Opinion

The 1997 Prevention of Bacterial Endocarditis Recommendations by the American Heart Association: Questions and Answers

Since the publication of the American Heart Association 1997 recommendations for the prevention of bacterial endocarditis, questions have arisen regarding the application of these guidelines. It is impossible for any such recommendations to include all conceivable clinical situations that might arise, and therefore questions are appropriate. Frequently asked questions are included in this article. Answers provided for the questions are the opinions of the authors, who participated in the formulation of these guidelines, and are not intended to supplant the judgment of the dental health professional who is privy to all the facts when the individual clinical decision is made.

The 1997 American Heart Association statement on the prevention of bacterial endocarditis has appeared in several professional journals^1,2 and has generally been well-received. The new guidelines have better defined clinical circumstances that require antibiotic prophylaxis, have simplified dosing, and have provided more alternative drug choices. As with any recommendation, it was impossible to include advice on all the potential clinical situations and nuances that might occur with the implementation of these guidelines. Accordingly, a number of questions have been raised that merit appropriate clarification.

This article addresses, in question-and-answer format, actual questions that have been frequently asked during the first 15 months after the publication of the original guidelines, and this article will best be read in conjunction with them. If the reader is unfamiliar with the AHA guidelines, the Circulation paper can be obtained from the American Heart Association, 7272 Greenville Ave., Dallas, TX 75231-4596 (reprint No. 71-0117). Selected references have been employed as deemed appropriate, but the guidelines should serve as the general reference source.¹

The answers provided are the opinions of the authors, all of whom answered these questions after inquiries to the American Heart Association (AHA). All of the authors also were members of the committee that formulated these guidelines. These opinions do not represent official statements of the AHA. These responses are the authors' best clinical judgment and are not intended to replace the health professional's own best judgment in a given clinical situation. At times, only the individual present and responsible for a given clinical decision will have all the facts necessary to perform the due diligence required.

The health professional is ultimately responsible for the final decision and might well be served to incorporate into the clinical written record a notation that: "In my best clinical judgment," the action taken was the most appropriate. This will alert any subsequent reviewer that particular attention was paid to this clinical situation. Key contributing circumstances to the decision process may also need to be appropriately placed in the patient's dental record.

Questions and Answers

Antibiotic prophylaxis is to be employed when dental procedures are associated with any significant bleeding. What precisely is meant by "significant bleeding?"

One of the major goals of the 1997 guidelines was to reduce any potential contribution of unwarranted antibiotic prophylaxis to the concern of microbial resistance to antibiotics. In the case of dentistry, this was done by limiting antibiotic prophylaxis to only those dental procedures associated with a significant risk for bacteremia and not to all procedures associated with any bleeding whatsoever. As a guide to the dentist, a table was prepared to differentiate between dental procedures most likely to be associated with significant bleeding (endocarditis prophylaxis recommended) and procedures not ordinarily associated with significant bleeding (endocarditis prophylaxis not recommended) (Table 1). This arrangement more closely agrees with recommendations of other current advisory statements in this regard. It is conceivable that procedures not recommended for prophylaxis might be associated with significant bleeding, particularly in patients with poor oral hygiene; and in such a situation antibiotic prophylaxis may be appropriate.

The table on Dental Procedures and Endocarditis Prophylaxis (Table 1) does not mention the placement of dental matrix bands. Where does this fit in the listing of dental procedures?

The dental matrix band would be analogous to the placement of a gingival retraction cord where significant bleeding is not likely to be encountered, particularly in a patient with good oral hygiene. As stated in Table 1, clinical judgment may indicate antibiotic use in selected circumstances associated with significant bleeding. The case circumstances and patient risk category should be weighed together in this decision.

Antibiotic prophylaxis is not recommended for suture removal. What about oral or periodontal surgery that may require considerably more sutures than simple extractions?

The relationship between bacteremia produced in this manner and development of infective endocarditis is not documented. If extensive suturing is employed and significant bleeding is anticipated at suture removal, then antibiotic prophylaxis may be employed.

If the patient forgets to take the recommended antibiotic, can I just give the antibiotic dose in the office and start my treatment immediately?

The guidelines allow for the addition of antibiotic prophylaxis if none was employed before the dental procedure and significant bleeding occurs during treatment with immediate resumption of treatment. This is intended to allow for clinical judgment and reduce unnecessary antibiotic use since antibiotic prophylaxis may be effective if given up to two hours after the bacteremia begins. However, antibiotic prophylaxis is optimally effective when high tissue and blood levels are present before the bacteremia begins. Therefore, if the patient has not taken the antibiotic before the dental procedure, it is best to give the antibiotic in the office and wait one hour before proceeding or to reappoint the patient. The provision for administration of the antibiotic in the case of significant unanticipated bleeding should not be employed to permit immediate dosing and treatment if the patient forgets to take the recommended antibiotic.

Is there ever a situation in which a second dose of the antibiotic might be appropriate?

There are two situations in which a second dose of the prophylactic antibiotic might be appropriate. If the dental patient is seen for two appointments on the same day (one in the morning and a second in the afternoon), then antibiotic prophylaxis should be employed prior to each appointment with the same antibiotic. The other situation would be when the patient undergoes a very long procedure exceeding four to six hours after the initial dose (as is possible in the dental school setting); then a second dose might be employed. In both of these cases, the full or one-half initial prophylactic dose should be employed. Additional antibiotic would not be necessary for azithromycin or clarithromycin due to their long half-lives.

Are there any periodontal procedures that do not require antibiotic prophylaxis?

It is possible to perform a clean mouth prophylaxis in a patient with good oral hygiene and not create any significant bleeding if tissue laceration is avoided; however, as a general rule, all periodontal treatment procedures should receive antibiotic prophylaxis.

Should the 1997 AHA recommendations be used when emergency treatment must be performed on patients who have taken either fenfluramine (Pondimin) -- part of the fen-phen regimen -- and/or dexfenfluramine (Redux)?

The current recommendations for the management of such patients is discussed in this journal issue. Such patients may have cardiac valve pathology that predisposes to a risk of endocarditis and should be managed according to the 1997 AHA guidelines (using the algorithm for mitral valve prolapse) for emergency procedures and referred for a cardiovascular examination before elective treatment. These patients may electively undergo treatment with dental procedures not associated with significant bleeding and for which no antibiotic prophylaxis is recommended as listed in Table 1 under Endocarditis Prophylaxis Not Recommended.

My patient is taking penicillin or a cephalosporin for an upper respiratory infection and required endocarditis prophylaxis. What should I do?

In a patient presently taking an antibiotic (for example, amoxicillin), merely increasing the dose of that antibiotic for prophylaxis is not advised since it is likely that significant resistant strains of microorganisms are present in the oral cavity and unlikely to be sensitive to higher antibiotic dosages.^3-5 A different class of antibiotic must be used for prophylaxis, and in this case clindamycin or one of the macrolides (azithromycin or clarithromycin) would be appropriate. Alternately, the dental treatment could be delayed for nine to 14 days after the patient has completed the current course of the antibiotic and then prophylaxis can be initiated as required.

Should patients with a history of scarlet fever or rheumatic fever receive endocarditis prophylaxis?

Scarlet fever does not cause cardiac valve pathology, and patients without evidence of such pathology from other causes do not require prophylaxis. Not all cases of rheumatic fever involve the heart; therefore, patients with a history of rheumatic fever without rheumatic heart disease do not require prophylaxis. If there is doubt about the presence of rheumatic heart disease, a reasonable attempt should be made to ascertain the cardiac valve status of the patient.

The patient has a history of allergy to penicillin, but I cannot determine the severity of the signs and symptoms that occurred. What should I do?

In such a patient, it is probably best to assume the allergy consisted of more than simple skin itching and erythema and avoid the use of a cephalosporin. Either clindamycin or one of the macrolides would be appropriate. In a patient who cannot take penicillin or a macrolide due to allergy or toxicity, clindamycin is the alternative drug of choice.

Periodontists sometimes place a patient on a two- or three-week course of antibiotics such as tetracycline for the management of periodontitis. How should I handle such a patient?

Older tetracyclines have a short half-life, but drugs such as doxycycline may have up to a 24-hour half-life in some patients. Bacteriostatic antibiotics such as the tetracyclines inhibit microbial replication while inhibitors of cell wall synthesis such as the bactericidal penicillins act only on dividing microorganisms, therefore the two drugs may be antagonistic. To ensure that doxycycline is no longer present in the patient before initiating amoxicillin prophylaxis, the doxycycline should be discontinued for at least three to four days (three to four times the half-life) prior to amoxicillin use. Also, it is imperative that the doxycycline not be resumed after the dental procedure during the most likely incubation period of endocarditis (usually two weeks) as its use may mask the signs and symptoms of endocarditis, should they occur, and delay the diagnosis. Masking of the initial symptoms of endocarditis by antibiotics generally doubles the time to hospitalization for the patient and significantly increases morbidity and mortality because early diagnosis and treatment of endocarditis are very important in its ultimate resolution.⁶ However, this scenario would not hold true for a patient at risk for endocarditis who presents with an active/acute orofacial infection (such as an abscess). In this case, therapeutic antibiotics should be aggressively employed for as long as it takes to resolve the infection.⁷

I am going to do a periodontal bone grafting procedure in a patient at risk for endocarditis. What should I do?

This patient should be managed the same way as any other patient with the appropriate AHA prophylaxis regimen without posttreatment antibiotics in order to prevent the masking of any signs and symptoms of endocarditis. The risk of delaying the diagnosis of endocarditis would appear to greatly outweigh any conceivable potential benefit of posttreatment antibiotics in otherwise healthy patients at risk for endocarditis without active infection.

Should a dental patient at risk for endocarditis be advised of its early signs and symptoms (fever, malaise, anorexia, night chills, arthralgia, myalgia) so that, if these should occur, the patient will seek medical attention as soon as possible?

Bacterial endocarditis is a rare disease, and the vast majority of cases are not associated with dental treatment procedures. Therefore, such advice is probably unnecessary under the concept of informed consent and might be unduly alarming. However, early diagnosis is a very important aspect of the successful treatment of endocarditis, and the dentist can simply advise the patient to report any unusual health changes to the dentist who in turn should be fully aware of the above early signs and symptoms.

I am seeing an increasing number of patients having had various stents placed for cardiovascular disease. How do I handle such patients?

Individuals who have had coronary or noncoronary artery stents placed do not require prophylaxis six months or longer after the surgery. Those who have undergone repair of intracardiac defects (atrial septal defect, patent ductus arteriosus, ventricular septal defect) also do not require prophylaxis six months or longer after the surgery if no residual hemodynamic abnormalities are present.

What is the rationale for advising that a nine- to 14-day interval occur between dental appointments in a patient requiring endocarditis prophylaxis?

It is well-documented that antibiotic use, including AHA prophylaxis, may select resistant microorganisms in the oral cavity but that such resistance is likely not to persist nine to 14 days after the antibiotic is terminated.^3-5,8 Therefore, this interval between treatments is recommended to lower the possibility of reduced antibiotic prophylaxis efficacy due to the presence of antibiotic-resistant microorganisms. If a shorter interval is necessary, then an antibiotic selected from the alternates listed in the AHA recommendations should be employed.

The patient had periodontal scaling and root planing yesterday with amoxicillin endocarditis prophylaxis and today has a periodontal abscess. How do I manage this?

In such a situation where two prophylactic regimens are required within a short interval (12 to 24 hours), it is unlikely that significant selection of resistant organisms has occurred and reuse of amoxicillin prophylaxis prior to management of the periodontal abscess would be appropriate. The use of an alternate regimen would also be acceptable.

I understand that for a patient with a cardiac transplant I should consult with the attending physician to determine if cardiac valve pathology is present and then employ antibiotic prophylaxis if appropriate, but what about other organ transplants such as kidneys and livers?

The AHA guidelines are directed toward the prevention of bacterial endocarditis and do not address the subject of solid organ transplants other than the heart.

It is my understanding that clindamycin is more commonly associated with antibiotic-induced pseudomembranous colitis. Should I be concerned about its use for endocarditis prophylaxis?

Antibiotic-induced pseudomembranous colitis is primarily but not exclusively a nosocomial (hospital-acquired) disorder as discussed in a companion article in this issue. Pseudomembranous colitis has been associated with all antibiotics but primarily with ampicillin/amoxicillin, cephalosporins, and clindamycin. It is very unlikely that a single dose of clindamycin in a dental outpatient setting will induce pseudomembranous colitis. The incidence of community-acquired Clostridium difficile-associated diarrhea is about 1 in 10,000 antibiotic prescriptions; however, patients who have had Clostridium difficile-associated diarrhea are at greater risk for recurrence or relapse if antibiotics are administered within two months of their recovery from the diarrhea. It is not known whether a single prophylactic antibiotic dose of any agent would predispose to diarrhea/colitis recurrence or relapse, but it would appear appropriate to delay any elective dental treatment until after this two-month period.⁹

What should I do if the physician recommends a prophylaxis regimen that is different from that of the AHA?

Although the 1997 AHA guidelines are not the exclusive standard of care, they are the most generally accepted standard and undergo intense scrutiny before publication. If the dental procedure is elective, then possibly the best approach would be to share a copy of the recommendations with the physician (via fax machine, for example) with later reconsultation to further discuss the matter. If a satisfactory resolution does not occur, the dentist must follow his or her best professional and clinical judgment as the responsibility ultimately rests with the dentist when the patient is in the dental office. In making the initial consult with the physician of record, the dentist should take the initiative to indicate in the consult letter or verbal consult that the 1997 AHA guidelines are going to be used. This approach may minimize physician-initiated recommendations that differ from the AHA guidelines.

It is well-known that oral hygiene procedures such as flossing, brushing, and using water-pressure devices cause bacteremias. Can't these procedures place the patient at a greater risk for endocarditis?

It is generally accepted that the healthier the mouth the less the incidence and magnitude of bacteremias due to a reduced likelihood of bleeding, and the AHA guidelines strongly encourage good oral hygiene as a primary preventive measure for endocarditis. Therefore, procedures that promote dental bacterial plaque reduction are to be encouraged. Home-use devices pose far less risk of bacteremias in a healthy mouth than does ongoing oral inflammation.^1,8 Any brief, temporary increase in bacteremias while the patient is undergoing inflammation reduction is more than offset by the future benefit of permanent elimination of inflammation.

Why was erythromycin not included in the list of alternative drugs for antibiotic prophylaxis for endocarditis?

Erythromycin was included in the 1990 AHA guidelines but generated extensive comments and complaints because of the two forms of erythromycin (succinate or stearate) and two doses (800 mg or 1 gm). The incidence of gastrointestinal complaints was significant with the larger doses of erythromycin; and, because dosing equivalence was troublesome for many, erythromycin was not included in the 1997 guidelines. Alternative macrolides, clarithromycin and azithromycin, were shown to be effective and were then substituted for erythromycin. These are more expensive drugs, but the single dose required should help reduce the impact of cost. If a patient was successfully managed in the past with erythromycin and neither the dentist nor the patient want to switch to one of the other recommended antibiotics, the 1990 AHA regimen for erythromycin can continue to be used to include the follow-up second dose.

Is clindamycin the preferred drug of choice for the patient who cannot take amoxicillin?

The alternative choices to amoxicillin were selected because of their usefulness and are not listed in specific order. Dentists should always consider the patient's prior antibiotic drug history before selecting an alternative to amoxicillin. Several choices are recommended to accommodate the patient's needs.

Does a patient with a total prosthetic joint replacement need prophylaxis for prevention of bacterial endocarditis?

Individuals with total joint prostheses are not at increased risk for endocarditis unless they have an underlying cardiac defect identified in the table of patients at risk for endocarditis. The recommendations regarding antibiotic prophylaxis for dental patients with total joint prostheses was addressed by a joint statement of the American Dental Association and the American Academy of Orthopaedic Surgeons and published in the Journal of the American Dental Association (128:1004-7, 1997).

A 30-year-old patient says that as a child she was told she had a heart murmur, and the patient has not been examined by a physician since age 18. Should I give antibiotic prophylaxis?

The patient should be questioned as to whether her murmur was referred to as "innocent" (also termed functional or physiological). Innocent heart murmurs are quite common in childhood, and most disappear when the child reaches adulthood. Innocent murmurs do not require antibiotic prophylaxis. If the patient does not know whether it was an innocent murmur, a medical consultation will be appropriate; and the physician examining the patient will have to determine if the murmur was (is) innocent or whether it is due to an actual cardiac valvular abnormality requiring AHA endocarditis prophylaxis.

Doses for children are based on body weight, and sometimes the dose calculated cannot be easily accommodated by available dose sizes for the recommended drug. Should the dose be rounded up or down?

If a child weighed 38 pounds, then the calculated dose of amoxicillin would be 38 pounds divided by 2.2 (1 kg equals 2.2 pounds), which equals 17.3 kg times 50 mg/kg, which equals 865 mg of amoxicillin. Because amoxicillin has a very low toxicity and pharmacist compounding of such a dose could be complicated, the most pragmatic solution to this problem would be to have the child take four of the 250 mg or two of the 500 mg tablets or capsules (1,000 mg), thereby adjusting the dose upward. Alternately, the correct volume of 250 mg/5 mg oral suspension could be used. In any case, the maximum calculated dose for children should not exceed the recommended adult dose.

When will the next revised guidelines appear?

The AHA recommendations for the prevention of bacterial endocarditis have been revised periodically as new pertinent data became available, and such a practice will continue at approximately five- to seven-year intervals.

Summary
The 1997 Prevention of Bacterial Endocarditis Recommendations by the American Heart Association have been favorably received. The simplification of the prophylaxis regimens and better delineation of patients at risk, dental procedures recommended for prophylaxis, and ancillary procedures to reduce bacteremic risk have likely improved compliance and reduced unwarranted antibiotic prophylaxis and subsequent adverse effects. Questions have arisen regarding aspects of implementation of these guidelines in the dental setting, and these have been addressed. Future revisions of these recommendations are to be anticipated and will incorporate all new pertinent data.