Endocarditis Flashcards
Definition of endocarditis
Infection of the endocardium and formation of a vegetation resulting in damage to the cusps of the valves (commonly mitral/aortic)
What is the vegetation associated with endocarditis made of?
- fibrin mesh
- platelets which adhere
- WBC
- RBC debris
- organisms (good at sticking to things by embedding in the fibrin mesh)
What is quorum sensing and why is it important in the context of endocarditis?
- 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
What are the bacterial causes of endocarditis?
Gram positive:
- staphylococci (eg. S aureus)
- streptococci (eg. S Viridans)
- enterococci
Gram negative:
- HACEK
- enterobacteriales (eg. E. coli)
- pseudomonas aeruginosa
What are the fungal causes of endocarditis?
Candida spp.
What are the classifications of endocarditis and the most common pathogen?
- native valve endocarditis (NVE) = S. Viridans
- endocarditis in IV drug users = S. aureus
- prosthetic valve endocarditis (PVE) = coagulase negative staphylococci
What are the risk factors for NVE:?
- underlying valve abnormalities (aortic stenosis, mitral valve prolapse)
- 30% cases have no identifiable underlying cause
Describe the pathophysiology of rheumatic heart disease
- 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
Clinical features of acute endocarditis
- toxic presentation
- progressive valve destruction
- metastatic infection
- days-weeks
- commonly S. aureus
Clinical features of sub-acute endocarditis
- mild toxicity
- presentation over weeks-months
- rarely metastatic
- commonly S. Viridans/enterococci
Describe the early manifestations of an endocarditis infection
- Fever + new murmur (KEY)
- incubation period = 2 weeks
- fatigue + malaise
Describe the possible embolism events in endocarditis
- small emboli (petechiae, splinter haemorrhages, haematuria)
- large emboli (CVA, renal infarction)
- right sided endocarditis (common in IV drug users = septic pulmonary emboli)
Describe the late effects of the infection in endocarditis
- immunological reaction (splenomegaly, nephritis, vasculitis lesions, clubbing)
- tissue damage (valve destruction, abscesses)
In what circumstances should you suspect infective endocarditis in patients?
- all patients with S. Aureus bacteraemia
- IV drug users with any positive blood culture
- all patients with prosthetic valves and positive cultures
How is a diagnosis processed in endocarditis?
- 3 sets of blood cultures (volume important for sensitivity)
- bloods before antibiotics
- echocardiograph (transthoracic/transoesophageal)
