A 34-year-old man who injects drugs presents with 10 days of fever. Examination shows splinter hemorrhages and a new pansystolic murmur at the left sternal border. Blood cultures grow Staphylococcus aureus in two of two bottles. Transthoracic echocardiography shows no vegetation. According to the modified Duke criteria, what is his diagnosis?

• A Definite infective endocarditis ✓
• B Possible infective endocarditis
• C Rejected diagnosis of infective endocarditis
• D Definite infective endocarditis only if transesophageal echocardiography shows a vegetation

Explanation

Two major criteria are present: typical microorganism (S aureus from two separate blood cultures) and evidence of endocardial involvement via a new valvular regurgitant murmur. Definite endocarditis requires either two major, one major plus three minor, or five minor criteria, so the absent vegetation does not matter. The best distractor is option D because imaging is only one way to satisfy the endocardial involvement criterion.

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

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Written and medically reviewed by the StethoPrep medical team.