Infective endocarditis is diagnosed using the modified Duke’s criteria.
Let’s look at them in an easy-to-remember way.
MAJOR CRITERIA
It’s, quite literally, proving the name Infective Endocarditis to be true.
Infective, that is, positive blood culture:
• Typical bugs in 2 separate cultures
• Persistently positive blood cultures, say > 12h apart
• Single positive blood culture for Coxiella burnetii
Endocarditis, that is, endocardium involvement:
• On imaging with 2D Echo or CT, look for vegetation, abscess, pseudoaneurysm or dehiscence of prosthetic valve
• On clinical exam, find new regurgitation murmur
MINOR CRITERIA
Remember, patients feel very ill when they have infective endocarditis.
Predisposing factors: congenital heart disease, prosthetic heart valves, iv drug abuse
Fever > 38 °C
Vascular phenomena: emboli, Janeway’s lesions
Immunologic phenomena: glomerulonephritis, Osler’s nodes
What if the blood culture is positive but does not meet the major criteria?
It’s considered as a minor criterion (casually speaking, problematic but not majorly problematic).
How do we use this for diagnosing?
2 major OR
1 major + 3 minor OR
All 5 minor criteria, make up the diagnosis.
Clinical Pearl: Fever with any new-onset murmur is taken as infective endocarditis, unless proven otherwise.
Hope this helps. Happy studying!
- Ashish Singh.