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Antimicrobial Prophylaxis for the Prevention of Infective Endocarditis...

Disclosure: Carole A. Warnes, MD 
Pub Date: Friday, August 10, 2007
Authors: Rick A. Nishimura, MD 
Article: Antimicrobial Prophylaxis for the Prevention of Infective Endocarditis: Truth or Consequences

Article Text

It has been more than 50 years since the American Heart Association (AHA) first made recommendations for the use of antimicrobial agents to prevent infective endocarditis.[1] The first AHA document on this subject was published in Circulation in 1955 and has been followed by nine revisions outlining which patients, which procedures, and what antibiotics should be used to "prevent" the devastating consequences of infective endocarditis. Since that time, there have been extensive efforts by caregivers, dentists, and patients to ensure that all patients at risk for developing endocarditis would follow these guidelines and take the "proper" regimen of antibiotics prior to selected dental or surgical procedures. However, a statement has recently been published by the AHA that simplifies the recommendations and proposes substantial changes to these guidelines, changes that may affect hundreds of thousands of patients in the United States alone.[2]

Why have these significant changes been introduced? First, the prior rationale for antimicrobial prophylaxis was that administration of antibiotics to control bacteremia before dental or surgical procedures could prevent infective endocarditis. However, this hypothesis was based primarily upon expert opinion with support from few case-controlled studies and descriptive studies. No controlled randomized study has ever shown the efficacy of infective endocarditis prophylaxis. Publications have subsequently emerged that have questioned the efficacy of infective endocarditis prophylaxis as well as whether the risk of giving antibiotics for prophylaxis actually outweighs the small, if any, benefit.[3,4] It has been suggested that the risk of a serious allergic reaction to amoxicillin is considerably greater than the risk of contracting infective endocarditis. A report from the Cochrane Collaboration in 2004 concluded "there is no evidence about whether penicillin prophylaxis is effective or ineffective against infective endocarditis in people at risk who are about to undergo an invasive dental procedure. There is lack of evidence to support published guidelines in this area and it is not clear whether the potential harm and costs of penicillin administration outweigh any beneficial effect."[5]

Second, scientific evidence is now moving from "procedure-related bacteremia" toward "cumulative bacteremia" as the cause of most cases of infective endocarditis. For instance, daily activities such as tooth brushing are estimated to produce bacteremia 6 million times higher than a single tooth extraction.[6]

A final impetus for change was that the guidelines themselves had become more complicated with each revision, with ambiguous recommendations on both the type of patient requiring the antibiotic prophylaxis as well as the procedure requiring the prophylaxis.[7]

On the basis of these controversies, the AHA convened a group of national and international experts in the field, including cardiologists, infectious disease specialists, pediatricians, and dentists. This writing group analyzed relevant literature regarding procedure-related bacteremia and infective endocarditis, in vitro susceptibility data of the organisms causing infective endocarditis, results of prophylactic studies and animal models of experimental infective endocarditis, as well as any retrospective or prospective study in the prevention of infective endocarditis. After several years of discussion and debate within the writing group, combined with input from experts from other learned societies, new recommendations were released.[2] The new AHA recommendations are clear, simple, and to the point:

  • Infective endocarditis prophylaxis should be given only to a high-risk subgroup of patients prior to dental procedures that involve manipulation in gingival tissue or periapical region of the teeth or perforation of the oral mucosa.
  • High-risk patients include only those with (1) a prosthetic cardiac valve, (2) previous infective endocarditis, (3) complex congenital heart disease, and (4) valvulopathy following cardiac transplantation.
  • Infective endocarditis prophylaxis is not recommended prior to gastrointestinal or genitourinary procedures.

These recommendations represent a major departure from our traditional practice of infective endocarditis prophylaxis. The committee wanted a shift in emphasis away from a focus on antibiotic prophylaxis prior to a single procedure, recommending a much greater emphasis on improved access to dental care and oral health in patients with underlying cardiac conditions. The "high-risk" patients recommended to receive prophylaxis were selected not on the basis of an increased risk of developing infective endocarditis over a lifetime, but rather based upon an increased risk of a marked adverse outcome should they develop infective endocarditis. In addition, these recommendations markedly simplified the regimen, so that caregivers or patients do not have to remember specific populations or procedures for which infective endocarditis prophylaxis is recommended.

Since the new guidelines represent a paradigm shift away from the traditional dogma and are based on expert consensus rather than compelling new data, they have generated considerable controversy among physicians, other caregivers, and patients. These substantive changes may violate long-standing expectations in practice patterns by patients and health care providers. Concern has been raised by many patients who have previously received antibiotic prophylaxis, who are now being advised that this is unnecessary. Health care providers have been reluctant to abruptly stop a practice that they were taught was necessary to prevent a devastating event. Other societies, such as the working party of the British Society for Antimicrobial Chemotherapy, have recommended their own simplified guidelines, but these did not reach the magnitude of change imposed by the current AHA guidelines. The British Society has recommended that infective endocarditis prophylaxis prior to dental procedures is not required for non—high-risk subgroups but still recommends prophylaxis for many patient groups prior to gastrointestinal and genitourinary procedures.[8]

Even the "experts" in the field of cardiovascular diseases have not been able to reach agreement regarding these new recommendations.[9] There are those who firmly believe that recommendations agreed upon by an expert panel of world-renowned experts should clearly be followed without exception. Others, however, have argued that, for antibiotic prophylaxis, "the lack of evidence of benefit is not necessarily the same as lack of benefit" and that insufficient new evidence exists to justify such a radical change in policy. It has been argued that there is "illogicality of the fudge in continuing to recommend prophylaxis for very high risk patients," as endocarditis is always dangerous.[10] If antibiotic prophylaxis is ineffective, why select just a "high-risk group" for prophylaxis? The young patient with a functionally normal bicuspid aortic valve undergoes a dramatic change in outlook and lifestyle if infective endocarditis occurs. The risk of taking a few antibiotic pills prior to a dental procedure seems, on the face of it, to be very low compared to the potentially catastrophic consequence of developing infective endocarditis. Even if the risk of infection is very small, the outcome can be devastating for the individual whose valve is destroyed.

Thus, physicians and patients are now faced with a dilemma. It must be remembered that the AHA statements are "guidelines" and not "standard of care." Thus, these statements do not mandate that all physicians, caregivers, and patients follow exactly what has been recommended. If, in the experience of the physician or other caregiver, it is felt strongly that infective endocarditis prophylaxis should be given to more moderate-risk patients not mentioned in the guidelines, this should be done. The risk of antibiotic prophylaxis, albeit present, is extremely low, and, as in any procedure in medicine, it is up to the individual physician to weigh the risks and benefits of any treatment or procedure after discussion with the patient. The Cochrane collaboration concluded that "it would appear to be ethically wrong to provide penicillin treatment to patients at risk of endocarditis without explaining the potential benefits and risks, and allowing those patients to make up their own mind about treatment."[8]

Despite the controversy and "angst" that these new recommendations have generated, there are some very beneficial outcomes. The document has raised awareness that meticulous oral hygiene and routine preventive care by dentists are of utmost importance in preventing infective endocarditis in patients at increased risk. Other sources of continued bacteremia, such as nail-biting, intrauterine devices, acne, and "body piercing," should also be addressed. As we are now faced with confusion about "evidence or lack thereof," the medical profession should proceed as it has in other similar situations and obtain the proper evidence. Randomized controlled trials will be the only solution to this treatment dilemma, recognizing the magnitude of the task and the numbers of patients who would need to be enrolled. We urge that these trials be run to answer our questions and hope that the confused caregivers and patients are willing to participate.

References

  1. Jones R. Prevention of rheumatic fever and bacterial endocarditis through control of streptococcal infections. Circulation 1955;11:317—320.
  2. Wilson W et al. Prevention of infective endocarditis. Guidelines from the American Heart Association. A guideline from the American Heart Association Rheumatic Fever, Endocarditis, and Kawasaki Disease Committee, Council on Lifelong Congenital Heart Disease and Heart Health in the Young, and the Council on Clinical Cardiology, Council on Cardiovascular Surgery and Anesthesia, and the Quality of Care and Outcomes Research Interdisciplinary Working Group. Circulation 2007; Apr 19 [Epub ahead of print].
  3. Durack DT. Prevention of infective endocarditis. N Engl J Med 1995;332(1):38—44.
  4. Durack DT. Antibiotics for prevention of endocarditis during dentistry: time to scale back?[comment]. Ann Intern Med 1998;129(10):829—831.
  5. Oliver R, Roberts GJ, Hooper L. Penicillins for the prophylaxis of bacterial endocarditis in dentistry [see comment]. Cochrane Database of Systematic Reviews 2004(2):CD003813.
  6. Roberts GJ. Dentists are innocent! "Everyday" bacteremia is the real culprit: a review and assessment of the evidence that dental surgical procedures are a principal cause of bacterial endocarditis in children. Pediatr Cardiol 1999;20(5):317—325.
  7. Dajani AS et al. Prevention of bacterial endocarditis. Recommendations by the American Heart Association [see comment]. JAMA 1997;277(22):1794—1801.
  8. Gould FK et al. Guidelines for the prevention of endocarditis: report of the Working Party of the British Society for Antimicrobial Chemotherapy [see comment]. J Antimicrob Chemother 2006;57(6):1035—1042.
  9. Ashrafian H, Bogle RG. Antimicrobial prophylaxis for endocarditis: emotion or science? Heart 2007;(1):5—6.
  10. British Cardiovascular Society. Endocarditis Guidelines 2007. http://www.bcs.com/pages/full_news.asp?NewsID=17423276 (accessed July 30, 2007).

-- The opinions expressed in this commentary are not necessarily those of the editors or of the American Heart Association. --