacteria can develop at the site of the infection. There is a risk of these clumps acting in a similar way to blood clots, travelling away from the heart and blocking the blood supply to the organs. This can cause organ failure or trigger a stroke.

How bacteria reach the heart

There are several ways that bacteria can enter your blood.


Everyday activities, such as brushing your teeth or chewing your food, can sometimes allow bacteria to enter the bloodstream.

The risk is increased if your teeth and gums are in bad condition, because it makes it easier for bacteria to enter.


Bacteria can spread from the site of a pre-existing infection, such as a skin infection or a gum infection.

Needles and tubes

Any medical procedure that involves placing a medical instrument inside the body carries a small associated risk of introducing bacteria into your bloodstream.

Who’s at risk

There are a number of things that can make your heart more vulnerable to infection and increase your chance of developing endocarditis.

These include:

  • heart valve disease
  • having prosthetic valves
  • hypertrophic cardiomyopathy
  • injecting drugs
  • congenital heart disease
  • you've had endocarditis before

Heart valve disease

Heart valve disease is a general term describing health problems that damage the valves of the heart.

2 types of heart valve disease known to increase your risk of endocarditis are:

  • valvular stenosis - where the valve(s) of the heart become narrowed, disrupting the blood flow through the heart
  • valvular regurgitation - where the valve(s) of the heart do not close properly, causing blood to leak back in the wrong direction

Heart valve disease can be either:

  • congenital heart disease - where you're born with the condition
  • acquired - where you develop the condition in later life

Causes of acquired heart valve disease include:

  • a previous heart attack - a heart attack can damage the muscles that surround and support the valve, preventing the valves functioning properly
  • high blood pressure - without treatment, high blood pressure (hypertension) can weaken the tissue around the valves
  • rheumatic fever - a type of bacterial infection that can damage the heart

Rheumatic fever is rare since the introduction of antibiotics. But older people who had rheumatic fever during childhood may go on to develop heart valve disease.

Prosthetic valves

The prosthetic (artificial) valves used in aortic valve replacement surgery replace heart valves that have been damaged by heart valve disease.

But bacteria can also take root around prosthetic valves, which can occasionally trigger endocarditis.

Hypertrophic cardiomyopathy

In hypertrophic cardiomyopathy, the heart muscle cells enlarge and the walls of the heart chambers thicken.

The chambers are reduced in size so they cannot hold much blood, and the walls cannot relax properly and may stiffen.

Injecting drugs

People who inject illegal drugs such as heroin or methamphetamine (crystal meth) have an increased risk of developing endocarditis.

This is because unsterilised needles allow bacteria to enter the bloodstream and repeated injections make the skin more vulnerable to infection.

Fungal endocarditis

Endocarditis caused by a fungal infection is rarer than bacterial endocarditis, and usually more serious.

You are more at risk of fungal endocarditis if you:

  • inject drugs
  • have a history of heart surgery
  • have a central venous catheter - a tube connected to a vein in the neck, groin or chest, which is used to deliver medicines or fluids to people who are seriously ill
  • have a weakened immune system - either as a result of a health condition affecting the immune system, such as HIV, or as a side effect of certain types of treatments, such as chemotherapy


To diagnose endocarditis, your GP will look closely at your medical history, paying particular attention to any problems you may have had with your heart.

Taking a medical history also allows your GP to identify whether you have undergone any recent medical procedures that may have put you at risk of developing endocarditis, such as surgery to the heart valves.

Physical examination

Your GP will check for the symptoms of endocarditis, such as fever or nodules (small lumps) on your fingers and toes.

They will also listen to your heart using a stethoscope to see if you have developed a heart murmur.

A heart murmur is where your heartbeat has an extra, or unusual, sound caused by a disturbed blood flow through the heart.

The symptoms of endocarditis are very similar to those of some other health conditions, so it is important that other possible causes are ruled out.

Sometimes you may be referred for further tests.

Blood tests

Blood tests may be used to help diagnose endocarditis or identify the most effective treatment.

Blood tests may include:

  • a blood culture test to check for a specific bacteria or fungi
  • an erythrocyte sedimentation rate (ESR) test
  • a C reactive protein (CRP) test

Find out more about these and other types of blood tests


An echocardiogram uses sound waves to scan your heart. The waves can produce accurate images of the heart muscle, chambers and valves.

This allows your doctor to examine the structure and function of your heart more closely.

An echocardiogram is often used to check for any clumps of bacteria that may have formed, and can help detect infected or damaged heart tissue.

These scans can be performed by either:

  • directly placing a probe on your chest
  • swallowing a probe to allow your heart to be studied from inside the gullet (transoesophageal echo)

The transoesophageal echo allows much clearer images of your heart, as the gullet is just behind the heart.

CT scan

A CT scan uses X-rays to take pictures of the inside of your body. A computer is then used to piece the images together.

It can be useful for identifying any collections of pus (abscesses) that may have developed in your body.


Most cases of endocarditis can be treated with a course of antibiotics. You will usually have to be admitted to hospital so the antibiotics can be given through a drip in your arm (intravenously).

Your doctor will usually take a blood sample before prescribing antibiotics to make sure you're given the most effective treatment.

If your symptoms are severe, you may be prescribed a mixture of different antibiotics before getting the result of the blood sample. This is a precautionary measure to prevent your symptoms becoming worse.

While you're in hospital, regular blood samples will be taken to see how well the treatment is working. 

Once your fever and any severe symptoms subside, you may be able to leave hospital and continue receiving antibiotics at home by a drip (IV).

If you're receiving antibiotics at home, you should have regular appointments with a nurse and your GP to check that the treatment is working and you're not experiencing any side effects.

You'll usually have to take antibiotics for 2 to 6 weeks.

Your doctor will usually take a blood sample before prescribing antibiotics to make sure you're given the most effective treatment.

If your blood sample shows that fungi are causing your infection, you'll be prescribed an antifungal medicine.


Endocarditis can cause serious damage to your heart. You may be referred to a cardiologist, a specialist in diseases of the heart and blood vessels, so your heart can be assessed more thoroughly.

You may need surgery to repair damage to the heart.

Surgery will usually be recommended if:

  • your symptoms or test results suggest you have experienced heart failure, a serious condition where your heart is not pumping blood around your body efficiently
  • you continue to have a high temperature (fever) despite treatment with antibiotics or antifungals
  • your endocarditis is caused by particularly aggressive fungi or drug-resistant bacteria
  • you experience 1 or more blood clots despite treatment with antibiotics or antifungals
  • you have a an artificial (prosthetic) heart valve
  • the results of your echocardiogram suggest that a collection of pus (abscess)  or an abnormal passageway (fistula) has developed inside your heart

The 3 main surgical procedures used to treat endocarditis are:

  • repair of the damaged heart valve
  • replacement of the damaged heart valves with prosthetic ones during aortic valve replacement surgery
  • draining of any abscesses and repair of any fistulas that may have developed in the heart muscle


If you have an increased risk of developing endocarditis, it's important to limit your exposure to any infection that could trigger it.

The same is true if you have previously been affected by endocarditis, as it can often recur in certain people.

Practise good oral hygiene

If you are at increased risk of developing endocarditis, it is important that you practise good oral and dental hygiene.

Do not let abscesses and gum disease go untreated.

Visit your dentist on a regular basis to ensure that you maintain good oral health and minimise the risk of bacteria entering your bloodstream through your mouth.

Take care of your skin

Regular handwashing will help to prevent bacteria spreading.

It's also very important to wash any cuts or grazes carefully as soon as you notice them to prevent them becoming infected.

Contact your GP for advice if you develop the symptoms of a skin infection. Your GP may prescribe antibiotics as a precaution.

Symptoms of a skin infection include:

  • redness and inflammation of the affected area of skin, but redness can be harder to see on brown and black skin
  • the skin feeling sore and warm to touch
  • a discharge of pus or fluid from the affected area of skin

A skin infection may also make you feel generally unwell, leading to symptoms such as:

  • a high temperature
  • feeling sick
  • shivering
  • chills

Also, avoid any cosmetic procedure that involves breaking the skin, such as body piercing and tattooing.

The role of antibiotics

Research has found that the benefits of antibiotics in preventing endocarditis are outweighed by the risk they'll cause serious side effects.

Antibiotics should only be used when absolutely necessary. Each time antibiotics are used, the chances that bacteria will become resistant to them are increased.

Antibiotics will only be prescribed as a precautionary measure if a medical procedure is taking place at a site in your body where there's a suspected infection, such as your:

  • gullet, stomach or intestines
  • reproductive or urinary system.

The information on this page has been adapted by NHS Wales from original content supplied by NHS UK NHS website nhs.uk
Last Updated: 08/05/2024 15:45:30