Treatment of Infective Endocarditis
The treatment of infective endocarditis requires a bactericidal antibiotic regimen targeted to the causative organism, with specific regimens based on pathogen, valve type, and patient factors, often requiring 4-6 weeks of therapy and possible surgical intervention for complications. 1, 2
Empiric Antibiotic Therapy
When the causative organism is unknown, empiric therapy should be initiated promptly after obtaining blood cultures:
For native valve endocarditis:
For prosthetic valve endocarditis:
- Vancomycin plus gentamicin plus rifampin 2
Targeted Antibiotic Therapy Based on Pathogen
Streptococcal Endocarditis
- Penicillin-susceptible viridans streptococci or S. bovis:
Enterococcal Endocarditis
- Ampicillin plus gentamicin for 4-6 weeks 1
- For beta-lactam resistance: Replace ampicillin with ampicillin-sulbactam 1
- For aminoglycoside resistance: Daptomycin plus ampicillin or linezolid 1
Staphylococcal Endocarditis
Methicillin-susceptible S. aureus (MSSA):
Methicillin-resistant S. aureus (MRSA):
HACEK Organisms
- Ceftriaxone 2 g/day for 4 weeks in native valve endocarditis (NVE) and 6 weeks in prosthetic valve endocarditis (PVE) 1
- Alternative: Ciprofloxacin (400 mg/8-12h IV or 750 mg/12h orally) 1
Blood Culture-Negative Endocarditis
Treatment based on likely pathogens:
| Pathogen | Proposed Treatment | Duration |
|---|---|---|
| Brucella spp. | Doxycycline + cotrimoxazole + rifampin | ≥3-6 months |
| C. burnetii (Q fever) | Doxycycline + hydroxychloroquine | >18 months |
| Bartonella spp. | Doxycycline + gentamicin | Doxycycline for 4 weeks, gentamicin for 2 weeks |
| Legionella spp. | Levofloxacin or clarithromycin | ≥6 weeks |
| Fungi | Antifungal therapy + surgical valve replacement | Long-term |
Right-Sided Endocarditis in IV Drug Users
- For MSSA with good response: 2-week treatment with oxacillin/cloxacillin may be sufficient 1
- Must meet criteria:
- MSSA infection
- Good response to treatment
- No metastatic infection or empyema
- No cardiac/extracardiac complications
Surgical Intervention
Surgical consultation should be obtained early when indicated:
Indications for surgery include:
- Heart failure due to valvular dysfunction
- Uncontrolled infection despite appropriate antibiotics
- Large mobile vegetations (>10mm) with embolic risk
- Perivalvular abscess or fistula formation
- Prosthetic valve infection
- Fungal endocarditis 1, 2
For right-sided endocarditis, surgery should be considered for:
- Right heart failure secondary to severe tricuspid regurgitation unresponsive to diuretics
- Persistent infection (bacteremia >7 days) despite adequate antibiotics
- Tricuspid valve vegetations >20mm with recurrent pulmonary emboli 1
Monitoring During Treatment
- Daily clinical assessment
- Serial blood cultures until sterilization
- Regular echocardiographic follow-up
- Monitoring of renal function
- Drug level monitoring:
- Gentamicin: target trough <1 mg/L, peak 10-12 mg/L
- Vancomycin: target trough 10-15 μg/mL, peak 30-45 μg/mL 2
Follow-up Care
- Clinical evaluation at 1,3,6, and 12 months
- Echocardiography at completion of therapy
- Blood cultures if recurrent fever
- Dental follow-up and emphasis on prophylaxis for future procedures 2
Common Pitfalls and Caveats
- Delayed diagnosis: Consider IE in patients with unexplained fever, new murmur, or embolic phenomena
- Inadequate duration of therapy: Most regimens require 4-6 weeks of treatment
- Failure to identify complications: Regular echocardiographic monitoring is essential
- Missing surgical indications: Early surgical consultation is critical for optimal outcomes
- Inadequate drug monitoring: Regular monitoring of antibiotic levels and renal function is necessary to prevent toxicity
- Incomplete follow-up: Patients require long-term monitoring for relapse or complications