Clinical Update: Dental Prophylaxis for Infective Endocarditis

US Pharm. 2008;33(2):HS-30-HS-33.

Patients who suffer from certain types of heart conditions are at risk for developing infective endocarditis (IE) after undergoing invasive dental procedures, according to the American Heart Association (AHA) and the American Dental Association (ADA).¹ This infection of the myocardium is caused by the colonization of bacteria in the heart that reach transient high levels in the bloodstream after soft-tissue manipulation during dental procedures. This rare condition, previously termed subacute bacterial endocarditis, is associated with high morbidity and mortality.¹ The AHA recommends that patients with certain types of heart conditions be treated prophylactically with antibiotics prior to the dental procedure to prevent IE. ¹ Recently, the AHA appointed a task force to review and amend the existing guidelines because of a lack of evidence regarding patients who acquire IE after dental treatment. As a result, new guidelines for prophylactic antibiotic treatment of cardiac patients undergoing dental procedures were issued by the AHA in March 2007.¹

The purpose of this article is twofold: to educate pharmacists about the revised recommendations for antibiotic prophylaxis for dental patients and to provide a summary of the AHA's newly updated guidelines.

History
The first AHA recommendation for the antibiotic prophylaxis of dental patients was made in 1955, when the emergence of IE after a dental procedure was first noted.¹ After several revisions were made based on ongoing evaluation of patient risk, the ADA endorsed the recommendations in 1972, placing heavy emphasis on the importance of excellent home care and oral hygiene.² Until the 2007 revisions were made, the most recent version of the guidelines dated from 1997 and was based on information that was taken from animal studies and extrapolated to humans.³ The ration!=ale for revising the 1997 guidelines comes from the theory that IE is more likely to result from frequent random exposure to oral microbes during daily activities such as eating, brushing the teeth, and flos!=sing than from exposure occurring during dental procedures.¹

It also is believed that the risk of adverse effects from antibiotic treatment outweighs the benefit of the treatment. The ADA further advises that maintenance of good oral health and daily practice of oral hygiene may decrease the patient's risk of bacteremia. This may be more important than the antibiotic regimen for preventing IE. ⁴

Pathogenesis
The pathogenesis of IE is complex. IE occurs when nonbacterial thrombotic endocarditis (NBTE) is pres!=ent at a site of endothelial damage or on the surface of one of the cardiac valves. During certain dental procedures, manipulation of and trauma to the oral mucosa, soft tissue, or teeth lead to a transient bacteremia. The most common microbes released into the bloodstream are Streptococcus viridans species, which are considered normal oral flora. The bacteremia may be more severe if inflammation of the soft tissues is present; this is often the case in patients with poor oral health and periodontal problems. The bacteria adhere to the NBTE and proceed to proliferate within the vegetation, resulting in clinical IE. Patients experiencing IE present with variable signs and symptoms; diagnosis of IE is based on the presence of bacteremia, evidence of active valvu!=litis, the presence of peripheral emboli, and immunologic vascular phenomena.⁵

Patients at Risk
Upon reviewing the existing body of literature and evidence supporting IE acquired following dental treatment, the AHA Science Advisory and Coordinating Committee removed from the list many heart conditions previously thought to put patients at high risk for IE. The heart conditions currently associated with high risk of IE are listed in TABLE 1. The cardiac conditions for which antibiotic prophylaxis is no longer indicated are specified in TABLE 2.¹ It is the hope of the committee that if fewer patients are receiving prophylaxis, there will be a decrease in adverse outcomes and in the drug resistance caused by antibiotic therapy.¹

Dental Procedures

Studies have shown that 50% of community-acquired IE cases (not associated with IV drug use) are caused by viridans group streptococci.⁶ S viridans is released into the bloodstream as a result of the manipulation of soft tissues and teeth during dental procedures and from routine daily brushing and flossing at home. For healthy patients, this transient bacteremia poses no health threat. Those patients with the cardiac conditions listed in TABLE 1, however, will require anti!=biotic treatment prior to specific dental procedures (TABLE 3 ); dental extractions and dental prophylaxis were the procedures found to be most highly associated with bacteremia.^7-9

The lack of prospective, randomized, placebo-controlled studies to determine precisely which dental procedures cause bacteremia and IE has led to a focus on maintenance of good oral health as a measure for IE prevention. The ADA currently emphasizes good oral hygiene and the prevention and treatment of active disease in cardiac patients to lower their risk of developing IE from bacteremia caused by daily brushing, flos!=sing, chewing food, and using toothpicks and irrigation devices.⁴

Antibiotic Regimen
The antibiotic regimen recommended for IE prophylaxis consists of a single dose 60 minutes prior to the dental procedure for oral medication, or 30 minutes prior to the dental procedure for IV or intramuscular medication. If the dose is not given in this manner, the antibiotic may be administered effectively for up to two hours after the dental treatment has been rendered. The antibiotics of choice are targeted to eradicate viridans group streptococci. The antibiotic regimens recommended for IE prophylaxis are outlined in TABLE 4.

Special Considerations
Several factors should be taken into consideration when antibiotic prophylaxis is prescribed for cardiac patients undergoing dental procedures. Cephalosporins should not be used in patients with a history of anaphylaxis, angioedema, or urticaria after the use of penicillins or ampicillin. Patients already taking an antibiotic for another illness should be prescribed a different antibiotic for dental prophylaxis (e.g., a child who is currently taking amoxicillin for an ear infection should be prescribed a second agent for dental prophylaxis). Intramuscular injections should be avoided in patients who are receiving anticoagulant therapy. Patients who will be undergoing cardiac surgery should have a preoperative dental evaluation, and all dental treatment should be completed before the surgery.

Conclusion
Pharmacists play a crucial role in patient education due to their accessibility and the more frequent contact they have with patients in the community. They should be cognizant of the current dental-prophylaxis guidelines and should inform patients who may have had antibiotics in the past that they no longer require them prior to dental treatment. Pharmacists also can educate physicians and dentists who may be unaware of the new guidelines regarding which patients require IE prophylaxis. Increased awareness of the current recommendations for prophylaxis may curtail the unnecessary prescribing of antibiotics and lead to decreased adverse events and antibiotic resistance as physicians and dentists manage their patients appropriately.

REFERENCES

1. Wilson W, Taubert KA, Gewitz M, et al. Prevention of infective carditis. Guidelines from the American Heart Association. A guideline from the American Heart Association Rheumatic Fever, Endocarditis, and Kawasaki Disease Committee, Council on Cardiovascular Disease 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;116:1736-1754.

2. Rheumatic Fever Committee and the Committee on Congenital Cardiac Defects, American Heart Association. Prevention of bacterial endocarditis.

Circulation. 1972;46:S3-S6.

3. Dajani AS, Taubert KA, Wilson W, et al. Prevention of bacterial endocarditis: recommendations by the American Heart Association. JAMA. 1997;277:1794-1801.

4. American Dental Association. Antibiotics and your heart. Available at: www.ada.org/public/topics/antibiotics/asp. Accessed October 5, 2007.

5. Baddour LM, Wilson WR, Bayer AS, et al. Infective endocarditis: diagnosis, antimicrobial therapy, and management of complications: a statement for healthcare professionals from the Committee on Rheumatic Fever, Endocarditis, and Kawasaki Disease, Council on Cardiovascular Disease in the Young, and the Councils on Clinical Cardiology, Stroke, Cardiovascular Surgery and Anesthesia. Circulation. 2005;111:e394-e434.

6. Fowler VG, Scheld WM, Bayer AS. Endocarditis and intravascular infections. In: Mandell GL, Bennett JE, Dolin R, eds. Principles and Practices of Infectious Diseases. Philadelphia, PA: Elsevier Churchill Livingstone; 2005:975-1021.

7. Lockhart PB. The risk of endocarditis in dental practice. Periodontology 2000. 2000;23:127-35.

8. Conner HD, Haberman S, Collings CK, Winford TE. Bacteremia following periodontal scaling in patients with healthy appearing gingiva. J Periodontol. 1967;38:466-472.

9. Lockhart PB, Brennan MT, Fox PC, et al. Decision-making on the use of antimicrobial prophylaxis for dental procedures: a survey of infectious disease consultants and review. Clin Infect Dis. 2002;34:1621-1626.

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