Infective Endocarditis

Question 1

Pathophysiology of infective endocarditis (IE)

Answer 1

Bacteraemia delivers organisms to surface of valve –> adherence of organisms –> eventual invasion of valvular leaflets (damaged endocardium promotes infection)

Question 2

What are the most commonly affected valves in IE?

Answer 2

1. mitral valve
2. aortic
3. mitral + aortic
4. tricuspid
5. pulmonary

Question 3

Which 3 types of valves are affected in IE?

Answer 3

1. Valves with congenital defects (usually on left side, right side is more common with IV drug users)
2. Normal valves affected by virulent organisms
3. Prosthetic valves and pacemakers

Question 4

Which organisms are most responsible for IE?

Answer 4

1. Staph aureus (prosthetic, IV drug use)
2. Strep viridans (oral surgery, most common cause in non-IV drug users)
3. Staph epidermis (prosthetic valves most affected)

Question 5

Sx and signs of IE (including cardinal signs)

Answer 5

Usually acute, rapidly progressive infection

Fever + new murmur = suspect IE

• new valve lesion/regurgitant murmur
• low grade fever
• flu-like illness
• pleuritic pain, back pain
• finger clubbing (longstanding disease)
• petechiae

JOSHER
Janeway lesions - haemorrhages and nodules on palms and soles
Osler nodes - tender nodules in digits, painful
Splinter Haemorrhages - on nail beds
Embolic skin lesions - black spots on skin (infarcts due to embolic vegetation blocking capillaries)
Roth spots - retinal haemorrhages with white/clear centres

Question 6

What is the most common type of murmur associated with IE?

Answer 6

aortic regurgitation

Question 7

Ix for IE (What criteria is used?)

Answer 7

Duke’s criteria (2 major/1 major + 3 minor/all 5 minor)

Major:
1. Blood culture positive
2. Evidence of endocardial involvement (echo positive, new valvular regurg)

Minor:
- predisposing heart condition/IV drug use
- fever
- vascular signs
- positive echo that doesnt meet major criteria
- positive culture that doesnt meet major criteria

CXR: cardiomegaly

ECG: long PR interval (due to aortic root abscess)

Echo: Transoeophageal** (gold standard)

Question 8

Tx for IE

Answer 8

Abx: decided by organism ascertained from cultures for 4-6 weeks
- if staph: flucloxacillin + rifampicin + gentamicin
- if NOT staph: benzylpenicillin + gentamicin

Blind therapy: ampicillin + flucloxacillin + gentamicin