Rationale for endocarditis prophylaxis
Infective endocarditis is a relatively uncommon illness with high morbidity and mortality. The incidence in Australia is approximately five cases per 100 000 person–years, and the in-hospital mortality is 15 to 20%.
For many years, antibiotic prophylaxis was routinely given before dental and other procedures to patients with cardiac conditions that have a high lifetime risk of infective endocarditis. However, endocarditis after these procedures is rare, so prophylaxis prevents very few cases.
Endocarditis-related bacteraemia is more likely to result from daily oral hygiene activities than from specific procedures, and is strongly associated with poor oral hygiene and gingival disease. Therefore, the maintenance of good oral health and hygiene is more important than the use of antibiotic prophylaxis. Oral hygiene is important for the general population but particularly for patients with a cardiac condition listed here; see General measures to prevent infective endocarditis.
Endocarditis can occur after hospitalisation, especially in older, sicker patients with diabetes or chronic kidney disease. This does not appear to be a sequel to a particular procedure but rather to problems such as intravascular catheter infections. This emphasises the need for infection prevention and control strategies in hospitals.
No randomised controlled trial has been performed to determine the role of antibiotic prophylaxis, and there are no human studies showing that it can prevent infective endocarditis. Consequently, guidelines rely on expert consensus. Since 2002, many international guidelines1 have significantly reduced the number of indications for endocarditis prophylaxis. The National Institute for Health and Care Excellence (NICE) in the United Kingdom (UK) went even further in 2008, recommending that antibiotic prophylaxis was not required for any person before dental or other procedures.
Studies examining the impact of the changes in guidelines have yielded conflicting results. Some studies indicate the incidence of infective endocarditis has not increased with restricted or no prophylaxis, but other studies suggest that infective endocarditis cases have increased after the adoption of new guidelines. In response to these data, NICE modified their recommendations in 2016 to state that endocarditis prophylaxis is not ‘routinely’ required. This update allows for clinical judgment to decide if endocarditis prophylaxis is required.
In the absence of high-quality evidence, the Antibiotic Expert Groups continue to recommend antibiotic prophylaxis against infective endocarditis for a restricted group of patients—see Indications for endocarditis prophylaxis below.