L21: Endocarditis (Fever and murmur)

Question 1

What is endocarditis and how can it present (3)

Answer 1

Endocarditis is an infection of endocardium (mainly heart valves)

Presents with
1.Signs of infection (eg. fever, lethargy

2. Embolic phenomena from broken vegetation:
   - splinter haemorrhage in peripheral capillaries + subsequent small areas of black infarction
   - Cerebral/retinal vessel embolism causing momentary loss of function which is regained.
3. Early diastolic murmur - abnormal heart valve showing regurgitation- most likely left v>right because of greater pressure

Question 2

Describe the pathogenesis of Endocarditis to its 100% mortality, including potential trigger bacteria

Answer 2

1. Turbulent flow through priorly damaged valve due to congenital abnormality, RHD,
2. Causes platelets and fibrin to attach to damaged valvular epithelium forming a sterile vegetation (healing)
3. Transient bacteremia arising from
   - Mouth = Viridans strep
   - Skin/nose = S.aureus
   -GI, GU = Enterococcus faecalis
   Seeds bacteria on sterile vegetation.
4. Infected vegetation enlarges
   a) sheds infected emboli and leads to infarction/stroke as COD
   b) valvular destruction/ impaired closure of valves which causes congestive HF and pulmonary oedema (COD)

Question 3

How is endocarditis diagnosed

Answer 3

1. Blood is cultured from 3 samples taken at least 20 min apart.

• Endocarditis there should be positive culture in all samples containing same microbe
• this unlikely with other infections in tissue that have intermittent bacteremia.

2. Evidence of infected vegetation on heart valves
   - regurgitant murmur
   - echocardiagram
   - embolic evidence

Question 4

How is contaminant bacteremia and transient bacteremia distinguished

Answer 4

• transient: gut/mouth organism only positive briefly with no apparent infective source
• Contaminant: skin commensal bacteria with no apparent infective source only once positive.

Question 5

Why doesn’t host defences work against endocarditis

Answer 5

This is because neutrophils which usually defend against bacteria cannot extravasate through capillaries or adhere to the avascular valve leaflets because blood flow is too high.

-ends up using bactericidal antibiotic treatment for weeks.

Question 6

How is endocarditis treated: administration route, dose, duration and cure rate

Answer 6

• Bactericidal Antibiotic: dependent on the sensitivity or resistance of specific organism to the achievable dose of an antibiotic.
• initial empiric treatment then susceptibility testing on blood culture.
  Viridans strep: penicillin
  S, aureus: flucoxacillin
• Dose: High by IV to avoid GI upset/ increase adherence
• Duration; 2 wks minimum, often 4 weeks.
• cure rate 70-90% otherwise 100% fatal

Question 7

Why and when is antibiotic prophylaxis given for prevention of endocarditis

Answer 7

• In persons with known abnormal heart valves before a procedure with risk of acquiring bacteremia
  eg. dental work
• Usually one dose only of penicillin.