Harrison's Manual of Medicine: Infective Endocarditis

Infective Endocarditis

Diagnosis

The Duke criteria (Table 87-1) constitute a sensitive and specific diagnostic schema. Definite endocarditis is defined by 2 major, 1 major plus 3 minor, or 5 minor criteria. Possible endocarditis is defined by 1 major plus 1 minor criterion or by 3 minor criteria.
If blood cultures are negative after 48-72 h, 2 or 3 additional cultures should be performed, and the laboratory should be asked for advice regarding optimal culture techniques.
Serology is helpful in the diagnosis of Brucella, Bartonella, Legionella, or C. burnetii endocarditis.
Echocardiography should be performed to confirm the diagnosis, to verify the size of vegetations, to detect intracardiac complications, and to assess cardiac function. Transthoracic echocardiography (TTE) does not detect vegetations <2 mm in diameter and is not adequate to evaluate prosthetic valves or to detect intracardiac complications; however, TTE may be used in pts with a low pretest likelihood of endocarditis (<5%). In other pts, transesophageal echocardiography (TEE) is indicated. TEE detects vegetations in >90% of cases of definite endocarditis and is optimal for evaluation of prosthetic valves and detection of abscesses, valve perforation, or intracardiac fistulas.
Other laboratory studies should be performed-e.g., a complete blood count, creatinine measurement, liver function tests, chest radiography, and electrocardiography. The erythrocyte sedimentation rate, C-reactive protein level, and circulating immune complex titer are typically elevated.

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