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 or wound
in another part of the body.
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
increased 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?
If you inject street drugs
Your risk of infective endocarditis can be reduced by always using a clean needle and other injecting equipment.
Dental health
Good oral and dental hygiene
is also thought to be important. In particular, if you have any
condition which increases your risk of developing infective
endocarditis (see above), then, don't let any dental problems such as a
dental abscess or gum disease go untreated. These dental conditions
increase the chance of bacteria getting into the bloodstream.
If you have dental and surgical procedures
Until
early 2008, it had been usual medical practice to advise people with an
increased risk of developing infective endocarditis to take a short
course of antibiotics (antibiotic cover) during certain procedures.
These included: various dental procedures; looking into the stomach
(endoscopy); looking into the bowel (colonoscopy); looking into the
bladder (cystoscopy). The logic was that these procedures might 'push'
some bacteria into the bloodstream and that antibiotic cover would kill
bacteria that get into the blood before they settle on the endocardium
or heart valves.
However, in March 2008 the National Institute
for Health and Clinical Excellence (NICE) published new guidance on the
use of antibiotic prophylaxis (antibiotic cover) against infective
endocarditis. This recommended an end to the practice of prescribing
antibiotics for 'at risk patients' during dental and other procedures.
NICE recommends that you should now only be offered antibiotic cover if
the procedure is at a site where there is already a suspected
infection. The reason for this change in practice is because NICE found
that research studies do not support the use of antibiotics to prevent
infective endocarditis during dental or other procedures. Also, taking
antibiotics carries its own risk (such as side effects, and sometimes
serious reactions to antibiotics).
However, this national NICE
guideline is controversial. It has caused a lot of debate, especially
from some cardiologists (heart doctors) and dentists. See the
references below for details of some articles that deal with this
controversy. Your own doctor or dentist will advise for your own
particular circumstance.
A final point
If you have an increased risk
of developing infective endocarditis, do report any symptoms promptly
to your doctor that you think may be due to infective endocarditis. The
earlier the condition is diagnosed and treated, the better the likely
outcome.
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
References
Disclaimer: This article is for information only and should not
be used for the diagnosis or treatment of medical conditions. EMIS and
PiP have used all reasonable care in compiling the information but make
no warranty as to its accuracy. Consult a doctor or other health care
professional for diagnosis and treatment of medical conditions.
© EMIS and PiP 2008 Updated: 20 Jun 2008
