Infective endocarditis (IE) is an infection of the inner layer of the heart including the valves (native/prosthetic), interventricular septum, intracardiac devices, chordae tendineae, and mural endocardium. IE occurs worldwide and is generally fatal if left untreated.
- An infection of the valvular (primarily) and/or mural (rarely) endocardium
- System(s) affected: cardiovascular, endocrine/metabolic, hematologic/lymphatic, immunologic, pulmonary, renal/urologic, skin/exocrine, neurologic
- Synonym(s): bacterial endocarditis; subacute bacterial endocarditis (SBE); acute bacterial endocarditis (ABE)
More common in males (range is 3:2 to 9:1). >50% of cases in the United States occur in individuals >60 years of age.
- Native valve endocarditis has variable rates of incidence due to changes in definition over the years.
- 1.5–3% incidence 1 year after prosthetic valve replacement; 3–6% 5 years postreplacement
- Increasing incidence of cardiovascular device–related infections due to higher frequency of implantable devices.
- Can be community- or hospital-acquired
- Most commonly affects the mitral valve and aortic valve (increased left-sided pressures and turbulent flow)
Etiology and Pathophysiology
IE is most commonly caused by a nonbacterial thrombus that adheres to an endocardial surface, coupled with a bacterial source sufficient to seed the thrombus. This can occur from direct bacterial invasion or valvular trauma:
- Native valve endocarditis
- Acute: Staphylococcus aureus; Streptococcus groups A, B, C, G; Streptococcus pneumoniae; Staphylococcus lugdunensis; Enterococcus spp.; Haemophilus influenzae or parainfluenzae; Neisseria gonorrhoeae
- Subacute: α-hemolytic streptococci, Streptococcus bovis, Enterococcus spp., S. aureus, Staphylococcus epidermidis; HACEK organisms
- Intravenous drug abuse endocarditis (IVDA) (most commonly tricuspid valve): S. aureus, Enterococcus spp.; Pseudomonas aeruginosa, Burkholderia cepacia, other bacilli (gram-negative); Candida spp.
- Prosthetic valve endocarditis
- Early (≥12 months after valve implantation): S. aureus, S. epidermidis; gram-negative bacilli; Candida spp., Aspergillus spp.
- Late (>12 months after valve implantation): α-hemolytic streptococci, S. aureus, Enterococcus spp., S. epidermidis, Candida spp., Aspergillus spp.
- Culture-negative endocarditis: 10% of cases; Bartonella quintana (homeless); Brucella spp., fungi, Coxiella burnetii (Q fever), Chlamydia trachomatis, Chlamydophila psittaci, HACEK organisms
- Device-related endocarditis: coagulase-negative staphylococci or S. aureus
- Injection drug use, IV catheterization, certain malignancies (colon cancer), poor dentition/infection, chronic hemodialysis, age >60 years, male sex
- High risk with:
- Structural heart disease, prosthetic cardiac valves, valvular disease, implantable devices, total parenteral nutrition
- Previous IE
- Good oral hygiene
- Procedures requiring prophylaxis
- Oral/upper respiratory tract procedures/biopsies: Amoxicillin 2 g PO 30 to 60 minutes before procedure or ampicillin 2 g IV/IM are first-line prophylactic choices. Clindamycin no longer recommended for dental prophylaxis because it is associated with more frequent and severe adverse effects (i.e., Clostridium difficile infection)
- Skin/soft tissue: incision and drainage of infected tissue; use agents active against skin pathogens (e.g., cefazolin 1 to 2 g IV q8h or vancomycin 15 mg/kg q12h; max 1 g) if penicillin-allergic or if methicillin-resistant S. aureus (MRSA) suspected.
Commonly Associated Conditions
Most patients with IE have preexisting conditions (see high-risk above).
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