Prevention of Bacterial Endocarditis
Sources: Dajani AS, JAMA 1997;277:1794-1801; Berney P, Francioli P. J Infect Dis 1990;161:281-285.
Although relatively uncommon, bacterial endocarditis continues to be a life-threatening disease. Because of the substantial morbidity and mortality associated with this infection, primary prevention is paramount. Recently, the American Heart Association published its updated recommendations for prevention of bacterial endocarditis.
These recommendations reflect an analysis of relevant literature regarding procedure-related endocarditis, antibiotic susceptibility of pathogenic bacteria, results studied in animal models of endocarditis, and retrospective analyses of human endocarditis cases in terms of antibiotic prophylaxis usage patterns and apparent prophylaxis failures. The guidelines are meant to aid practitioners but are not intended as the standard of care or as a substitute for clinical judgment.
Prophylaxis Strategy
Three important points must be kept in mind. First, there are no randomized, controlled human trials in patients with underlying structural heart disease to prove that antibiotic prophylaxis provides protection against endocarditis during bacteremia-inducing procedures. Second, most cases of endocarditis are not attributable to an invasive procedure. Third, the incidence of procedure-related endocarditis in patients with underlying structural heart disease is low.
A reasonable approach for endocarditis prophylaxis should consider the degree of risk for endocarditis of the patient's underlying heart disease, the risk of bacteremia for the given procedure, the potential adverse reactions of the antibiotic prophylaxis, and the cost-benefit aspects of the recommended antibiotic prophylaxis.
Which Cardiac Patients are at Risk?
Certain cardiac conditions are associated with more frequent and severe endocarditis. Data from more than 20 publications were used to create a table that separates cardiac conditions associated with endocarditis based on the severity (high-risk, moderate-risk, and negligible-risk) of endocarditis if it develops. (See Table 1.)
Mitral valve prolapse (MVP) appears twice in this table, and the need for prophylaxis for this condition is controversial. Only a few patients with MVP develop complications at any age. When prolapsed mitral valves do not leak and there is no Doppler-demonstrated regurgitation, the risk of endocarditis is not increased, and antibiotic prophylaxis is not necessary. Patients with leaking, prolapsed mitral valves should receive prophylactic antibiotics.
Bacteremia-Producing Procedures
Bacteremias caused by organisms associated with endocarditis may be attributable to certain procedures. Procedures for which prophylaxis is recommended as well as those in which prophylaxis is not recommended are listed in Table 2.
Table 1
Cardiac Conditions Associated With Endocarditis
Endocarditis prophylaxis recommended:
High-risk: Moderate-risk:
prosthetic cardiac valves or conduits; VSD, PDA, valve stenosis, or dysfunction; previous bacterial endocarditis; bicuspid aortic valve; complex cyanotic congenital heart mitral valve prolapse with disease; valvular dysfunction surgical shunts and/or thickened leaflets
Endocarditis prophylaxis not recommended:
Negligible-risk (no greater risk than the general population):
secundum ASD; surgical repair of ASD, VSD, or PDA (beyond 6 months); previous Kawasaki disease, mitral valve prolapse, or previous rheumatic fever without valvular dysfunction; pacemakers and defibrillators functional murmur
Poor dental hygiene and periodontal infections may produce bacteremia even in the absence of dental procedures. Individuals who are at risk should maintain good oral health to reduce potential sources of bacterial seeding.
Data from experimental animal models suggest that antimicrobial prophylaxis administered within two hours following the procedure will provide effective prophylaxis.2 Antibiotics administered more than four hours after the procedure probably have no prophylactic benefit.
Prophylactic Regimens
Practitioners must use their clinical judgment in determining the choice of antibiotics and duration of treatment. Because endocarditis may occur in spite of appropriate antibiotic prophylaxis, physicians must maintain a high index of suspicion if fever, night chills, weakness, myalgia, arthralgia, lethargy, or malaise occur following procedures in at-risk patients.
Table 2
Endocarditis Prophylaxis
Procedures for which endocarditis prophylaxis is recommended:
Dental:
Dental extractions; periodontal procedures; dental implants; root canal surgery only beyond the apex; placement of orthodontic bands but not brackets; cleaning of teeth where bleeding is anticipated
Respiratory tract:
T&A; operations involving the respiratory mucosa; rigid bronchoscopy
Gastrointestinal tract:
Sclerotherapy; esophageal dilation; biliary tract surgery or
cholangiography; operations involving the intestinal mucosa
Genitourinary tract:
Cystoscopy, urethral dilation, prostate surgery
Procedures for which endocarditis prophylaxis is not recommended:
Dental:
Restorative dentistry; local anesthetic injections; placement of rubber dams; suture removal; placement of removable prosthodontic or orthodontic appliances; taking oral impressions;fluoride treatments; radiographs; orthodontic appliance adjustment; shedding of primary teeth
Respiratory tract:
Endotracheal intubation; flexible bronchoscopy; PE tube insertion
Gastrointestinal tract:
Transesophageal echo; ECG; endoscopy without biopsy
Genitourinary tract:
Circumcision; vaginal or caesarean delivery; In uninfected tissue: urethral catheterization; uterine D & C; therapeutic abortion; sterilization procedures; insertion or removal of intrauterine devices
Other:
Cardiac catheterization; balloon angioplasty; implantation of pacemakers, defibrillators, and stents; incision of surgically prepared skin
Antibiotic prophylaxis should be directed at the most likely organism. Streptococcus viridans is the most common cause of endocarditis following dental, oral, and upper respiratory tract procedures.
The new recommended standard prophylactic regimen for these procedures is a single dose of oral amoxicillin (2 g in adults, 50 mg/kg in children) administered one hour before the anticipated procedure. A second dose is not necessary.
Individuals who are allergic to penicillins should receive an alternative such as clindamycin hydrochloride. Erythromycin is no longer recommended.
Endocarditis following genitourinary and gastrointestinal tract surgery or instrumentation is most often caused by Enterococcus faecalis (enterococci). For high-risk patients, ampicillin plus gentamycin is recommended. IM or IV ampicillin (50 mg/kg) plus gentamicin (1.5 mg/kg) should be administered within 30 minutes of starting the procedure. Six hours later, an additional dose of parenteral ampicillin or oral amoxicillin (25 mg/kg) should be given. In moderate-risk patients requiring prophylaxis, enteral ampicillin or oral amoxicillin 30-60 (50 mg/kg) minutes before the procedure is recommended.
Dr. Friedman is Assistant Professor of Pediatrics, Yale University School of Medicine.
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