Infective endocarditis is a rare condition with an incidence of less than 10 per 100 000 population/year. It is, however, associated with a high mortality and morbidity. Accepted clinical practice has been to use antibiotic prophylaxis in those at risk of infective endocarditis undergoing dental and certain non-dental interventional procedures, in the belief that this may prevent its development. The effectiveness of such antibiotic prophylaxis in humans is, however, not proved1 and the recent American Heart Association guideline2 recommends a much more limited role for antibiotic prophylaxis against infective endocarditis. This article summarises the most recent guidance from the National Institute for Health and Clinical Excellence (NICE) on antibiotic prophylaxis against infective endocarditis.3

In summary, this guideline recommends that antibiotic prophylaxis to prevent infective endocarditis should not be given to adults and children with structural cardiac defects at risk of infective endocarditis undergoing dental and non-dental interventional procedures. The basis for this recommendation is:

• There is no consistent association between having an interventional procedure, dental or non-dental, and the development of infective endocarditis.

• Regular tooth brushing almost certainly presents a greater risk of infective endocarditis than a single dental procedure because of repetitive exposure to bacteraemia with oral flora.

• The clinical effectiveness of antibiotic prophylaxis is not proved.

• Antibiotic prophylaxis against infective endocarditis for dental procedures is not cost effective and may lead to a greater number of deaths through fatal anaphylaxis than a strategy of no antibiotic prophylaxis.

In addition, given the difficulties of defining relative risk, a simple classification of conditions into groups at risk and those considered not to be at any risk greater than the general population was undertaken.

The detailed consideration of the evidence for this guideline is available in the full version (http://www.nice.org.uk/CG064, accessed 24 April 2008). A systematic review of the literature was undertaken and a health economic model for dental antibiotic prophylaxis was developed.

RECOMMENDATIONS

NICE recommendations are based on systematic reviews of best available evidence. With a rare condition such as infective endocarditis research using experimental study designs is difficult and the evidence base consists of predominantly observational studies.

PEOPLE WITH STRUCTURAL CARDIAC DEFECTS AT RISK OF DEVELOPING INFECTIVE ENDOCARDITIS

Healthcare professionals should regard people with the following cardiac conditions as being at risk of developing infective endocarditis:

• acquired valvular heart disease with stenosis or regurgitation;

• valve replacement;

• structural congenital heart disease, including surgically corrected or palliated structural conditions, but excluding isolated atrial septal defect, fully repaired ventricular septal defect or fully repaired patent ductus arteriosus, and closure devices that are judged to be endothelialised;

• previous infective endocarditis;

• hypertrophic cardiomyopathy.

[Based on moderate quality evidence from medium-sized observational studies]

PATIENT ADVICE

Healthcare professionals should offer people at risk of infective endocarditis clear and consistent information about prevention, including:

• the benefits and risks of antibiotic prophylaxis, and an explanation of why antibiotic prophylaxis is no longer routinely recommended;

• the importance of maintaining good oral health;

• symptoms that may indicate infective endocarditis and when to seek expert advice;

• the risks of undergoing invasive procedures, including non-medical procedures such as body piercing or tattooing.

[Based on the experience of the Guideline Development Group]

PROPHYLAXIS AGAINST INFECTIVE ENDOCARDITIS

Antibiotic prophylaxis against infective endocarditis is not recommended:

• for people undergoing dental procedures;

[Based on moderate quality evidence from medium-sized observational studies and small randomised controlled trials (RCTs)]

• for people undergoing non-dental procedures at the following sites*:

• • upper and lower gastrointestinal tract

  • genitourinary tract; this includes urological, gynaecological and obstetric procedures, and childbirth

  • upper and lower respiratory tract; this includes ear, nose and throat procedures and bronchoscopy.

[Based on moderate quality evidence from medium-sized observational studies, expert opinion and the experience of the Guideline Development Group]

*The evidence reviews for this guideline covered only procedures at the sites listed in this recommendation. Procedures at other sites are outside the scope of the guideline (http://www.nice.org.uk/guidance/index.jsp?action = download&o = 37136, accessed 24 April 2008).

Chlorhexidine mouthwash should not be offered as prophylaxis against infective endocarditis to people at risk of infective endocarditis undergoing dental procedures.

[Based on moderate quality evidence from small RCTs]

INFECTION

• Any episodes of infection in people at risk of infective endocarditis should be investigated and treated promptly to reduce the risk of endocarditis developing.

[Based on the experience of the Guideline Development Group]

• If a person at risk of infective endocarditis is receiving antimicrobial therapy because they are undergoing a gastrointestinal or genitourinary procedure at a site where there is a suspected infection, the person should receive an antibiotic that covers organisms that cause infective endocarditis.

[Based on the experience of the Guideline Development Group]

UNANSWERED RESEARCH QUESTIONS

Infective endocarditis is a rare condition and research in this area in the UK would be facilitated by the availability of a national register of cases.

• What is the risk of developing infective endocarditis in those with acquired valvular disease and structural congenital heart disease? Such research should use a population-based cohort study design to allow direct comparison between groups and allow estimation of both relative and absolute risk.

• What is the frequency and level of bacteraemia caused by non-oral daily activities (eg, urination or defecation)? Such research should quantitatively determine the frequency and level of bacteraemia.