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on their excellent paper that showed no significant increase in infective endocarditis (IE) following the 2007 AHA guidelines that recommend discontinuation of antibiotic prophylaxis (AP) for “moderate-risk” patients.
However, we note the falls in native valve predisposing conditions (nonrheumatic valvular disease plus chronic rheumatic heart disease) and streptococci-associated IE—the groups most likely to be affected by stopping AP for moderate-risk patients, plateau or even rise after 2007 (Fig. 1, data extracted using DigitizeIt).
Figure 1Proportion of cases due to native valve heart disease or streptococci—from the paper by Mackie et al.
Lack of prescribing data makes it difficult to evaluate the presence or absence of a causal relationship between changes in AP guidelines and the magnitude and timing of changes in IE incidence. Nonetheless, most studies assessing the effect of restricting AP to those at high risk show no, or minimal, impact.
Although other studies examined the cessation of AP for moderate-risk patients, our studies are the only ones that examined cessation of AP for those at high risk as well. Furthermore, our incidence data were coupled with data quantifying the fall in AP prescribing. Although we agree that it is unlikely that all the IE incidence increase we observed was due to guideline change, we did not find evidence that population-based changes confounded the results—as the editorial suggests.
Most studies examining the effects of restricting AP to high-risk patients support the AHA guidelines. Our data also support these guidelines but suggest that stopping AP altogether, as occurred in the UK, could be a step too far and carry significant risk for patients.
Although the 2015 NICE guideline review referred to in the editorial decided to maintain its guidance, the European Society of Cardiology, which produces guidance for the whole of Europe, examined the same evidence and drew the opposite conclusion—strongly recommending continuation of AP for high-risk patients. The NICE review was controversial in the UK, particularly because it did not appear to consider the risk of its decision for patients.
The result is confusion about which guidelines to follow. Recent changes in UK law, however, require that patients are provided with all the information they need to make a decision for themselves
In 2007, the American Heart Association (AHA) published revised guidelines for infective endocarditis (IE) prophylaxis. Population-based data with respect to the potential impact of these revised guidelines are lacking.
The practice of using antibiotic prophylaxis before dental procedures dates back to the early days of antibiotics, when Northrop and Crowley—2 oral surgeons—were interested in the relationship of dental procedures to infective endocarditis (IE).1 They found that only a minority of patients with IE had a preceding dental procedure. However, they also demonstrated that antibiotics preceding dental procedures could reduce the incidence of bacteremia. In what now can only be considered a leap of faith, they concluded that there was a “responsibility” to administer antibiotics before dental procedures in individuals at risk for IE.
We appreciate the interest of Professor Thornhill and colleagues regarding our analysis of infective endocarditis (IE) hospitalizations before and after the 2007 American Heart Association (AHA) prophylaxis guidelines.1
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