Infective Endocarditis

Question 1

Causes of infective endocarditis (3)

Answer 1

1. Subacute infective endocarditis - underlying abnormalities - Strep viridans, Strep faecalis & other gram negs
2. Acute infective endocarditis - normal valves, more virulent pathogens - Staph aureus - esp in IVDA
3. Prosthetic valve endocarditis - Staph epidermidis

Question 2

Pathogenesis of infective endocarditis

Answer 2

Subacute

1. Derangement of blood flow - jet streams, low pressure areas, turbulence
2. Formation of sterile platelet-fibrin deposits on endocardium & valves (vegetations)
3. Seeding by blood-borne organisms
4. Clumping of bacteria due to agglutinating antibodies

Acute
1. High virulence pathogens - directly invade the endocardium & heart valves - rapidly destructive lesions

Question 3

Morphology of infective endocarditis

Answer 3

G:
- friable, bulky bacteria laden vegetation on heart valves
M:
- tangled mass of fibrin & masses of organisms

Question 4

Effects of infective endocarditis (2)

Answer 4

1. Local
   - valve rupture, scarring
   - myocardial ring abscess
   - suppurative pericarditis
2. Distant
   - emboli - organ infarction, abscess formation
   - immune complex mediated disorders - vasculitis, GN
   - others - anemia of chronic disease, splenomegaly

Question 5

Clinical presentations of infective endocarditis

Answer 5

• splinter hemorrhages in nails - microthromboemboli
• Janeway lesions - erythematous/hemorrhagic non-tender lesions on palms/soles
• Osler nodes - subcutaneous nodules in the pulp of digits
• Roth spots - retinal hemorrhages