A 52-year-old woman with a prosthetic aortic valve (bioprosthetic, inserted 8 years ago for aortic stenosis) presents with fever, night sweats, and progressive fatigue for 6 weeks. On examination, blood pressure is 145/55 mmHg with a wide pulse pressure. A new early diastolic murmur is heard at the left sternal border. Blood cultures grow viridans group streptococci (penicillin-susceptible). Transoesophageal echocardiography (TEE) shows a 6 mm vegetation on the aortic valve with mild aortic regurgitation and no dehiscence. What is the most appropriate management strategy?

Explanation

## Diagnosis: Prosthetic Aortic Valve Endocarditis (PVE) with Penicillin-Susceptible Viridans Streptococci **Key Point:** Early prosthetic valve endocarditis (PVE) — occurring within 1 year of surgery — is typically nosocomial (Staph epidermidis, enterococci). Late PVE (>1 year post-op) resembles native valve IE and is often caused by viridans streptococci, as in this case. ### Classification & Timing | Timing | Typical Organisms | Pathophysiology | Management | | --- | --- | --- | --- | | **Early PVE** (<1 year) | Staph epidermidis, MRSA, enterococci, gram-negatives | Perioperative contamination; prosthetic material involvement | Often requires surgery + prolonged antibiotics | | **Late PVE** (>1 year) | Viridans streptococci, MSSA, enterococci | Community-acquired; similar to native valve IE | Medical management if uncomplicated; surgery if complications | **High-Yield:** This patient has **late PVE** (8 years post-op) with viridans streptococci — a scenario that can often be managed medically if there is no evidence of prosthetic dehiscence, large vegetation, or heart failure. ### Antibiotic Regimen for Penicillin-Susceptible Viridans Streptococci on Prosthetic Valve **Mnemonic: PVE-VS-4W** — **P**rosthetic **V**alve **E**ndocarditis **V**iridans **S**treptococci **4** weeks. - **Penicillin G 4 million units IV every 4 hours + gentamicin 3 mg/kg IV once daily for 4 weeks** is the standard regimen for penicillin-susceptible viridans streptococci on a prosthetic valve. - Gentamicin provides synergy and reduces vegetation burden. - Repeat TEE at 2 weeks is recommended to assess vegetation response and rule out complications (dehiscence, abscess, new regurgitation). **Clinical Pearl:** The wide pulse pressure (145/55) and early diastolic murmur indicate aortic regurgitation from the vegetation. The absence of prosthetic dehiscence on TEE is a favorable prognostic sign and supports medical management. ### Indications for Surgical Intervention in PVE 1. **Prosthetic dehiscence or abscess** — most common surgical indication 2. **Large vegetation (>10 mm) with embolic phenomena** 3. **Acute heart failure** (severe regurgitation or obstruction) 4. **Fungal endocarditis** 5. **Failure to sterilize blood cultures after 7–10 days of appropriate antibiotics** 6. **Recurrent septic emboli despite appropriate therapy** This patient has none of these; therefore, medical management is appropriate with close clinical and echocardiographic monitoring.