Endocarditis

Basics

Description

An inflammation of the endothelial surface of the heart
  • Various cardiac structures may be involved:
    • Native heart valves (most common)
    • Prosthetic valves
    • Interventricular septum
    • Chordae tendineae
    • Mural endocardium
    • Intracardiac devices
  • Characterized by a vegetation (a thrombus with superimposed microorganisms)
    • Bacterial colonization of the initially sterile vegetation composed of fibrin and platelets
    • Bacterial growth enlarges the vegetation, further impeding blood flow and inciting inflammation
    • Propagation of the infection through systemic emboli
  • Almost always secondary to bacterial infection
  • Rare noninfectious causes
    • Nonbacterial thrombotic endocarditis or marantic endocarditis:
      • Often due to a hypercoagulable state
      • Small sterile vegetation
    • Libman–Sacks endocarditis:
      • Complications of lupus erythematosus
      • Due to the deposition of immune complexes that cause an inflammatory reaction
      • Small vegetation

Epidemiology

  • More common in men:
    • Incidence 3–7 cases/100,000 person-yr
    • Third most common life-threatening infection
  • Risk factors:
    • Older patients
    • Poor dental hygiene or dental procedure
    • Comorbidities:
      • Rheumatic and congenital heart disease
      • Prosthetic valve/intracardiac device
      • Hemodialysis/indwelling catheters
      • Diabetes and immunosuppression
    • IV drug abuse (IVDA):
      • Greater risk than rheumatic heart disease or prosthetic valves
      • Predilection for right-sided heart valves
  • Septic embolization:
    • Cerebral complications:
      • Cerebral embolism
      • Intracranial hemorrhage
      • Cerebral abscess
    • Extracerebral embolic events:
      • Pulmonary
      • Splenic
      • Renal
      • Mycotic aneurysms (aorta, renal artery, splenic artery, hepatic artery, mesenteric arteries, etc.)
      • Hepatic
      • Coronary
  • Risk factor for recurrent endocarditis:
    • Structural heart disease serves as common vegetative site due to altered intracardiac flow:
      • Mitral valve prolapse
      • Aortic valve dysfunction
    • Congenital heart disorders in the pediatric populations:
      • Tetralogy of Fallot
      • Aortic stenosis
      • Patent ductus arteriosus
      • Ventricular septal defects
      • Aortic coarctation
    • Prosthetic valves
    • Indwelling catheters
    • Any mechanical device may serve as a portal of entry or attachment for microorganisms

Etiology

  • Major categories:
    • Bacterial endocarditis
    • Prosthetic valve endocarditis
    • Nonbacterial thrombotic endocarditis:
      • Malignancy
      • Uremia
      • Burns
      • Systemic lupus erythematosus
  • Common organisms:
    • Staphylococcus aureus (most common pathogen):
      • Seen in all populations, especially IVDA and toxic illness
      • Acute and destructive
      • Sometimes metastatic
    • Streptococcus viridans:
      • Found in oropharynx, common agent in native valve endocarditis
    • Streptococcus bovis:
      • Common association with colonic polyps or GI malignancy
    • Streptococcus pneumoniae:
      • Causes rapid valvular destruction, abscess, and CHF
      • Risk factor: Alcoholism
    • Staphylococcus epidermidis
    • Enterococci:
      • Seen in young women and old men following instrumentation or infection
    • Candida and Aspergillus:
      • Found in IVDA, prosthetic valves, or immunocompromised patients
    • HACEK (Haemophilus sp.) slow growing
    • Culture-negative endocarditis (Q fever, psittacosis, Bartonella, brucellosis)

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