What is the current algorithm for diagnosis and management of infective endocarditis?

Current Algorithm for Diagnosis and Management of Infective Endocarditis

The diagnosis and management of infective endocarditis (IE) requires a multidisciplinary "Endocarditis Team" approach with early referral to a specialized center for complicated cases to reduce mortality and improve outcomes. 1

Diagnostic Algorithm

Step 1: Clinical Suspicion and Initial Evaluation

• Suspect IE in patients with:
  • Fever plus new/changing heart murmur
  • Prosthetic valve or cardiac device
  • History of previous IE
  • Congenital heart disease
  • Injection drug use
  • Unexplained embolic phenomena
  • Persistent bacteremia

Step 2: Immediate Diagnostic Workup

1. Blood Cultures:

   • Obtain 3 sets from separate venipuncture sites
   • First and last samples drawn at least 1 hour apart
   • Before antibiotic administration when possible

2. Echocardiography:

   • Transthoracic echocardiography (TTE) is the first-line imaging modality for all suspected IE cases 1
   • Proceed to transesophageal echocardiography (TOE/TEE) if:
     • TTE is negative/non-diagnostic but clinical suspicion remains high
     • Prosthetic valve or intracardiac device is present
     • Complications are suspected (abscess, perforation)

3. Additional Imaging (when indicated):

   • Cardiac CT: to identify paravalvular lesions
   • 18F-FDG PET/CT: for prosthetic valve IE (if implanted >3 months)
   • Cerebral MRI: to detect silent embolic events
   • Whole-body CT or labeled leukocyte SPECT/CT: to identify embolic complications

Step 3: Diagnostic Classification

Apply the modified Duke criteria with 2015 ESC updates 1:

Major Criteria:

• Positive blood cultures (specific organisms or persistently positive)
• Positive imaging (vegetation, abscess, new prosthetic valve dehiscence)
• Abnormal activity around prosthetic valve on 18F-FDG PET/CT or leukocyte SPECT/CT

Minor Criteria:

• Predisposition (heart condition, IV drug use)
• Fever (>38°C)
• Vascular phenomena (emboli, septic infarcts, mycotic aneurysm)
• Immunological phenomena (glomerulonephritis, Osler nodes, Roth spots)
• Microbiological evidence not meeting major criteria

Diagnostic Categories:

• Definite IE: 2 major criteria OR 1 major + 3 minor criteria OR 5 minor criteria
• Possible IE: 1 major + 1 minor criteria OR 3 minor criteria
• Rejected IE: Firm alternate diagnosis OR resolution with ≤4 days antibiotics OR no pathological evidence

Step 4: For Culture-Negative IE

If blood cultures remain negative after 48 hours:

1. Consult microbiology laboratory
2. Consider serological testing for:
   • Coxiella burnetii (Q fever)
   • Bartonella species
   • Brucella species
   • Legionella pneumophila
   • Mycoplasma pneumonia
   • Aspergillus species
3. Consider PCR testing for fastidious organisms
4. Consider stopping antibiotics and repeating cultures if patient is stable

Management Algorithm

Step 1: Referral Decision

• Refer to specialized "Endocarditis Team" center if:
  • Complicated IE (heart failure, abscess, embolic/neurological events)
  • Prosthetic valve IE
  • Cardiac device-related IE
  • Congenital heart disease
  • Early surgical intervention may be needed

Step 2: Antimicrobial Therapy

• Start appropriate empiric therapy after blood cultures are obtained
• Adjust based on culture results and antimicrobial susceptibility testing
• Duration typically 4-6 weeks depending on pathogen and valve type

Step 3: Surgical Evaluation

Urgent surgery indications (Class I recommendations) 1:

• Heart failure due to valve regurgitation or obstruction
• Uncontrolled infection (abscess, false aneurysm, fistula, enlarging vegetation)
• Prevention of embolic events (persistent vegetation >10mm after ≥1 embolic episode)
• Infection caused by fungi or multiresistant organisms

Step 4: Management of Complications

• Neurological complications:

  • After silent embolism or TIA: proceed with cardiac surgery without delay if indicated
  • After intracranial hemorrhage: postpone surgery for ≥1 month if possible
  • Neurosurgery indicated for large/ruptured infectious aneurysms

• Cardiac device-related IE:

  • Complete hardware removal (device and leads)
  • Percutaneous extraction recommended even with vegetations >10mm
  • Reassess need for reimplantation after extraction

Step 5: Follow-up

• Regular outpatient visits (1,3,6, and 12 months after discharge)
• Blood tests and echocardiography to monitor for recurrence
• Education about prophylaxis for future procedures

Common Pitfalls and Caveats

1. Delayed diagnosis: Maintain high suspicion in high-risk patients even with atypical presentations
2. Inadequate blood cultures: Obtain cultures before antibiotics when possible
3. Overreliance on TTE: Proceed to TEE when clinical suspicion is high despite negative TTE
4. Missing prosthetic valve IE: Use additional imaging (PET/CT) for suspected prosthetic valve IE
5. Inappropriate timing of surgery: Early surgical consultation is essential for complicated IE
6. Failure to identify source: Thorough evaluation for portals of entry (dental, GI, skin)
7. Inadequate follow-up: Regular monitoring is needed due to risk of relapse

The modified Duke criteria with the 2015 ESC updates provide the most current framework for diagnosis, but clinical judgment remains paramount in the management of IE, particularly in culture-negative cases or when diagnostic findings are equivocal 1.