Subacute Bacterial Endocarditis

1. Epidemiology
   1. Males older than 50 years are more commonly affected
2. Etiology: Predisposing lesion (60-80% of patients)
   1. Prosthetic Heart Valve
   2. Rheumatic Heart Disease (30%)
      1. Mitral valve more affected than Aortic valve
   3. Congenital Heart Disease (10-20%)
      1. Bicuspid aortic valve
      2. Pulmonary stenosis
      3. Ventricular Septal Defect
   4. Mitral Valve Prolapse (10-33%)
   5. Calcific Aortic Stenosis
   6. Asymmetric septal hypertrophy
   7. Marfan's Syndrome
3. Etiology: Infection sources
   1. IV Drug Abuse or IV Catheter related phlebitis
      1. Staphylococcus aureus
      2. Group A Streptococcus
      3. Gram Negative Rods
      4. Candida
   2. Dental procedures (including routine tooth cleaning)
      1. Viridans Streptococci
   3. Genitourinary procedures (includes Prostatic Massage)
      1. Enterococcus
      2. Gram Negative Rods
   4. Prosthetic Valve Recipient
      1. Staphylococcus epidermidis
      2. Staphylococcus aureus
      3. Diphtheroids
      4. Gram Negative Rods
      5. Candida
      6. Enterococcus
   5. Colonic neoplasm, villous adenoma or polyp
      1. Streptococcus bovis
   6. Obstetric delivery
   7. Respiratory infection
   8. Skin Infection
   9. Cardiac surgery or cardiac catheterization
4. Signs: Classic Presentation (Osler)
   1. Petechiae on mucus membranes (mouth, Conjunctiva)
   2. Splinter Hemorrhages beneath nails
   3. Osler's nodes
   4. Janeway lesions
      1. Painless hemorrhage Nodules on palms or soles
   5. Roth spots
      1. Retinal hemorrhages with central pallor
   6. Cerebral emboli
      1. Focal Cerebrovascular Accident findings
   7. Systolic Murmur from Heart Valve
      1. Most often a valve regurgitation murmur
      2. Changes over time
   8. Digital Clubbing
5. Signs: Typical Presentation
   1. Viral prodrome type symptoms
      1. Fever
      2. Chills
      3. Sweats
      4. Weight loss
      5. Anorexia
      6. Arthralgia
      7. Malaise
      8. Pallor
   2. Non-productive cough
      1. Present in up to 24% of cases
      2. Better when supine, worse when upright
   3. Classic endocarditis symptoms as above
      1. May only be present in severe Acute Endocarditis
6. Labs
   1. Blood Culture (obtain over several days)
      1. Four cultures: >90% sensitive
      2. Six cultures: 100% sensitive
   2. Complete Blood Count
      1. Leukocytosis
      2. Normochromic, Normocytic Anemia
   3. Sedimentation Rate (ESR) elevated
   4. Urinalysis
      1. Proteinuria
      2. Microscopic Hematuria
   5. Complement
      1. CH50 or C3 decreased
   6. Rheumatoid Factor positive
      1. Circulating immune complex
7. Diagnosis: Echocardiogram
   1. Vegetation in up to 80% of native valve endocarditis
   2. Cannot differentiate active from healed lesion
8. Differential Diagnosis
   1. Viral syndrome
   2. Acute Rheumatic Fever
   3. Atrial myxoma
   4. Systemic Lupus Erythematosus
   5. Primary neurologic disorder
   6. Occult neoplasm
9. Complications
   1. Ventricular Heart Failure (right or left)
   2. Glomerulonephritis
   3. Renal infarction
   4. Splenic infarction
   5. Pulmonary infarction
   6. Cerebral Infarction
   7. Meningitis
   8. Cerebral mycotic aneurysm
   9. Cerebral abscess
   10. Encephalitis
   11. Mycotic aneurysm
10. Management: Medical
    1. Antibiotics IV for 4-6 week course
       1. Specific to organisms cultured
11. Management: Cardiovascular Surgery
    1. Indications
       1. Fungal endocarditis
       2. Prosthetic valve endocarditis
       3. Persistently positive Blood Culture despite therapy
       4. Recurrent emboli
       5. Valve ring or myocardial abscess
       6. Heart Failure
       7. Large vegetation
    2. Efficacy
       1. Based on retrospective study
       2. Early surgery improves survival over antibiotic alone
          1. Surgery within first 2 days of admission
          2. After 8 years of follow-up
             1. Surgery patient survival: 60%
             2. Medical therapy (antibiotics) survival: 35%
       3. Bishara (2001) Clin Infect Dis 33:1636-43
12. Prevention
    1. SBE Prophylaxis for indicated predisposing factors
13. References
    1. Pelletier (1991) in Harrison's Medicine, p. 972