• Infective endocarditis is due to microbial infection of the heart valve (native or
prosthetic), the lining of the heart chamber or blood vessel or a congenital anomaly e.g.
septal defect.
• The causative organisms are
Streptococcus viridans 30-40%
Enterococci 10-15%
Other Streptococci 20-25%
Staphylococcus aureus 9-27%
Gram negative bacilli
Haemophilus spp
Anaerobes
• There are two types of infective endocarditis namely acute and sub-acute endocarditis.
Acute endocarditis caused by virulent organisms and infection occurs in normal
valves and endocardium.
Sub-acute endocarditis caused by less virulent organisims and infection more
commonly in the damaged valves and endocardium.
Pathophysiology
• Infective endocarditis typically occurs at sites of pre-existing endocardial damage.
• Virulent or aggressive organisms e.g. Staphylococcus aureus can cause endocarditis in a
previously normal heart such as in intravenous drug misuse.
• Infection tends to occur at sites of endothelial damage because these areas attract deposits
of platelets and fibrin, which are vulnerable to colonisation by blood-borne organisms.
• The avascular valve tissue and presence of fibrin aggregates help to protect proliferating
organisms from host defence mechanisms.
• The affected valves develop vegetations composed of organisms, fibrin and platelets and
the vegetation may become large enough to cause obstruction or may break away as
emboli. Regurgitations may develop or increase.
 
Clinical Features, Differential Diagnosis and Investigations of Sub-acute
Bacterial Endocarditis
Clinical Features
• Persistent fever
• Complain of unusual tiredness
• Night sweats
• Weight loss
• Development of new signs of valve dysfunction
• Infective endocarditis should be considered when a patient with congenital or valvular
heart disease develops some of features mentioned above.
• In patients with sub acute presentations
Fever is typically low-grade and rarely exceeds 39.4°C (103°F).
In contrast, temperatures between 39.4 and 40°C (103 and 104°F) are often noted in
acute endocarditis.
• In acute endocarditis involving a normal valve, murmurs are heard on presentation in only
30 to 45% of patients but ultimately are detected in 85%.
• Congestive heart failure develops in 30 to 40% of patients; it is usually a consequence of
valvular dysfunction.
• Occasionally endocarditis-associated myocarditis or an intracardiac fistula may cause
congestive heart failure.
• Other features include purpura and petechial haemorrhages in the skin and mucous
membranes, and splinter haemorrhages under the fingernails or toe nails.
• Osler's nodes (rare).
Painful and tender swellings at the fingertips.
Probably the product of vasculitis.
• Digital clubbing is a late sign.
• The spleen is frequently palpable, in coxiella infections the spleen and the liver may be
considerably enlarged.
• Microscopic hematuria is common.
 
Differential Diagnosis
• Rheumatic Heart Disease
• Congenital Heart Disease
• Myocardial Infarction
• Congestive Cardiac failure
• Septicaemia
Investigations
• It is better that patient suspected of having endocarditis be referred for specific
investigations at hospital level. This is because facilities for such diagnosis are lacking in
the primary health care facilities (dispensary and health centre).
• Investigations done at hospital levels include
Blood culture
FBP and ESR
Chest X-ray
Echocardiography
ECG
 
Duke Criteria for Diagnosis of Infective Endocarditis
Major Criteria
Positive Blood culture for Infective Endocarditis
• Typical microorganism consistent with IE from 2 separate blood cultures, as noted below:
viridans streptococci, Streptococcus bovis, or HACEK group (H. parainfluenzae,
Actinobacillus actinomycetemcomitans, Cardiobacterium hominis, Eikenella
corrodens, Kingellae kingae) or
community-acquired Staphylococcus aureus or enterococci, in the absence of a
primary focus
Or
• Microorganisms consistent with IE from persistently positive blood cultures defined as:
2 positive cultures of blood samples drawn >12 hours apart, or
all of 3 or a majority of 4 separate cultures of blood (with first and last sample drawn
1 hour apart)
Evidence of endocardial involvement
• Positive echocardiogram for IE defined as :
oscillating intracardiac mass on valve or supporting structures, in the path of
regurgitant jets, or on implanted material in the absence of an alternative anatomic
explanation, or
abscess, or
new partial dehiscence of prosthetic valve
Or
• New valvular regurgitation (worsening or changing of preexisting murmur not sufficient)
 
Minor Criteria
Predisposition: predisposing heart condition or intravenous drug use
Fever: temperature > 38.0° C (100.4° F)
Vascular phenomena: major arterial emboli, septic pulmonary infarcts, mycotic aneurysm,
intracranial hemorrhage, conjunctival hemorrhages, and Janeway lesions.
Immunologic phenomena: glomerulonephritis, Osler's nodes, Roth spots (white-centered
retinal haemorrhages), and rheumatoid factor.
Microbiological evidence: positive blood culture but does not meet a major criterion as
noted above (Excludes single positive cultures for coagulase-negative staphylococci,
diphtheroids, and organisms that do not commonly cause endocarditis) or serological
evidence of active infection with organism consistent with IE.
Echocardiographic findings: consistent with IE but do not meet a major criterion as noted
above
 
Clinical criteria for infective endocarditis requires
• Two major criteria, or
• One major and three minor criteria, or
• Five minor criteria
Treatment, Prevention and Complications of Sub-acute Bacterial
Endocarditis
Treatment
• Refer the patient immediately after initial antibiotic doses for expert care.
• The case fatality of bacterial endocarditis is approximately 20% and even higher in those
with prosthetic valve endocarditis and those infected with antibiotic-resistant organisms.
• Empirical treatment depends on the mode of presentation, the suspected organism, and
whether the patient has a prosthetic valve and/or penicillin allergy. For example, if the
presentation is acute, flucloxacillin and gentamicin are recommended.
• In sub-acute or indolent presentation, benzyl penicillin and gentamicin can be used.
• Those with penicillin allergy, a prosthetic valve or suspected Methicillin Resistant
Staphylococcus aureus (MRSA) infection, should be treated with vancomycin and
gentamicin.
• The duration of treatment is usually 4-6 weeks with intravenous antibiotics.
Doses
• Benzylpenicillin (Penicillin G) - 7.2g daily IV in 6 divided doses. In children, 75-
100mg/kg daily in divided doses.
• Ampicillin 500mg IV every 4-6 hours
• Gentamycin 3-5mg/kg daily in divided doses every 8 hours.
• Vancomycin 500mg IV infusion over at least 60 minutes every 6 hours or 1g over at least
100m minutes every 12 hours. In children 10-15mg/kg every 6-12 hours.
• Flucloxacillin 12g daily in 6 divided doses
Prevention
• Make sure that antibiotics have been administered in conjunction with selected
procedures considered to entail a risk for bacteremia and endocarditis.
• Maintaining good oral hygiene is probably more effective in the overall prevention of
valvular infection because gingivitis is the most common source of spontaneous
bacteremia.
• Prevention of vascular catheter infections is an important prophylactic approach in
preventing nosocomial infective endocarditis (NIE).
Complications
• Monitor patients for the development of the following complications.
Valvular dysfunction, usually insufficiency of the mitral or aortic valves
Myocardial or septal abscesses
Congestive heart failure
Metastatic infection
Embolic phenomenon
Organ dysfunction resulting from immunological processes.
Congestive heart failure resulting from valvular insufficiency and embolization may
occur after bacteriologic cure has been achieved.       
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