Diagnosis

The symptoms and signs of endocarditis are often constitutional and, when localized, often result from a complication of IE rather than reflect the intracardiac infection itself. Consequently,inorder to avoid over looking the diagnosis of IE, a high index of suspicion must be maintained.The diagnosis must be investigated when patients with fever present with one or more of the cardinal elements of IE: a predisposing cardiac lesion or behaviour pattern, bacteremia,embolic phenomenon, and evidence of the active endocardial process. Because patients with prosthetic heart valves are always at risk for PVE, the presence of fever or new prosthesis dysfunction at any time warrants considering this diagnosis.

Even when the illness seems typical of endocarditis, the definitive diagnosis requires positive blood cultures or positive cultures (or histology or polymerase chain reaction recovery of a microorganism’s DNA) from the vegetation or embolus.

Duke Criteria of Infective Endocarditis (Modified)
A)Definitive Infective Endocarditis

1) Pathological Criteria
•Micro organism: demonstrated by culture or histology in a vegetation; or in a vegetation that has embolized, or in an intra cardiac abcess, or

•Pathological lesions: vegetation or intracardiac abscess present, confirmed by histology showing active endocarditis.

2) Clinical Criteria, using specific definitions listed below:

Two major criteria, or

• One major and three minor criteria, or

• Five minor criteria.

B) Possible Infective Endocarditis

• One major +1 minor or 3 minor.
 

C)Rejected

• Firm alternative diagnosis for manifestations of endocarditis, or Sustained resolution of manifestations of endocarditis, with antibiotic therapy for 4 days or less, or

• No pathological evidence of infective endocarditis at surgery or autopsy, after antibiotic therapy for 4 days or less.
Clinical Criteria for Diagnosis of Infective Endocarditis

Major Criteria

1)Positive blood culture

•Typical microorganism for infective endocarditis from two separate blood cultures Viridans streptococci, Streptococcus bovis, HACEK group or Community-acquired Staphylococcus aureus or enterococci in the absence of a primary focus, or

•Persistently positive blood culture, defined as recovery of a microorganism consistent with infective endocarditis from:
Blood cultures drawn more than 12 hours apart, or All of three or a majority of four or more separate blood cultures, with first and last drawn at least 1 hr apart Q fever serology

2)Evidence of Endocardial Involvement
 

•Positive echocardiogram

•Oscillating intracardiac mass, on valve or supporting structures, or in the path of regurgitant jets, or on implanted material, in the absence of an alternative anatomical explanation, or Abscess, or

• New partial dehiscence of prosthetic valve, or

• New valvular regurgitation (increase or change in preexisting murmur not sufficient)

Minor Criteria

• Predisposition: predisposing heart condition or intravenous drug use

• Fever > 38.0 o C (100.4 o F)

•Vascular phenomena: major arterial emboli, septic pulmonary infarcts, mycotic aneurysm,intracranial hemorrhage, conjunctival hemorrhage, Janeway lesions

•Immunological phenomena: glomerulonephritis, Osler’s nodes, Roth’s spots, rheumatoid factor

Microbiological evidence: positive blood culture but not meeting major criterion as noted previously (excluding single positive cultures for coagulase-negative staphylococci and organisms that do not cause endocarditis) or serologic evidence of active infection with organism consistent with infective endocarditis.

Adapted from Durack, D.T., Lukes, A.S., Bright, D.K., “New Criteria for Diagnosis of Infective Endocarditis: Utilization of Specific Echocardiographic Findings”, Am J Med 96:200, 1994.For the clinical diagnosis of infective endocarditis, the Duke criteria has an overall sensitivity of more than 80 per cent and a specificity of 99 per cent. To improve the diagnostic sensitivity for the clinical diagnosis of infective endocarditis certain modifications to the original Duke criteria have been suggested.

Proposed Modifications to the Duke Criteria for the Diagnosis of Infective Endocarditis (Li et al.,Clin Infect Diseases, 2000)

•The category “possible IE” should be defined as having at least 1 major criterion and 1 minor criterion or 3 minor criteria.

•The minor criterion “echocardiogram consistent with IE but not meeting major criterion” should be eliminated, given the widespread use of transesophageal echocardiography (TEE).

•Bacteremia due to S. aureus should be considered a major criterion, regardless of whether the infection is nosocomially acquired or whether a removable source of infection is present.

• Positive Q-fever serology should be changed to a major criterion.