Description

Infective endocarditis (IE) is a microbial infection of the endocardium of the heart, especially of the heart valves.

Epidemiology

Risk Factors

• Preexisting heart disease (congenital or acquired such as rheumatic heart disease)
• Prior history of endocarditis
• Cardiac surgery/intervention (Risk increases 5-fold with a procedure within the last 6 months.)
• Intracardiac pacemakers and implantable cardioverter-defibrillators
• Prosthetic valves or conduits
• Indwelling catheters
• IV drug use
• IE occurs in 8–10% of children without known risk factors.

General Prevention

• The degree to which antibiotics decrease the incidence, duration, or extent of bacteremia with at-risk procedures is controversial. In 2007, the guidelines for subacute bacterial endocarditis (SBE) prophylaxis from the American Heart Association (AHA) were changed due to the lack of evidence that prophylactic antibiotic administration prevents IE.
• SBE prophylaxis is recommended by the AHA only for the following cardiac conditions:
  • Prosthetic cardiac valve or prosthetic material used for cardiac valve repair
  • Prior history of IE
  • Unrepaired cyanotic congenital heart disease, including palliative shunts and conduits
  • Congenital heart defect repaired with prosthetic material or device for the first 6 months after the procedure
  • Repaired congenital heart disease with residual defect near the site of prosthetic patch or device
  • Cardiac transplantation recipients with cardiac valvulopathy
• SBE prophylaxis is recommended only for the following procedures:
  • Dental procedures involving manipulation of the gingival or periapical region of teeth or perforation of the oral mucosa
  • Surgery involving prosthetic intravascular or intracardiac material, including heart valves
  • Invasive respiratory tract procedures involving incision or biopsy, such as tonsillectomy/adenoidectomy or abscess drainage
• Prevention should focus on education regarding rationale behind current guidelines, discussion of potential risk, signs and symptoms of IE, and maintaining optimal oral hygiene.
• Risk can be further decreased by correction of the cardiovascular anomaly by surgery or interventional catheterization techniques if indicated and by minimizing or decreasing the use of central lines.

Pathophysiology

• IE is primarily seen in patients with preexisting heart disease (congenital or acquired) who develop bacteremia with organisms that are likely to cause infection.
• IV drug abusers and patients with indwelling central venous catheters may develop endocarditis even in the absence of prior heart disease.
• Local turbulence secondary to the cardiovascular abnormality is thought to result in damage of the endocardial surface. The development of a fibrin and platelet network occurs in which bacteria may then become entrapped, leading to formation of a vegetation.
• Bacteremia may be a complication of focal infection (e.g., pneumonia, cellulitis, or urinary tract infection) or may be associated with various dental and surgical procedures. Bacteremia, however, occurs most commonly with daily activities, such as chewing, flossing, and brushing teeth.
• Peripheral manifestations in chronic endocarditis are mediated by embolic or immune complex reactions.

Etiology

• Gram-positive cocci account for 90% of culture-positive endocarditis.
  • Streptococcus viridans and Staphylococcus aureus are the most common agents.
  • Other organisms that can cause endocarditis are enterococci sp., coagulase-negative staphylococci, β-hemolytic streptococci, and the HACEK group (Haemophilus aphrophilus, Haemophilus paraphrophilus, Haemophilus parainfluenzae, Actinobacillus actinomycetemcomitans, Cardiobacterium hominis, Eikenella corrodens, Kingella species). IE can also be caused by Candida, Aspergillus, Abiotrophia, and Granulicatella species.
• Approximately 5% of endocarditis cases in children are reported as culture negative.