Guidelines for the diagnosis of infective endocarditis
Infective endocarditis is a rare condition that is often initially missed as a diagnosis. It
is a serious condition and 1 in 6 patients will die in hospital. It is important to have
infective endocarditis as a differential in patients presenting with sepsis, particularly
those who are at higher risk. It typically no longer presents with classical peripheral
stigmata. Whereas traditionally endocarditis was caused by oral bacteria,
staphylococcus aureus is increasingly common.
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The most reliable clinical symptoms and signs are:
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Fever.
Chills.
Poor appetite.
Weight loss.
A heart murmur.
No other obvious focus of infection.
Recurrent infection after shorter courses of antibiotics for presumed
sepsis elsewhere.
o Sepsis in the context of an embolic event, e.g. a stroke.
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Patients typically have raised inflammatory markers and a mild anaemia. The
white cell count may be normal or minimally elevated in many cases.
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Patients will often have risk factors for infective endocarditis:
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Known valvular heart disease.
Valve replacement.
Congenital heart disease.
Previous infective endocarditis.
Hypertrophic cardiomyopathy.
Permanent pacemaker or other device.
Recent central line insertion or other indwelling device.
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A urine dipstick may show haematuria.
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Presentation may be
immunocompromised
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Blood cultures are the key to diagnosis.
even
more
subtle
in
the
elderly
and
o In patients who are acutely septic two sets of blood cultures, taken at
different times within an hour before the start of empirical treatment
should be taken.
o In relatively well patients, antibiotics should be delayed pending
investigation.
o Three sets of blood cultures should be taken but with at least 6 h
between sampling times; the aim is to demonstrate the presence of
sustained or persistent bacteraemia.
o Meticulous aseptic technique is required to avoid contamination with
skin commensals. Guidance on blood culture collection is on the
infection control pages of the Trust intranet.
o The volume of blood collected is also important: the bottles should be
properly filled.
o There is no need to collect successive blood cultures from separate
sites.
o Positive blood cultures from a single set out of a series should be
interpreted with caution.
o Cultures should be collected from peripheral veins, not indwelling
vascular devices, unless paired collections are made to diagnose
catheter-related bloodstream infection.
o If blood cultures remain negative after 48 hours, consider repeating a
further 3 sets of blood cultures and take clotted blood for serological
investigation, e.g. Q fever, Bartonella. Consider fungal IE, especially if
immunocompromised.
o Where the diagnosis of IE is suspected in patients already on
antibiotics, consideration should be given to discontinuing them to
obtain viable bacteria from blood cultures. Antibiotics may need to be
discontinued for 7-10 days before cultures become positive.
o If the patient remains febrile after seven days of treatment, cultures
should be repeated.
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Transthoracic echocardiography should be considered where
o Blood cultures are positive for an organism that typically causes IE and
there are other features to suggest endocarditis or risk factors for
endocarditis, or no other obvious source of infection.
o The patient has a persistent inflammatory state and no other cause
has been found.
o Blood cultures are negative, but there are strong clinical grounds to
suspect infective endocarditis.
o Note that transthoracic echocardiography is neither 100% sensitive or
specific and a normal transthoracic echocardiogram does not exclude
endocarditis.
o Transoesophageal echocardiography may be considered after a
transthoracic echo after discussion with a cardiologist.
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The detailed management of infective endocarditis is beyond the scope of
this guideline, but links can be found below. The trust policy for antibiotic
usage in patients with infective endocarditis (either suspected or confirmed)
can be found here.
o Patients with suspected infective endocarditis do not necessarily need
immediate antibiotics unless clinically unwell and advice should be
sought from the infection specialists and/or cardiologists before
commencing antibiotics.
o Patients may be started on antibiotics prior to a definitive diagnosis if
blood cultures are positive, after discussion with the infection
specialist.
o All cases of confirmed endocarditis should be managed by the
cardiologists on Fielding ward/CCU in conjunction with the infection
specialists.
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Further reading
o BSAC 2011 Guidelines for Infective Endocarditis
o ESC 2009 Guidelines for Infective Endocarditis
o The Modified Duke Criteria