Endocarditis Cases Rise After Predental Antibiotic Use Falls

Marlene Busko

November 18, 2014

Editor's note: Due to an editing error, the original title of this story was incorrect. It has now been corrected. heartwire regrets the error and any confusion it caused.

CHICAGO, IL — In a 5-year study in England, after guidelines stopped recommending prophylactic antibiotics prior to dental surgery to prevent infective endocarditis, the number of expected cases of this potentially fatal condition increased[1].

Presenting this research to the press here at American Heart Association (AHA) 2014 Scientific Sessions, senior author Prof Martin H Thornhill (University of Sheffield School of Clinical Dentistry, Sheffield, UK) cautioned, "We want to emphasize that although we have demonstrated a temporal association, we have not demonstrated a cause-effect relationship, and other explanations for the change are possible."

The study is being published online today, and "as a direct result of the publication, the National Institute for Health and Care Excellence (NICE) has issued a press release[2] indicating that practitioners should not change their practice . . . while NICE reviews the guidelines," he told heartwire . The best evidence would from a clinical trial, and "so far that trial has not happened," he added.

Dr Dhruv S Kazi (University of California, San Francisco), who was not involved in the study, told heartwire that when the most recent 2007 US AHA guidelines recommended prophylaxis for individuals at high risk (such as patients with a prosthetic heart valve), "they acknowledged that the benefits of this strategy were unknown. So it was with reluctance that they even agreed to that. The direct link between antibiotic use and protection from endocarditis is nonexistent, and there are no recommendations for a change in practice at present," he said.

"The AHA guidance wasn't so much looking at the higher risk of getting endocarditis, but it was the higher risk that if you got it you would not tolerate endocarditis well," Dr William T Mahle (Emory University School of Medicine, Atlanta, GA), also not affiliated with the study, commented. "Hopefully, as more and better data sets get linked, we will have more information about it."

Life-Threatening Heart Infection

With invasive dental procedures, Viridans streptococci may be released into the bloodstream, which may lead to infective endocarditis in susceptible individuals. Thus, as far back as 1955, a guideline recommended giving antibiotics targeting these bacteria, immediately before dental surgery.

In the UK, until 2008, antibiotic prophylaxis had been recommended for patients at high or moderate risk of endocarditis.

The researchers had an opportunity to study the impact on the UK population, before and up to 5 years after the guidelines were published.

They identified all prescriptions of a single oral dose of amoxicillin 3 g or clindamycin 600 mg (the recommended prophylaxis prior to invasive dental procedures) that were dispensed in England from January 1, 2004 to March 31, 2013. A total of 19 804 patients had been hospitalized with a primary diagnosis of infective endocarditis during that time.

Prior to the 2008 guidelines, clinicians wrote 10 900 prescriptions a month for these prophylactic drugs, and most prescriptions (90%) were written by dentists.

The rate of prescriptions fell off exponentially after the guidelines were introduced, so that by the March 2013, the average number of prescriptions fell by almost 90% (to 1307 a month).

At the same time, the number of cases of endocarditis per month rose by 0.11 cases per 10 million people in England, and by March 2013 this amounted to an extra 35 cases per month. There were 420 additional hospitalizations and 18 additional deaths related to endocarditis a year.

Time for a Definitive Trial

In an accompanying commentary in the Lancet[3], Drs Xavier Duval and Bruno Hoen (Association pour l'Etude et la Prévention de l'Endocardite Infectieuse, Paris, France) commend the study authors for "not jumping to conclusions about the causality of the link between cessation of antibiotic prophylaxis and subsequent increased incidence of infective endocarditis."

However, the findings could cause confusion. A randomized controlled trial is long overdue, they add.

"More than 20 years [after a call for a definitive study], no such study has been done. We strongly suggest that experts stop elaborating guidelines for infective endocarditis prophylaxis and urgently join forces to mount an international collaboration to do the appropriate clinical trials that are needed to answer this important question," they conclude.

The authors and editorialists have reported they have no relevant financial relationships.


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