In 1955, the American Heart Association (AHA) started making recommendations for the prevention of infective endocarditis.¹ Since then, patients considered at increased risk of infective endocarditis who were undergoing certain dental procedures or upper respiratory, gastrointestinal (GI), or genitourinary (GU) tract procedures were prescribed antibiotics. The first guidelines recommended a regimen of penicillin administered intramuscularly 30 minutes before an operative procedure.¹ The most recent guidelines, summarized in this issue of American Family Physician,² are the ninth revision of the original recommendations and represent a significant change because the AHA no longer recommends endocarditis prophylaxis for most patients.³ Although some of the recommendations are radical departures from previous versions, they are in other ways a step in the evolution of the guidelines that began more than 50 years ago. Through the years, subsequent revisions have changed the dosing to cover a five-day period, a two-day period, two doses on the same day, and, finally, a single dose. It was not until the mid-1980s that an option for an all-oral dosing regimen was given.

There has also been an evolution over the years with regard to patients for whom prophylaxis is recommended. From the 1950s to the mid-1970s, recommendations were made for persons with rheumatic or congenital heart disease. Stratification of patients into higher- and lower-risk groups began in the mid-1970s. In 1990, a more complete list of cardiac conditions for which prophylaxis was and was not recommended was presented. The last revision before the current 2007 guidelines was in 1997; that document provided a stratification of cardiac conditions into high-, moderate-, and negligible-risk groups, with prophylaxis not recommended for those persons at negligible risk.⁴ The 1997 guidelines also, for the first time, emphasized that most cases of infective endocarditis are not attributable to an invasive procedure.

The writing group for the 2007 guidelines conducted an extensive literature review and had two years of discussion within the group and with outside national and international experts in the field. The group then weighed the available evidence and the opinions of experts. Because there have not been randomized controlled studies addressing the effectiveness of endocarditis prophylaxis, final recommendations were based on case-control or descriptive studies, and expert consensus. For the first time, a classification of recommendations and levels of evidence were used.

The AHA concluded that infective endocarditis is much more likely to result from frequent exposure to random bacteremia associated with daily activities than from bacteremia caused by a dental or GI or GU tract procedure. For example, tooth brushing twice a day for one year is thought to have a risk of exposure to bacteremia more than 150,000 times greater than that of a single tooth extraction.⁵

The AHA also stated that prophylaxis may prevent an exceedingly small number of cases of infective endocarditis (if any) in persons who undergo a dental or GI or GU tract procedure, and that the risk of antibiotic-associated adverse events exceeds the benefit (if any) from antibiotic prophylaxis. Thus, the AHA no longer recommends endocarditis prophylaxis based solely on an increased lifetime risk of endocarditis. Rather, prophylaxis is deemed reasonable only in patients who have the highest risk of adverse outcomes from endocarditis. This includes patients with four cardiac conditions: (1) prosthetic cardiac valve (or prosthetic material used for valve repair); (2) history of endocarditis; (3) certain congenital heart disease; or (4) cardiac valvulopathy in cardiac transplant recipients. No other cardiac conditions are listed, which means that the AHA no longer recommends endocarditis prophylaxis for most patients, such as those with mitral valve prolapse who have been prescribed antibiotics in the past.

The AHA concluded that, for patients at highest risk of adverse outcomes from infective endocarditis who are undergoing a dental procedure involving perforation of the oral mucosa or manipulation of gingival tissue or the periapical region of teeth, prophylaxis is reasonable, although its effectiveness is unknown. As in the 1997 guidelines, a single dose of antibiotic (preferably amoxicillin) is recommended. In reality, rather than focusing on prophylaxis for a single dental procedure, available evidence supports emphasis on establishing and maintaining good oral hygiene and eradicating dental disease to decrease the frequency of bacteremia from routine daily activities. A major departure from previous guidelines is that administration of antibiotics solely to prevent endocarditis is not recommended for any patients who undergo a GI or GU tract procedure. This change was made because there are no published data demonstrating a conclusive link between procedures of the GI or GU tract and the development of endocarditis.

Although the 2007 AHA recommendations are more straightforward than previous ones, there is likely to be some confusion until physicians, dentists, and patients learn about these changes and get used to them. The current guidelines may violate longstanding expectations and practice patterns of health care professionals and patients. Patients who previously received prophylaxis may feel anxious about suddenly having a dental procedure without taking an antibiotic. Physicians and dentists may feel a reluctance to suddenly stop a practice that had been drilled into them in medical or dental school. Over time, however, health care professionals and patients will adopt (and adapt to) the new guidelines and become much more comfortable implementing them.