Background

Approach

The presumed benefit of antibiotic prophylaxis depends on the cardiac abnormality for which prophylaxis is being considered and the procedure causing bacteremia. Certain cardiac conditions are more susceptible to endocarditis than others; furthermore, established endocarditis is more dangerous in certain settings (such as prosthetic valves) than others. Both the risk of bacteremia and the likely organisms vary according to the procedure being performed; some organisms are more likely to cause endocarditis than others. 

As a result, the decision whether or not to prophylax and the choice of antibiotics will depend both on the cardiac abnormality and on the procedure (as well as on certain other patient-specific factors). 

Cardiac conditions

Cardiac conditions are classified into high, moderate and negligible risk. The latter category is felt not to require prophylaxis. The principal differences between the high and moderate risk categories lie in the antibiotic regimens recommended for GI and GU procedures, and in whether or not prophylaxis is needed for certain lower-risk procedures. 

• Negligible risk 


These cardiac conditions are felt not to require prophylaxis. 
 

• Isolated ostium secundum ASD and surgically repaired ASD, VSD and PDA (beyond 6 months and without sequelae). 
• Mitral valve prolapse without mitral regurgitation and without thickened leaflets. 
• Innocent or physiologic murmurs (echo required in the adult population to rule out valvular lesion). 
• Cardiac pacemakers and defibrillators. 
• History of isolated bypass surgery, history of Kawasaki disease without valvular dysfunction and history of rheumatic fever without valvular dysfunction. 

• High risk 


These conditions are: 
 

• All prosthetic heart valves (including bioprostheses and homografts). 
• Any history of previous bacterial endocarditis. 
• Complex cyanotic congenital heart disease and surgically constructed systemic pulmonary shunts. 

• Moderate risk 


Most cardiac conditions requiring prophylaxis will fall into this category. 
 

• Congenital cardiac malformations, not falling into the high or negligible risk categories (such as PDA, VSD, ostium primum ASD, bicuspid aortic valve and coarctation). 
• Acquired valvular heart disease (such as rheumatic heart disease, valvular stenosis and regurgitation). 
• MVP with regurgitation and/or myxomatous leaflets. 
• Hypertrophic cardiomyopathy. 

In the article text is a more detailed description of the issue of mitral valve prolapse, including the significance of valve morphology and audible clicks. The only patients with MVP who are not recommended for prophylaxis are those patients with isolated prolapse, normal appearing leaflets, no doppler evidence of regurgitation and no murmurs (with maneuvers). Patients with MVP and only a systolic click represent a controversial subset and warrant either prophylaxis or a very vigilant search for intermittent regurgitation (doppler and auscultation with maneuvers). The importance of MVP as an etiology for endocarditis in the pediatric age group is stressed. See text for more details. 

Principal recommendations

In the following, prophylactic regimens for adults are listed. For dosages in the pediatric population, please refer to the article. 
 

Procedure and situation	Prophylactic regimen recommended
Dental, oral, respiratory tract and esophageal procedures
Standard regimen	Amoxicillin 2.0 g orally one hour before procedure
Unable to take orally	Ampicillin 2.0 g IM or IV, within 30 minutes before procedure
Penicillin allergic	Clindamycin 600 mg or  Azithromycin 500 mg or  Clarithromycin 500 mg or   for patients who have not had an immediate local or systemic reaction to a pencillin (urticaria, angioedema or anaphylaxis) and who can tolerate first generation cephalosporins: Cephalexin or Cefadroxil 2.0 g  orally, 1 h before procedure
Pencillin allergic and unable to take orally	Clindamycin 600 mg IV or  Cefazolin 1.0 g IM or IV (for patients who can tolerate, see above)  within 30 minutes before procedure
Genitourinary and gastrointestinal (not esophageal) procedures
High risk patients	Ampicillin 2.0 g IV or IM plus gentamycin 1.5 mg/kg (up to 120 mg) within 30 min of starting procedure  followed by ampicillin 1.0 g IV/IM or amoxicillin 1 g orally 6 hours later
High risk patients allergic to ampicillin	Vancomycin 1.0 g IV over 1-2 h plus gentamycin 1.5 mg/kg IV/IM (up to 120 mg) to be completed within 30 min of starting procedure
Moderate risk patients	Amoxicillin 2.0 g orally 1 h before procedure or ampicillin 2.0 g IM/IV within 30 min of starting procedure
Moderate risk patients allergic to ampicillin	Vancomycin 1.0 g IV over 1-2 hr, to be completed within 30 min of starting procedure

It should be noted that the current recommendations do not include an erythromycin-based regimen for oral prophylaxis, because of problems with pharmacokinetics and gastro-intestinal tolerability. The authors note, however, that patients who previously used erythromycin for endocarditis prophylaxis and who tolerated it at the recommended doses can continue to do so. 

Specific situations