A 35-year-old IV drug user with fever and a new tricuspid regurgitation murmur has blood cultures growing Staphylococcus aureus. Echo shows a 1.2 cm vegetation on the tricuspid valve. No left-sided involvement. According to Duke criteria, how should this be classified?

• A Possible infective endocarditis — 1 major + 1 minor criteria
• B Rejected — right-sided endocarditis does not fulfil Duke criteria
• C Definite infective endocarditis — 3 minor criteria
• D Definite infective endocarditis — 2 major criteria (positive blood cultures + echocardiographic evidence of vegetation) ✓

Explanation

The modified Duke criteria for definite IE requires either 2 major criteria, 1 major + 3 minor, or 5 minor criteria. Here, major criterion 1 is positive blood cultures for a typical organism (S. aureus, among others) in ≥2 separate cultures; major criterion 2 is echocardiographic evidence of vegetation. Meeting 2 major criteria establishes definite IE. Right-sided endocarditis is fully encompassed by Duke criteria. This patient clearly meets definite IE with 2 major criteria.

Reference: Harrison's Principles of Internal Medicine, 21st ed.

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Written and medically reviewed by the StethoPrep medical team.