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Antibiotic prophylaxis of endocarditis:
the rest of the world and NICE
John B Chambers1, David Shanson2, Roger Hall3, John Pepper4, Graham Venn1
On behalf of the British Valve Group
1 Cardiothoracic Centre, Guy’s and St Thomas’ Hospitals, London, UK 3 Department of Cardiology, University of East Anglia, UK 2 Department of Medical Microbiology, Great Ormond Street 4 Cardiac Surgery, Royal Brompton Hospital, London, UK Previous guidelines1,2 recommended antibiotic prophylaxis an inconsistent relationship between bacterial load and the for the majority of patients with congenital and heart valve likelihood of IE depending on the strain of alpha-haemolytic disease. Almost all current national or international guide- streptococcus. There may also be genetic differences in lines including those from the USA3,4, Europe5, and susceptibility16. These possibilities may help to explain vari- Australia6,7, have narrowed these recommendations radical- ly, but still recommend prophylaxis for certain dental proce-dures in high risk cardiac patients (Table 1). NICE8 is alone The NICE committee correctly stated that, in the absence of in recommending no antibiotic prophylaxis for any cardiac a prospective randomised clinical trial, the clinical effective- patients undergoing dental or non-dental procedures ness of antibiotic prophylaxis is not proven. However a except for manipulations at an infected non-dental site.
number of studies suggest a benefit. A Dutch case-con- Most cardiologists and cardiac surgeons still follow trolled study13, which was also the only study found eligible International guidelines rather than NICE. Is this justified? for a Cochrane review17, suggested a reduction in risk ofonly 49%. This was based on 48 cases with endocarditis The NICE committee8 based their advice on the after a dental or non-dental procedure, but, importantly, excluded high-risk patients with prosthetic valves. In astudy specifically of prosthetic valves12 there were 6 cases (1) there is no consistent association between having an of IE in 304 who were unprotected by antibiotics, but no interventional procedure, dental or non-dental, and the cases in 229 protected patients. A French study18 estimated development of infective endocarditis (IE). Regular an incidence of IE in patients with valve disease of 1 case toothbrushing almost certainly represents a greater risk per 46,000 unprotected dental procedures compared with 1 case per 149,000 protected procedures. The protectiveeffect of antibiotics has been estimated at 46%11, 49%13, (2) the clinical effectiveness of antibiotic prophylaxis is not 70%18 and 91%19. These clinical observations suggests that animal work showing the effectiveness of a single doseof amoxicillin in preventing streptococcal endocarditis20,21 (3) antibiotic prophylaxis for dental procedures may lead to a greater number of deaths through fatal anaphylaxisthan a strategy of no antibiotic prophylaxis and is not The NICE8 committee considered, but decided against, defining a high risk group, to include patients with pros-thetic valves, because it felt that this would be confusing.
Although NICE dismissed an association between a dental Patients with prosthetic valves have a 5-fold higher risk of procedure and the development of endocarditis, many of developing IE than those with native valve disease17. The the studies cited (para 2.3.2) suggest a link. A case- mortality is substantially higher, about 25% during the matched study9 of 273 patients with IE found no associa- acute event22, and up to 41% at 30 days23. Long-term sur- tion with dental work in general, but extractions occurred vival rates are only 55% at 5 years and 38% at 10 years24.
in 6 patients with IE and in no case-controls (p= 0.03).
This is largely because 10-35% of survivors need further However, only about a third had IE as a result of mouth cardiac surgery which is at markedly increased risk24,25.
organisms and the extractions were not performed in International guideline groups3-7, clinical studies11,18 and a patients with valve disease. A Dutch study showed that a study modelling cost-effectiveness26 conclude, differently combination of a heart lesion, natural dentition and a den- from NICE, that antibiotic prophylaxis, while no longer tal procedure gave a relative risk for IE of 4.910. A French generally advisable, should be focused on such high-risk case-controlled study11 showed a significant association between IE and repeated scaling and canal treatmentalthough not for all dentistry. Other studies12-14 have also The NICE committee quoted a risk of fatal anaphylaxis of found an association between IE and extraction or, less approximately 20 per million administrations of penicillin.
frequently, with root canal work. Animal models15 suggest This figure is based mainly on data published in the 1960s few patients at high risk of endocarditis (Table 1) compared when most of the subjects dying received parenteral to those with native valve disease. The cost saved by penicillin27, often to treat syphilis. There is little published adopting the NICE guidelines would therefore be relatively information on the risks of oral amoxicillin, but yellow card small. We suspect it would be offset by unnecessary deaths returns in the UK suggest that fatal anaphylaxis is extremely since there is good reason to think that antibiotic prophy- rare and the figures quoted by NICE may be an over esti- laxis may be effective in high-risk groups before high risk mate28. In the world literature there have been no reports of fatal anaphylaxis after oral amoxicillin prophylaxis forendocarditis. Patients with prosthetic valves who have There is no national surveillance programme for endocarditis received amoxicillin prophylaxis in the past without any to alert us to any potential increase in the incidence of problems are unlikely to develop anaphylaxis. Testing for prosthetic endocarditis as a result of the NICE guidelines.
In our current state of knowledge, International guidelinesthat continue to recommend antibiotic prophylaxis for high All guidelines agree that the main measure for preventing risk cardiac patients, particularly those with prosthetic IE is the maintenance of excellent oral hygiene. There are heart valves, remain preferable to NICE.
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