Infective Endocarditis Prophylaxis
Once universally fatal, infective endocarditis remains a serious disease, with a mortality rate of about 25%. The pathogenesis of endocarditis suggests that individual infections might be prevented by judicious use of prophylactic antibiotics, yet the incidence of this infection has not changed much despite the widespread availability of antibiotics and efforts to promote their use prophylactically. Recent data directly question the effectiveness of prophylaxis among patients undergoing dental procedures, and it has become clear that the frequency of bacteremia from routine daily practices is far greater than that associated with any identifiable procedure. In the absence of clear evidence for effectiveness from randomized trials, there is the real concern that widespread use of antibiotic prophylaxis could do more harm than good. As a result, recent recommendations from the American Heart Association (AHA) and others advocate prophylaxis only among patients with the highest-risk cardiac conditions who undergo procedures that involve manipulation of gingival tissue or perforation of the oral mucosa. The primary care provider should understand the rationale for prophylaxis and its limitations to properly apply these recommendations. Patient education is essential to improving the likelihood of compliance when prophylaxis is indicated.
During the last several decades, there has been a shift in the incidence of endocarditis to older age groups; the current mean age is about 50 years. Men predominate in those older than 50 years; in people younger than 50 years, the gender ratio is more nearly equal.
Risk Factors
Individual risk of endocarditis is typically viewed as a function of cardiac conditions that predispose the person to endocarditis and the risk of high-grade or sustained bacteremia induced by dental or medical procedures. However, 50% or more of cases of endocarditis occur in the absence of underlying heart disease, and spontaneous transient bacteremia confers far greater cumulative risk among susceptible individuals than do dental or medical procedures. Clearly, all individuals have some finite risk of developing endocarditis. Because of the difficulty in predicting who is most susceptible and when, it has been estimated that no more than 6% of endocarditis cases can be prevented. The number of patients who would need to be treated to prevent a single case is extraordinarily high. The risk of endocarditis among persons with high- and moderate-risk predisposing cardiac conditions has been estimated at 1 in 46,000 procedures with antibiotic prophylaxis and 1 in 150,000 without antibiotic prophylaxis. Nonetheless, the historical inclination to prescribe antibiotics prior to procedures has a strong influence on physician practice and patient expectations, and the morbidity and mortality of endocarditis may well be sufficient justification to use such preventive measures discerningly for patients at the highest levels of risk.
Predisposing Cardiac Conditions
In the preantibiotic era, chronic rheumatic heart disease was the underlying lesion in up to 90% of endocarditis cases. Now, prosthetic cardiac valves, previous endocarditis (recurrence rate as high as 10%), complex congenital heart disease, and surgically constructed pulmonary shunts are the high-risk cardiac lesions (Table 16-1). Moderate risk is associated with other cardiac anomalies, including rheumatic and other acquired valvular disease, idiopathic hypertrophic subaortic stenosis, and mitral valve prolapse. Until recently, many authorities, including the authors of the 1997 AHA guidelines, recommended that prophylactic antibiotics be prescribed in these patients as well. That is also true for the European recommendations published in 2004. However, the recognition that endocarditis often occurs without known predisposing cardiac disease and that cumulative risk of bacteremia due to routine daily activities is much greater than that attributed to procedures led to the revised 2007 AHA recommendation that only those with the highest-risk cardiac lesions (Table 16-1) receive antibiotic prophylaxis.
Procedures That Induce Bacteremia
Data on incidence of bacteremia with procedures are fragmentary, but it is clear that risk is greatest with dental procedures that involve manipulation of gingival tissue or the perforation of the oral mucosa. Tooth extraction (10% to 100%) and periodontal surgery (36% to 88%) have the highest reported incidence rates, but bacteremia has also been documented during routine activities, including tooth brushing and flossing (20% to 68%), using toothpicks or water picks (7% to 50%), and even chewing food (7% to 51%).
Case reports suggest increasing incidence of endocarditis after body piercing, especially tongue piercing, but it is unclear whether prophylaxis or prompt treatment of postpiercing local
infection is most effective in lowering risk. Endocarditis risk is minimal with coronary artery bypass graft surgery or placement of pacemakers or implanted defibrillators. Some nondental procedures also have a substantial incidence of subsequent bacteremia, but others have little. Bacteremia rates are sufficiently high to warrant recommendations for prophylaxis before procedures on the respiratory tract or infected skin, skin structures, or musculoskeletal tissue for patients with the highest-risk cardiac conditions. Antibiotic administration solely to prevent endocarditis is no longer recommended before genitourinary or gastrointestinal tract procedures.
infection is most effective in lowering risk. Endocarditis risk is minimal with coronary artery bypass graft surgery or placement of pacemakers or implanted defibrillators. Some nondental procedures also have a substantial incidence of subsequent bacteremia, but others have little. Bacteremia rates are sufficiently high to warrant recommendations for prophylaxis before procedures on the respiratory tract or infected skin, skin structures, or musculoskeletal tissue for patients with the highest-risk cardiac conditions. Antibiotic administration solely to prevent endocarditis is no longer recommended before genitourinary or gastrointestinal tract procedures.
TABLE 16-1 Cardiac Conditions with Highest Risk for Endocarditis | ||||||||||||||
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