Infective endocarditis (IE) is an inflammation of the endothelial lining of the heart muscle, valves and great vessels. The valves have a particularly high propensity for infection due to the lack of blood supply and limited access to immune cells. IE is relatively rare in children.
Bacteremia and the presence of endothelial damage are important factors in the pathogenesis of IE. Cyanosis and polycythemia, if present, increase the viscosity of the blood and further enhance the likelihood of developing IE. Foreign materials such as prosthetic valves or shunts also significantly increase the risk for developing IE. All types of CHD, except for secondum ASD, predispose to IE. It is not surprising that cyanotic CHD with an artificial shunt or prosthetic valves constitutes the highest risk for IE.
Neonatal endocarditis frequently occurs on the right side of the heart and is associated with disruption of endocardium or valvular endothelial tissue by catheter-induced trauma in a hospitalized infants. Premature neonates often experience transient episodes of bacteremia from trauma to the skin and mucous membranes, vigorous endotracheal suctioning, parenteral hyperalimentation, or placement of umbilical or peripheral venous catheters. The combination of endothelial damage and bacteremia is critical for the induction of IE.
Vegetations develop at the site of endothelial damage, which is usually located at the lower pressure side of the lesion i.e. in the RV in patients with VSD and on the atrial surface of the mitral valve with MR.
After bacteria adhere to the damaged endothelium, platelets and fibrin are deposited over the organisms, leading to formation of a "vegetation". The organisms trapped within the vegetation are protected from phagocytic cells and other host defense mechanisms.
Viridans group streptococcus, enterococci and S. aureus are responsible for most cases of IE. Streptococcus pneumoniae, coagulase negative staphycoccus, gram negative bacilli and fungi may also cause IE. The blood cultures may be negative in some patients with IE especially those who have already received antibiotics.
Persistent or recurrent low grade fever is the most common symptom of IE. Other symptoms are nonspecific and include malaise, myalgia, arthralgia, anorexia, night sweats and headaches. Splenomegaly can be found in 15-50% of patients with IE. A new or changing murmur indicates valvular involvement.
The classic peripheral manifestations of IE are rarely seen nowadays. These include petichiae, splinter hemorrhages (hemorrhages in the nail beds), Osler's nodules (small, tender nodules on the pads of fingers and toes), Janeway's lesions (painless hemorrhages on palms and soles), and Roth's spots (hemorrhage in the retina with a white center).
Making the diagnosis
- The above signs and symptoms in a patient with underlying CHD following transient bacteremia should raise the suspicion of IE.
- In the absence of prior anti-microbial therapy, positive blood cultures are found in >90% of patients.
- Other supporting laboratory evidence includes anemia, leukocytosis with a left shift, positive rheumatoid factor, hematuria and elevated ESR.
- The finding of vegetations on echocardiography is confirmatory. However; since IE is a clinical diagnosis, a negative echocardiogram does not rule out IE and treatment should not be delayed if there is strong clinical suspicion of IE. Recently, certain criteria were developed to help in making the diagnosis of IE.
The management of IE includes 4-6 weeks of high dose IV antibiotics. The choice of antibiotics depends on the organism isolated and the results of antibiotic sensitivity testing. Surgical intervention may be necessary if there is CHF, if vegetations causing obstruction, or if there is significant malfunction of a prosthetic valve.
Antimicrobial prophylaxis to prevent IE is indicated in any patient with CHD (except secondum ASD) in situations that may produce bacteremia such as invasive dental or urological procedures.
Prevention of Infective Endocarditis. 2007 Guidelines From the American Heart Association. Circulation. 116:1736-1754.
Ferrieri, P, et al. Unique Features of Infective Endocarditis in Childhood. Circulation. 2002;105:2115. Scientific statement from American Heart Association