Infective Endocarditis

What is infective endocarditis?

Infective endocarditis is an infection that affects some part of the endocardium. The endocardium is the tissue that lines the inside of the heart chambers. The infection usually involves one or more heart valves which are part of the endocardium. It is a serious infection that is life-threatening.

How does infective endocarditis occur and progress?

Most cases are caused by infection with bacteria. A small number of cases are caused by infection with fungi. To develop this infection you need to have some bacteria or fungi in the bloodstream. The blood usually does not contain any bacteria or fungi. However, some may get into the blood if you have an infection in another part of the body.

Also, some bacteria may be 'pushed' into the bloodstream during some surgical procedures, and possibly during some types of dental treatment. (Certain types of bacteria live on the skin, in the mouth, and in the bowel. They normally do no harm unless they get into the bloodstream.) People who inject street drugs may also inject bacteria or fungi into their bloodstream if they use dirty or contaminated needles.

Most bacteria that get into the bloodstream are killed by the immune system. However, sometimes some bacteria survive and settle on a heart valve (particularly if the valve is already damaged in some way), or on another section of the endocardium. Once a small focus of infection develops in the endocardium it is difficult for the immune system to clear it.

In time, small clumps of material called vegetations may develop on infected valves. The vegetations contain bacteria or fungi, small blood clots, and other 'debris' from the infection. The vegetations may prevent affected valves from opening and closing properly. The infection can also damage affected valves, and may spread to other areas of the endocardium or heart tissue. Fragments of the vegetations may also break off and travel in the bloodstream to other parts of the body.

Who gets infective endocarditis?

Endocarditis is uncommon. In the UK it occurs in about 20 in a million people each year. It can occur in anybody, but the risk of developing it is greater in people who have:

• Heart valve problems or an artificial heart valve. Heart valves that are already damaged or abnormal are more likely to become infected.
• Had surgery to a heart valve.
• Certain congenital heart defects.
• A heart condition called hypertrophic cardiomyopathy.
• Had a previous episode of infective endocarditis.
• Been injecting street drugs such as heroin with dirty or contaminated needles.
• A poor immune system. For example, people with AIDS.

What are the symptoms and signs of infective endocarditis?

Slowly developing infection

In many cases the infection develops quite slowly. This is sometimes called 'sub-acute bacterial endocarditis' or 'SBE'. Symptoms can develop gradually, over weeks or months, and can be vague at first. You tend to feel generally unwell and may have general aches and pains, tiredness, and be off your food. A fever (a high temperature) develops at some stage in most cases. As these first symptoms can be caused by a lot of other conditions; the cause of the symptoms may not be diagnosed for some time.

Heart murmurs tend to develop. These are sounds that can be heard by a doctor listening to your heart with a stethoscope. Murmurs are caused by abnormal flow of blood through faulty or damaged valves. If you already have a heart murmur from an existing valve problem, the murmur may change or become more intense. A new or changing murmur is often what alerts a doctor to suspect infective endocarditis.

Rapidly developing infection

In some cases the symptoms develop quite quickly and you can become very unwell over a few days. The speed at which the illness develops partly depends on which bacterium or fungus is causing the infection. Some bacteria are more 'virulent' than others.

What are the possible complications?

Complications usually develop if the infection is left untreated, or if treatment is delayed.

Complication in the heart

The infection can damage heart valves. This can lead to serious problems such as heart failure. (See separate leaflet called 'Heart Failure'.) In some cases, the infection spreads and can damage other parts of the heart. For example, the infection may spread to affect the conducting ('electrical') system of the heart and cause the heartbeat to become erratic. In some cases an abscess (ball of pus) forms in the heart muscle nearby.

Complications in other parts of the body

Small bits may break off from the vegetations on the infected heart valves. These get carried in the bloodstream, and lodge in other parts of the body. This can cause various symptoms. For example:

• Small spots may appear under the fingernails, in the eyes, or other parts of the body.
• Infections may develop in other parts of the body.
• The spleen may enlarge as it is the main organ that fights off blood infections.
• If a larger chunk of vegetation breaks off then it can block the blood flow in a main artery. For example, if it gets stuck in an artery in the brain it can cause a stroke or sudden loss of vision in one eye.

What tests are needed?

You will be admitted to hospital if infective endocarditis is suspected. You will have several blood samples taken which are tested for bacteria and fungi. If any bacteria are detected in the blood, they are tested against various antibiotics to find which is the best one to use. (Some bacteria are resistant to some antibiotics. Therefore, the best antibiotic to use can vary from case to case.)

An ultrasound scan of the heart called echocardiography is the most useful test to confirm infective endocarditis. This test uses reflected sound waves to create an image of the heart. It can detect vegetations, and look for damage to heart valves and other heart structures.

Various other tests or scans may be done to find out the extent of the infection, and to assess the damage to the heart or other affected organs.

What is the treatment for infective endocarditis?

Medication

As soon as the condition is suspected you will be given regular doses of antibiotics that are injected directly into a vein. Sometimes the type of the antibiotics are changed once the results of the blood samples are back and the best antibiotics to use are found. The course of antibiotics is for at least 2-4 weeks, but it is often longer. The length of course depends on the bacterium causing the infection, and whether there are complications.

If the cause of the infection is found to be a fungus then anti-fungal drugs will be given.

If you develop complications to the heart or other parts of the body you may need other medication. For example, drugs to counter heart failure, or erratic heart beats, should they develop.

Surgery

Antibiotic treatment is all that is required in most cases. However, an operation is needed in about 1 in 4 cases where the infection is more severe. An operation can be life-saving. Operations that may be done include:

• Replacing a damaged valve with an artificial valve.
• Valve repair if the damage is less severe and repair is possible.
• Drainage of any abscesses (collections of pus) that may develop in the heart muscle or other parts of the body.

What is the prognosis (outlook)?

The outlook is good if the infection is diagnosed and treated early. Many people are cured with a course of antibiotics. However, in some cases the infection is quite advanced before the diagnosis is made and treatment is started. Therefore, serious damage to the heart occurs in some cases. Some people die from the complications.

Can infective endocarditis be prevented?

Some heart conditions put you at increased risk of developing infective endocarditis (see above). If you have one of these conditions you should take a short course of antibiotics before any medical procedure that may 'push' bacteria into the bloodstream. This should kill any bacteria that get into the blood before they can settle on the endocardium or heart valves.

Common procedures where antibiotics are advised include: looking into the stomach (endoscopy); looking into the bowel (colonoscopy); looking into the bladder (cystoscopy). This is not an exhaustive list. Your doctor will advise if antibiotic cover is recommended if you are to have a medical procedure or operation. The British Heart Foundation (contact details below) also lists a range of procedures that require antibiotic cover.

If you inject street drugs then your risk of infective endocarditis can be reduced by always using a clean needle and other injecting equipment.

Good oral and dental hygiene is also thought to be important. Therefore, don't let any dental problems such as a dental abscess or gum disease go untreated. These conditions increase the chance of bacteria getting into the bloodstream.

Dental treatments

Until recently, it has also been advised that people with heart valve disease should take antibiotic cover when they have dental treatment. However, a guideline published in 2006 from the British Society for Antimicrobial Chemotherapy (BSAC) says that this is not needed in most situations. Their information aimed at patients says:

"A BSAC group of experts has spent a lot of time carefully looking at whether dental treatment procedures are a possible cause of infective endocarditis (IE) [sometimes called bacterial endocarditis (BE)], which is infection of the heart valve.

After a very detailed analysis of all the available evidence they have concluded that there is no evidence that dental treatment procedures increase the risk of these infections.

Therefore it is recommended that the current practice of giving patients antibiotics before dental treatment be stopped for all patients with cardiac abnormalities, except for those who have a history of healed IE, prosthetic heart valves and surgically constructed conduits.

The main reasons for this are the lack of any supporting evidence that dental treatment leads to IE and the increasing worry that administration of antibiotics may lead to other serious complications such as anaphylaxis (severe allergy) or antibiotic resistance.

The advice from the BSAC is that patients should concentrate on achieving and keeping a high standard of oral and dental health, as this does reduce the risk of endocarditis. Help for this will be provided by your Dental Professional."

However, this guideline is controversial. It has caused a lot of debate, especially from some cardiologists (heart doctors) and dentists who maintain that antibiotic cover is still needed for dental procedures. See references below for details of some articles that deal with this controversy. Your own doctor or dentist will advise for your own particular circumstance.

Further help and information

British Heart Foundation

14 Fitzhardinge Street, London, W1H 6DH
Tel - Heart Information Line: 08450 70 80 70
Web: www.bhf.org.uk