Incidence of Infective Endocarditis due to Viridans Group Streptococci Before and After Publication of the 2007 American Heart Association's Endocarditis Prevention Guidelines

Study Questions:

Has the 2007 revision in the American Heart Association (AHA) guidelines for antibiotic prophylaxis against infective endocarditis (IE) resulted in a change in incidence of viridans group streptococcus (VGS)-IE?


A retrospective, population-based review of all definite or possible cases of VGS-IE was performed using the Rochester Epidemiology Project of Olmsted County, MN. Patient demographics and microbiologic data were collected for all VGS-IE cases diagnosed from January 1, 1999 through December 31, 2010. The Nationwide Inpatient Sample (NIS) hospital discharge database also was examined to determine the number of VGS-IE cases that were included between 1999 and 2009.


A total of 22 cases with VGS-IE were identified in Olmsted County over the 12-year study period. Incidence rates (per 100,000 person-years) during time intervals of 1999–2002, 2003–2006, and 2007–2010, were 3.19 (95% confidence interval [CI], 1.20-5.17), 2.48 (95% CI, 0.85-4.10), and 0.77 (95% CI, 0.00-1.64), respectively (p = 0.06). The number of hospital discharges with a diagnosis of VGS-IE in the NIS database during 1999–2002, 2003–2006, and 2007–2009 ranged between 15,318–15,938, 16,214–17,433, and 14,728–15,479, respectively.


Based on data complete through 2010, the authors concluded that there has been no perceivable increase in incidence of VGS-IE in Olmsted County, MN, following publication of the 2007 AHA endocarditis prevention guidelines.


In 2007, the AHA published updated guidelines for IE prevention that markedly reduced the use of antibiotic prophylaxis in most at-risk patients undergoing dental and other invasive procedures. The guideline revision was based not on data suggesting that IE prophylaxis was ineffective or deleterious, but based on absence of data proving efficacy. Some clinicians have felt that, in the absence of compelling data for or against prophylaxis efficacy, informed patient decision making might be an appropriate (and ethical) option (see Methodist DeBakey Cardiovasc J 2010;6:48-52). Despite its conclusions, the present publication probably sheds little light on the important question of whether the 2007 guideline change has resulted in a change in IE incidence. With only 22 cases of VGS-IE diagnosed over a 12-year interval, the experience of Olmsted County is not powerful enough to have reliably detected a change in incidence of this relatively uncommon disease. This, combined with an apparent decline in the incidence of IE predating the guideline change (probably due to a change in the prevalence of at-risk valve disease) and unknown levels of adherence to the revised guidelines, leaves this important issue still open to debate.

Keywords: Viridans Streptococci, Prevalence, Incidence, Endocarditis, Demography, Cardiovascular Diseases, Confidence Intervals, Inpatients, Antibiotic Prophylaxis, United States

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