Makindo Medical Notes

The Modified Duke Criteria provide a structured and evidence-based approach to diagnosing infective endocarditis. By integrating clinical, microbiological, and imaging findings, the criteria help distinguish definite from possible or rejected cases of endocarditis.

Pathological Criteria

• Positive histology or microbiology of pathological material obtained from autopsy or cardiac surgery. This can include:
  • Valve tissue
  • Vegetations
  • Embolic fragments
  • Intracardiac abscess contents

Major Criteria

• Microbiological Evidence:
  • Two positive blood cultures with organisms typical of infective endocarditis (e.g., Streptococcus viridans, HACEK group).
  • Persistent bacteremia: two blood cultures taken >12 hours apart, or three or more positive blood cultures of less typical organisms (e.g., Staphylococcus aureus or Staphylococcus epidermidis).
  • Positive serology for Coxiella burnetii, Bartonella species, or Chlamydia psittaci.
  • Positive molecular assays (e.g., PCR) for specific gene targets associated with known endocarditis pathogens.
• Imaging Evidence:
  • Positive echocardiogram (transthoracic or transesophageal) showing:
    • Oscillating intracardiac mass on the valve or supporting structures
    • Abscess formation
    • New partial dehiscence of a prosthetic valve
    • New valvular regurgitation (not just an increase in severity of an existing murmur)

Minor Criteria

• Predisposing heart condition or intravenous drug use
• Fever >38°C
• Vascular phenomena (e.g., major arterial emboli, septic pulmonary infarcts, mycotic aneurysm, intracranial hemorrhage, conjunctival hemorrhages, Janeway lesions)
• Immunological phenomena (e.g., glomerulonephritis, Osler’s nodes, Roth’s spots, rheumatoid factor positivity)
• Microbiological evidence that does not meet a major criterion (e.g., single positive blood culture of an organism not typically causing endocarditis)
• Elevated inflammatory markers (e.g., C-reactive protein, erythrocyte sedimentation rate)

Definite Infective Endocarditis

• Pathological criteria met OR
• Two major criteria OR
• One major and two minor criteria OR
• Five minor criteria

The Modified Duke Criteria are invaluable for guiding clinical decisions, prompting further investigations, and determining the need for specific therapies such as prolonged antibiotic administration, surgical intervention, or close monitoring for complications.