[Circulation 2015; 132:1435-86, European Heart J 2015;36:3075-128]


- 10-20% of patients who develop endocarditis have no pre-existing heart disease.

- Diagnosis includes:

  • multiple positive blood cultures

  • new murmur

  • definite emboli

  • vegetations on echocardiogram.

- For more specific diagnostic criteria, refer to Modified Duke Criteria (Clin Infect Dis 2023;77:518–26)

- Blood cultures:

  • NB: in patients who are stable (no heart failure) with subacute presentation, wait for results of blood cultures before starting antibiotic therapy.

  • draw maximum 2 sets/day

  • adults – 8-10mL of blood/bottle

  • consult microbiology laboratory if unusual/fastidious (Bartonella, Chlamydia, Coxiella, Brucella, Legionella, Tropheryma whippleii) organism suspected

  • repeat blood cultures every 48h until clearance of bacteremia to guide duration of therapy. Duration of therapy should start from date of first negative blood culture.

- For positive cultures or blood culture negative endocarditis, see Recommended Therapy of Culture-Directed Infections; Treatment of Culture-proven Endocarditis and Blood Culture Negative Endocarditis (BCNE) respectively.

- Echocardiogram:

  • transthoracic echocardiogram (TTE) - sensitivity: 70% native valve; 50% prosthetic valve

  • transesophageal echocardiogram (TEE) - sensitivity: 96% native valve; 92% prosthetic valve

  • TEE recommended if:

    • prosthetic valves (TTE < 50% sensitivity) or intracardiac device

    • congenital heart disease

    • previous endocarditis

    • TTE negative AND:

      • new murmur

      • heart failure

      • stigmata of endocarditis

      • persistent (> 5 days) bacteremia.

  • if initial TTE and/or TEE is negative, repeat TTE/TEE 5 days later if clinical suspicion of endocarditis remains high, persistent fever and/or bacteremia; or sooner if persistent S. aureus bacteremia or clinical findings change.

  • should be repeated following treatment for endocarditis to establish a new baseline.

- Ophthalmological exam recommended for patients with endocarditis due to fungi.

- For surgical indications (heart failure, uncontrolled infection, prevention of embolic events) and timing see Circulation 2015; 132:1435-86, or European Heart J 2015; 36:3075-128, Table 22.

Duration of antibiotic therapy post-valve replacement:

  • negative valve cultures - duration as for native valve endocarditis, starting from date of first negative blood culture (not from day of surgery).

  • positive valve cultures - full course of therapy starting from day of surgery.


  • Vancomycin is less rapidly bactericidal than ß-lactams so should only be used when β-lactams contraindicated (due to severe allergy, or resistance). Longer duration of therapy may be required.

  • Desired vancomycin trough is 10-20mg/L. Monitor renal function closely. See Vancomycin Dosing & Monitoring Guidelines.