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Infective endocarditis


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Infective endocarditis is an infection of the inner lining or valves of the heart. It is caused by bacteria, or sometimes fungi, entering the bloodstream and sticking to heart structures.

It is quite rare, affecting 30 people in every million each year. It can be serious, particularly if there are complications, so early diagnosis and treatment are vital.

Treatment requires hospital admission and a course of antibiotics given through a an IV drip (a small tube into your vein). Up to half of people affected need surgery to repair or replace a damaged heart valve.

Even with the highest standards of medical care, 1 in 5 people are at risk of dying from infective endocarditis.

What causes infective endocarditis?

Your heart is usually well protected against infection, and most bacteria pass by harmlessly. However, if your heart valves are damaged or you have an artificial valve, it is easier for bacteria to get past your normal immune defence and cause problems. This can mean that bacteria settle on the inner lining of your heart (endocardium). These organisms are sometimes referred to as vegetations. They cause inflammation of the endocardium, and that can damage your heart valves.

Clumps of cells form around the bacteria or fungi, which can break off and sometimes cause conditions such as stroke.

Ways of getting infective endocarditis

  • Bacteria can enter the bloodstream through the mouth during everyday activities like brushing teeth or chewing food, especially if teeth and gums are in bad condition or decayed. Bacteria can also enter the bloodstream through needles and tubes (for example, when you are receiving haemodialysis or chemotherapy).
  • Some invasive dental procedures, like extractions or deep scaling, can increase the risk.
  • Some medical conditions lower immunity to infection, for example HIV and diabetes.
  • Intravenous drug abuse commonly leads to infective endocarditis.
  • Bacteria in your gut can sometimes enter the bloodstream through ulcers or tumours in the bowel.
  • Rarely, bacteria can be introduced during heart surgery or when a pacemaker is put in.
  • Sometimes, urinary catheters introduce infection into the blood through the bladder.

Who is at risk of infective endocarditis?

You are at higher risk of developing infective endocarditis if you have:

  • had infective endocarditis before
  • a prosthetic (artificial) or repaired heart valve
  • some types of congenital heart disease (heart defects from birth)

You are at moderately increased risk if you have:

  • thickened or leaking heart valves (including bicuspid aortic valve)
  • enlarged heart muscles and thickened walls (hypertrophic cardiomyopathy)

You are also at risk if:

  • you have tubes (cannulas) in your veins for cancer treatment or dialysis
  • you self-inject non-prescription drugs


Symptoms can develop quickly in days, or slowly over weeks. It is vital to seek medical attention at the earliest signs, so that you can have blood tests for bacterial infection and to try to identify any bug. If endocarditis is a possibility, antibiotics should not be started before these tests have been done, unless you are very unwell.

The most common symptoms of endocarditis include:

  • unexplained flu-like symptoms (high temperature or fever, sweats, chills) that are severe or last longer than a week
  • weight loss, poor appetite
  • general fatigue and feeling unwell
  • new back pain

Without early treatment you can have complications. These include:

  • confusion or drowsiness
  • shortness of breath from severe valve damage
  • stroke
  • ‘cold leg’ from a blocked artery
  • boils or black patches on the toes or fingers

You will need to be admitted to hospital to confirm the diagnosis, and a course of antibiotics will be given through an IV drip.

When to see your GP

You should contact your GP as soon as you have any of the symptoms, unless there is an obvious explanation like flu.

When you visit your GP:

  • if you know you are in a higher risk category, you should tell your GP, who might be trained to think of more common conditions first
  • they should arrange for blood tests, including blood cultures (to identify the bug), before starting antibiotics for an unknown infection. This is very important because antibiotics might affect your test results
  • if they suspect infective endocarditis, they will probably arrange a hospital visit because tests are most easily and quickly done in hospital

When to get emergency help

If you suspect stroke, you should dial 999 immediately for an ambulance, even if you do not have any symptoms of endocarditis. Stroke is one of the most serious complications of endocarditis.

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

Face. Their face might have fallen on one side, they might not be able to smile, or their mouth or eye might have drooped.

Arms. They might be unable to raise both arms and keep them there, as a result of weakness or numbness.

Speech. Their speech might be slurred.

Time. It is time to call 999 immediately if there are any of these signs or symptoms.

How is infective endocarditis diagnosed?

The diagnosis is made by assessing your signs and symptoms, and by doing blood tests and an echocardiogram (ultrasound scan of the heart).


At first, all cases of infective endocarditis need to be treated in hospital with high-dose antibiotics given through an IV drip, usually in your arm.

Regular blood samples will be taken to see how well the treatment is working.

You will be under the care of a cardiologist with input from an infection specialist and sometimes a cardiac surgeon. They will form the endocarditis team and will discuss your case at regular meetings.

Depending on how bad your condition is, you will usually need antibiotics through a drip for 2 to 6 weeks. You might need to continue antibiotics by mouth for several weeks after this, especially if there are complications, such as an abscess in the spleen or a bone infection.

Sometimes it is possible to finish a course of IV antibiotics at home. Antibiotics might be administered by you, a family member or a district nurse, and you will usually need to return to hospital every week to be checked.


Surgery will usually only be recommended if:

  • there is serious valve damage and a risk of heart failure
  • the infection does not settle with antibiotics alone, or there is an abscess in the heart
  • infected tissue breaks off the valve and travels around the body despite antibiotic treatment

Surgery consists of the repair or replacement of the damaged heart valve. If there is an abscess near your heart valve, it might be necessary to replace part of the main artery (aorta) as well.

Surgery for endocarditis can be very challenging and risky, particularly because a person who needs this surgery will usually be very ill to start with.

IV antibiotics will be continued after surgery until your team are satisfied that the infection has gone.

Recovery after treatment

Infective endocarditis is a major illness and it is normal to feel weak for several weeks afterwards, even if you have had no complications.


You should find ways to remember to take your medicines at the right time and at the right dose. You might want to put a reminder on your phone, keep a diary, or use a dosette box (a plastic box with small compartments that show which pills need to be taken at what time of day).

Physical and emotional wellbeing

Before you received treatment, you might have been very physically unwell. If you had surgery, you will be seen by the cardiac rehabilitation ream to help you cope with pain and discomfort afterwards. You might have difficulty with thinking skills, such as concentration or memory, or emotional problems for a number of weeks or even months.

Although not all people are affected in the same way, you might feel worried, depressed, guilty, shamed or angry. If you feel any of these things, please speak with your GP.

Return to normal activity

You will not be able to do much while you feel physically and emotionally weakened. However, you should consider returning to normal activity as soon as you feel physically able. Not doing your normal activities for a long time, and perhaps being stuck in bed, can lead to problems (such as tiredness (fatigue) and muscle weakness) when you start to move around again.

Gradually increasing physical activity can be a good treatment for negative feelings. You should also try to have a good diet and sleep routine, and make time for enjoyable things, like hobbies and socialising. This will create a positive cycle of improvement.

Being too inactive, or activities like smoking and drinking too much alcohol or caffeine, can have negative effects on your physical wellbeing even though they might seem to help in the short term.

Avoiding infective endocarditis in the future

Follow-up appointments

You will be seen as an outpatient by the heart team 4 to 6 weeks after leaving hospital.

Unfortunately, you have an increased risk of developing endocarditis again at some time in the future, but there are things you can do to minimise this risk. The most important is to look after your teeth.

Practise good oral hygiene

You should visit your dentist, usually every 6 months, to make sure the earliest signs of tooth or gum disease are treated. Do not ignore abscesses or gum disease.

You should discuss with your cardiologist if antibiotic protection is needed before invasive dental procedures (such as extractions, scaling, or any procedure that involves manipulating or cutting the gums). If antibiotic protection is necessary, you will usually be given amoxicillin or clindamycin to take by mouth 1 hour before your dental treatment.

If you think you are allergic to penicillin, consider asking your GP to refer you to an allergy specialist for testing. Only 1 in 10 people who think they are allergic to penicillin are actually allergic.

You should have been given an endocarditis warning card. The card explains the antibiotics you need to take. You should show this to your doctor, dentist or healthcare professional before you have any treatment (especially dental).

Take care of your skin

You should avoid any cosmetic procedure that involve breaking the skin, such as body piercing or tattooing.

If you have any questions or concerns about infective endocarditis, contact your GP.


If you have a persistent fever with no obvious cause, you should go to your GP or Emergency Department (A&E) and take your infective endocarditis warning card with you.

Blood cultures must be taken before starting antibiotics for an undiagnosed illness.

Useful information

British Heart Foundation

A charity who fund research into all heart and circulatory diseases and their causes. They have a lot of information on heart-related topics including: tests for heart conditions, heart valve disease, caring for someone with a heart condition, and cardiac rehabilitation. 

British Heart Valve Society

A professional organisation with links to the British Cardiovascular Society. They aim to improve the care of patients with valve disease through educational and training programmes, and by defining standards of care. They have produced an endocarditis information and warning card that you can carry in your wallet.

Heart Valve Voice

A collection of people with real experiences of heart valve disease, including a multidisciplinary group of experts (cardiologists, surgeons, GPs), cardiac patient societies, and patients. Information includes ‘Recovering from treatment’, ‘Post-treatment checklist’ and ‘10 surprising things you might not be able to do right after your treatment’. 


Ref number: 4802/VER1

Date published: September 2019 | Review date: September 2022

© 2019 Guy’s and St Thomas’ NHS Foundation Trust

A list of sources is available on request


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