Infective Endocarditis

Clinical assessment

Suspect in patients with fever and a heart murmur, especially with risk factors or embolic phenomena. The diagnostic triad is persistent fever, emboli, and changing murmur. Differential diagnosis includes other causes of fever/sepsis, heart failure, autoimmune disease (e.g., SLE with Libman-Sacks endocarditis), malignancy (marantic endocarditis).

Investigations

• Blood Cultures: Crucial. Obtain at least 3 sets from separate venipunctures over time (ideally before starting antibiotics) to identify the causative organism and guide therapy.
• Echocardiography: Transthoracic (TTE) first-line. Transesophageal (TOE/TEE) is more sensitive, especially for prosthetic valves, abscesses, or small vegetations.
• Complete Blood Count (CBC): May show anaemia, leucocytosis.
• Erythrocyte Sedimentation Rate (ESR) / C-Reactive Protein (CRP): Usually elevated.
• Urinalysis: Microscopic haematuria, proteinuria.
• ECG: May show conduction abnormalities (if abscess extends).
• Chest X-ray: May show cardiomegaly, signs of heart failure, or septic pulmonary emboli (right-sided IE).

Diagnostic criteria

Diagnosis often based on modified Duke Criteria, combining clinical findings, positive blood cultures, and echocardiographic evidence of endocardial involvement (vegetation, abscess, dehiscence of prosthetic valve, new valvular regurgitation).

Non-pharmacological management

• Bed rest initially.
• Management of complications (e.g., heart failure treatment - see CV003).
• Surgical intervention may be required for: Severe heart failure due to valve dysfunction, persistent infection despite antibiotics, fungal endocarditis, large vegetations with high embolic risk, perivalvular abscess, prosthetic valve dehiscence/dysfunction (Referral to cardiac surgery centre).

Pharmacological treatment

• Antibiotic Therapy: Prolonged course (typically 4-6 weeks) of high-dose IV antibiotics is required.
• Initial Empirical Therapy (while awaiting cultures, or if cultures negative):
• - Native valve, non-IVDU, non-acute presentation (suspect Strep. viridans): Benzylpenicillin 5 MU IV Q6H PLUS Gentamicin 1 mg/kg IV Q8H (for first 2 weeks).
• - Acute onset, IVDU, post-operative/prosthetic valve (suspect Staph. aureus): Add Cloxacillin 3g IV Q6H (or Vancomycin 500mg IV Q6H if MRSA suspected/prevalent).
• Pathogen-Directed Therapy: Adjust antibiotic regimen based on identified organism and susceptibility results. Requires specialist consultation (Infectious Diseases/Cardiology).
• Anticoagulation: Generally avoided unless other indication exists (e.g., mechanical prosthetic valve, atrial fibrillation), due to risk of hemorrhagic stroke from septic emboli.
• Prophylaxis (Prevention): Antibiotic prophylaxis before certain high-risk procedures (mainly dental procedures involving gingival manipulation or perforation of oral mucosa; respiratory tract procedures involving incision/biopsy; procedures on infected skin/musculoskeletal tissue) is recommended ONLY for patients at highest risk of IE: Prosthetic cardiac valve, Previous IE, Congenital heart disease (specific types), Cardiac transplant recipients with valvulopathy. Standard regimen: Amoxicillin 2g PO (Child 50mg/kg) 1 hour before procedure. Alternatives if penicillin allergic (e.g., Clindamycin).

Monitoring

• Monitor clinical response (fever resolution, symptom improvement).
• Monitor inflammatory markers (ESR, CRP).
• Monitor for complications (emboli, heart failure worsening).
• Monitor renal function and drug levels (e.g., Gentamicin, Vancomycin).
• Repeat echocardiography may be needed.
• Monitor for antibiotic side effects.