Infective Endocarditis

Infective Endocarditis is an infection of the endocardial surface of the heart, typically involving the heart valves.

Causes

  • Bacteria:
    • Staphylococcus aureus: Most common cause, particularly in intravenous drug users (IVDU) and healthcare-associated cases.
    • Viridans group streptococci: Common in subacute IE, often following dental procedures or poor oral hygiene.
    • Enterococci: Often linked to genitourinary or gastrointestinal tract infections.
    • Coagulase-negative staphylococci: Common in prosthetic valve endocarditis.
    • HACEK organisms: Haemophilus, Aggregatibacter, Cardiobacterium, Eikenella, Kingella; less common but notable causes.
  • Fungi:
    • Such as Candida and Aspergillus, usually in immunocompromised patients or those with prosthetic valves.
  • Culture-negative IE:
    • Occurs due to fastidious organisms (e.g., Coxiella burnetii, Bartonella spp., or previous antibiotic therapy).

History (Hx)

  • Risk Factors:
    • Previous history of IE,
    • congenital heart disease,
    • prosthetic heart valves,
    • valvular heart disease (e.g., rheumatic heart disease),
    • recent cardiac surgery,
    • intravenous drug use,
    • immunosuppression, or
    • recent dental or surgical procedures.
  • Systemic:
    • Fever, chills, night sweats, weight loss, malaise, anorexia.
  • Cardiac:
    • New or changing heart murmur, signs of heart failure (dyspnea, orthopnea).
  • Embolic:
    • Symptoms of stroke (neurological deficits), abdominal pain (splenic infarction), or acute limb ischemia.
  • Non-specific:
    • Fatigue, arthralgia, myalgia, and back pain.

Differential Diagnosis (DDx)

  • Other causes of fever:
    • Sepsis of other origins, tuberculosis, lymphoma, or autoimmune diseases (e.g., systemic lupus erythematosus).
  • Non-infective endocarditis:
    • Libman-Sacks endocarditis (associated with SLE) or marantic endocarditis (non-bacterial thrombotic endocarditis).
  • Other cardiac conditions:
    • Myocarditis, pericarditis, acute coronary syndrome, or heart failure due to other etiologies.
  • Other causes of embolic events:
    • Atrial fibrillation, atherosclerotic emboli, or hypercoagulable states.

Examination (Ex)

  • General Findings:
    • Fever, pallor, splenomegaly, and weight loss.
  • Cardiac Findings:
    • New or changing heart murmur (often mitral or aortic regurgitation),
    • signs of heart failure (elevated JVP, peripheral edema, pulmonary crackles).
  • Peripheral Stigmata of IE:
    • Osler’s nodes: Painful nodules on fingers or toes.
    • Janeway lesions: Painless erythematous macules on palms and soles.
    • Splinter hemorrhages: Linear lesions under the nail beds.
    • Roth’s spots: Retinal hemorrhages with pale centers.
  • Signs of Embolic Events:
    • Neurological deficits (stroke),
    • limb ischemia, or
    • abdominal tenderness (splenic infarction).
  • Other Signs:
    • Clubbing,
    • petechiae (skin, conjunctiva, or mucous membranes).

Investigations (Ix)

  • Blood Cultures (3 sets):
    • At least three sets from different venipuncture sites before starting antibiotics to identify the causative organism.
  • Echocardiography:
    • Transthoracic echocardiography (TTE): First-line imaging to detect vegetations, abscesses, or new valvular regurgitation.
    • Transesophageal echocardiography (TEE): More sensitive, particularly for detecting small vegetations, prosthetic valve endocarditis, or abscesses.
  • Full Blood Count (FBC):
    • May show leukocytosis, anemia of chronic disease.
  • Inflammatory Markers:
    • Elevated ESR and CRP.
  • Renal Function Tests:
    • To assess for renal impairment due to glomerulonephritis or embolic events.
  • ECG:
    • To detect heart block or arrhythmias, suggestive of abscess formation.
  • Chest X-ray:
    • To evaluate for pulmonary emboli or infiltrates from septic emboli.

Management (Mx)

  • Empirical Antibiotic Therapy:
    • Initiate after obtaining blood cultures; choice depends on the likely organism:
      • For native valve endocarditis: Vancomycin plus gentamicin.
      • For prosthetic valve endocarditis: Vancomycin plus ceftriaxone (or cefazolin) and gentamicin.
  • Targeted Antibiotic Therapy:
    • Based on culture results; typically prolonged course (4-6 weeks) depending on the organism and presence of prosthetic material.
  • Surgical Intervention:
    • Considered in cases of heart failure due to valve dysfunction, uncontrolled infection despite appropriate antibiotic therapy, large vegetations (>10 mm) with embolic events, fungal endocarditis, or presence of abscess.
  • Supportive Care:
    • Management of heart failure, monitoring for complications (e.g., embolic events, renal impairment), nutritional support.
  • Patient Education and Prophylaxis:
    • Educate high-risk patients about signs of IE recurrence and reinforce the importance of dental hygiene to prevent future episodes.
    • Prophylactic antibiotics may be recommended before dental or certain surgical procedures.

Follow-Up

  • Regular Monitoring:
    • Echocardiography to assess resolution of vegetations and cardiac function, serial blood cultures to confirm clearance of bacteremia.
  • Rehabilitation:
    • Address any sequelae such as stroke, heart failure, or other embolic complications.
  • Prevention:
    • Reinforce the importance of prophylaxis in high-risk patients for invasive procedures (e.g., dental work), continuous surveillance for symptoms suggestive of recurrence, and optimizing management of comorbidities.