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FHHD > M13 - Infective Endocarditis > Flashcards

M13 - Infective Endocarditis Flashcards

1
Q

What is IE and infection of

A

The endocardium

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2
Q

What is the endocardium

A

Membrane layer of endothelial cells lining the heart that is continuous with the artery and vein lining and also forms the valve cusps

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3
Q

What happens to valves in patients with IE

A

They basically keep the valves open a little bit at rest and causes some back flow

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4
Q

What are the majority of IE cases caused by

A

Streptococci, mainly “oral streptococci” or enterococci

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5
Q

What is the next most common IE causing organism after strepto/enterococci

A

Staphylococci, S.aureus

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6
Q

Name the HACEK organisms and what they do

A 
Haemophilus
Aggregatibacter
Cardiobacterium
Eikenella
Kingella 
These are gram -ve bacteria that are an unusual cause of infective endocarditis
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7
Q

Name some risk factors of IE

A

Rheumatic heart disease
Ageing population
Degenerative heart disease
Intravenous drug use

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8
Q

What parts of the body does IE tend to affect

A

Usually affects a heart valve but can involve a septal defect or mural endocardium in a left ventricular aneurysm. It can also complicate cardiac abnormalities such as arteriovenous shunts, coarctation (narrowing) of the aorta and developmental defects

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9
Q

What is a ventricular aneurysm

A

Balloon-like swelling in the wall (may develop after myocardial infarction)

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10
Q

Describe the pathogenesis of IE

A
  • During a bacteraemia micro-organisms get deposited on, adhere to and multiply on an endothelial breach which has developed a platelet thrombus
  • They then become encased in additional layers of fibrin and platelets and these layers help protect the bacteria from phagocytic cells
  • Results in a “vegetation”, which is the characteristic lesions that form in endocarditis, mainly occur on valve leaflets and when blood flows from a high to a low pressure chamber
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11
Q

What types of IE are there

A
  1. Affecting previously normal valve
  2. Affecting previously abnormal native valve
  3. Affecting prosthetic valves
  4. Iatrogenic (a condition resulting from treatment)
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12
Q

What are the clinical features of abnormal native valve

A
  • Rheumatic fever, degenerative (calcific) disease
  • Congenital defects (especially turbulent flow)
  • Mitral valve prolapse (5-10x risk)
  • Degenerative valve disease
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13
Q

What pathogens tend to cause Abnormal Native Valve IE

A

Streptococcus spp. or Enterococcus spp.

usually mouth/gut/urinary tract?

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14
Q

Name some oral streptococci that can cause abnormal native valve IE

A

Strep sanguinis. S. mitis, S. mutans

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15
Q

Describe the virulence factors of oral streptococci that can cause IE

A
  • Ability to bind to fibronectin - a protein on the surface of host cells including heart endothelium
  • Production of extra-cellular polysaccharide
  • Ability to bind to platelets (PAAP = platelet aggregation associated protein produced by the streptococci)
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16
Q

When does prosthetic valve IE happen

A

Greatest risk within first few months after surgery

>1 year after surgery - mainly as in native

17
Q

What pathogens tend to cause prosthetic valve IE

A

S.aureus

Coagulase negative staphylococci

18
Q

What are the virulence factors of staphylococcus aureus IE

A

MSCRAMMS - microbial surface components recognising adhesion matrix molecules:
- Surface exposed staphylococcal protein A
- fibrinogen binding protein
Evasion/defence against immune system:
- Leukocidin subunit
- Superantigen-like protein

19
Q

What is used to diagnose IE

A

It is difficult to diagnose IE due to variable signs an symptoms
- Duke criteria is used: lab and clinical criteria that uses a major/minor scoring system

20
Q

What are the major factors that fulfill the duke criteria for IE

A
  1. Blood culture:
    - typical micro-orgs for endocarditis from 2 separate blood cultures e.g. oral streps, HACEK etc OR
    - Persistently +ve blood cultures for ANY microbe OR
    - all of 3 or most of 4 blood cultures
  2. Evidence of endocardial involvement:
    - echocardiogram +ve for IE, vegetation or abscess
    - new damage to artificial valve
    - new valvular regurgitation
21
Q

What are the minor factors that fulfill the duke criteria for IE

A
  1. Predisposition - to heart condition, injecting drug use
  2. Fever > 37C
  3. Vascular phenomena - arterial embolism, septic pulmonary infarcts
  4. Immunological phenomena - glomerulonephritis
  5. Echocardiogram - findings consistent with IE BUT not meeting major criteria
  6. Microbiological - +ve blood culture but not meeting major criteria, antibody response indicating active infection with typical IE micro-org
22
Q

What criteria of the Duke criteria must be fulfilled to diagnose definite IE

A
  • 2 major;
  • 1 major + 3 minor;
  • 5 minor
23
Q

What criteria of the Duke criteria must be fulfilled to diagnose possible IE

A
  • 1 major + 1 minor

- 3 minor

24
Q

What criteria of the Duke criteria must be fulfilled to reject IE

A
  • Alternative diagnosis established OR
  • Resolution within 4 days on antibiotics OR
  • No pathological findings with 4 days on antibiotics OR
  • Does not meet “possible” criteria
25
Q

How are blood cultures processed for IE bacteria

A
  1. Incubate 5 days at 37C or longer in IE
  2. After growth detection do Gram stain
  3. Clue about ID: Gram positive cocci in chains, probably streps (presumptive)
  4. Full ID: culture on solid media
26
Q

What +ve serology findings suggest culture negative endocarditis

A

Serology for Coxiella burnetii, chlamydia, mycoplasma, Bartonella

27
Q

What treatment options are there for IE

A
  • Vegetation impenetrable by phagocytes
  • Bacteriocidal antibiotics required
  • Synergisitic combination
  • Intravenous minimum 2 weeks
  • MIC of micro-organism essential
  • Isolation of micro-organism essential
  • Surgical backup essential
28
Q

What medications are used to treat the acute presentation of IE

A
  • Flucloxacillin 8-12g IV in 4-6 divided doses plus gentamicin 1mg/kg body weight IV 8 hrly (modified according to renal function_
29
Q

What medications are used to treat the indolent presentation of IE

A
  • Penicillin 7.2g IV daily in 6 divided doses or ampicillin/amoxicillin 2g IV 6 hrly gentamicin. 1mg/kg body weight IV 8 hrly (modified according to renal function)
30
Q

What medications are used in penicillin allergic patients with inrtacardiac prosthesis or suspected MRSA

A
  • 1g 12 hrly vancomycin IV modified according to renal function plus rifampicin 300-600mg twice daily orally plus gentamicin 1mg/kg 8 hrly (modified according to renal function)
31
Q

What could be the causes of persistent fever after drug treatment of IE

A
  • Abscess at aortic root/prosthetic valve ring
  • Drug hypersensitivity
  • IV line infection
  • Other supervening nosocomial infection

FHHD (21 decks)

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