Infective Endocarditis Prophylaxis

The following article is a summary of the guidelines issued by the American Heart Association (AHA). The guidelines conclude that only an extremely small number of cases of infective endocarditis (IE) might be prevented by prophylaxis. Hence prophylaxis is recommended only for patients with underlying cardiac condition associated with the highest risk of adverse outcome from infective endocarditis. For patients with such cardiac conditions, prophylaxis is  recommended for all dental procedures that involve the manipulation of gingival tissue or periapical region of teeth or perforation of the oral mucosa. Prophylaxis is not recommended based solely on an increased lifetime risk of acquisition of IE. Also the administration of antibiotics solely to prevent endocarditis is not recommended for gastrointestinal and genitourinary procedures. 
 
AHA-Recommended Antibiotic Regimens from 1955 to 1997 for Dental Procedures
Year- Primary Regimens for Dental Procedures
1955 - Aqueous penicillin 600 000 U and procaine penicillin 600 000 U in oil containing 2% aluminum monostearate administered IM 30 minutes before the operative procedure
1957 - For 2 days before surgery, penicillin 200 000 to 250 000 U by mouth 4 times per day. On day of surgery, penicillin 200 000 to 250 000 U by mouth 4 times per day and aqueous penicillin 600 000 U with procaine penicillin 600 000 U IM 30 to 60 minutes before surgery. For 2 days after, 200 000 to 250 000 U by mouth 4 times per day.
1990-Amoxicillin 3 g orally 1 hour before procedure, then 1.5 g 6 hours after initial dose
1997-Amoxicillin 2 g orally 1 hour before procedure
 
Reasons for Revision of the IE Prophylaxis Guidelines
The following are the main reasons for the revision of the previous guidelines
1)      IE is much more likely to result from frequent exposure to random bacteremias associated with daily activities than from bacteremia caused by a dental, GI tract, or GU tract procedure.
2)      Prophylaxis may prevent an exceedingly small number of cases of IE, if any, in individuals who undergo a dental, GI tract, or GU tract procedure.
3)      The risk of antibiotic-associated adverse events exceeds the benefit, if any, from prophylactic antibiotic therapy.
4)      Maintenance of optimal oral health and hygiene may reduce the incidence of bacteremia from daily activities and is more important than prophylactic antibiotics for a dental procedure to reduce the risk of IE.
5)      Guidelines overly complicated and difficult to interpret
 
Pathogenesis of the Infective Endocarditis
1)      Formation of the NBTE
2)      Transient Bacteremia
3)      Bacterial Adherence
4)      Proliferation of Bacteria within the Vegetation
 
Rationale for and against prophylaxis for Infective Endocarditis
A)    Frequency, Nature, Magnitude, and Duration of Bacteremia Associated With a Dental Procedure
Transient bacteremia common with the manipulation of the teeth and the periodontal tissue but transient bacteremia also occurs frequently during daily activities like brushing, chewing food. Cases of IE caused by oral bacteria probably result from the exposures to low inocula of bacteria in the bloodstream that result from routine daily activities and not from a dental procedure
 
B)     Impact of Dental Disease, Oral Hygiene, and Type of Dental Procedure on Bacteremia
More than 80 years ago, it was suggested that poor oral hygiene and dental disease were more important as a cause of IE than were dental procedures. There is no evidence-based method to decide which procedures should require prophylaxis, because no data show that the incidence, magnitude, or duration of bacteremia from any dental procedure increase the risk of IE
 
C)    Impact of Antibiotic Therapy on Bacteremia From a Dental Procedure
The ability of antibiotic therapy to prevent or reduce the frequency, magnitude, or duration of bacteremia associated with a dental procedure is controversial. Some studies reported that antibiotics administered before a dental procedure reduced the frequency, nature, and/or duration of bacteremia,  whereas others did not. However, no data show that such a reduction as a result of amoxicillin therapy reduces the risk of or prevents IE.
 
D)    Cumulative Risk Over Time of Bacteremias From Routine Daily Activities Compared With the Bacteremia From a Dental Procedure
It is estimated that tooth brushing 2 times daily for 1 year had a 154 000 times greater risk of exposure to bacteremia than that resulting from a single tooth extraction. The cumulative exposure during 1 year to bacteremia from routine daily activities may be as high as 5.6 million times greater than that resulting from a single tooth extraction.
 
E)     Other Factors
Results of Clinical Studies of IE prophylaxis for dental procedures
Absolute risk of IE resulting from a dental procedure
Risk of adverse reactions and cost-effectiveness of prophylactic therapy.
 
Cardiac Conditions Associated With the Highest Risk of Adverse Outcome From Endocarditis for Which Prophylaxis With Dental Procedures Is Recommended
Prosthetic cardiac valve
Previous IE
Congenital heart disease (CHD)*
Unrepaired cyanotic CHD, including palliative shunts and conduits
Completely repaired congenital heart defect with prosthetic material or device, whether placed by surgery or by catheter intervention, during the first 6 months after the procedure†
Repaired CHD with residual defects at the site or adjacent to the site of a prosthetic patch or prosthetic device (which inhibit endothelialization)
Cardiac transplantation recipients who develop cardiac valvulopathy
 
 
*Except for the conditions listed above, antibiotic prophylaxis is no longer recommended for any other form of CHD.
†Prophylaxis is recommended because endothelialization of prosthetic material occurs within 6 months after the procedure.
 
Antibiotic regimens for IE prophylaxis with Dental Procedure
Regimen: Single Dose 30 to 60 min
Before Procedure
Oral Amoxicillin 2 g (adult) 50 mg/kg (Children),
If unable to take oral medication then Ampicillin 2g IM/IV(adult), 50 mg/kg (Children), or Cefazolin or ceftriaxone 1 g IM or IV, 50mg/kg IM orIV
If allergic to penicillins or ampicillin—oral
Cephalexin 2g (adult), 50mg/kg (children)IM or IV or Clindamycin 600mg (adult) , 20mg/kg (children) or Azithromycin or clarithromycin 500mg (adult), 15mg/kg (children)
If allergic to penicillins or ampicillin and unable to take oral medication then
Cefazolin or ceftriaxone 1 g IM or IV (adult),  50 mg/kg IM/IV (children) or Clindamycin 600 mg IM or IV (adult),  20 mg/kg IM or IV (children)
 
 
Reference
Circulation: Journal of American Heart Association DOI: 10.1161/CIRCULATIONAHA.106.183095