Endocarditis is a rare and potentially fatal type of heart infection.

It's specifically an infection of the inner lining of the heart (the endocardium), most commonly caused by bacteria entering the blood and travelling to the heart.

The heart is well protected against infection and bacteria usually pass by without causing any harm. However, if the heart valves are damaged, or if a person has an artificial valve (see below), it's easier for bacteria to take root and bypass your normal immune response to infection.

Symptoms of endocarditis

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

a high temperature (fever) of or above 38C (101.4F)



joint and muscle pain

Left untreated the infection will damage the valves of the heart, disrupting 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 will need to be admitted to hospital for this.

Around one in five people will 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. Even with the highest standard of medical care the risk of dying is high – at around one in five. Early diagnosis and treatment is vital to improve the outlook for the condition.

Who is affected

You are more at risk of developing endocarditis if you:

have a prosthetic (artificial) heart valve – valve replacement surgery is increasingly being used when people experience narrowing of one of their heart valves

have congenital heart disease – congenital heart disease means a person is born with heart defects

have damaged heart valves because of infection or heart disease

inject drugs such as heroin – heroin users are three times more likely to develop endocarditis than the population at large

Even in these higher-risk groups, endocarditis remains a rare condition. In England, for example, endocarditis is estimated to affect around one in every 3,000 people in any given year.

Endocarditis is more common in older people, with half of all cases developing in people over 50. However, 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 advancements in medical care. This is because an increasing number of people are now being treated with valve replacement surgery or surgery to repair congenital heart disease.







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Symptoms of endocarditis 

There are two ways that the symptoms of endocarditis can develop:

over the course of a few days, rapidly getting worse (acute endocarditis)

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 (fever) of 38C (100.4F) or above


night sweats


shortness of breath, especially during physical activity


heart murmurs (where your heart makes a whooshing or swishing noise between beats) 

tiredness (fatigue)

muscle and joint pain 

Other symptoms can include:

the appearance of a spotty red rash on the skin (this is known as petechiae)

narrow, reddish-brown lines of blood that run underneath the nails

painful raised lumps that develop on the fingers and toes

painful red spots that develop on the palms of your hand and soles of your feet

mental confusion

When to seek medical advice

You should contact your GP as soon as possible if you develop any of the above symptoms, particularly if you are at a higher risk of developing endocarditis, such as having a history of heart disease.

These symptoms are more likely to be caused by a less serious type of infection. However, your doctor will want to investigate.

When to seek emergency medical advice

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

If you suspect that you or someone else are having a stroke, you should 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 fallen on one side, the person may be unable to smile, or their mouth or eye may have drooped.

Arms: the person may be unable to raise both arms and keep them there as a result of weakness or numbness.

Speech: the person’s speech may be slurred.

Time: it is time to dial 999 immediately if there are any of these signs or symptoms.

Causes of endocarditis 

Your heart is usually well protected against infection, and bacteria usually pass harmlessly by.

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

The bacteria multiply and spread across the inner lining of your heart (the endocardium). The endocardium becomes inflamed, causing damage to your heart valves.

Once damaged, the valves may no longer be able to supply your heart with the blood it needs, leading to heart failure.

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

How bacteria reach the heart

The most common ways that bacteria can enter your blood are explained below.


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.

Bacteria can also enter your body as a result of a sexually transmitted infection (STI), such as chlamydia or gonorrhoea.

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.

Instruments that have been linked to endocarditis include:

Who’s at risk

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

Heart valve disease

Heart valve disease is a general term describing conditions that damage the valves of the heart. Two types of heart valve disease known to increase your risk of endocarditis are:

Heart valve disease can be congenital (where you are born with the condition), or acquired (where you develop the condition in later life).

Causes of acquired heart valve disease include:

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

Prosthetic valves

Prosthetic (artificial) valves are used to replace heart valves that have been damaged by heart valve disease.

However, bacteria can also take root around prosthetic valves, which can occasionally trigger endocarditis. This risk is relatively low, estimated to be less than one in 100.

Intravenous drug use

People who habitually inject illegal drugs such as heroin or methamphetamine (crystal meth) into their veins have an increased risk of developing endocarditis. This is because of unsterilised needles allowing bacteria to enter the bloodstream and repeated injections making 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:


catheters (a tube that is used to drain the bladder)

the tubes that are used during dialysis (a treatment that involves replicating the functions of the kidneys)

laparoscopes (a small, flexible tube that has a light source and a camera at one end and is used to help diagnose a wide range of conditions)

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

Having a previous heart attack. A heart attack can damage the muscles that surround and support the valve, preventing the valves from functioning properly.

High blood pressure. Left untreated, high blood pressure (hypertension) can weaken the tissue around the valves.

Rheumatic fever. Rheumatic fever is a type of bacterial infection that can damage the heart.

inject drugs

have a history of heart surgery

have a central venous catheter (a tube that is connected to a vein in the neck, groin or chest, and is used to deliver medicines and/or fluids to people who are seriously ill)

have a weakened immune system, either as a result of a condition affecting the immune system, such as HIV, or as a side effect of certain types of treatments, such as chemotherapy

Diagnosing endocarditis 

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

Taking a medical history will also allow 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 other conditions, so it is important that other possible causes are ruled out. You may therefore be referred for further tests.

Blood tests

A blood culture test is usually taken to check for bacteria or fungi. It can be used to isolate the specific organism responsible for the infection. If bacteria or fungi are identified, they can be tested against a variety of antibiotics to find the most effective treatment.

Another type of blood test is known as erythrocyte sedimentation rate (ESR) test. During an ESR test, a sample of your red blood cells is placed into a test tube of liquid. It is then timed to see how fast the cells fall to the bottom of the tube in millimetres per hour.

If they are sinking faster than usual, it could indicate that you have an inflammatory condition, such as endocarditis.

Another way of measuring inflammation is with a C reactive protein (CRP) test. CRP is produced by the liver and if there is more than usual, there is inflammation in your body.

About 90% of endocarditis patients have an elevated ESR or CRP.


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: 

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

Computerised tomography (CT) scan

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

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

directly placing a probe on your chest

swallowing a probe to allow your heart to be studied from inside the gullet (transoesophageal echo) 

Treating endocarditis 

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

While you are in hospital, blood samples will be taken regularly to see how well the treatment is working. When any fever and any severe symptoms subside, you may be able to leave hospital and continue taking your antibiotics at home.

If you are taking antibiotics at home, you should have regular appointments with your GP to check that the treatment is working and that you are not experiencing any side effects. The antibiotics you will usually be prescribed are penicillin and gentamicin.

However, if you are allergic to penicillin, you may be prescribed vancomycin instead.

Vancomycin may also be used if tests reveal that your infection is caused by bacteria that have developed a resistance to penicillin and gentamicin, such as the meticillin-resistant staphylococcus aureus (MRSA) strain of bacteria.

Depending on the severity of your condition, you will usually have to take these antibiotics for between two and six weeks. It is likely that your doctor will take a blood sample before prescribing antibiotics. This is because the antibiotics must be specific to the bacteria causing the infection. If your blood sample shows that fungi are causing your infection, you will be prescribed an antifungal medicine.

If your symptoms are particularly severe, you will initially be prescribed a mixture of different antibiotics before the results of the blood samples become known. This is a precautionary measure to prevent your symptoms becoming worse. Once the results of the blood samples are known, you will be given a specific antibiotic (or antifungal).


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 the condition of your heart can be assessed more thoroughly.

Between 15% and 25% of people with endocarditis will need some form of surgery. This is usually to repair damage to the heart. Surgery will usually be recommended if:

The three main surgical procedures that are used to treat endocarditis are:

Surgery for endocarditis can be very challenging, not least because a person who needs surgery will usually be very ill to begin with. Despite the best efforts of their surgical teams, approximately one in 10 people will die during or shortly after surgery for endocarditis.

your symptoms and/or test results suggest that 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 one or more blood clots despite treatment with antibiotics or antifungals

you have a prosthetic (artificial) heart valve

the results of your echocardiogram suggest that an abscess (a collection of pus) or a fistula (an abnormal passageway) has developed inside your heart

the repair of the damaged heart valve

the replacement of the damaged heart valves with prosthetic ones

the draining of any abscesses and the repair of any fistulas that may have developed in the heart muscle

Preventing endocarditis 

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

The same is true if you have previously been affected by endocarditis, because the condition can often reoccur 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.

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

Take care of your skin

Regularly washing your skin with an antibacterial soap will help to lower your risk of developing a skin infection. It is 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 (see below). Your GP may prescribe antibiotics as a precaution. Symptoms of a skin infection include:

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

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

The role of antibiotics

Before 2008, antibiotics were routinely prescribed as a precautionary measure to people with an increased risk of endocarditis, before they underwent routine invasive medical procedures such as:

However, antibiotics are no longer prescribed in these situations because research has found that the benefits of antibiotics in preventing endocarditis are outweighed by the risks that the antibiotics will cause serious side effects.

For example, it is estimated that somebody with a prosthetic heart valve has a one in 500,000 chance of developing a fatal case of endocarditis after routine dental treatment. In comparison, the risk of experiencing a fatal allergic reaction after taking an antibiotic, while still very low, is only one in 100,000.

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

As a result of this, antibiotics will only be used if you are having a medical procedure at a site in your body where there is a suspected infection, such as in your gullet, stomach or intestines, or in your reproductive or urinary system.

redness and inflammation (swelling) of the affected area of skin

the skin feels tender and warm to the touch

a discharge of pus or fluid from the affected area of skin

a high temperature (fever) of 38C (100.4F) or above

feeling sick



dental treatment


a bronchoscopy (where a thin, flexible tube with a small camera at the end is used to examine the inside of your throat)