- Results from bacterial infection of the endothelial surface of the heart
- Produces characteristic vegetations
- Vegetations consist of platelets, fibrin and bacteria
Predisposing factors
- Rheumatic valve disease
- Degenerative heart disease
- Mitral valve prolapse
- Congenital heart disease
- Hypertrophic cardiomyopathy
- Intravenous drug abuse
- Prosthetic valve
Microbiology
- Relative proportions of infecting organisms depends on underlying valve disease
- Native-valve endocarditis usually caused by:
- viridans streptococci
- Streptococcus bovis
- Staphylococcus aureus
- enterococci
- Gram-negative coccobacilli (HACEK group)
- Nosocomial native-valve endocarditis
- Often occurs as a complication central venous catheter infection
- Usually caused by:
- Staphylococcus aureus
- enterococci
- coagulase-negative staphylococci
- Prosthetic-valve endocarditis accounts for 10% cases of infective endocarditis
- Greatest risk is during the first 6 months after surgery
- MRSA responsible for most cases seen in the first year
Diagnosis
- Clinical presentation can be varied
- At one extreme acute systemic toxicity with rapid progression to cardiac complications
- At other extreme indolent low-grade febrile illness with minimal cardiac dysfunction
- 90% patients have a fever
- 85% patients have murmur, usually that of underlying cardiac lesion
- 10-40% have a changing murmur
- Peripheral signs are rare
- 95% patients have positive blood cultures
- Echocardiography allows
- visualisation of vegetations
- detection of cardiac complications
- Transthoracic echocardiography has a low sensitivity but high specificity
- Transoesophageal echocardiography has a higher sensitivity
Duke clinical criteria
- Requires the presence of :
- Two major criteria or
- One major and three minor criteria or
- Five minor criteria
Major criteria
- Positive blood cultures
- Evidence of endocardial involvement
Minor criteria
- Predisposing heart condition or intravenous drug abuse
- Fever (>38.0 deg C)
- Vascular phenomenon
- Major arterial emboli
- Septic pulmonary infarcts
- Mycotic aneurysm
- Intracranial haemorrhage
- Conjunctival haemorrhages
- Immunological phenomenon
- Glomerulonephritis
- Osler's nodes
- Roth spots
- Microbiological evidence (but less than major criteria)
- Echocardiographic findings (but not meeting major criteria)
Management
- Recommended antibiotic therapy depends on infecting organism
- Parenteral therapy required to ensure bactericidal concentration
- When empirical treatment is necessary need to consider
- Risk factors for certain organisms
- Local bacterial resistance patterns
- Need to determine
- Antibiotic sensitivities
- Minimum inhibitory concentrations
Indications for surgical intervention
- Moderate-to-severe heart failure as a result of valvular dysfunction
- Partial dehiscence of a prosthetic valve
- Persistent bacteraemia despite optimal antimicrobial therapy
- Absence of effective bactericidal treatment
- Fungal infective endocarditis
- Relapse of prosthetic-valve endocarditis
- Staphylococcus aureus prosthetic-valve endocarditis
Bibliography
Bayer A S, Bolger A F, Taubert K A et al. Diagnosis and management of infective
endocarditis and its complications. Circulation 1998; 98: 2936-2948.
Working Party of the British Society for Antimicrobial Chemotherapy. Antibiotic treatment of
streptococcal, enterococcal and staphylococcal endocarditis. Heart 1998; 79: 207-210. |