Commentary for Prevention of Viridans Group Streptococcal Infective Endocarditis

There is both lingering uncertainty and wide practice variation among medical and dental professionals in the application of clinical practice guidelines for the prevention of infective endocarditis. It is widely recognized that the American Heart Association, after careful review and broad input, pivoted away from prior recommendations in 2007 with publication of revised guidelines that restricted the use of prophylactic antibiotics to patients at highest risk of major complications from infective endocarditis undergoing dental procedures involving manipulation of gingival tissue or the periapical region of teeth or perforation of the oral mucosa¹. Four high risk groups were identified, namely patients with a prior history of endocarditis, those with prosthetic heart valves or annuloplasty rings, selected patients with congenital heart disease and cardiac transplant recipients with acquired valvulopathy. These guidelines acknowledged the lack of randomized controlled trials to inform practice and emphasized the need for long-term dental hygiene, especially when considered from the perspective that infective endocarditis is more likely to develop from transient bacteremia related to daily activities (chewing, brushing, flossing) than from a single dental procedure. The guidelines recommended against the use of prophylactic antibiotics for moderate-risk patients (such as those bicuspid aortic valve disease or mitral valve prolapse) and for patients of any risk group prior to non-dental procedures including upper endoscopy, colonoscopy or cystoscopy. In 2008, the National Institute for Health and Care Excellence (NICE) recommended against the use of antibiotic prophylaxis for any patient undergoing a dental procedure², but later revised this prohibition in 2016 with the statement that prophylaxis should not be given routinely prior to dental procedures, thus leaving room for clinical judgement and shared decision-making with patients with deference to individual values and preferences³. The 2015 European Society of Cardiology guideline recommendations for antibiotic prophylaxis mirror those of the 2007 American Heart Association document, except for the lack of a recommendation for cardiac transplant recipients with acquired valvulopathy⁴. Implicit across all sets of recommendations is the understanding that dental prophylaxis is only targeted against oropharyngeal pathogens, of which the viridans group streptococci are the most important species. Accordingly, dental prophylaxis cannot address the scourge of injection drug use related endocarditis or intra-cardiac infections that arise from other community or nosocomial sources.

Clinicians will be reassured by reading the 2021 American Heart Association Scientific Statement on the Prevention of Viridians Group Streptococcal Infective Endocarditis, if only to learn that no changes to the 2007 guideline recommendations are required after an interim literature review and expert writing committee adjudication. The writing committee again emphasizes that there are no prospective randomized trials to establish (or refute) the efficacy of antibiotic prophylaxis prior to dental procedures. Although the overall incidence of infective endocarditis has increased over recent years, the writing committee found no convincing epidemiologic evidence of an increase in viridans group streptococcal infection since publication of the 2007 guideline recommendations. Their updated review highlights the excess risk of adverse outcomes from endocarditis among the previously identified high-risk patient groups, although robust data for immunocompromised transplant valvulopathy patients are lacking. Potential downside risks of antibiotic prophylaxis are acknowledged, including adverse drug reactions and the emergence of drug resistance. Clindamycin is generally to be avoided in penicillin allergic patients. Azithromycin, in the absence of QTc prolongation, should be considered in this circumstance.

Another important take home message from the Scientific Statement is the observed variability in awareness of and adherence with the 2007 guideline recommendations. It is widely acknowledged that some clinicians have continued their prior prescribing patterns for moderate or low-risk patients undergoing dental (and in some cases, non-dental) procedures. More worrisome, however, is the observation that antibiotics may not be prescribed for a sizeable proportion of high-risk patients undergoing dental procedures. Clearly, continued educational efforts targeted at clinicians and patients are required to close important treatment gaps.

It is doubtful that a randomized trial of antibiotic prophylaxis will ever be performed. Accordingly, practice recommendations must stem from the best available observational evidence scrutinized by a panel of trusted experts and interested stakeholders, such as that assembled to revisit this important issue.