Endocarditis Flashcards
What is endocarditis?
An infection of the endocardium resulting in damage to the valve cusps due to formation of a vegetation.
What order are the valves most likely to be affected by endocarditis?
mitral
aortic
tricuspid
pulmonary (very rare).
How do biofilms form?
- bacteria settle on a surface and multiple.
- bacteria use quorum sensing to signal to each other.
- if enough cells are present, the frequency of signalling may reach a threshold where it can trigger gene regulation.
- bacteria produce pili to attach to the surface and each other.
- can adjust their position using twitching motility.
- bacteria secrete an ECM of proteins, polysaccharides and nucleic acids. This clumps bacteria together and gives protection from external stressors.
How do bacteria from biofilms move to other sites?
- over time, the oxygen and nutrients reaching the bottom of the biofilm deplete and the film may start to degrade.
- cells in the upper layers detach and can be carried away by currents.
- cells can produce flagella and swim or drift to more favourable locations and form new biofilms.
What is the most causitive agent in native valve endocarditis?
Steptococcus - normally viridans or enterococci.
What is the most causitive agent in IV drug user endocarditis?
Staph aureus.
Could also be a gram -ve or fungal cause.
What is the most causitive agent in prosthetic valve endocarditios?
Staphs or CoNS.
Could also be gram -ve or fungal.
What are risk factors for getting endocarditis?
- older population
- males
- IVDU
- underlying valve abnormalities
What is the aeitiology of rheumatic heart disease?
- Strep pyogenescan cause strep throat.
- if partially/not treated, it can release its streptolysin ‘O’ exotoxin.
- Anti-streptolysin O (ASO) antibodies are produced against the toxin.
- ASO antibodies have a cross-reactivity reaction and can damage valves.
- Valves undergo fibrosis and scarring leading to stenosis or regurgitation.
What valve is most commonly affected in IV drug users?
Tricuspid.
Why is the right side of the heart more commonly affected by endocarditis in IVDU?
- particulate induced endothelial damage to R-sided valves.
- increased bacterial load in IVDU
- direct physiological affects of injected drugs
- deficient immune response caused by drug use.
Why could someone get sepsis from endocarditis?
Due to septic emboli flying off the vegetation and causing metastatic infection.
Describe the early manifestations of infection?
- fever and murmur.
- fatigue and malaise.
What is the incubation period in endocarditis?
2 weeks.
What embolic events can occur as a result of endocarditis?
Splinter haemorhages, conjunctival petichiae, haematuria.
Can have larger ones causing stroke or renal infarction.
