Antibiotic Limits in 2007 Endocarditis Guidance 'About Right'

June 11, 2012

June 11, 2012 (Rochester, Minnesota) — There has been no increase in the incidence of infective endocarditis (IE) in patients with specific underlying cardiac conditions, despite what was considered a "sea change" in AHA recommendations in 2007, whereby antibiotic prophylaxis for this--previously given to all considered "at risk"--was restricted to just four very high-risk groups, new research published online today in Circulation shows [1].

The findings show that the updated recommendations are "about right," says lead author Dr Daniel C DeSimone (Mayo Clinic, Rochester, MN). "There remained a lingering concern from the medical community that the 2007 AHA dental-prophylaxis guidelines may be leaving patients at risk for viridans group streptococci (VGS)-IE. This study aims to reduce this fear, as we found no increase in incidence of VGS-IE in our population-based study," he told heartwire .

Writing in an accompanying editorial [2], dentist Dr Peter Lockhart (Carolinas Medical Center, Charlotte, NC) says, "DeSimone and colleagues have provided further data to reinforce the trend toward a greatly decreased number of patients recommended for antibiotic prophylaxis."

There remained a lingering concern from the medical community. . . . This study aims to reduce this fear, as we found no increase in incidence of IE.

And in fact, says DeSimone, the idea that those undergoing dental procedures are most at risk of developing IE is a fallacy. "Since 1955, patients have been told that dental procedures place them at a higher risk of developing IE, when brushing your teeth, flossing, and/or chewing food is more likely to cause IE," he observes.

Lockhart agrees, adding that there is a need "for a more definitive study to determine the extent to which oral hygiene, periodontal disease, and oral bacteria are associated with IE. These data would improve our understanding of the risk factors and refocus efforts on prevention of IE to improving oral hygiene." Such data would be "immediately transferable to everyday clinical practice, and it would inform future AHA and other international guidelines on preventive strategies for IE."

First Population-Based Study in US to Look at IE Incidence Post-2007

IE is an uncommon but potentially lethal infection, and for more than 50 years, in most Western countries, administration of antibiotics as prophylaxis to patients with specific underlying cardiac conditions was routine, although often controversial. In the past 10 years, this started to change--as well as the AHA, the European Society of Cardiology now also concludes that only those patients at the very highest risk should still take preventive antibiotics. Other regulatory bodies have gone even further; UK National Institute for Health and Clinical Excellence (NICE) has concluded that nobody should receive preventive antimicrobials for these purposes any longer.

DeSimone and colleagues say that "to the best of their knowledge" their new work is the "first population-based study in the US to examine the incidence of IE in adults after the publication of the updated 2007 AHA guidelines."

Brushing your teeth, flossing, and/or chewing food is more likely to cause IE.

Population-based investigations are "critical" in the evaluation of IE-prevention practices, they add, because there are no prospective randomized placebo-controlled trials to evaluate the risk of IE attributable to dental procedures or the efficacy of antibiotic prophylaxis in this setting, and the likelihood of such trials being conducted "is low."

The researchers analyzed local hospital discharge records in the Rochester Epidemiology Project. Olmstead County was used because of its unique medical records linkage system that encompasses all residents of the county. They also evaluated national rates using the US Nationwide Inpatient Sample (NIS)

Over a 12-year period--from the beginning of 1999 to the end of 2010--22 patients in Olmsted County were diagnosed with IE. Rates of incidence (per 100 000 person-years) during time intervals of 1999–2002, 2003–2006 and 2007–2010 were 3.19, 2.48, and 0.77, respectively (p=0.061).

The national annual IE diagnosis rates showed no increase either, ranging from 15 300 to 17 400 in 1999–2006 (before the updated guideline) to 14 700 to 15 500 in 2007–2009 (after the updated guideline).

"On the basis of data complete through 2010, there has been no perceivable increase in the incidence of IE in Olmsted County, Minnesota, since the publication of the 2007 AHA endocarditis prevention guidelines," DeSimone et al conclude.

Findings Support a Similar UK Study

We were giving preventive antibiotics like we were treating an entire iceberg, when we only needed to treat the very tip of that iceberg.

They add that these findings support three other previous investigations of this issue. The first was their own, earlier, evaluation of the NIS database from 1999 to 2009; the second was a preliminary hospital-based US survey published in 2008 that found that the number of patients with IE before and after the new AHA guidance had not changed.

"The third and most supportive study is from NICE," the researchers note. Using the UK national database [3], scientists there found a 78.6% reduction in the prescribing of antibiotic prophylaxis after the introduction of the 2008 NICE guidelines, "yet they did not detect a significant increase in the number of IE cases above the long-term baseline trend during their study period."

"We were giving preventive antibiotics like we were treating an entire iceberg, when we only needed to treat the very tip of that iceberg. These findings are reassuring," DeSimone says.

But he adds that further studies from across the US are still needed, because of the limitations of this work. For example, the majority of Olmsted County residents are white, so the results may not hold true for nonwhite populations.

DeSimone has no conflicts of interest; disclosures for the coauthors are listed in the paper. Lockhart declares no conflicts of interest.

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