What is the recommended therapy for infective endocarditis (IE) in patients with rheumatic heart disease (RHD)?

Therapy for Infective Endocarditis in Patients with Rheumatic Heart Disease

Patients with rheumatic heart disease (RHD) who develop infective endocarditis should be treated according to the causative organism identified on blood cultures, following the same antimicrobial regimens as other native valve endocarditis cases, with treatment duration of 4-6 weeks depending on the pathogen and clinical presentation. 1

Initial Approach and Blood Culture Acquisition

• Obtain three sets of blood cultures at 30-minute intervals before initiating antibiotics 1
• RHD patients are at high risk for IE and require prompt treatment initiation once cultures are obtained 1
• The damaged valves from RHD behave as native valve endocarditis for treatment purposes 1

Pathogen-Specific Treatment Regimens

Viridans Group Streptococci (Most Common in RHD)

For highly penicillin-susceptible strains (MIC ≤0.12 µg/mL):

• Aqueous crystalline penicillin G 12-18 million units/24h IV in 4-6 divided doses for 4 weeks 1
• Alternative: Ceftriaxone 2g IV/IM once daily for 4 weeks 1
• For penicillin-allergic patients: Vancomycin 30 mg/kg/24h IV in 2 divided doses for 4 weeks 1

For relatively resistant strains (MIC 0.12 to 0.5 µg/mL):

• Penicillin G 24 million units/24h IV for 4 weeks PLUS gentamicin 3 mg/kg/24h IV for the first 2 weeks 1
• Alternative: Ceftriaxone 2g/24h IV for 4 weeks PLUS gentamicin for first 2 weeks 1

For highly resistant strains (MIC >0.5 µg/mL):

• Treat as enterococcal endocarditis with ampicillin 12g/24h IV in 6 divided doses PLUS gentamicin 3 mg/kg/24h for 4-6 weeks 1

Enterococcal Endocarditis

For penicillin and aminoglycoside-susceptible strains:

• Ampicillin 12g/24h IV in 6 divided doses PLUS gentamicin 3 mg/kg/24h IV in 3 divided doses for 4-6 weeks 1
• Alternative: Penicillin G 18-30 million units/24h IV PLUS gentamicin 1
• For penicillin-allergic patients: Vancomycin 30 mg/kg/24h IV in 2 divided doses PLUS gentamicin for 6 weeks 1

For gentamicin-resistant but streptomycin-susceptible strains:

• Ampicillin 12g/24h IV PLUS streptomycin 15 mg/kg/24h IV/IM in 2 divided doses for 4-6 weeks 1
• Streptomycin should achieve peak serum concentration of 20-35 µg/mL and trough <10 µg/mL 1

Staphylococcal Endocarditis

For acute presentations with suspected S. aureus:

• Nafcillin or oxacillin 12g/24h IV in 4-6 divided doses for 4-6 weeks 1, 2
• Alternative: Cefazolin or cephalothin for 4-6 weeks 2
• For methicillin-resistant strains: Vancomycin 30 mg/kg/24h IV in 2 divided doses 1

HACEK Organisms

• Ceftriaxone 2g/24h IV/IM once daily for 4 weeks 1
• Alternative: Ampicillin-sulbactam 12g/24h IV in 4 divided doses for 4 weeks 1
• For intolerance to cephalosporins: Ciprofloxacin 1000 mg/24h PO or 800 mg/24h IV in 2 divided doses for 4 weeks 1

Empiric Therapy for Culture-Negative Cases

For subacute presentation (most common in RHD):

• Ampicillin-sulbactam 3g IV every 6 hours PLUS gentamicin 1 mg/kg IV every 8 hours 1
• This covers S. aureus, viridans streptococci, enterococci, and HACEK organisms 1

For acute presentation:

• Coverage for S. aureus is essential with nafcillin or oxacillin PLUS gentamicin 1

Treatment Duration Considerations

• Native valve with symptoms <3 months: 4 weeks of therapy 1
• Native valve with symptoms ≥3 months: 6 weeks of therapy 1
• If prosthetic material present (rare in RHD): Minimum 6 weeks of therapy 1

Critical Monitoring Parameters

• Gentamicin peak levels should be 3-4 µg/mL and trough <1 µg/mL 1
• Vancomycin trough levels should be 15-20 µg/mL 1
• Monitor renal function closely when using aminoglycosides, especially in older patients 1
• Repeat blood cultures 48-72 hours after treatment initiation to document clearance 3

Common Pitfalls to Avoid

• Do not delay treatment waiting for culture results in acutely ill patients; start empiric therapy after blood cultures are drawn 1
• Do not use aminoglycoside monotherapy for enterococcal or streptococcal endocarditis; synergy with cell-wall active agents is essential 3
• Do not use cephalosporins alone for enterococcal endocarditis; they have limited activity 1
• Do not shorten aminoglycoside duration below recommended 2 weeks for streptococcal synergy or 4-6 weeks for enterococcal treatment 1
• Vancomycin must be infused over 1 hour to prevent "red man syndrome" from histamine release 1

Infectious Disease Consultation

• Consultation with an infectious disease specialist is recommended for culture-negative endocarditis, resistant organisms, or complicated cases 1, 4
• Early surgical consultation should be obtained for large vegetations (≥10 mm), heart failure, or persistent bacteremia 4