Published June 19, 2002
Robin
K.
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BACKGROUND
AND AMERICAN HEART ASSOCIATION GUIDELINES |
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Background and American Heart Association GuidelinesConclusions
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The risk of endocarditis is increased in persons with certain cardiac disorders, particularly valvular heart disease. Transient bacteremia may result in bacterial seeding of a previously abnormal endovascular surface, such as a heart valve, resulting in the formation of a vegetation. Although most cases of endocarditis are not attributable to medical procedures, antibiotic prophylaxis for endocarditis has focused on the risks associated with transient bacteremias during dental, respiratory, gastrointestinal, or genitourinary procedures.1-4 Various organizations have published guidelines for endocarditis prevention, but the American Heart Association (AHA) guidelines are most commonly followed in the United States. These guidelines were revised in 1997.1-2 The following discussion is largely based on these recommendations1 and on an expanded discussion of their rationale in American Family Physician.2 The AHA recommendations involve a categorization of the patient's cardiac condition into one of three groups: high-risk, moderate-risk, and "endocarditis prophylaxis not recommended." The last low-risk category includes previous coronary artery bypass surgery, presence of a pacemaker or implantable defibrillator, mitral valve prolapse without valvular regurgitation, and previous rheumatic fever without valvular dysfunction, among other conditions. Patients with mitral valve prolapse (MVP) with valvular regurgitation and/or thickened leaflets on echocardiogram, however, as well as those with audible clicks and murmurs in association with MVP, fall into the moderate risk category. The three categories of endocarditis risk are summarized in Table 1. The AHA guidelines also summarize the risk of bacteremias with various procedures. Table 2 lists the dental procedures for which endocarditis prophylaxis is recommended, and Table 3 lists respiratory, gastrointestinal, and genitourinary tract procedures for which prophylaxis is recommended. Notably, endocarditis prophylaxis is not routinely recommended for incisions of surgically scrubbed skin, cardiac catheterization and angioplasty, coronary stents, endotracheal intubation, flexible bronchoscopy, endoscopy, transesophageal echocardiography, vaginal delivery or Caesarean section among other conditions, although the guidelines leave open the option for prophylaxis in high-risk patients with some of these conditions (Table 3). The organisms most likely to cause endocarditis after dental and upper respiratory procedures are alpha-hemolytic streptococci of the viridans group. Genitourinary tract and gastrointestinal tract procedures are more likely to produce bacteremias with enterococci or Gram-negative bacilli. Since enteric Gram-negative bacilli rarely cause endocarditis, prophylaxis for procedures at these latter sites is primarily intended to prevent enterococcal bacteremia1-2 as well that due to other streptococci which may be found in the gastrointestinal tract. The recommended regimens for endocarditis prevention have changed in the most recent 1997 guidelines. Instead of a pre- and post-procedure antibiotic dose for standard dental prophylaxis, the current recommendations (Table 4) include only a pre-procedure dose which is reduced compared to that in the previous guidelines.5-6 Erythromycin is no longer recommended for penicillin-allergic patients due to gastrointestinal adverse effects and the complicated pharmacokinetics of its various formulations.1-2 Oral amoxicillin remains the mainstay of dental prophylaxis. For penicillin-allergic patients, alternatives are clindamycin, azithromycin, or clarithromycin, with cefadroxil or cephalexin also possible for patients who have not had immediate-type hypersensitivity reactions (urticaria, angioedema, or anaphylaxis) to penicillin. The guidelines also include recommendations for patients unable to take oral medications.1-2 Although not required by the guidelines, some clinicians prefer intravenous prophylaxis for high-risk patients, especially those with histories of recurrent endocarditis or prior prosthetic valve endocarditis. For genitourinary and gastrointestinal procedures, regimens vary including intravenous pre- and post-procedure therapy for high-risk patients, and oral or IV therapy for moderate-risk patients (Table 5). In all areas, special precautions and prophylaxis may be necessary when infected tissues are involved. There are no large randomized controlled trials of prophylaxis versus no prophylaxis, and none could be ethically performed at the present time given that prophylaxis has become the standard of care within the guidelines described above. Similarly, no randomized trials of one type of prophylaxis versus another have been performed. Since endocarditis is a relatively uncommon condition, and many episodes of endocarditis are not linked to procedures, such a study would require a huge sample size of patients and is unlikely ever to take place. What has been studied is which cardiac conditions most commonly give rise to endocarditis, and the risk of bacteremia after various procedures. Given the limitations of the available data, the current guidelines should be viewed as the minimum recommendations for prophylaxis. It is important that the guidelines incorporate latitude for clinician preference for more aggressive prophylaxis for certain high-risk patients. Consultation with an infectious disease specialist can be helpful in such cases. Antibiotic prophylaxis for procedures performed in patients with total joint replacements remains a controversial issue. The American Dental Association and American Academy of Orthopaedic Surgeons have issued an advisory statement which states that antibiotic prophylaxis is not routinely indicated for most dental patients with total joint replacements, but that it is advisable to consider prophylaxis in a small number of high-risk patients.7 |
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| CONCLUSIONS | ||||||
Certain medical and dental procedures pose a risk of transient bacteremia, which can lead to endocarditis in patients with certain underlying cardiac conditions. The American Heart Association recommendations for prevention of bacterial endocarditis are the most widely followed guidelines in the United States. Some exceptionally high-risk patients may warrant more aggressive prophylaxis. |
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