DESCRIPTION

Infective endocarditis (IE) is a microbial infection of the endocardium and/or heart valves that results in growths known as vegetations on the heart valves and possible long-term tissue damage to the valves.

EPIDEMIOLOGY

• IE is relatively uncommon in children in the United States, accounting for 0.05 to 0.12 cases per 1,000 pediatric admissions.
• Frequency increased from 1960 to 2000 due to improved survival in patients with congenital heart disease and the widespread, and often prolonged use, of central vascular catheters, especially in premature infants.
• Rates have plateaued since 2000, even with the 2007 change in endocarditis prophylaxis guidelines.

ETIOLOGY

• Gram-positive cocci account for 90% of culture-positive endocarditis.
  • Staphylococcus aureus and Streptococcus viridans are the most common agents.
  • Other organisms: other streptococcal and staphylococcal organisms, gram-negative bacilli, or polymicrobial infections; IE can also be caused by fungus, especially in premature infants with indwelling catheters.
  • S. viridans is most common in children with underlying heart disease. S. aureus is most common in those without heart disease.
• Anywhere from 5–30% of endocarditis cases in children are reported as culture negative.

RISK FACTORS

• Preexisting heart disease (congenital or acquired)
  • Accounts for 35–60% of IE cases
  • Highest risk congenital lesions: tetralogy of Fallot, ventricular septal defect, endocardial cushion defect, left-sided lesions
• Prosthetic valves or conduits (i.e., tetralogy of Fallot status-post bovine pulmonary valve prosthesis)
• Cardiac surgery/intervention: The risk increases 5-fold with a procedure within the last 6 months.
• Prior history of endocarditis
• Indwelling catheters, leads or devices
• IV substance use disorder
• IE occurs in 8–10% of children without known risk factors.

GENERAL PREVENTION

• 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.
• Persons with an IV substance use disorder users 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 results 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.