The principle of antibiotic prophylaxis for infective endocarditis (IE) was developed from observational studies and animal models and aimed at preventing the attachment of bacteria onto the endocardium after transient bacteraemia following invasive procedures. Historically antibiotic prophylaxis was recommended in a large number of patients with predisposing conditions undergoing a wide range of procedures.
In the 2009 European Society of Cardiology (ESC) guidelines antibiotic prophylaxis was restricted for use in the highest-risk patients only (patients with the highest incidence of IE and/or highest risk of adverse outcome from IE). Latest ESC guidelines published in 2015 maintain this principle of antibiotic prophylaxis for high-risk patients (1,2). The reasons for restricting antibiotic prophylaxis included changes in pathophysiological conceptions and risk-benefit analyses as follows:
- Bacteraemia occurs daily during tooth brushing.
- The risk of IE following dental procedures is low.
- Most case-control studies do not report an association between dental procedures and IE.
- Antibiotic administration carries a low risk of anaphylaxis.
- Widespread antibiotic use may result in resistant micro-organisms.
- Prospective randomized controlled trial data is lacking.
In the UK, the National Institute for Health and Care Excellence (NICE) went a step further and advised against any antibiotic prophylaxis for dental and non-dental procedures whatever the patient’s risk (3). The authors concluded that there was an absence of benefit of antibiotic prophylaxis which was cost ineffective, although this conclusion has been challenged subsequently, since estimations of the risks of IE are based on low levels of evidence due to multiple extrapolations.
A recent analysis of UK data published in the Lancet in 2015 showed a decrease in prescriptions for antibiotic prophylaxis and a significant increase in the incidence of IE in both high-risk and lower-risk patients which started in 2008, the same year that NICE issued its guidance against antibiotic prophylaxis in all patients. By 2013 there were 35 more cases of IE reported per month than would have been expected based on the trend prior to the change in NICE guidelines (4). It has been argued that this temporal relationship cannot establish a causal relationship and it may be influenced by confounding factors, but the dramatic increases are concerning.
- Habib G, Hoen B, Tornos P et al. Guidelines on the prevention, diagnosis, and treatment of infective endocarditis (new version 2009): the Task Force on the Prevention, Diagnosis, and Treatment of Infective Endocarditis of the European Society of Cardiology (ESC). Endorsed by the European Society of Clinical Microbiology and Infectious Diseases (ESCMID) and the International Society of Chemotherapy (ISC) for Infection and Cancer. Eur Heart J 2009;30:2369–2413.
- Habib G, Lancellotti P, Antunes MJ et al. 2015 ESC Guidelines for the management of infective endocarditis: The Task Force for the Management of Infective Endocarditis of the European Society of Cardiology (ESC). Endorsed by the European Association for Cardio-Thoracic Surgery (EACTS) and the European Association of Nuclear Medicine (EANM). Eur Heart J 2015 Aug 29 (Epub ahead of print).
- Prophylaxis against infective endocarditis: antimicrobial prophylaxis against infective endocarditis in adults and children undergoing interventional procedures (CG64). National Institute for Health and Care Excellence (NICE). http://www.nice.org.uk/guidance/CG64.
- Dayer MJ, Jones S, Prendergast B et al. Incidence of infective endocarditis in England, 2000 – 13: a secular trend, interrupted time-series analysis. Lancet 2015;385:1219-1228.
Antibiotic Prophylaxis for Endocarditis
Up until the last decade it was standard teaching and practice for all patients with valvular disease to have antibiotic prophylaxis prior to any invasive procedure. The procedure that affected most patients were dental procedures. However, with increased antibiotic resistance worldwide, institutions around the world were keen to understand and re-rationalise this process. It was difficult to find studies that could prove that giving antibiotics prior to invasive procedures did reduce the risk of endocarditis. Between 2007 and 2009, the American Heart Association and the European Society of Cardiology posted new guidelines for antibiotic prophylaxis. Both guidelines set were broadly similar. They advised restriction use for endocarditis prophylaxis only to high risk patient. These were patient with congenital heart disease, prosthetic valves, significant valvular heart disease and patients with other prosthetic material within the heart such as pacing leads and defibrillators. This has led to significantly reduced usage of antibiotic prophylaxis. The overall incidence of endocarditis does continue to rise worldwide, but the rate of rise in North America and most parts of Europe has not changed since the new antibiotic guidelines were issued. In the United Kingdom, the National Institute for Clinical Excellence have placed more restrictions on patients that should be offered antibiotic prophylaxis than the European and North American guidelines. This has led to significant reductions in antibiotic usage but the trends within the United Kingdom are that the incidence of endocarditis has increased since these guidelines have been instituted.
Given the different guidelines and the differing evidence-base, it is understandable that clinicians working day to day still remain slightly confused as to what advice we should be following. I would suggest based on the evidence we have, that we continue to adopt the North American and European guidelines for antibiotic prophylaxis. Firstly, it should always be the operator who will know how invasive their particular procedure is. If they feel that this will be generally invasive, I think they should always consult with the local Consultant Cardiologist on individual cases. My own practice is that I do advocate antibiotic prophylaxis for patients with previous valve surgery, congenital heart disease, a significant organic valvular disease and patients with pacemakers or defibrillators. For other groups, I do not advocate antibiotic prophylaxis in keeping with guidelines.