L22: Fever and new murmur - endocarditis

Question 1

Endocarditis features

Answer 1

• Signs and symptoms of infections (fever, lethargy)
• Embolic phenomena (clots blocking arteries causing splinter haemorrhages in nail bed, lower eyelid, soles of feet, hands)
• Abnormal heart valve (mostly aortic and mitral)
• Murmur in endocarditis usually due to regurg not stenosis
• May see vegetations on mitral/aortic valve cusps, renal/splenic embolic infarcts, cerebral embolic infarct, perforation of aortic valve

Question 2

Valve abnormalities and murmurs

Answer 2

Mitral stenosis:

• Diastolic
• Soft, long

Aortic stenosis:

• Systolic
• High-pitched crescendo-decrescendo

Aortic regurg:

• Diastolic
• Soft, early diastolic

Question 3

Endocarditis pathogenesis

Answer 3

1. Turbulent flow through abnormal valve (.e.g congenital, nodules from RHD)
2. Platelets and fibrin attach to damaged valvular epithelium forming sterile vegetations
3. Transient bacteraemia from skin, mouth, gut, urinary tract etc seeds bacteria on sterile vegetations
4. Infected vegetation enlarges and sheds infected emboli leads to valvular destruction

Question 4

Consequences of endocarditis

Answer 4

Emboli can break off and lodge –> infarcts or stroke

Impaired valve function –> heart failure (leaky valve causing backflow putting pressure on ventricles, then atrium, then pulmonary circulation –> pulmonary oedema)

0% chance of cure by host defences

Question 5

Causative bacteria

Answer 5

Viridans streptococci (MOST): from mouth (alpha/green-haemolysis)

Staph aureus: from nose/skin

Enterococcus faecalis: from gut/urinary tract

Question 6

Why do host defences not work?

Answer 6

• Valves are avascular = no capillaries to deliver neutrophils
• Flow across valve is too fast to allow neutrophil adhesion = minimal neutrophil infiltration
• Thus infection cannot be eradicated without antimicrobials

Question 7

Diagnostic methods

Answer 7

Continuous bacteria:

• High conc of bacteria in and on vegetations, with bacteria continually shed into blood
• Constant bacteraemia: expect all blood cultures to be positive
• Culture blood on 3-4 occasions at least 20mins apart (90-100% positive)
• Culture excised valve
• Organism identified in 95% of cases

Then listen for murmur, perform echocardiogram and look for evidence of emboli (+ask about episodes of transient ischaemic attacks)

Question 8

Bacteraemia

Answer 8

True bacteraemia: pathogen cultured, sometimes more than one set of cultures positive, clinically compatible infective source identified

Contaminant bacteraemia: skin commensal cultured, only one set of cultures positive (e.g. staph epidermidis), no apparent infective source

Transient bacteraemia: gut or mouth organism cultured, only positive briefly, no apparent infective source

Question 9

Treatment

Answer 9

(all high dose and IV)
Initially (before knowing cause): penicillin + gentamicin + flucloxacillin

Viridans streptococcus: penicillin + gentamicin
S. aureus: flucloxacillin
Enterococcus faecalis: amoxicillin + gentamicin

For 2 weeks (sometimes 4)
Cure rate 70-90%

Question 10

Rheumatic fever pathogenesis

Answer 10

Not the same as endocarditis

Rheumatic fever: pharyngitis due to S. pyogenes -> immune response to GAS throat infection -> inflammation of joints, heart valves, skin, brain

Question 11

Comparison of rheumatic fever and endocarditis

Answer 11

RF:

• S. pyogenes only
• Immunological damage to valves, nodules
• Treatment w oral penicillin for 10 days
• Prophylaxis w IM penicillin for many yrs

Endocarditis:

• Viridans streptococci + others
• Mouth commensals
• Infection of valves, vegetations on valves
• Treatment w IV penicillin for one month
• Prophylaxis w oral penicillin when dental work