Endocarditis

Question 1

Definition of endocarditis

Answer 1

Infection of the endocardium and formation of a vegetation resulting in damage to the cusps of the valves (commonly mitral/aortic)

Question 2

What is the vegetation associated with endocarditis made of?

Answer 2

• fibrin mesh
• platelets which adhere
• WBC
• RBC debris
• organisms (good at sticking to things by embedding in the fibrin mesh)

Question 3

What is quorum sensing and why is it important in the context of endocarditis?

Answer 3

• the way organisms communicate with each other through chemical messages
• either communicated to start proliferating or become biochemically inert (makes antimicrobials inactive against them)
• if this process can be stopped then aggregation of organisms will cease and treating the infection will be easier

Question 4

What are the bacterial causes of endocarditis?

Answer 4

Gram positive:
- staphylococci (eg. S aureus)
- streptococci (eg. S Viridans)
- enterococci

Gram negative:
- HACEK
- enterobacteriales (eg. E. coli)
- pseudomonas aeruginosa

Question 5

What are the fungal causes of endocarditis?

Answer 5

Candida spp.

Question 6

What are the classifications of endocarditis and the most common pathogen?

Answer 6

• native valve endocarditis (NVE) = S. Viridans
• endocarditis in IV drug users = S. aureus
• prosthetic valve endocarditis (PVE) = coagulase negative staphylococci

Question 7

What are the risk factors for NVE:?

Answer 7

• underlying valve abnormalities (aortic stenosis, mitral valve prolapse)
• 30% cases have no identifiable underlying cause

Question 8

Describe the pathophysiology of rheumatic heart disease

Answer 8

• S. Pyogenes infection = strep throat
• immune system/antibiotic fights infection
• release of M protein from lysis of organism
• anti-M antibodies produced against M protein
• cardiomyocytes share molecular similarities to M-protein (molecular mimicry) resulting in anti-M antibodies targeting cells causing valve damage

Question 9

Clinical features of acute endocarditis

Answer 9

• toxic presentation
• progressive valve destruction
• metastatic infection
• days-weeks
• commonly S. aureus

Question 10

Clinical features of sub-acute endocarditis

Answer 10

• mild toxicity
• presentation over weeks-months
• rarely metastatic
• commonly S. Viridans/enterococci

Question 11

Describe the early manifestations of an endocarditis infection

Answer 11

• Fever + new murmur (KEY)
• incubation period = 2 weeks
• fatigue + malaise

Question 12

Describe the possible embolism events in endocarditis

Answer 12

• small emboli (petechiae, splinter haemorrhages, haematuria)
• large emboli (CVA, renal infarction)
• right sided endocarditis (common in IV drug users = septic pulmonary emboli)

Question 13

Describe the late effects of the infection in endocarditis

Answer 13

• immunological reaction (splenomegaly, nephritis, vasculitis lesions, clubbing)
• tissue damage (valve destruction, abscesses)

Question 14

In what circumstances should you suspect infective endocarditis in patients?

Answer 14

• all patients with S. Aureus bacteraemia
• IV drug users with any positive blood culture
• all patients with prosthetic valves and positive cultures

Question 15

How is a diagnosis processed in endocarditis?

Answer 15

• 3 sets of blood cultures (volume important for sensitivity)
• bloods before antibiotics
• echocardiograph (transthoracic/transoesophageal)

Question 16

Describe the Duke criteria for infective endocarditis

Answer 16

• 2 major, 1 major + 2 minor, or 5 minor = IE
  Major:
• typical organism in 2 separate blood cultures
• positive echo/new valve regurgitation
  Minor:
• predisposition
• fever >38 degrees
• vascular phenomena
• immunological phenomena
• positive blood cultures

Question 17

Describe the antibiotic therapy for infective endocarditis

Answer 17

• strep = benzylpenicillin +/- gentamicin
• enterococci = amoxicillin/vancomycin +/- gentamicin
• S. Aureus MSSA = flucloxacillin +/- gentamicin
• S. Aureus MRSA = vancomycin +/- gentamicin
• CoNS = vancomycin +/- gentamicin +/- rifampicin

Question 18

When is surgical management considered for patients with infective endocarditis?

Answer 18

• HF
• uncontrollable infection (abscess, persisting fever + positive cultures 7 days, infection by multi-drug resistant organism
• to prevent PE