Infective Endocarditis (IE): Treatment Guidelines (2023 ESC / AHA)

1. Guiding Principles

• Treatment requires prolonged high-dose intravenous antibiotics that are bactericidal - the dense bacterial biofilm within vegetations demands this approach.
• Targeted therapy is always preferred over empirical therapy; every effort must be made to identify the causative organism and susceptibilities before starting antibiotics.
• Management requires a multidisciplinary "Endocarditis Team": cardiologist, cardiac surgeon, infectious disease specialist, and often a neurologist.
• In-hospital mortality remains 15-30%.

2. Initial Workup Before Starting Therapy

• At least 3 sets of blood cultures (aerobic and anaerobic) from separate venipuncture sites, separated by >30 minutes if clinically stable.
• Echocardiography: Transthoracic echo (TTE) first; if negative but IE still suspected, proceed to transesophageal echo (TEE) - TEE is the screening method of choice for perivalvular complications.
• Multimodality imaging (new in 2023 ESC): 18F-FDG PET/CT and cardiac CT significantly enhance sensitivity for prosthetic valve IE (PVIE) and paravalvular extension.

3. Empirical Antibiotic Therapy

Rifampin is never used as monotherapy due to rapid resistance development.

4. Organism-Specific (Targeted) Antibiotic Therapy

Streptococcal IE (Viridans group, S. gallolyticus)

• Penicillin-susceptible (MIC ≤0.125 mg/L): Penicillin G or Ceftriaxone for 4 weeks (native valve). For low-risk patients, a 2-week regimen of Ceftriaxone + Gentamicin is an acceptable alternative.
• Penicillin-intermediate (MIC 0.125-2 mg/L): Higher-dose penicillin + gentamicin.
• Penicillin-resistant (MIC >2 mg/L): Vancomycin.

Staphylococcal IE

• MSSA, native valve: Nafcillin or Oxacillin 2 g IV q4h for 4-6 weeks.
• MRSA or prosthetic valve: Vancomycin for 6 weeks; prosthetic valve MRSA adds Rifampin + Gentamicin.

Enterococcal IE

• First-line: Ampicillin (or Amoxicillin) + Gentamicin for 4-6 weeks. Duration of 4 weeks may suffice if symptoms <3 months (both ESC and AHA), but 6 weeks is generally preferred given severity.
• Alternative (aminoglycoside resistance): Ampicillin + Ceftriaxone (double beta-lactam regimen).

HACEK Organisms

• Ceftriaxone 2 g IV once daily for 4 weeks. Fungal IE with HACEK is often a stand-alone indication for surgery.

Fungal IE

• IV Amphotericin B ± azole agents (fluconazole step-down for Candida). Traditionally a primary surgical indication; selected patients may be managed medically with close infectious disease collaboration.

Culture-Negative IE / Zoonotic IE

• Bartonella: Doxycycline 100 mg IV/PO q12h for 6 weeks + Gentamicin for the first 2 weeks.
• Coxiella burnetii (Q fever): Doxycycline + Hydroxychloroquine for at least 18 months.
• Brucella: Doxycycline + Rifampin ± gentamicin.

5. Surgical Management

Indications for Surgery

• Severe aortic or mitral regurgitation causing acute pulmonary edema or cardiogenic shock.
• Intracardiac fistula or valve obstruction.

• Persistent bacteremia/fever >7 days despite appropriate antibiotics.
• Perivalvular abscess, pseudoaneurysm, fistula formation.
• IE due to fungi, MDR organisms, or gram-negative bacteria.
• Increasing vegetation size on repeat echo.

• Large (>10 mm), mobile vegetations - especially after an embolic event during antibiotic therapy.
• Vegetation >10 mm + severe valvular dysfunction or abscess = strong indication even without prior embolism.

Timing of Surgery (2023 ESC Classification)

Key principle from Braunwald's: "Delaying surgery in patients with deteriorating cardiac function in an attempt to sterilize the affected valve is ill-advised because the risk of progressive heart failure usually outweighs the relatively small risk of recurrent IE after valve replacement."

Neurologic Complications and Surgical Timing

• After silent cerebral embolism or TIA: surgery without delay if indication remains (Class I).
• After stroke without hemorrhage: delay surgery 1-2 weeks if neurologically stable.
• After cerebral hemorrhage: delay surgery at least 4 weeks.
• Neurosurgery or endovascular therapy is indicated for large/enlarging mycotic aneurysms.

6. Special Situations

Prosthetic Valve Endocarditis (PVE)

• Early PVE (<1 year post-surgery): usually coagulase-negative staphylococci or S. aureus - associated with high mortality, surgical threshold is lower.
• Late PVE (>1 year): viridans streptococci predominate, similar management to native valve IE.
• Always add Rifampin to staphylococcal PVE regimens.

IV Drug Users (IVDU)

• S. aureus accounts for >50% of cases; right-sided (tricuspid) valve most frequently affected.
• Right-sided IE carries a favorable prognosis (mortality <10%).
• 4-6 weeks of IV antibiotics; select patients with right-sided MSSA IE may qualify for 2-week regimens.
• Surgical indications are the same but must be weighed carefully given significant recidivism risk. Early addiction medicine consultation is strongly recommended.

Cardiac Device IE (Pacemaker, ICD, TAVI)

• Device removal (lead extraction) is generally necessary in addition to antibiotics.
• TAVI-related IE increasingly recognized; valve explantation often required.

7. Monitoring During Therapy

• Daily clinical examination for new murmurs, pulse pressure changes (aortic insufficiency), or conduction abnormalities (ECG - which may suggest myocardial abscess).
• Serial blood cultures: particularly for S. aureus or gram-negative IE to confirm microbiological response.
• Repeat echocardiography if: persistent fever, new embolic events, new murmur, or suspected conduction abnormality.
• Renal function and gentamicin levels (trough ≤1-3 µg/mL) monitored twice weekly.
• Fever resolution: ~50% defervesce within 3 days, 75% by 1 week, 90% by 2 weeks. Fever >1 week should prompt repeat blood cultures and search for abscesses.

8. Anticoagulation

• New anticoagulation in native valve IE provides no benefit and is not recommended.
• For mechanical prosthetic valve IE: continuing anticoagulation may be advisable.
• For S. aureus PVE + CNS embolic event: discontinue all anticoagulation for at least the first 2 weeks to allow clot organization and prevent hemorrhagic transformation.
• Aspirin 325 mg/day does not prevent embolic events and increases bleeding - not recommended.

9. Prophylaxis

• Prosthetic valve (mechanical or biological)
• Previous IE
• Congenital heart disease (certain types: unrepaired cyanotic CHD, repaired CHD with residual defects, first 6 months post-repair)
• Heart transplant recipients with valvulopathy

Routine prophylaxis for GI endoscopy or genitourinary procedures is no longer recommended for IE prevention.

10. Novel/Emerging Evidence

• 2023 ESC Guidelines for Endocarditis (Vahanian et al., Eur Heart J 2023;44:3948)
• Goldman-Cecil Medicine, 26th Ed., Chapter 61
• Braunwald's Heart Disease, 15th Ed., Chapter 80
• Frameworks for Internal Medicine, Chapter 29
• AHA 2025 Scientific Statement on Blood Culture-Negative Endocarditis (PMID 40094211)