AHA Guidelines for Viridans Group Streptococcal Endocarditis Prevention

There are no recommended changes to the previously published American Heart Association (AHA) guidelines on preventing viridans group streptococcal infective endocarditis, according to the latest guideline statement published in Circulation.¹

Initial guidelines from the AHA were first published over 50 years ago. A 2007 update revisited these recommendations, challenging the “historical, but theoretical” idea that antibiotic prophylaxis would be effective against infective endocarditis caused by viridans group streptococci.² The authors of the current guidelines sought to further update and refine these suggestions.¹

In creating these updated guidelines, the AHA writing group asked several questions of import, with the following goals in mind: to review the studies published since 2007 to determine their impact on the practice guidelines, to determine if the incidence of viridans group streptococcal infective endocarditis had increased since 2007, to assess whether the changes in the 2007 guidelines remain valid, to review whether the 4 underlying cardiac conditions associated with poor outcomes should be expanded or reduced, and to suggest revisions needed based on a review of the current literature. An overview of the questions and their summarized responses are below.  

Question 1: How well were the 2007 guidelines implemented?

Two general data sources were reviewed to determine acceptance and compliance: clinician practice surveys and study results that published the compliance rates.

In a random sample survey of 5500 US dentists, more than 75% of 878 respondents indicated that they were either satisfied or very satisfied with the 2007 guidelines; however, 70% of these respondents also reported having patients who continued taking antibiotic prophylaxis despite it no longer being recommended — in particular, patients with mitral valve prolapse, due to either physician recommendation or patient preference (57% and 33%, respectively).

An additional survey of 450 dentists in Alberta, Canada, indicated a general lack of compliance among the 194 survey respondents.

Question 2: What incidence and mortality were associated with viridans group streptococcal infective endocarditis in patients with a high risk of adverse outcomes who were recommended antibiotic prophylaxis?

No high-quality data were identified to suggest an increased frequency of mortality associated with native valve viridans group streptococcal infective endocarditis in either the US or Canada following the 2007 guideline publication.

Question 3: What is the current frequency of morbidity or mortality from viridans group streptococcal infective endocarditis in the 4 high-risk groups defined in the 2007 guidelines?

The decision to include only 4 high-risk patient groups was one of the most controversial changes in the 2007 guidelines. The 4 groups, and their observed outcomes, are summarized below.

Group 1: Patients with a prosthetic cardiac valve or prosthetic material used for cardiac valve repair, or other implantable cardiac devices such as transcatheter aortic valve implantation

The mortality rate in patients with viridans group streptococcal prosthetic valve endocarditis is 20% or greater compared with 5% or less in patients with native valve viridans group streptococcal infective endocarditis. Patients with prosthetic valve endocarditis are also more likely to develop heart failure or heart block, or to require cardiac valve replacement surgery due to perivalvular extension, abscess, and other complications.

Group 2: Patients with previous, relapsed, or recurrent infective endocarditis

Patients with a history of infective endocarditis are at a higher risk of heart failure and have an increased need for cardiac valve replacement surgery, as well as a higher mortality rate compared with patients having their first episode of native valve infective endocarditis. Antibiotic prophylaxis for dental procedures is suggested in these patients.

Group 3: Patients with congenital heart disease

This is the most common underlying condition for children at risk for infective endocarditis in middle- and high-income countries. Data on infective endocarditis risk in congenital heart disease are consistent and have not demonstrated an increase in viridans group streptococcal infective endocarditis since 2007.

Group 4: People who are cardiac transplant recipients

The published data are insufficient to accurately assess adverse outcome risk in people who received a cardiac transplant and who develop valvulopathy. However, as the guideline authors note, these patients are immunosuppressed, have multiple underlying comorbidities, and are at a higher risk for adverse outcomes from any infections; antibiotic prophylaxis is suggested.

Ultimately, there is “no convincing evidence from retrospective and observational studies” demonstrating an increase in the frequency of and morbidity and mortality associated with viridans group streptococci since 2007 in these 4 high-risk groups.

However, the authors noted, “if prophylaxis is effective, we believe that such therapy should be suggested only for those with the highest risk of adverse outcomes…although we acknowledge that the effectiveness of such prophylaxis is unproven.”

Question 4: Should the current high-risk categories be expanded to include patients with rheumatic heart disease, aortic stenosis, bicuspid aortic valve, mitral valve prolapse, or other valvular heart disease?

As of 2007, antibiotic prophylaxis is no longer recommended for patients at moderate or low risk of adverse outcomes associated with viridans group streptococcal infective endocarditis.

Although infective endocarditis caused by any microorganism is a serious, life-threatening condition, complicated by the presence of comorbid factors, the administration of prophylactic antibiotics is not risk-free — even in patients who receive only 1 dose. Reclassifying risk categories would “greatly expand” the number of patients who qualify for these antibiotics for dental procedures, but the emergence of multidrug-resistant microorganisms is a serious global threat.

In answering these questions, the guideline authors considered all potential outcomes for patients. In terms of adverse outcomes, the authors noted that the “overall risks of a serious adverse reaction such as hives, angioedema, and anaphylaxis” are low when antibiotics are used as dental prophylaxis. Before any antibiotics are administered, a thorough patient history should be obtained.

Antibiotic resistance among viridans group streptococci is also of concern, with 2 particular areas of interest: (1) what is the level of resistance among viridans group streptococci as part of the normal flora; and (2) for patients who require serial invasive dental procedures over a short period, what is the likelihood that antibiotic prophylaxis will result in “the selection of antibiotic resistance among colonizing strains of [viridans group streptococci]?”

Currently, there are no high-quality analyses to evaluate the cost-effectiveness of antibiotic prophylaxis in the setting of the US health care system. Although data from the UK has shown that antibiotic prophylaxis is less costly and more effective compared with no prophylaxis at all, it is challenging to extrapolate data from one health system to another.

Key findings and suggestions of the 2021 guidelines are summarized below.

Key Findings:

• Viridans group streptococcal infective endocarditis is more likely to develop as a result of transient viridans group streptococcal bacteremia from routine daily activities than from dental procedures.
• An “exceedingly small” number of cases of viridans group streptococcal infective endocarditis could be prevented through antibiotic prophylaxis for a dental procedure, even if the prophylaxis is 100% effective.
• If antibiotic prophylaxis is effective in preventing a small number of cases, it should be suggested only in patients with the highest risk for adverse infection outcomes.
• There is no new evidence since the 2007 guidelines to show an increased frequency of morbidity or mortality from viridans group streptococcal infective endocarditis in patients at low, moderate, or high risk for adverse outcomes.
• Antibiotic prophylaxis for dental procedures is not suggested solely on the basis of an increased lifetime risk of developing viridans group streptococcal infective endocarditis.

Suggestions:

• Antibiotic prophylaxis for a dental procedure that involves the manipulation of gingival tissues, the periapical region of the teeth, or perforation of the oral mucosa is suggested only in patients with the highest adverse outcome risk from viridans group streptococcal infective endocarditis.
• Maintaining good oral health and regularly seeking dental care are more important prevention methods than using antibiotic prophylaxis for dental procedures. Biannual dental examinations are recommended when available.
• Shared decision-making between health care providers and patients is key. When patients and providers disagree, providers should understand these 2021 recommendations and appropriately inform patients of the risks and benefits of antibiotic prophylaxis.   

References

1. Wilson WR, Gewitz M, Lockhart PB, et al; American Heart Association Young Hearts Rheumatic Fever, the Endocarditis and Kawasaki Disease Committee of the Council on Lifelong Congenital Heart Disease and Heart Health in the Young, the Council on Cardiovascular and Stroke Nursing, and the Council on Quality of Care and Outcomes Research. Prevention of viridans group streptococcal infective endocarditis: a scientific statement from the American Heart Association. Circulation. Published online April 15, 2021. doi:10.1161/CIR.0000000000000969

2. Wilson W, Taubert KA, Gewitz M, et al; American Heart Association Rheumatic Fever, Endocarditis, and Kawasaki Disease Committee; the American Heart Association Council on Cardiovascular Disease in the Young; the American Heart Association Council on Clinical Cardiology; the American Heart Association Council on Cardiovascular Surgery and Anesthesia; and the Quality of Care Outcomes and Research Interdisciplinary Working Group. Prevention of infective endocarditis: 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(15):1736-1754. doi:10.1161/CIRCULATIONAHA.106.183095