Knowledge versus consensus: the endocarditis prophylaxis paradigm



Antibiotic prophylaxis against endocarditis used to be implemented according to outdated ideas, based on the limited knowledge available in previous times [1, 2]. Identification of streptococci of oral origin in cases of endocarditis was associated with the demonstration that patients often had poor dental condition. When receiving dental care, they develop bacteraemia. These facts convinced doctors and dentists of the need to implement antibiotic prophylaxis during dental care, and this became the basis of an international consensus, which was thus based on deduction instead of evidence.

Since then, many things have changed. It was found that the oral streptococcal bacteraemia occurred on multiple occasions [3, 4]. It was estimated that, over 1 year, the cumulative everyday-risk of bacteremia was 6 million times higher than bacteremia from a dental extraction [5].

In addition, the risk of having endocarditis is dependent on the type of valve disease; this led to the risk being put aside and thus to base antibiotic prophylaxis being prescribed according to the type of underlying valvulopathy. Finally, indications for antibiotics have been extended to different risks of bacteraemia, always by deduction, including various invasive procedures, and endoscopies in particular.

In fact, given the low incidence of endocarditis, it is impossible to demonstrate that antibiotic prophylaxis is really protective, given the dramatic number of patients needed to be included in such a randomized study [6]. Therefore there will never be evidence that antibiotic prophylaxis protects against endocarditis [7]. Moreover, it was shown that low-grade bacteraemia can also cause endocarditis [8].

Under these conditions, antibiotic prophylaxis may simply be abandoned, but this would be so much against the grain of what appeared to be obvious, that different cultures have reacted in different ways and different speeds to this challenge of the 21st century.

Among the most radical structures, the National Institute of Health and Clinical Excellence (NICE) no longer offers any prophylaxis, whatever the patient's situation and whatever action is proposed [9]. Others continue to recommend antibiotic prophylaxis for dental care and other invasive treatments, including patients with a low risk of endocarditis [10, 11]. Finally, some find a middle-of-the-road solution, providing antibiotic prophylaxis only for patients with a high risk of endocarditis and for most invasive procedures [12].

What should the clinician do in such conditions?

We are no longer within a scientific debate that knowledge may solve, because there is little chance to demonstrate the effectiveness of antibiotic prophylaxis. However, given the cultural background, and in order to avoid law suits [13], the clinician must adapt to national consensus, even though this consensus reflects the cultural orientation of society rather than a choice based on evidence.