Antimicrobial prophylaxis for endocarditis: Emotion or science

John A C Chalmers, Consultant Cardiac Surgeon,

Other Contributors:

February 07, 2007

Dear Editor,

As cardiac surgeons we read and reread the editorial by Ashrafian and Bogle initially with interest and subsequently bemusement looking for a definitive message. The title was clear enough; the editorial was not.

The conclusion that good practice will be served if “patients are adequately counselled on the benefits of good dental hygiene and a discussion is undertaken and documented on the risks/benefits of antibiotic prophylaxis” is superficially attractive if one ignores the practicalities of who is making the decision and on what basis. Is this the responsibility of cardiologist or dentist? Does this mean the patient agreeing to bad advice is acceptable? I agree that dental practitioners are independent practitioners and carry legal responsibility for their commission (antibiotic administration) – but omission is equally legally liable. Whose advice should they follow and on what basis?

The representative cardiological bodies in UK, USA and Europe have all published guidelines on the prevention of infective endocarditis. Their guidance is clear. The guidance from BSAC on the other hand carries with it a feeling of selfrighteousness but its position is not rational. Ideally the working party felt a prospective double blind trial should be carried out and that withholding antibiotic prophylaxis for dental procedures was radical but logical. That being the case why compromise? If there are 1.35 million dental procedures performed on “at risk” patients each year (and how reliable is that figure?) there is certainly a substantial pool available for randomisation – why not push hard for what is believed to be right?

The science of endocarditis is clear enough – valves become infected secondary to bacteraemia. The argument that rabbit models do not replicate strictly the pathogenesis of endocarditis in humans and as such the evidence is questionable confines much of 20th century progress to the intellectual dustbin. The incidence of endocarditis will depend on the organism type, the immune status of the patient and the bacteriological load. The argument that the patients with cardiac abnormalities are at risk all year round and therefore should not be covered at recognizable points when bacteraemia is predictable and can be adequately covered beggars belief. People die in cars despite or because of seatbelts – this does not render ‘belting up’ impractical or inappropriate nor reduce its effectiveness in saving lives. The risk of antibiotic related death from penicillin anaphylaxis (quoted in the editorial) as five times higher that the risk of IE is unreferenced (and in our experience unbelievable) and gives no indication of IE risk without antibiotics. Patients undergoing dental procedures develop bacteraemias with a higher bacteriological load than the background risk from chewing or brushing. Doctors and dentists cannot cover patient risk at all times. However they have a duty to reasonably cover risks that are recognizable and potentially treatable. No treatment is 100% effective: antibiotic prophylaxis should not be expected to be so. Failure to stop all events does not indicate ineffectiveness in the majority. If the philosophy followed is that the risk of dental treatment is tiny why cover any patients at all – the argument of covering patients at particularly high risk if they become infected applies to all patients not just those with prostheses or shunts. Endocarditis as a whole carries a mortality of at least 20% despite best available management. Likewise, if the background risk is so small, why should a patient who has suffered endocarditis represent a higher risk of infection than one, with equivalent pathology, who has not? This does not appear a rational stance (from a group who require hard evidence). Isn’t this emotion rather than science?

The BSAC guidelines go on to outline indications for non-dental procedures which by their own admission are “inferred by two equally unsatisfactory sources” – the chance of a procedure causing bacteraemia and whether such procedures have been anecdotally linked to endocarditis – exactly the evidence they find uncompelling in relation to dental prophylaxis. It does not appear reasonable to adopt two differing levels of proof for the same type of evidence.

Bacterial endocarditis is a severe life threatening infection with significant mortality and morbidity which despite best efforts and prophylactic therapy continues to present on a regular basis in a typical cardiological and cardiac surgical practice. Most clinicians can anecdotally confirm the association of infection following dental intervention. Appendix 1 in the BSAC guidelines states “patients should concentrate on achieving and keeping a high standard of oral and dental hygiene, as this does reduce the risk of endocarditis.” The presumption is minimisation of the level of bacteraemia associated with chewing and brushing will reduce the background risk of endocarditis. The same rational should therefore be applied to recognizable periods of increased bacteraemia.

The advice from BSAC has produced a situation where confusion reigns. Although dentists may not use the defence of the “the cardiologist made me do it” likewise “BSAC told me so” is unlikely to be more effective.

Recommendations of this nature adopted unilaterally against the best advice of representative cardiological bodies put dentists in an invidious position. They will be liable for omissions in cover and are unlikely to be supported if the treatment given runs contrary to the recommendations of the patient’s cardiologist. I would doubt clinicians outside the UK are likely to find the reasoning of BSAC compelling or defensible.

Patients deserve clear and consistent advice from their clinicians. Unfortunately the advice inherent in the guidelines and your editorial will not have helped to foster either.

Mr John AC Chalmers FRCS
Consultant Cardiac Surgeon
The Cardiothoracic Centre
Thomas Drive
Liverpool
L14 3PE

Mr D M Pullan FRCS
Consultant Cardiac Surgeon and Clinical Director
The Cardiothoracic Centre

References

1. Ashrafian H, Bogle R.
Antimicrobial prophylaxis for endocarditis: Emotion or science
Heart 2007; 93:5-6

2. Gould FK, Elliott TSJ, Foweraker J et al.
Guidelines for the prevention of endocarditis: report of the Working Party of the British Society for Antimicrobial Therapy
J Antimicrob Chemother 2006; 57: 1035-42

Conflict of Interest

None declared