Infective Endocarditis (IE)
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The infective process of endocardial layer of the heart can involve native or prosthetic valve and congenital defects/shunts. Alpha–haemolytic streptococci are the most common causes of native valve endocarditis but Staphylococcus aureus is more likely if the disease is rapidly progressive with high fever or is related to a prosthetic valve (Staphylococcus epidermidis).
Diagnostic Criteria
- Use Modified Dukes Criteria below and consult microbiologist where possible. Three sets of blood cultures should be taken before starting treatment.
Modified Dukes Criteria
Major Criteria
- Positive blood cultures of typical organism for IE from at least two separate blood cultures
- Evidence of endocardial involvement by echocardiogram (Trans–thoracic Echo/Trans–oesophageal Echo)
Minor Criteria
- Fever > 38ºC
- Presence of Rheumatic heart disease, congenital heart disease
- Vascular phenomena; Major arterial emboli, septic pulmonary infarcts, mycotic aneurysm, intracranial haemorrhage, conjuctival hemorrhage, Janeway lesions
- Immunological phenomena; glomerulonephritis, Osler's nodes, Roth's spots
- Rheumatoid factor
- Serologic evidence of active infective endocarditis or blood culture not meeting major criterion
Definition of infective endocarditis according to the modified Duke criteria: Definitive diagnosis of IE
Pathological criteria
Microorganisms demonstrated by culture or on histological examination of a vegetation, a vegetation that has embolized, or an intracardiac abscess specimen
OR
Pathological lesions: vegetation or intracardiac abscess confirmed by histological examination showing active endocarditis
Clinical criteria
- Two major criteria OR
- One major and three minor criteria OR
- Five minor criteria
Possible Diagnosis of IE
- One major and one minor OR
- Three minor criteria
Rejected IE
- Firm alternate diagnosis.
- Resolution of symptoms suggesting IE with antibiotic therapy for ≤4 days; or
- No pathological evidence of IE at surgery or autopsy, with antibiotic therapy for ≤4 days; OR
- Does not meet criteria for possible IE, as above.
Note
- Positive blood cultures remain the cornerstone of diagnosis and provide live bacteria for both identification and susceptibility testing
- To improve yield of culturing bacteria at least three blood sample sets are taken at 30 minutes apart each containing 10mL of blood and should be incubated in both aerobic and anaerobic atmospheres
- Sampling should be obtained from a peripheral vein using a meticulous sterile technique
Pharmacological Treatment
Empirical Treatment
Consider for negative blood culture, or if risk of delaying treatment for blood culture outweighs the benefit of starting treatment early
Treatment for native valves:
A: benzyl penicillin G (IV) 18–24milllion Units/24hours 4hourly in equally divided dose 4–6weeks
OR
B: ceftriaxone (IV) 2g 24hourly 4–6weeks
AND
B: cloxacillin (IV) 2g 6hourly 4–6 weeks
AND
A: gentamicin (IV) 1–1.5mg/kg 8 hourly for at least 2weeks
OR
If methicillin–resistant staphylococci anaerobes (MRSA)
S: vancomycin (IV) 30mg/kg 24 hourly in two equally divided doses, not to exceed 2gm in 24hours unless serum levels are monitored 4–6weeks.
Note: It is important to assay serum gentamicin levels every 3–4days. One–hour peak concentration should not exceed 10mg/l and trough concentration (2–hours pre–dose) should be less than 2mg/l.
Prosthetic valve empirical treatment
A: benzyl penicillin G (X–Pen) (IV) 6 – 8 weeks
OR
B: ceftriaxone (IV) 2g 24hourly >6 weeks
AND
B: cloxacillin (IV) 2g 6 hourly >6 weeks
AND
A: rifampicin 300 – 600mg (IV) 8hourly >6 weeks
AND
A: gentamicin 1mg/kg (IV) 8hourly 2 weeks.
Note
- It is important to assay serum gentamicin levels every 3–4days. One–hour peak concentration should not exceed 10mg/l and trough concentration (2-hour pre-dose) should be less than 2mg/L.
- Gentamycin in renal failure should be given based on CrCl.
- Patients with complicated IE should be evaluated and managed in high level of care or centre, with immediate surgical facilities and the presence of a multidisciplinary including an Infectious Disease specialist, a microbiologist, cardiologist, imaging specialists, and cardiac surgeons