MD, DDS George K B Sándor

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	 JADC	•	www.cda-adc.ca/jadc • Juin 2008, Vol. 74, No 5 • 449
Pratique
Clin ique
Prevention of Infective Endocarditis: Revised 
Guidelines from the American Heart Association 
and the Implications for Dentists
David K. Lam, DDS; Ahmed Jan, DDS;  
George K.B. Sándor, MD, DDS, PhD, FRCD(C), FRCSC, FACS;  
Cameron M.L. Clokie, DDS, PhD, FRCD(C) 
soMMAIRE
L’endocardite infectieuse est une infection microbienne rare, mais délétère, des valvules 
cardiaques ou endocarde, le plus souvent liée à des défauts cardiaques congénitaux ou 
acquis. L’American Heart Association (AHA) a récemment mis à jour ses recommanda-
tions pour la prophylaxie pendant les procédures dentaires. Les révisions auront une 
incidence profonde à la fois sur le patient et sur le dentiste. Le but du présent article est 
d’examiner la pathogenèse et le tableau clinique de l’endocardite infectieuse et de dis-
cuter des lignes directrices de 2007 de l’AHA et de leurs implications pour les dentistes.
Dr Sándor
Courriel : george.sandor@
utoronto.ca
	Auteur-ressource
Infective endocarditis is an uncommon but potentially life-threatening microbial infec-tion of the heart valves or endocardium, most 
often related to congenital or acquired cardiac 
defects. High morbidity and mortality rates 
remain associated with the infection despite 
advances in diagnosis, antimicrobial therapy, 
surgical techniques and management of asso-
ciated complications. Since the American Heart 
Association (AHA) produced guidelines on the 
prevention of infective endocarditis in 1997,1 
many groups have questioned the efficacy of an-
timicrobial prophylaxis in patients who undergo 
dental procedures and have suggested that this 
recommendation be revised.2–6 
The AHA appointed a writing group, inclu-
ding experts in the prevention and treatment 
of infective endocarditis from the American 
Dental Association, the Infectious Diseases So-
ciety of America and the American Academy 
of Pediatrics, to review input from national and 
international experts on the disease. The recom-
mendations of this group culminated in the 2007 
AHA guidelines on prophylaxis for infective en-
docarditis, which will have a profound impact 
on both patients and dental practitioners. 
The purpose of this paper is to review the pa-
thogenesis and clinical presentation of infective 
endocarditis and discuss the new guidelines on 
prophylaxis and their implications for dentists.
Pathogenesis	of	Infective	Endocarditis
Turbulent blood flow produced by certain 
types of congenital or acquired heart disease 
may traumatize the endothelium and result in 
the deposition of platelets and fibrin on the da-
maged endocardium or endothelial surface. This 
may result in the formation of sterile vegetations, 
a condition known as nonbacterial thrombotic 
endocarditis.6,7 Invasion of the bloodstream by 
Pour les citations, la version définitive de cet article est la version électronique : www.cda-adc.ca/jcda/vol-74/issue-5/449.html
450	 JADC	•	www.cda-adc.ca/jadc • Juin 2008, Vol. 74, No 5 •
–––  Sándor –––
microbes that can colonize this damaged site may result in 
infective endocarditis.
Odontogenic	Sources	of	Transient	Bacteremia
In 1909, Horder discovered an association between 
dental health and infective endocarditis, when he noted 
that “infection is grafted upon a previously sclerosed endo-
cardium... the source of the infecting agent, in most of the 
cases, is the mouth.”8 Oral mucosal surfaces are populated 
by a dense endogenous microflora. Trauma to these surfaces, 
particularly the gingival crevice around teeth, releases these 
microbial species transiently into the bloodstream.
Transient bacteremia caused by the viridans group of 
streptococci and other oral microflora commonly occurs 
during dental extractions, other procedures and even du-
ring routine daily activities.6,7 The frequency and intensity 
of the resulting bacteremias is related to the nature and ma-
gnitude of the tissue trauma, the density of microbial flora 
and the degree of inflammation or infection at the trauma 
site. The species entering the bloodstream depends on the 
endogenous microflora that colonize the traumatized site.
Microbial	Adherence
The focus of infection is determined by the ability of va-
rious microbial species to adhere to specific anatomic sites.6 
Mediators of bacterial adherence serve as virulence factors 
in the pathogenesis of infective endocarditis. Some strepto-
cocci in the viridans group contain a lipoprotein receptor 
antigen I (LraI) that acts as a major adhesin to the fibrin 
platelet matrix of nonbacterial thrombotic endocarditis.6,9
Microbial	Proliferation	within	a	Vegetation
Once attached to an anatomic focus, these microorga-
nisms stimulate further deposition of fibrin and platelets on 
their surface. Thus buried, the microorganisms can multiply 
rapidly, apparently uninhibited by host defenses.6 More than 
90% of the microorganisms in mature valvular vegetations 
are unresponsive to antibiotics as they are metabolically 
inactive.6,10
Thus, infective endocarditis arises from complex 
interactions between the bloodstream microbial pathogen 
and the matrix molecules and platelets at sites of endocar-
dial cell damage.
Clinical	Presentation	of	Infective	Endocarditis
Signs and Symptoms
The classic symptoms of infective endocarditis include 
fever, anemia, positive blood cultures and heart murmur.7 
However, diagnosis must always involve a high level of 
clinical suspicion, as these classic findings may not always 
be present (Table 1). Other symptoms may include fatigue, 
weight loss, night sweats, anorexia and arthralgia. Emboli 
may result in chest pain, abdominal pain, blindness, para-
lysis and hematuria. Petechiae may occur on skin or mu-
cosal tissues and linear hemorrhages may be visible under 
the nails. Osler’s (subcutaneous) nodes, Janeway lesions (flat, 
nontender, red spots on palms and soles that blanch on pres-
sure) and retinal hemorrhages may also be noted.
Laboratory Findings
• Leukocytosis with neutrophilia
• Increased erythrocyte sedimentation rate 
• Positive C-reactive protein 
• Increased levels of serum immunoglobulins 
• Blood cultures positive for pathogen
• Positive rheumatoid factor
Electrocardiogram Findings
• Prolonged PR interval (caused by abscess)
• Silent myocardial infarction (caused by emboli in 
coronary artery)
Echocardiography
• Vegetations
• Valvular perforations
• Other abnormalities (e.g., abscesses, pericarditis)
Prophylaxis	for	Infective	Endocarditis	during	
Dental	Procedures
Rationale for Prophylaxis 
The 1997 AHA guidelines1 recommended antimicrobial 
prophylaxis to prevent infective endocarditis among patients 
with underlying cardiac conditions who must undergo bac-
teremia-producing procedures. The recommendation was 
based on the following factors: infective endocarditis is an 
uncommon but life-threatening disease and prevention is 
Table	1 Diagnosis of infective endocarditis7
Major	criteria
Positive blood culture
Echocardiogram evidence of endocardial involvement 
New valvular regurgitation
Minor	criteria
Predisposing heart condition
Intravenous drug use
Fever
Vascular phenomena (emboli, septic pulmonary infarcts, 
mycotic aneurysm, intracranial hemorrhage, Janeway 
lesions)
Immunologic phenomena (glomerulonephritis, Osler’s 
nodes, Roth’s spots, rheumatoid factor)
Isolated blood culture or serologic evidence of active 
infection
Echocardiogram findings consistent with endocarditis 
but not diagnostic of the disease
	 JADC	•	www.cda-adc.ca/jadc • Juin 2008, Vol. 74, No 5 • 451
–––  Infective Endocarditis –––
preferable to treatment of established infection; certain un-
derlying cardiac conditions predispose patients to infective 
endocarditis; bacteremia with organisms known to cause in-
fective endocarditis is common during invasive dental pro-
cedures; antimicrobial prophylaxis is effective in preventing 
infective endocarditis in animals; and antimicrobial pro-
phylaxis was thought to be effective in preventing infective 
endocarditis associated with dental procedures in humans.
Primary Reasons for Revision of the Guidelines
Although the rationale for prophylaxis of infective 
endocarditis remains valid, it does not compensate for the 
lack of data demonstrating a benefit. Moreover, antibiotic 
prophylaxis is not risk free. Penicillins cause allergic reac-
tions among 1%–10% of patients. The risk of death from ana-
phylactic reaction is 5 times greater than that from treating 
infective endocarditis.11 Maintenance of optimal oral health 
and hygiene may reduce the incidence of bacteremia from 
daily activities and is more important than prophylactic 
antibiotics for a dental procedure in reducing the risk of 
infective endocarditis.
Revised AHA Guidelines on Prophylaxis for Infective 
Endocarditis 
In its 2007 guidelines,6 the AHA concluded that bac-
teremia resulting from daily activities is much more likely 
to cause infective endocarditis than bacteremia associated 
with a dental procedure. Moreover, they concluded that only 
an extremely small number of cases of infective endocarditis 
might be prevented by antibiotic prophylaxis even if prophy-
laxis is 100% effective. Thus, antibiotic prophylaxis is not 
Box	1	 Cardiac conditions with the highest risk of adverse 
outcome from infective endocarditis and for which 
prophylactic dental procedures are recommended6
• Prosthetic cardiac valve
• Previous infective endocarditis
• Congenital heart diseasea
- Unrepaired cyanotic congenital heart disease, 
including palliative shunts and conduits
- Completely repaired congenital heart defect with 
prosthetic material or device, whether placed by 
surgery or by catheter intervention, during the 
first 6 months after the procedureb
- Repaired congenital heart disease with residual  
defects at the site or adjacent to the site of a pros-
thetic patch or prosthetic device (which inhibit 
endothelialization)
• Cardiac transplantation with subsequent cardiac 
valvulopathy
aExcept for the conditions listed here, antibiotic prophylaxis is no longer recom-
mended for any other form of congenital heart disease.
bProphylaxis is recommended because endothelialization of prosthetic material 
occurs within 6 months after the procedure.
recommended based solely on an increased lifetime risk of 
acquisition of infective endocarditis. 
As a result, the revised guidelines were greatly simpli-
fied. The major changes include the following: infective 
endocarditis prophylaxis for dental procedures is recom-
mended only for patients with underlying cardiac condi-
tions associated with the highest risk of adverse outcome 
from infective endocarditis (Box 1). Antibiotic prophylaxis 
is no longer recommended for those with any other form of 
congenital heart disease.
Prophylaxis is recommended for all dental procedures 
that involve manipulation of gingival tissue or the periapical 
region of teeth or perforation of the oral mucosa only for 
patients at highest risk of adverse outcome from infective 
endocarditis (Box 1). Prophylaxis is no longer needed for 
routine anesthetic injections through noninfected tissue, 
dental radiographs, placement of removable prosthodontic 
or orthodontic appliances, adjustment of orthodontic ap-
pliances, placement of orthodontic brackets, shedding of 
deciduous teeth or bleeding from trauma to the lips or oral 
mucosa.
The recommended antibacterial regimens for dental pro-
cedures remain unchanged (Table 2). 
Discussion
The vast majority of cases of infective endocarditis 
caused by oral microflora likely result from random bacte-
remias caused by routine daily activities, such as chewing 
food, brushing teeth, flossing, use of water irrigation devices 
and other activities.6,7 These transient bacteremias usually 
clear within 10 minutes.7 For example, tooth brushing was 
found to introduce bacteria into the bloodstream in about 
40% of people tested7; similarly, chewing paraffin or oral 
irrigation produced transient bacteremias in 50% of people.7 
Guntheroth12 estimated that with normal physiologic use of 
the oral cavity, about 5,376 minutes of transient bacteremias 
occur each month in the average person. Thus based on the 
high frequency of physiologic bacteremias and the low inci-
dence of dental procedures preceding the onset of infective 
endocarditis, the odds of a case of infective endocarditis oc-
curring from physiologic “seeding” of oral bacteria is 1,000 
times greater than after a dental procedure.12 However, the 
presence of dental disease may increase the risk of bacte-
remia associated with these routine activities.
As health care providers, dentists must consider the 
benefits of infective endocarditis prevention along with the 
risks of administering antibiotics: adverse drug events, the 
financial cost of antibiotics, the development of bacterial 
drug resistance and medicolegal concerns. But no matter 
how we weigh the risks and benefits of prophylaxis for 
infective endocarditis, until prospective clinical trials are 
conducted, its true efficacy will remain unclear.
Based on the revised 2007 AHA guidelines,6 substan-
tially fewer patients will meet the criteria for infective en-
docarditis prophylaxis before dental procedures. The new 
452	 JADC	•	www.cda-adc.ca/jadc • Juin 2008, Vol. 74, No 5 •
–––  Sándor –––
Dr. Sándor is clinical director of the graduate program in 
oral and maxillofacial surgery and anesthesia, Mount Sinai 
Hospital; coordinator of pediatric oral and maxillofacial 
surgery, The Hospital for Sick Children and Bloorview Kids 
Rehab; professor of oral and maxillofacial surgery, University 
of Toronto, Toronto, Ontario; professor at the Regea Institute 
for Regenerative Medicine, University of Tampere, Tampere, Finland; 
and docent in oral and maxillofacial surgery, University of Oulu, Oulu, 
Finland.
Dr. Clokie is a professor and head of oral and maxillofa-
cial surgery and anesthesia, University of Toronto, Toronto, 
Ontario.
Correspondence to: Professor George K.B. Sándor, The Hospital for Sick 
Children, S-525, 555 University Avenue, Toronto, ON  M5G 1X8.
The authors have no declared financial interests.
This article has been peer reviewed.
References
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Table	2	 Prophylactic antibiotic regimens before a dental procedure6
Patient	group Antibiotic
Dose	(single,	30–60	min	before	procedure)
Adults Children
Able to take oral medication Amoxicillin 2 g 50 mg/kg 
Unable to take oral medication Ampicillin 2 g IM or IV 50 mg/kg IM or IV
OR
Cefazolin or ceftriaxone 1 g IM or IV 50 mg/kg IM or IV
Allergic to penicillins or ampicillin 
and able to take oral medication
Cephalexina,b 2 g 50 mg/kg
OR
Clindamycin 600 mg 20 mg/kg
OR
Azithromycin 
or clarithromycin
500 mg 15 mg/kg
Allergic to penicillins or  ampicillin
and unable to take oral medication
Cefazolin or ceftriaxoneb 1 g IM or IV 50 mg/kg IM or IV
OR
Clindamycin 600 mg IM or IV 20 mg/kg IM or IV
Note: IM = intramuscular, IV = intravenous.
aOr other first- or second-generation oral cephalosporin at equivalent adult or pediatric dose.
bCephalosporins should not be given to a patient who has a history of anaphylaxis, angioedema or urticaria with penicillins or ampicillin.
recommendations may understandably cause concern at 
multiple levels. There will be concern among patients who 
have previously received antibiotic prophylaxis to prevent 
infective endocarditis before dental procedures and are now 
advised that such prophylaxis is unnecessary. Moreover, 
there may be concerns amongst physicians, who in the 
past have supported antibiotic prophylaxis and may not be 
aware of the recent changes to the guidelines. There may 
be concern on the part of regulators who now must decide 
whether to modify their practice guidelines to mirror those 
of the current AHA recommendations. Similarly there may 
be initial resistance within certain hospitals to follow the 
new recommendations. 
It is thus important for dentists to be familiar with both 
the AHA guidelines and the rationale behind them. This 
will allow them to alleviate their own concerns, re-educate 
their patients about the changes and communicate effecti-
vely with their medical colleagues to optimize the continued 
safe delivery of patient care. a
THE AuTHoRs
Dr. Lam is the chief resident in the division of oral and maxillo-
facial surgery and anesthesia, Mount Sinai Hospital; Ph.D. 
Harron Scholar, Collaborative Program in Neuroscience; and 
clinician-scientist fellow at the University of Toronto Centre 
for the Study of Pain, Toronto, Ontario.
Dr. Jan is a senior resident in the division of oral and 
maxillofacial surgery and anesthesia, Mount Sinai Hospital, 
University of Toronto, Toronto, Ontario.
	 JADC	•	www.cda-adc.ca/jadc • Juin 2008, Vol. 74, No 5 • 453
–––  Infective Endocarditis –––
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Prevention of Infective Endocarditis: Revised Guidelines from the American Heart Association and the Implications for Dentists

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Prevention of Infective Endocarditis: Revised Guidelines from the American Heart Association and the Implications for Dentists

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