Methicillin-susceptible Staphylococcus aureus (MSSA) prosthetic valve endocarditis — case discussion

Objectives

• Apply the 2023 ESC criteria and imaging algorithm to suspected prosthetic valve endocarditis.^[1]
• Choose the antibiotic regimen and surgical timing for staphylococcal prosthetic valve endocarditis (PVE).^[1]
• Manage anticoagulation and plan prevention after recovery.^[1]

Candidate brief

You are the cardiology registrar. The patient in the presentation has just been admitted. Talk the consultant through your assessment and plan for the first week.

Expected actions

1. Recognise the risk. A prosthetic valve and a recent dental procedure are both risk factors for infective endocarditis (IE).^[1] Prophylaxis was recommended before his extraction, because prophylaxis is recommended in patients with surgically implanted prosthetic valves, a high-risk group (Class I, Level C), and antibiotic prophylaxis is recommended for dental extractions in high-risk patients (Class I, Level B).^[1] Its main target is oral streptococci, whereas his organism is S. aureus.^[1]
2. Complete the cultures. At least three sets at 30-minute intervals before antibiotics, from a peripheral vein.^[1]
3. Image the prosthesis. Transthoracic echocardiography (TTE) is recommended as the first-line imaging modality in suspected IE (Class I, Level B).^[1] Transoesophageal echocardiography (TOE) is recommended in suspected IE when a prosthetic valve is present (Class I, Level B), and echocardiography should be considered in S. aureus bacteraemia (Class IIa, Level B).^[1] In PVE, echocardiography and blood cultures each have a sensitivity of only 60% for definite IE, so if TOE is inconclusive, [18F]FDG-PET/CT(A) and cardiac computed tomography angiography (CTA) are recommended in possible PVE to detect valvular lesions and confirm the diagnosis (Class I, Level B).^[1] Cardiac CTA is recommended to diagnose periprosthetic complications if echocardiography is inconclusive (Class I, Level B). If he has symptoms suggesting septic emboli, brain and whole-body imaging are recommended to detect peripheral lesions or add minor criteria (Class I, Level B); if not, they may be considered for screening (Class IIb, Level B).^[1]
4. Classify. S. aureus in two separate cultures is one major criterion.^[1] A predisposing heart condition (his prosthetic valve) and fever above 38°C are two minor criteria; splinter haemorrhages are not among the listed 2023 ESC minor criteria.^[1] With 1 major and 2 minor criteria he has possible IE; it becomes definite if imaging adds a second major criterion or if a third minor criterion is found (for example embolic lesions detected by imaging only).^[1]
5. Treat. For PVE due to methicillin-susceptible staphylococci (which include his methicillin-susceptible S. aureus): (flu)cloxacillin 12 g/day intravenous (i.v.) in 4–6 doses or cefazolin 6 g/day i.v. in 3 doses, with rifampin 900 mg/day i.v. or orally in 3 equally divided doses for at least 6 weeks and gentamicin 3 mg/kg/day i.v. or intramuscular (i.m.) in 1 (preferred) or 2 doses for 2 weeks (Class I, Level B); cloxacillin is not recommended with penicillin allergy, and gentamicin is limited to a maximum of 240 mg/day with weekly renal function and gentamicin levels.^[1] Rifampin starts after 3–5 days of effective therapy, once bacteraemia has cleared.^[1]
6. Involve the Heart Valve Centre. If his IE is complicated, diagnosis and management are recommended at an early stage in a Heart Valve Centre with immediate surgical facilities and an Endocarditis Team, to improve outcomes (Class I, Level B); if uncomplicated and managed in a Referring Centre, early and regular communication with the Heart Valve Centre team is recommended (Class I, Level B).^[1]
7. Plan surgery. Urgent surgery (within 3–5 days) should be considered in PVE caused by S. aureus or non-HACEK Gram-negative bacteria (Class IIa, Level C).^[1] S. aureus PVE carries mortality above 45% and often needs early valve replacement.^[1] TOE is mandatory in suspected PVE, and identification of a new periprosthetic leak is a major criterion of IE; in aortic or mitral native valve endocarditis (NVE) or PVE, severe acute regurgitation or obstruction causing heart failure (HF) symptoms or echocardiographic signs of poor haemodynamic tolerance is an indication for urgent surgery, within 3–5 days (Class I, Level B).^[1] If he requires cardiac surgery and is at high risk for coronary artery disease (CAD): with aortic valve vegetations and haemodynamic stability, high-resolution multislice coronary CTA is recommended (Class I, Level B); without aortic valve vegetations, invasive coronary angiography is recommended (Class I, Level C); and invasive angiography may be considered despite aortic valve vegetations in selected patients with known CAD or at high risk of significant obstructive CAD (Class IIb, Level C). Intra-operative echocardiography is recommended in all IE requiring surgery (Class I, Level C).^[1]
8. Manage warfarin. Without stroke, replacing oral anticoagulation with closely monitored unfractionated heparin should be considered when surgery is likely, for example in S. aureus IE (Class IIa, Level C).^[1]
9. Look for complications. New atrioventricular block (AVB) on serial electrocardiograms (ECGs) would indicate paravalvular extension and an indication for urgent surgery.^[1] Brain and whole-body imaging are recommended if symptoms suggest septic emboli, to detect peripheral lesions or add minor criteria (Class I, Level B).^[1]
10. Plan beyond the acute phase. If he is clinically stable after at least 10 days of appropriate i.v. treatment (or at least 7 days after cardiac surgery) and TOE shows no abscess or valve abnormality requiring surgery, outpatient parenteral or oral treatment should be considered (Class IIa, Level A), with TOE before any switch to oral treatment (Class I, Level B).^[1] If he does not have valve surgery, TTE and/or TOE are recommended at the end of antibiotics (Class I, Level C).^[1] Cardiac rehabilitation should be considered once he is clinically stable, based on an individual assessment (Class IIa, Level C), and psychosocial support may be considered within follow-up care (Class IIb, Level C).^[1]

Marking

The 2020 ACC/AHA text adds that staphylococcal PVE has been associated with mortality as high as 70%, driven by resistant staphylococcal species.^[2]