Fever and a New Murmur: Endocarditis Flashcards
What are the 3 main requirements to diagnose/determine endocarditis?
- Symptoms and signs of infection: fever
- Embolic phenomena: splinter haemorrages
- Abnormal heart valve: probably where the emboli have come from!
What are splinter haemorrages and what do they look like?
- Red black linear bleeds under the skin that look like splinter, where blood has seeped out of the arteriole
- May be surrounding fresh bleeding
- Due to a small clot blocking the arteriole in the nail bed, leading to damage and blood leakage.
- Can also be in the conjunctiva; ‘conjunctival haemorrages
- Larger ones cause larger areas of thrombosis and infarction → red and tender → black necrotic tissue (as seen on the feet)
You can have abnormalities of the mitral and aortic sounds to produce a murmur. What are these caused?
- Mitral valve stenosis (soft, long diastolic, hard to hear)
- Aortic Valve stenosis (high pitched crescendo)
- Aoortic valve regurgitation (soft, early diastolic)
These will all result in a murmur and are extremely common abnormalities in endocarditis.
What does an individuals with endocarditis’s heart valves look and why?
Abnormal vegetations of the surface of the valves due to infection, looks like warty/cauliflower lumps.
Bacterial colonisation → clumps of fibrin/platelets/bacterial species forming lumps → damaging/thickening/weakening of the heart valve.
Why is it important to know what valves are more commonly affected?
aortic/mitral: common
Tricuspid/pulmonary: less common
Therefore if these break off they will be entering the arterial circulation causing embolic phenomena which you can see.
Or they may cause issues elsewhere;
eg; block a renal arteriole → area of renal infarction → blood in urinee
Into muscle of back → back pain
Up a carotid artery to block a brain blood vessel → temp. transient ischaemic event (until blood is restored and the person may have a perior of a few hours in which the have a neuro deficit
Up a carotid artery to block a brain blood vessel → permanent ischaemic effect → stroke
Why do valves perforate in endocarditis?
The multiplication and colonisation of the infectious organisms on the valve cna lead to weakening and eventual rupture/perforation of a valve leaflets.
ALso weakening and rupture of chordi tendini is a concern → inability to close → regurgitation from v to a → heart failure and death
Why is endocarditis such a catastrophic infection in comparison to other bodily infections?
Heart valves are avascular with no capillaries, and therefore no route of access for neutrophils. Neutrophils are only flowing past the valves throught the highly-pressured and fast-moving bloodstream of the heart.
Therefore the neutrophils can’t get out into the vegetation, and antibiotics are essential for survival, as our host-defence is invalid.
Has a 100% mortality rate!!
Draw the flow diargram of pathogenesis of endocarditis.
The heart valve is always abnormal (for a variety of reasons).
It is normal to have abnormalities and fibrin/platelet clots but NOT to have bacteria present on these valves!
- Those with poor dental care with loose rotting teeth (eg; the gingival cresent) that are very sticky to the clot will be a usual cause of endocarditis.
- Therefore the agents that can stick to the thormbis are the ones to be nervous about!!! Usually are clear but there is a chance they will not!
Should you be concerned if your blood test came back with bacteria in it?
Not if these are in trace amounts, as we always have small amounts circulating that our immune system can fight off,
Describe continuous bacteraemia as a diagnostic method
- high concentration of bacteria in and on vegetation, with bacteria continually shed from vegetation into blood
- Constant bacteraemia; expect all blood cultures to be postive (with an organism likely to cause endocarditis)
- Culture blood on 3 occasions at least 20mins apart (90-100% +ve)
- Culture excised valve
- normally with infections you have intermittant bacteraemia; but those with endocarditis have constant bacteraemia
- expect they will all grow the same microbe
Organism identified in about 95% cases
What do you need to form a diagnosis?
- hear murmur
- see embolic phenomena
- ECG
- 3x culture to find continuous bacteremia of the same individual microbe
Whats the difference between True bacteraemia, contaminant, or transient bacteraemia.
True Bacteraemia:
- pathogen cultured (s. aureus, E.coli etc)
- Sometime more then one set of cultures +
- clinically compatible infective source identified
Contaminant bacteraemia from injection picking up bacteria missed by alcohol wipe
- skin commensual cultured (staph epidermidis etc)
- only one set of blood cultures +
- No apparent infective source
Transient Bacteraemia
- gut or mouth organism cultured
- blood cultures only + briefly
- no apparent infective source
What is the treatment for endocarditis?
Luckily this is cause by infective agents that are relatively easy to treat. (mainly viridans streptococcil that turn the agar green; alpha haemolytic organisms, usually harmless, it’s just that they’re sticky)
Antibiotic: depends on organism
Method: always IV
Dose: always high dose
Duration: usually ~2-4 weeks
Cure rate: 70-90%
Why are rheumatic fever and endocarditis a common area of confusion, and how do we distinguish between!
These both involve heart valves:
Endocarditis:
- caused mainly by streptococci in the mouth
- ECG
- Treat with penicillin
Rheumatic fever
- streptococcuous pyogenes
- doesn’t actually infect heart valves but is instead due to a immune response against the heart valves!!!
- doesn’t require a blood culture as it’s only in the throat!!
- ECG
- Prevent with penicillin to treat throat infection
DIagnosis of Rheumatic Fever!
- Inflammation (NOT infection) of heart, joints, skin, brain
- Fever
- Raised ESR and CRP
- S.pyogenes
- ANtibody repsonse to S.pyogenes
