Description

• 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)

Epidemiology

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.

Incidence

• Incidence at ~15 in 100,000, increasing from previous years
• The predominant form of IE is community associated. Up to one-third of cases are health care-acquired in resource-rich countries.
• Increasing incidence of cardiovascular device-related infections due to a 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

Risk Factors

• Injection drug use, IV catheterization, certain malignancies (colon cancer), poor dentition/infection, chronic hemodialysis, age >60 years, male sex, implantable devices
• Highest risk with (1):
  • Previous IE
  • Prosthetic cardiac valves (including transcatheter-implanted prostheses and homografts)
  • Cardiac transplant with valvular regurgitation
  • Prosthetic material used for cardiac valve repair (such as annuloplasty rings or chords)
  • Congenital heart disease (CHD): unrepaired cyanotic CHD or repaired CHD residual shunts of valvular regurgitation at the site of or adjacent to the site of a prosthetic patch or prosthetic device

General Prevention

• Good oral hygiene
• Antibiotic prophylaxis is only recommended in patients with a high risk of adverse outcomes if IE were to occur—(see “Risk Factors”). Administer 30 to 60 minutes prior to the procedure (exception vancomycin which should be administered 120 minutes prior to the procedure).
• In high-risk patients, consider antibiotic prophylaxis for dental procedures involve manipulation of gingival tissue, manipulation of the periapical region of teeth, or perforation of the oral mucosa.
• 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 the first-line prophylactic choices. Clindamycin is no longer recommended for dental prophylaxis because it is associated with more frequent and severe adverse effects (i.e., Clostridium difficile infection).
  • GI/GU: Only consider coverage for Enterococcus (with penicillin, ampicillin, piperacillin, or vancomycin) for patients with an established infection undergoing procedures.
  • Cardiac valvular surgery or placement of prosthetic intracardiac/intravascular materials: perioperative cefazolin 1 to 2 g IV 30 minutes preoperative or vancomycin 15 mg/kg (max of 1 g) (penicillin-allergic patients) 60 minutes preoperative
  • 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 of 1 g) if penicillin-allergic or if methicillin-resistant S. aureus (MRSA) is suspected.

Commonly Associated Conditions

Most patients with IE have preexisting conditions (see “Risk Factors”).