Time to End Antibiotic Prophylaxis for Infective Endocarditis?

Introduction

During my emergency medicine training in the early 1990s, antibiotic prophylaxis for infective endocarditis (IE) was routine for many types of patients before undergoing any one of myriad procedures. I was taught to consider prophylaxis for patients who had any type of indwelling cardiac device; prosthetic valve; congenital cardiac or valvular disorder; or acquired valvular disorder, including mitral valve prolapse or prior IE. Procedures that generally would receive prophylaxis included any major dental, gastrointestinal, genitourinary, or respiratory procedure.

If this sounds a bit vague, it was! In fact, I remember two attendings (an emergency physician and a cardiologist) discussing whether we should provide prophylaxis to high-risk patients who are undergoing various "minor" procedures, such as anoscopy, digital rectal examination, Foley catheterization, and incision and drainage of a skin abscess. It wasn't long before I learned that the indications for antibiotic prophylaxis were not based on any good literature, but rather on the beliefs and dogma of the attending with whom I was working that day.

As literature finally began to emerge, it became apparent that we were overusing antibiotics for IE prophylaxis. In 2007, the American Heart Association (AHA) published guidelines^[1] based on this improved literature. The new guidelines significantly reduced the indications for antibiotic prophylaxis, recommending them only before major dental procedures in only very high-risk patients (patients with prosthetic cardiac valves, previous IE, congenital heart disease, and cardiac transplant recipients who develop a valvulopathy).

Mackie and colleagues wanted to evaluate the impact of the 2007 AHA guidelines on the rates of IE in Canada, which adopted these guidelines. The authors used the Canadian Institute for Health Information Discharge Abstract Database to identify hospitalizations between April 2002 and March 2013 where IE was a primary diagnosis. A total of 9431 hospitalizations among 8055 patients were evaluated.

A time/trend analysis showed that there was a slight overall increase in rates of IE during the 11 years studied, which was presumed to be related to the aging of the population as well as the increased use of prosthetic valves, pacemakers, and defibrillators during the time frame. However, there was no significant change in the slope of the rise of IE before vs after the publication of the 2007 AHA guidelines. The guidelines also had no impact on the incidence of IE hospitalizations.

Viewpoint

What I found most interesting among other findings in the study was that the number of cases of IE due to streptococcal species, the organisms most likely to be increased by the reduction in antibiotic use with dental procedures, actually decreased over the 11-year period. Comparable results have been reported in France,^[2] which adopted guidelines similar to those of the AHA. This lends further support for the reduced indication for antibiotics to prevent IE.

In an accompanying editorial, Morris and colleagues^[3] point out that the UK National Institute for Health and Care Excellence in 2008 stopped recommending antibiotic prophylaxis for IE entirely, which resulted in a 79% reduction in prescribing of IE prophylaxis but no increase in IE incidence or mortality.^[4] If there has been an overall increase in cases of IE, it largely appears to be associated with staphylococci acquired through such risk factors as increases in injection drug use and the increased prevalence of prosthetic valves, pacemakers, defibrillators, and surgically repaired congenital heart disease, rather than an increase in dental microbes resulting from reduced antibiotic use.

The authors appropriately list limitations of this study, which I will not detail here. But this study and others should certainly make us question how much of a difference antibiotic prophylaxis for IE makes. To quote Morris and colleagues, "In the current era of 'antimicrobial stewardship,' [healthcare providers] should resist the urge to prescribe antibiotics with no substantive evidence of benefit."

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