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Prevention of Bacterial Endocarditis

Recommendations by the American Heart Association

Adnan S. Dajani, MD; Kathryn A. Taubert, PhD; Walter Wilson, MD; Ann F. Bolger, MD; Arnold Bayer, MD; Patricia Ferrieri, MD; Michael H. Gewitz, MD; Stanford T. Shulman, MD; Soraya Nouri, MD; Jane W. Newburger, MD; Cecilia Hutto, MD; Thomas J. Pallasch, DDS, MS; Tommy W. Gage, DDS, PhD; Matthew E. Levison, MD; Georges Peter, MD; Gregory Zuccaro, Jr, MD

Abstract

Objective To update recommendations issued by the American HeartAssociation last published in 1990 for the prevention of bacterialendocarditis in individuals at risk for this disease.

Participants An ad hoc writing group appointed by the American HeartAssociation for their expertise in endocarditis and treatment withliaison members representing the American Dental Association,the Infectious Diseases Society of America, the American Academyof Pediatrics, and the American Society for Gastrointestinal Endoscopy.

Evidence The recommendations in this article reflect analysesof relevant literature regarding procedure-related endocarditis,in vitro susceptibility data of pathogens causing endocarditis,results of prophylactic studies in animal models of endocarditis,and retrospective analyses of human endocarditis cases in termsof antibiotic prophylaxis usage patterns and apparent prophylaxisfailures. MEDLINE database searches from 1936 through 1996 weredone using the root words endocarditis, bacteremia, and antibioticprophylaxis. Recommendations in this document fall into evidencelevel III of the US Preventive Services Task Force categoriesof evidence.

Consensus Process The recommendations were formulated by the writinggroup after specific therapeutic regimens were discussed. The consensusstatement was subsequently reviewed by outside experts not affiliatedwith the writing group and by the Science Advisory and CoordinatingCommittee of the American Heart Association. These guidelinesare meant to aid practitioners but are not intended as the standardof care or as a substitute for clinical judgment.

Conclusions Major changes in the updated recommendations includethe following: (1) emphasis that most cases of endocarditisare not attributable to an invasive procedure; (2) cardiac conditionsare stratified into high-, moderate-, and negligible-risk categoriesbased on potential outcome if endocarditis develops; (3) proceduresthat may cause bacteremia and for which prophylaxis is recommendedare more clearly specified; (4) an algorithm was developed tomore clearly define when prophylaxis is recommended for patientswith mitral valve prolapse; (5) for oral or dental proceduresthe initial amoxicillin dose is reduced to 2 g, a follow-upantibiotic dose is no longer recommended, erythromycin is nolonger recommended for penicillin-allergic individuals, butclindamycin and other alternatives are offered; and (6) forgastrointestinal or genitourinary procedures, the prophylacticregimens have been simplified. These changes were institutedto more clearly define when prophylaxis is or is not recommended,improve practitioner and patient compliance, reduce cost andpotential gastrointestinal adverse effects, and approach moreuniform worldwide recommendations.

Key Words: cardiovascular disease • endocarditis • prevention • AHA Medical/Scientific Statements • antibiotic prophylaxis

Endocarditis is a life-threatening disease, although it is relativelyuncommon. Substantial morbidity and mortality result from thisinfection, despite improvements in outcome due to advances inantimicrobial therapy and enhanced ability to diagnose and treatcomplications. Primary prevention of endocarditis whenever possibleis therefore very important.

Endocarditis usually develops in individuals with underlyingstructural cardiac defects who develop bacteremia with organismslikely to cause endocarditis. Bacteremia may occur spontaneouslyor may complicate a focal infection (eg, urinary tract infection,pneumonia, or cellulitis). Some surgical and dental proceduresand instrumentations involving mucosal surfaces or contaminatedtissue cause transient bacteremia that rarely persists for morethan 15 minutes. Blood-borne bacteria may lodge on damaged orabnormal heart valves or on the endocardium or the endotheliumnear anatomic defects, resulting in bacterial endocarditis orendarteritis. Although bacteremia is common following many invasiveprocedures, only certain bacteria commonly cause endocarditis.It is not always possible to predict which patients will developthis infection or which particular procedure will be responsible.

There are currently no randomized and carefully controlled humantrials in patients with underlying structural heart diseaseto definitively establish that antibiotic prophylaxis providesprotection against development of endocarditis during bacteremia-inducingprocedures. Further, most cases of endocarditis are not attributableto an invasive procedure. The following recommendations reflectanalyses of relevant literature regarding procedure-relatedendocarditis, including in vitro susceptibility data of pathogenscausing endocarditis, results of prophylactic studies in experimentalanimal models of endocarditis, and retrospective analyses ofhuman endocarditis cases in terms of antibiotic prophylaxisusage patterns and apparent prophylaxis failures.

The incidence of endocarditis following most procedures in patients withunderlying cardiac disease is low. A reasonable approach for endocarditisprophylaxis should consider the following: the degree to whichthe patient’s underlying condition creates a risk of endocarditis;the apparent risk of bacteremia with the procedure (as definedin these recommendations); the potential adverse reactions of theprophylactic antimicrobial agent to be used; and the cost-benefitaspects of the recommended prophylactic regimen. Failure toconsider all of these factors may lead to overuse of antimicrobialagents, excessive cost, and risk of adverse drug reactions.

This statement provides guidelines for prevention of bacterial endocarditis.It is not intended as the standard of care or as a substitutefor clinical judgment. The current recommendations are an updateof those made by the committee in 1990¹ and incorporate newdata and include opinions voiced by national and internationalexperts at endocarditis meetings around the world.

Cardiac Conditions

Certain cardiac conditions are associated with endocarditis moreoften than others.² Furthermore, when endocarditis developsin individuals with underlying cardiac conditions, the severityof the disease and the ensuing morbidity can be variable. Prophylaxisis recommended in individuals who have a higher risk for developingendocarditis than the general population and is particularly importantfor individuals in whom endocardial infection is associated withhigh morbidity and mortality.

Table 1 ² ³ ⁴ ⁵ ⁶ ⁷ ⁸ ⁹ ¹⁰ ¹¹ ¹² ¹³ ¹⁴ ¹⁵ ¹⁶ ¹⁷ ¹⁸ ¹⁹ ²⁰ ²¹ ²²stratifies cardiac conditions into high- and moderate-riskcategories primarily on the basis of potential outcome if endocarditisoccurs.

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Table 1. Cardiac Conditions Associated With Endocarditis² ³ ⁴ ⁵ ⁶ ⁷ ⁸ ⁹ ¹⁰ ¹¹ ¹² ¹³ ¹⁴ ¹⁵ ¹⁶ ¹⁷ ¹⁸ ¹⁹ ²⁰ ²¹ ²²

High Risk
Individuals at highest risk are those who have prosthetic heartvalves, a previous history of endocarditis (even in the absence ofother heart disease), complex cyanotic congenital heart disease,or surgically constructed systemic pulmonary shunts or conduits.² ³ These individuals are at a much higher risk for developingsevere endocardial infection that is often associated with highmorbidity and mortality.

Moderate Risk
Individuals with certain other underlying cardiac defects areat moderate risk for severe infection.² ³ ⁴ Congenital cardiac conditionslisted in the moderate-risk category include the following uncorrectedconditions: patent ductus arteriosus, ventricular septal defect,primum atrial septal defect, coarctation of the aorta, and bicuspidaortic valve. Acquired valvar dysfunction (eg, due to rheumaticheart disease or collagen vascular disease) and hypertrophiccardiomyopathy are also moderate-risk conditions.

Mitral valve prolapse (MVP) is common, and the need for prophylaxisfor this condition is controversial. Only a small percentageof patients with documented MVP develop complications at anyage.⁵ ⁶ ⁷ Mitral valve prolapse represents a spectrum of valvular changesand clinical behavior.⁵ ⁶ ⁷ In view of the controversy surroundingthe need for prophylaxis of the individual patient with MVP,a detailed description of the spectrum of MVP is warranted.

Normal mitral valve leaflets close at or below the plane ofthe mitral annulus. This closure position is controlled by thelengths of the leaflets, their attached chordae and papillarymuscles, and the systolic size of the ventricle. The closureposition will shift beyond the annular plane toward the leftatrium, or prolapse, if the lengths of the valve apparatus,which are constant, become too large for the size of the end-systolicventricle, which is variable and dynamic. Dehydration and tachycardiaare common causes of intermittent MVP. Abnormal motion of normalmitral valves is found on echocardiographic examination in a smallpercentage of the adult and adolescent ambulatory population.The high prevalence of such motion abnormalities in young adults underscoresthat MVP is often an abnormality of volume status, adrenergicstate, or growth phase and not of valve structure or function.When normal valves prolapse without leaking, as in patients withone or more systolic clicks but no murmurs and no Doppler-demonstratedmitral regurgitation, the risk of endocarditis is not increasedabove that of the normal population.² ⁶ ⁷ Antibiotic prophylaxisagainst bacterial endocarditis is therefore not necessary. Thisis because it is not the abnormal valve motion but the jet ofmitral insufficiency that creates the shear forces and flowabnormalities that increase the likelihood of bacterial adherenceon the valve during bacteremia.

Normal mitral valves with normal motion often have minimal leaks detectableby Doppler examination. This does not appear to increase therisk of endocarditis. In contrast, the regurgitation that occurswith structurally normal but prolapsing valves originates fromlarger regurgitant orifices and creates broader areas of turbulentflow. Patients with prolapsing and leaking mitral valves, evidencedby audible clicks and murmurs of mitral regurgitation or byDoppler-demonstrated mitral insufficiency, should receive prophylactic antibiotics.⁷ ⁸ ⁹ ¹⁰ ¹¹ This is supported by formal cost-benefit analysis.¹²

Mitral valve prolapse also occurs in the setting of myxomatous degenerationof the mitral valve. This is a progressive disorder that hasa spectrum of manifestations.¹³ ¹⁴ The mitral leaflets of thesepatients appear thickened on the echocardiogram, due to accumulationsof proteoglycan deposits.¹⁵ The amount of thickening is variableand may increase with age.¹⁶ There is a range of valve motionin these patients as well: they may prolapse continuously oronly with changes in heart rate or volume. Further, when prolapseoccurs, it may or may not create valvular insufficiency. Inpatients of any age, myxomatous mitral valve degeneration withregurgitation is an indication for antibiotic prophylaxis.¹¹ ¹⁷ ¹⁸

Anterior mitral valve thickening is commonly found in both competent andinsufficient myxomatous mitral valves, but its presence increases thelikelihood of significant mitral regurgitation.¹⁶ Those withsignificant regurgitation were older and more likely to be men.¹⁶Other studies have shown that male sex and age older than 45years represent increased risk for developing endocarditis.⁸ ¹⁰ ¹¹ ¹⁹ Patients with thickened valves that do not leak onresting examination often develop regurgitation with exercise.These patients with exercise-induced mitral insufficiency havebeen shown to constitute a higher-risk subset for common complications(syncope, congestive heart failure, progressive regurgitationrequiring valve replacement); endocarditis and cerebral embolicevents, occurring far less frequently, were not demonstratedto be increased in this small series.²⁰ Men older than 45 yearswith MVP, without a consistent systolic murmur, may warrantprophylaxis even in the absence of resting regurgitation.¹² ¹⁹

Some experts feel that an audible nonejection click even withouta murmur may identify patients with a potential for intermittent regurgitationand therefore a risk of developing endocarditis. While thereare insufficient data on this issue, an isolated click may bean indication for more thorough evaluation of valve morphologyand function, including Doppler-echocardiographic imaging orauscultation during maneuvers that elicit or augment mitral regurgitation.

While children and adolescents with MVP may have the same symptomsas adults, such as palpitations or syncope, the developmentof symptoms in childhood is relatively unusual. The vast majorityof children with chest pain or fatigue do not have any formof heart disease, including MVP. Careful evaluation is neverthelessrequired in children who have isolated clinical findings, suchas nonejection systolic click, since this may be the only indicatorof important mitral valve abnormality requiring prophylaxis.²¹In the most recent series of reports, MVP has emerged as animportant underlying diagnosis associated with endocarditisin the pediatric age group.³ ²¹

A clinical approach to determination of the need for prophylaxisin individuals with suspected MVP is given in the Figure.²³

Negligible Risk
Although endocarditis may develop in any individual, includingpersons with no underlying cardiac defect, the negligible-riskcategory lists cardiac conditions in which the development ofendocarditis is not higher than in the general population. Whereasin pediatric patients innocent heart murmurs may be clearlydefined on auscultation, in the adult population other studies suchas echocardiography may be necessary to confirm that a murmuris innocent. Individuals with innocent heart murmurs have structurallynormal hearts and do not require prophylaxis.

Bacteremia-Producing Procedures

Bacteremias commonly occur during activities of daily living suchas routine tooth brushing or chewing. With respect to endocarditis prophylaxis,significant bacteremias are only those caused by organisms commonlyassociated with endocarditis and attributable to identifiable procedures.The procedures for which prophylaxis is recommended are thoseknown to induce such bacteremias and are discussed below. Invasiveprocedures performed through surgically scrubbed skin are not likelyto produce such bacteremias. Many centers do employ periprocedureprophylaxis for transcatheter insertion of prosthetic devices(septal occluders and vascular coils), however, although thereare no data to support the use of antibiotics in the procedures.Routine cardiac catheterization and angioplasty do not requiresuch precautions.

Dental and Oral Procedures

Poor dental hygiene and periodontal or periapical infectionsmay produce bacteremia even in the absence of dental procedures.The incidence and magnitude of bacteremias of oral origin aredirectly proportional to the degree of oral inflammation and infection.²⁴ ²⁵ Individuals who are at risk for developing bacterial endocarditisshould establish and maintain the best possible oral healthto reduce potential sources of bacterial seeding. Optimal oralhealth is maintained through regular professional care²⁴ ²⁶ ²⁷ and the use of appropriate dental products such as manualand powered toothbrushes, dental floss, and other plaque-removaldevices. Oral irrigator or air abrasive polishing devices usedinappropriately or in patients with poor oral hygiene have beenimplicated in producing bacteremia, but the relationship to bacterialendocarditis is unknown.²⁴ ²⁸ ²⁹ ³⁰ ³¹ Home-use devices posefar less risk of bacteremia in a healthy mouth than does ongoingoral inflammation.²⁴ ²⁸ ²⁹ ³⁰ ³¹

Antiseptic mouth rinses applied immediately prior to dental proceduresmay reduce the incidence or magnitude of bacteremia.²⁴ Agentsinclude chlorhexidine hydrochloride and povidone-iodine. Fifteenmilliliters of chlorhexidine can be given to all at-risk patientsvia gentle oral rinsing for about 30 seconds prior to dentaltreatment; gingival irrigation is not recommended. Sustainedor repeated frequent interval use is not indicated as this mayresult in the selection of resistant micro-organisms.²⁴

Antibiotic prophylaxis for at-risk patients is recommended fordental and oral procedures likely to cause bacteremia (Table2 ²² ²⁴ ²⁵ ²⁶ ²⁸ ²⁹ ³⁰ ³¹ ). In general, prophylaxis is recommendedfor procedures associated with significant bleeding from hardor soft tissues, periodontal surgery, scaling, and professional teethcleaning. Similarly, antimicrobial prophylaxis is recommendedfor tonsillectomy or adenoidectomy. It is recognized that unanticipated bleedingmay occur on some occasions. In such an event, data from experimentalanimal models suggest that antimicrobial prophylaxis administeredwithin 2 hours following the procedure will provide effectiveprophylaxis.³² Antibiotics administered more than 4 hours afterthe procedure probably have no prophylactic benefit. Proceduresfor which antimicrobial prophylaxis is not recommended are alsolisted (Table 2).

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Table 2. Dental Procedures and Endocarditis Prophylaxis²² ²⁴ ²⁵ ²⁶ ²⁸ ²⁹ ³⁰ ³¹

Edentulous patients may develop bacteremia from ulcers causedby ill-fitting dentures. Denture wearers should be encouragedto have periodic examinations or to return to the practitionerif discomfort develops. When new dentures are inserted, it isadvisable to have the patient return to the practitioner tocorrect any problems that could cause mucosal ulceration.

If a series of dental procedures is required, it may be prudentto observe an interval of time between procedures to both reducethe potential for the emergence of resistant organisms and allow repopulationof the mouth with antibiotic susceptible flora. Various studieshave suggested an interval of 9³³ to 14³⁴ days. If possible,a combination of procedures should be planned within the sameperiod of prophylaxis.

Respiratory, Gastrointestinal, and Genitourinary Tract Procedures

Surgical procedures involving the respiratory mucosa may leadto bacteremia; therefore, antimicrobial prophylaxis is recommended(Table 3 ³⁵ ³⁶ ³⁷ ³⁸ ³⁹ ⁴⁰ ⁴¹ ⁴² ⁴³ ⁴⁴ ⁴⁵ ⁴⁶ ⁴⁷ ⁴⁸ ⁴⁹ ⁵⁰ ⁵¹ ⁵² ⁵³ ⁵⁴ ⁵⁵ ⁵⁶ ⁵⁷ ⁵⁸ ). The use of a rigid bronchoscope may causemucosal damage, whereas such damage is unlikely with a flexiblebronchoscope. Endotracheal intubation per se is not an indicationfor antibiotic prophylaxis.

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Table 3. Other Procedures and Endocarditis Prophylaxis³⁵ ³⁶ ³⁷ ³⁸ ³⁹ ⁴⁰ ⁴¹ ⁴² ⁴³ ⁴⁴ ⁴⁵ ⁴⁶ ⁴⁷ ⁴⁸ ⁴⁹ ⁵⁰ ⁵¹ ⁵² ⁵³ ⁵⁴ ⁵⁵ ⁵⁶ ⁵⁷ ⁵⁸

The risk of endocarditis as a direct result of an endoscopicprocedure is small. Transient bacteremia may occur during orimmediately after endoscopy; however, there are few reportsof infective endocarditis attributable to endoscopy.³⁵ ³⁶ ³⁷ ³⁸ ³⁹ ⁴⁰ ⁴¹ ⁴² ⁴³ For most gastrointestinal endoscopic procedures,the rate of bacteremia is 2% to 5%, and the organisms typicallyidentified are unlikely to cause endocarditis.⁴⁴ ⁴⁵ The rateof bacteremia does not increase with mucosal biopsy, polypectomy,or sphincterotomy.⁴⁶ ⁴⁷ ⁴⁸ There are no data to indicate that deepbiopsy, as may be performed in the rectum or stomach, leadsto a higher rate of bacteremia.

Some gastrointestinal procedures are associated with a higher rateof transient bacteremia; for these procedures, antimicrobial prophylaxisis recommended, particularly for patients in the high-risk category(Table 3). Esophageal stricture dilation has been associated withbacteremia rates as high as 45%.⁴⁴ However, this number isan average result of several clinical studies in which the rateof bacteremia ranged from 0% to 100%.⁴⁹ ⁵⁰ ⁵¹ ⁵² In only onestudy was the oropharynx the documented source of infection.⁵²These studies were performed with differing methods and involvedrelatively small numbers of patients. Until more data documentingthe true rate of bacteremia associated with stricture dilationbecome available, it is prudent to consider this procedure as onepotentially associated with an increased risk of transient bacteremia.

The bacteremia rate associated with sclerotherapy of esophagealvarices is approximately 31%.⁴⁴ Bacteremia appears to be most associatedwith increased sclerosant volumes, as can occur with emergencysclerosis for active bleeding, and with relatively longer injectionneedles. The bacteremia rate is lessened with the use of shorterinjection needles and sterile water.⁵³ ⁵⁴ Endoscopic ligationof varices, or banding, is not associated with increased ratesof transient bacteremia.⁵⁵

An obstructed biliary tree, due to benign or malignant disease,may be colonized with a variety of organisms. A prime risk factorfor dissemination of infection from an obstructed biliary treeis instrumentation of the obstructed region without provisionof adequate drainage. The bacteremia rates for endoscopic retrograde cholangiographyin the absence of ductal obstruction are approximately equalto most other endoscopic procedures. Prophylaxis should be consideredprimarily in cases in which biliary obstruction is known or suspected.

In biliary tract surgery, or in any operative procedure thatinvolves the intestinal mucosa, there is a potential for bacteremiawith organisms known to cause endocarditis. It is thereforeprudent to provide prophylaxis for patients at high risk todevelop endocarditis.

Surgery, instrumentation, or diagnostic procedures that involvethe genitourinary tract may cause bacteremia. Although the riskthat any particular patient will develop endocarditis is low,the genitourinary tract is second only to the oral cavity asa portal of entry for organisms that cause endocarditis. Therate of bacteremia following urinary tract procedures is highin the presence of urinary tract infection (UTI). Sterilizationof the urinary tract with antimicrobial therapy in patientswith bacteriuria should be attempted prior to elective procedures,including lithotripsy. Results of a preprocedure urine culturewill allow the practitioner to choose antibiotics appropriateto the recovered organisms. Procedures for which antimicrobialprophylaxis is or is not recommended are listed in Table 3.

Many procedures involving the urethra and prostatic bed are associatedwith high rates of bacteremia. The incidence of bacteremia wasstudied in 300 patients undergoing one of four different urologic procedures:transurethral resection (TUR) of the prostate, cystoscopy, urethraldilation, and urethral catheterization.⁵⁶ Bacteremia was most frequentafter TUR of the prostate, occurring in 31% of the patients. Inthe other procedures, bacteremia occurred in 24% following urethral dilatation,in 17% following cystoscopy, and in 8% following urethral catheterization.Bacteremia was significantly associated with both prostatitison histological examination of resected prostate and prior UTIfollowing TUR and with prior UTI following urethral dilatationand cystoscopy. Preexisting UTI was the major source of organismscausing the bacteremia following TUR but was the source in onlyabout one third of patients following the other procedures.Enterococci and Klebsiella were the most frequent organisms.Although bacteremia due to gram-negative bacilli is unlikelyto cause endocarditis unless a prosthetic valve is present,it may nevertheless cause life-threatening sepsis. Therefore,an antimicrobial regimen effective against the infective urinarypathogen, eg, enteric gram-negative bacilli, in addition tothe enterococcus, should be administered before the invasivegenitourinary procedures.

Bacteremia follows uncomplicated vaginal delivery in only 1%to 5% of procedures, usually with various types of streptococci²²; well-documented cases of endocarditis after normal vaginaldelivery are uncommon.⁵⁷ Therefore, antibiotic prophylaxisfor normal vaginal delivery is not recommended. If an unanticipatedbacteremia is suspected during vaginal delivery, intravenousantibiotics can be administered at that time. No bacteremiahas been detected in studies following cervical biopsy or manipulationof an intrauterine device (IUD) in the absence of obvious infections.²²Bacteremia following removal of an infected IUD is unresolved⁵⁸but would seem possible and should warrant prophylaxis, aswould other genitourinary procedures in the presence of infection.

Prophylactic Regimens

Prophylaxis is most effective when given perioperatively indoses that are sufficient to assure adequate antibiotic concentrationsin the serum during and after the procedure. To reduce the likelihoodof microbial resistance, it is important that prophylactic antibioticsbe used only during the perioperative period. They should beinitiated shortly before a procedure and should not be continuedfor an extended period (no more than 6 to 8 hours). In the caseof delayed healing, or of a procedure that involves infectedtissue, it may be necessary to provide additional doses of antibioticsfor treatment of the established infection.

Practitioners must exercise their own clinical judgment in determiningthe choice of antibiotics and number of doses that are to beadministered in individual cases or special circumstances. Furthermore,because endocarditis may occur in spite of appropriate antibioticprophylaxis, physicians and dentists should maintain a high indexof suspicion regarding any unusual clinical events (such as unexplainedfever, night chills, weakness, myalgia, arthralgia, lethargy,or malaise) following dental or other surgical procedures in patientswho are at risk for developing bacterial endocarditis.

Regimens for Dental, Oral, Respiratory Tract, or Esophageal Procedures
Streptococcus viridans ( {alpha} -hemolytic streptococci) is the mostcommon cause of endocarditis following dental or oral procedures,certain upper respiratory tract procedures, bronchoscopy witha rigid bronchoscope, surgical procedures that involve the respiratorymucosa, and esophageal procedures. Prophylaxis should be specificallydirected against these organisms. The same regimens are recommendedfor all these procedures (Table 4 ¹ ²² ⁵⁹ ⁶⁰ ⁶¹ ). The recommendedstandard prophylactic regimen for all these procedures is asingle dose of oral amoxicillin. The antibiotics amoxicillin,ampicillin, and penicillin V are equally effective in vitroagainst {alpha} -hemolytic streptococci; however, amoxicillin is recommendedbecause it is better absorbed from the gastrointestinal tractand provides higher and more sustained serum levels. Previouslythe recommended dose was 3.0 g 1 hour before a procedure andthen 1.5 g 6 hours after the initial dose.¹ Recent comparisonsof 2.0-g and 3.0-g dosing indicate that a 2.0-g dose resultsin adequate serum levels for several hours and causes less gastrointestinaladverse effects.⁵⁹ The newly recommended adult dose is 2.0g of amoxicillin (pediatric dose is 50 mg/kg not to exceed theadult dose) to be administered 1 hour before the anticipatedprocedure. A second dose is not necessary, both because of theprolonged serum levels above the minimal inhibitory concentrationof most oral streptococci⁵⁹ and the prolonged serum inhibitoryactivity induced by amoxicillin against such strains (6 to 14hours).⁶⁰ For individuals who are unable to take or unableto absorb oral medications, a parenteral agent may be necessary.Ampicillin sodium is recommended because parenteral amoxicillinis not available in the United States. Individuals who are allergicto penicillins (such as amoxicillin, ampicillin, or penicillin)should be treated with the provided alternative oral regimens.Clindamycin hydrochloride is one recommended alternative. Individualswho can tolerate first-generation cephalosporins (cephalexinor cefadroxil) may receive these agents, provided they have nothad an immediate, local, or systemic IgE-mediated anaphylactic allergicreaction to penicillin. Azithromycin or clarithromycin are alsoacceptable alternative agents for the penicillin-allergic individual,⁶¹although they are more expensive than the other regimens. Whenparenteral administration is needed in an individual who isallergic to penicillin, clindamycin phosphate is recommended;cefazolin may be used if the individual does not have an immediatetype local or systemic anaphylactic hypersensitivity to penicillin.The previous recommendations from this committee listed erythromycinas an alternate agent for the penicillin-allergic patient. Erythromycinis no longer included because of gastrointestinal upset andcomplicated pharmacokinetics of the various formulations.⁶²Practitioners who have successfully used erythromycin for prophylaxisin individual patients may choose to continue with this antibiotic.The regimen is included in our previous recommendations.¹

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Table 4. Prophylactic Regimens for Dental, Oral, Respiratory Tract, or Esophageal Procedures¹ ²² ⁵⁹ ⁶⁰ ⁶¹

Regimens for Genitourinary and Nonesophageal Gastrointestinal Procedures
Bacterial endocarditis that occurs following genitourinary and gastrointestinaltract surgery or instrumentation is most often caused by Enterococcusfaecalis (enterococci). Although gram-negative bacillary bacteremiamay follow these procedures, gram-negative bacilli are onlyrarely responsible for endocarditis. Thus, antibiotic prophylaxisto prevent endocarditis that occurs following genitourinaryor gastrointestinal procedures should be directed primarilyagainst enterococci.

Table 5 ¹ ²² outlines the recommended regimens for prophylaxisfor genitourinary or gastrointestinal tract procedures (excludingesophageal procedures). The committee continues to recommendparenteral antibiotics, particularly in high-risk patients.In medium-risk patients requiring prophylaxis, a parenteral (ampicillin)or oral (amoxicillin) regimen is provided. For procedures inwhich prophylaxis is not routinely recommended, physicians may chooseto administer prophylaxis in high-risk patients.

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Table 5. Prophylactic Regimens for Genitourinary/Gastrointestinal (Excluding Esophageal) Procedures²²

Specific Situations and Circumstances

Patients Already Receiving Antibiotics
Occasionally, a patient may be taking an antibiotic when comingto the physician or dentist. If the patient is taking an antibiotic normallyused for endocarditis prophylaxis, it is prudent to select a drugfrom a different class rather than to increase the dose of the currentantibiotic. In particular, antibiotic regimens used to prevent therecurrence of acute rheumatic fever are inadequate for the preventionof bacterial endocarditis. Individuals who take an oral penicillinfor secondary prevention of rheumatic fever or for other purposesmay have viridans streptococci in their oral cavities that are relativelyresistant to penicillin, amoxicillin, or ampicillin. In suchcases, the physician or dentist should select clindamycin, azithromycin,or clarithromycin (Table 4) for endocarditis prophylaxis. Becauseof possible cross-resistance with the cephalosporins, this classof antibiotics should be avoided. If possible, one could delay theprocedure until at least 9³³ to 14³⁴ days after completionof the antibiotic. This will allow the usual oral flora to bereestablished.

Procedures Involving Infected Tissues
Incision and drainage or other procedures involving infected tissuesmay result in bacteremia with the same organism causing the infection.In individuals at risk for endocarditis (the high- and moderate-riskcategories in Table 1), it is advisable to administer antimicrobialprophylaxis before the procedure. Prophylaxis should be directedat the most likely pathogen causing the infection. For nonoral softtissue infections (cellulitis), or bone and joint infections (osteomyelitisand pyogenic arthritis), an antistaphylococcal penicillin orfirst-generation cephalosporin is an appropriate choice. Forpatients who are allergic to penicillins, clindamycin is an acceptablealternative. For those unable to take oral antibiotics or whoare known to have methicillin sodium–resistant Staphylococcusaureus bacteremia, vancomycin is the regimen of choice. ForUTI, agents active against enteric gram-negative bacilli (suchas aminoglycosides or third-generation cephalosporins) are advisable.

Patients Who Receive Anticoagulants
Intramuscular injections for endocarditis prophylaxis shouldbe avoided in patients who receive heparin. The use of warfarinsodium is a relative contraindication to intramuscular injections. Intravenousor oral regimens should be used whenever possible.

Patients Who Undergo Cardiac Surgery
A careful preoperative dental evaluation is recommended so that requireddental treatment can be completed before cardiac surgery wheneverpossible. Such measures may decrease the incidence of late postoperativeendocarditis.

Patients who have cardiac conditions that predispose them to endocarditisare at risk for developing bacterial endocarditis when undergoingopen heart surgery. Similarly, patients who undergo surgery forplacement of prosthetic heart valves or prosthetic intravascularor intracardiac materials are also at risk for the developmentof bacterial endocarditis. Because the morbidity and mortalityof endocarditis in such patients are high, perioperative prophylacticantibiotics are recommended. Endocarditis associated with openheart surgery is most often caused by S aureus, coagulase-negativestaphylococci, or diphtheroids. Streptococci, gram-negativebacteria, and fungi are less common. No single antibiotic regimenis effective against all these organisms. Furthermore, prolongeduse of broad-spectrum antibiotics may predispose to superinfectionwith unusual or resistant micro-organisms. Prophylaxis at thetime of cardiac surgery should be directed primarily againststaphylococci and should be of short duration. First-generationcephalosporins are most often used, but the choice of an antibioticshould be influenced by the antibiotic susceptibility patternsat each hospital. For example, high prevalence of infectionby methicillin-resistant S aureus in a particular inpatientunit should prompt consideration of vancomycin for perioperativeprophylaxis. It should be noted, however, that although themajority of nosocomial coagulase-negative staphylococci exhibitthe methicillin-resistance phenotype in vitro, endocarditisprophylaxis with first-generation cephalosporins is effectivefor most patients undergoing cardiac valve surgery.⁶³ Prophylaxiswith the chosen antibiotic should be started immediately beforethe operative procedure, repeated during prolonged proceduresto maintain levels intraoperatively, and continued for no morethan 24 hours postoperatively to minimize emergence of resistant micro-organisms.The effects of cardiopulmonary bypass and compromised postoperativerenal function on antibiotic levels in the serum should be consideredand doses timed appropriately before and during the procedure.

Status Following Cardiovascular Procedures
Many reparative cardiac procedures do not modify the patient’slong-term risk for infective endocarditis, which continues indefinitely(Table 1). In the case of prosthetic valve replacement, therisk of endocarditis increases postoperatively. In other conditions,such as closure of ventricular septal defect or patent ductusarteriosus without residual leak, the risk of endocarditis diminishesto the level of the general population after a 6-month healingperiod. Data are insufficient to make recommendations for prophylactictherapy after closure of these lesions by transcatheter devices.There is no evidence that coronary artery bypass graft surgeryintroduces a risk for endocarditis. Therefore, antibiotic prophylaxisis not needed for individuals who have previously undergonethis procedure. Noncoronary vascular grafts may merit antibioticprophylaxis for the first 6 months after implantation.

There are insufficient data to support recommendations for patientswho have had heart transplants. However, such patients are at riskof acquired valvular dysfunction, especially during episodesof rejection. Because of this, and the continuous use of immunosuppressionin such patients, most transplant physicians administer prophylaxisaccording to regimens for the moderate-risk category

Other Considerations

A case of endocarditis, perceived as result of failure to administera recommended prophylactic regimen, requires careful analysis.It is important to consider the following factors: (1) the timeperiod between the putatively responsible invasive procedureand the onset of clinical symptoms compatible with endocarditis;(2) the etiologic organism causing endocarditis; (3) the likelihoodthat the putative invasive procedure resulted in bacteremia; and(4) knowledge by the patient of the presence or severity ofthe underlying lesion and communication of this informationto the treating physician or dentist prior to the procedure.Most cases of procedure-related endocarditis occur with a shortincubation period of approximately 2 weeks or less followingthe procedure.⁶⁴ A longer incubation period between the invasiveprocedure and the onset of symptoms significantly lessens thelikelihood that the procedure was the proximate cause of theendocarditis. A national registry established by the AmericanHeart Association in the early 1980s analyzed 52 cases of apparentfailures of endocarditis prophylaxis.⁶⁵ Only 6 (12%) of the52 cases had received prophylactic regimens that were currentlyrecommended by the American Heart Association. The vast majorityof endocarditis due to oral organisms is not related to dentaltreatment procedures.²⁴ ²⁷ One recent large-scale, population-based, case-controlstudy, done in 54 Philadelphia area hospitals from 1988 to 1990,was unable to demonstrate any independent risk for endocarditis attributableto prior dental treatment.⁶⁶ In addition, it is unlikely thatcases of viridans streptococcal endocarditis would complicateinvasive nonesophageal gastrointestinal or genitourinary procedures.Similarly, enterococcal endocarditis would be a very unusualconsequence of dental procedures.

The use of prophylactic antibiotics to prevent infection of jointprostheses during potentially bacteremia-inducing proceduresis not within the scope of issues addressed by this committee.

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Figure 1. Clinical approach to determination of the need for prophylaxis in patients with suspected mitral valve prolapse. For more details on the role of echocardiography in the diagnosis of mitral valve prolapse, see the text and the 1997 American College of Cardiology/American Heart Association guidelines for the clinical application of echocardiography.²³

Acknowledgments

The authors thank Jeanette Allison for her superb secretarialskills.

Footnotes

“Prevention of Bacterial Endocarditis” was approved by the AmericanHeart Association Science Advisory and Coordinating Committeein October 1996, and published in the June 11, 1997 issue ofthe Journal of the American Medical Association. It is reprintedin Circulation with permission. The Council on Scientific Affairsof the American Dental Association has approved the statementas it relates to dentistry. The American Society for GastrointestinalEndoscopy has approved the statement as it relates to gastroenterology.

A single reprint is available by calling 800-242-8721 (US only)or writing the American Heart Association, Public Information,7272 Greenville Avenue, Dallas, TX 75231-4596. Ask for reprintNo. 71-0117. To purchase additional reprints: up to 999 copies,call 800-611-6083 (US only) or fax 413-665-2671; 1000 or morecopies, call 214-706-1466, fax 214-691-6342, or

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