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20.11 Infective Endocarditis (IE)

Table of Contents

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) 24.

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.

Definitive diagnosis of IE

  • 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

Key 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 10mLof 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 delaying treatment for blood culture outweigh the befit of starting treatment early

Table 20.7: Treatment for native valves

Antibiotics Dosage & Route* Duration
Benzyl Penicillin G or 18–24milllion Units/24hoursIVI,4 hourly in 4–6weeks
Ceftriaxone e2qg IV daily ually divi ded dose 4–6 weeks
Plus cloxacillin 2g IV 6 hourly 4–6weeks
plus, gentamicin ** 1–1.5mg/kg IV every 8 hours at least 2 weeks

Staphylococci Anaerobes (MRSA) add vancomycin

30mg/kg/24hours IV in two equally divided dose, not to exceed 2gm/24 hours unless serum levels are monitored 4–6 weeks

*Dosage patient with normal renal function **It is important to assay serum gentamicin levels every 3–4 days. One–hour peak concentration should not exceed 10mg/l and trough concentration (2–hour pre– dose) should be less than 2mg/l.


Table 20.8: Prosthetic valve empirical treatment

Antibiotics Dosage & Route* Duration
Benzyl Penicillin G (X– Pen) or 18 –24 milllion Units/24 hours IVI, 4 hourly in equally divided dose 6 – 8 weeks
Ceftriaxone 2mg once daily IVI >6 weeks
plus cloxacillin 2g IVI 6 hourly >6 weeks
plus, rifampicin 300 –600mg every 8 hourly >6 weeks
and gentamicin** 1mg/kg IVI every 8 hours 2 weeks

*Dosage patient with normal renal function

**It is important to assay serum gentamicin levels every 3–4 days. One–hour peak concentration should not exceed 10mg/l and trough concentration (2–hour pre– dose) should be less than 2mg/L

At any stage, treatment may have to be modified according to:

  • Detailed antibiotic sensitivity tests
  • Adverse reactions allergy
  • Failure of response

Endocarditis leading to significant cardiac failure or failure to respond to antibiotics may well require early cardiac surgery within few days


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

Infective Endocarditis Prophylaxis

Antibiotic prophylaxis should be considered for patients at highest risk for IE:

Patients with any prosthetic valve, including a trans catheter valve, or those in whom any prosthetic material was used for cardiac valve repair.

Patients with a previous episode of IE.

Patients with Congenital Heart Disease (CHD):

  • Any type of cyanotic CHD.
  • Any type of CHD repaired with a prosthetic material, whether place surgically or by percutaneous techniques, up to 6 months after the procedure or lifelong if residual shunt or valvular regurgitation remains.

Antibiotic prophylaxis is not recommended in other forms of valvular or CHD.

Prophylaxis of Endocarditis Infective

To reduce the risk of bacterial endocarditis, antibiotic prophylaxis should be given to patients undergoing dental procedures requiring manipulation of the gingival or periapical region of the teeth or perforation of the oral mucosa.

Antibiotic prophylaxis is not recommended for,

  • Respiratory tract procedures including bronchoscopy or laryngoscopy, or trans nasal or endotracheal intubation
  • Gastrointestinal or urogenital procedures or Trans–oesophageal Echocardiogram, gastroscopy, colonoscopy, cystoscopy, vaginal or caesarean delivery.
  • Skin and soft tissue procedures

Table 20.9: Recommended prophylaxis for high–risk dental procedures in high– risk patient

Situation Antibiotic Single–dose 30–60 minutes before procedure
Adults Children
No allergy to penicillin or ampicillin Amoxicillin or ampicillin* 2 g orally or i.v 50 mg/kg orally or i.v.
Allergy to penicillin or ampicillin Clindamycin 600 mg orally

or i.v

20 mg/kg orally or i.v.

*Alternatively, C: cephalexin 2g iv for adults or 50 mg/kg iv.for children, cefazolin or ceftriaxone 1 g iv. for adults or 50 mg/kg i.v. for children. Cephalosporins should not be used in patients with anaphylaxis, angio–oedema, or urticaria after intake of penicillin or ampicillin due to cross–sensitivity.

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