Infective Endocarditis

Valencia Bailey

Definition

Infective endocarditis is characterized by colonization or invasion of the heart valves or

the mural endocardium by a microbe, leading to the formation of bulky,

friable vegetations composed of thrombotic debris and organisms, often associated with destruction of the underlying cardiac tissues.

Incidence

In the United States, the incidence of IE is approximately 2-4 cases per 100,000 persons

per year.

The incidence is similar worldwide.

Pathophysiology

• Bacteremia (nosocomial or spontaneous) that delivers the organisms to the surface of the valve

• Adherence of the organisms• Eventual invasion of the valvular leaflets

Infection tends to occur at sites of endothelial damage because they attract platelets and fibrin, which are vulnerable to colonisation.

Aetiology

• Bacteraemia– Strep viridans, Staph aureus, Enterococcus faecalis,

E. faecum, Strep bovis– Rarely HACEK (Haemophilus, Actinobacillus,

Cardiobacterium, Eikenella, Kingella), Coxiella burnetti, Chlamydia

• Fungi– Candida, Aspergillus, Histoplasma

• Other causes– SLE (Libman- Sacks endocarditis), malignancy

Clinical Features

Investigations

• Blood Cultures (3-5 sets within the first 60-90 mins)• Other blood tests – CBC, U&Es, Mg, LFTs, ESR, CRP

• Urinalysis• CXR• ECG• Echocardiogram

Diagnostic Criteria (Modified Duke Criteria)

Requirement: 2 major OR 1 major + 3 minor OR 5 minor criteria

Modified Duke Criteria

• Major Criteria– Positive blood culture• Typical organism in 2 separate cultures• Persistently +ve blood cultures taken > 12hrs apart• 3 or more +ve cultures taken over >1hr

– Endocardial involvement• +ve echocardiographic findings of vegetations, abscess,

dehiscence of prosthetic valves• New valvular regurgitation

Modified Duke Criteria

• Minor Criteria– Predisposition (valvular or cardiac abnormality/ IV

drug use)– Pyrexia ≥ 38oC– Embolic Phenomenon– Vasculitic phenomenon– Blood cultures suggestive (organism grown, but not

achieving major criteria)– Suggestive echocardiographic findings that do not

meet major criteria

Prophylaxis

• Only 10% of cases of IE can be prevented by preprocedure antibiotics.

• Maintaining good oral hygiene is probably more effective in the overall prevention of valvular infection because gingivitis is the most common source of spontaneous bacteraemias.

Prophylaxis

Patients at higher risk include those with the following conditions:• Presence of prosthetic heart valve• History of endocarditis• Cardiac transplant recipients who develop

cardiac valvulopathy• Congenital heart disease with a high-pressure

gradient lesion

Prophylaxis

Also consider prophylaxis in patients before they undergo procedures that may cause transient bacteremia, such as the following :• Any procedure involving manipulation of gingival

tissue or the periapical region of teeth, or perforation of the oral mucosa

• Any procedure involving incision in the respiratory mucosa

• Procedures on infected skin or musculoskeletal tissue including incision and drainage of an abscess

Treatment

Antibiotics are the mainstay of treatment for infective endocarditis (IE). Goals to maximize

treatment success are early diagnosis, accurate microorganism identification, reliable susceptibility testing, prolonged intravenous (IV) administration

of bactericidal antimicrobial agents, proper monitoring of potentially toxic antimicrobial

regimens, and aggressive surgical management of correctable mechanical complications.

Treatment• Culture-directed• Empirical– Native valve: penicillin G and gentamicin

(streptococci)– H/O IV drug use: nafcillin and gentamicin

(methicilin-sensitive staph)– Prosthetic valve: vancomycin, gentamicin and

oral rifampin (MRSA or coagulase-negative staph)

– Unstable renal function: substitute linezolid for vancomycin

References

• Davidson’s Principles and Practice of Medicine• Oxford Handbook of Clinical Medicine• http://emedicine.medscape.com/article/

216650-overview#a0101• http://www.medscape.com/viewarticle/

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