Prevention of Endocarditis

Antibiotic prophylaxis aims to reduce the incidence of infective endocarditis.¹

Antibiotic prophylaxis for infective endocarditis aims to work at one of three steps in the pathogenic process:

• Killing the pathogen in the bloodstream before it can adhere to the heart valve.
• Preventing adherence of bacteria to the thrombus forming on the valve.
• Eradicating organisms that do attach to the thrombus.

Infective endocarditis is a serious condition and often difficult to diagnose. This can be appreciated from the linked article on infective endocarditis.² However:

• Guidelines for use of antibiotic prophylaxis of infective endocarditis have been developed often with international consensus.³ It should be remembered that:
  • They are unproven by randomised controlled trials.¹
  • Even when guidelines are followed appropriately they may fail to prevent infective endocarditis.²
  • The guidelines exist to guide and inform, but may occasionally be modified to fit particular circumstances.²
• The scope for prevention is limited:
  • Only 15-20% of cases of infective endocarditis result from the bacteraemia produced by an invasive procedure.
  • Only half of patients developing infective endocarditis after invasive procedures were identified beforehand as candidates for antibiotic prophylaxis.
  • This means that only 10% of all cases of infective endocarditis can be prevented by prophylactic antibiotics.

Guidelines are shaped by a number of important factors:

• It is important to identify at risk patients. Patients at high, moderate and low risk of infective endocarditis can be identified:
  • Highest risk patients include:
    • Those with all types of prosthetic valve
    • Previous infective endocarditis
    • Surgically produced systemic or pulmonary shunts
    • Congenital cyanotic heart disease
  • Moderate risk patients are:
    • Congenital cardiac conditions(other than cyanotic) but excluding isolated atrial septal defects (ASD) and surgical repairs of ASD or patent ductus arteriosus over 6 months ago
    • Bicuspid aortic valves
    • Acquired valve disease including rheumatic heart disease and calcific aortic stenosis
    • Hypertrophic cardiomyopathy
    • Mitral valve prolapse with regurgitation and with or without thickened leaflets
  • Low risk patients include:
    • Mitral valve prolapse without significant regurgitation
    • Implanted pacemakers, defibrillators and coronary stents
    • Innocent murmurs (except elderly patients where this may represent an at risk calcified leaflet)
• It is important to identify the procedures which require prophylaxis. Different procedures carry different risk and type of bacteraemia (and subsequent infective endocarditis):
  • High/moderate risk procedures include invasive respiratory tract manipulation (for example tonsillectomy and rigid bronchoscopy), gastrointestinal surgery, biliary surgery, urological surgery (including prostate surgery, cystoscopy and even urethral dilatation).¹
  • Low risk procedures not requiring prophylaxis include:
    • Most gynaecological procedures ranging from hysterectomy to insertion and removal of intrauterine devices where there is no infection
    • Vaginal deliveries and caesarean section
    • Cardiac catheterisations and angioplasties
    • Endoscopy with or without biopsy (note that ERPC with biliary obstruction, dilatation of oesophageal strictures, and injection of varices are moderate risk procedures)
• It is important to select an appropriate antibiotic or combination of antibiotic. These should be taken correctly at an appropriate time and dose. Bactericidal drugs are often used although bacteristatic drugs can be used effectively.

Good oral hygiene is very important and good dental care should be facilitated. Patients with a cardiac anomaly putting them at risk of endocarditis should be referred for dental assessment. Any interventions should be performed at least 14 days before surgery to allow mucosal healing. If surgery is performed as an emergency before dental assessment can be made, the assessment should be made at the earliest opportunity after surgery. Elective dental procedures should be delayed for 3 months post-surgery.

Prophylaxis for dental procedures

For high risk patients prophylaxis should be given for all dental procedures involving dento-gingival manipulation or endontics. Streptococci are in theory the most likely organisms. However it has recently been concluded that there is no evidence to support the use of antibiotics to prevent endocarditis in dental procedures.¹ However there is reluctance to give up prophylaxis and definitive trials balancing risk and benefit are unlikely to be forthcoming. However it should be restricted to only those at high risk of endocarditis (previous endocarditis, cardiac valve replacements, surgical systemic or pulmonary shunts).

Endocarditis prophylaxis for non-dental procedures

This is likely to be the most important form of prophylaxis and a cautious approach has been taken.¹ Enterococci, streptococci and staphylococci are the most prominent organisms. All patients at risk (high and medium) should be given prophylaxis.¹ Different procedures have been looked at to see what percentage of different procedures are associated with bacteraemia and whether anecdotally procedures are associated with endocarditis.¹ This enables possible high risk procedures (see above) to be identified.

General measures and health education have enormous potential to prevent infective endocarditis. For example:

• Education of patients to inform doctors and health care workers of the need for prophylaxis and any underlying diagnosis.
• Since gingivitis is the commonest cause of spontaneous bacteraemia, meticulous oral hygeine is important. Similarly, attention to skin hygeine is important in prevention.
• Many cases of hospital-acquired infection can be prevented by better asepsis during handling and insertion of vascular catheters, and prompt removal if infected. Poor hospital hygeine has been blamed for the rise in MRSA.
• Needle-exchange programmes, education, and addiction treatment for drug-abusers.