Endocarditis and Endocarditis Prophylaxis

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Chapter 33

Endocarditis and Endocarditis Prophylaxis

1. What are believed to be the first steps in the development of infective endocarditis (IE)?

    IE is believed to occur only after one first develops what is termed nonbacterial thrombotic endocarditis (NBTE). According to the most recent American Heart Association (AHA) statement on endocarditis, it is believed that turbulent blood flow produced by certain types of congenital or acquired heart disease traumatizes the endothelium. This turbulent blood flow may be the result of flow from a high- to a low-pressure chamber or across a narrowed orifice. This trauma of the endothelium then creates a predisposition for deposition of platelets and fibrin on the surface of the endothelium, resulting in what is called NBTE. If bacteremia (or fungemia) occurs, the organisms may then colonize this site, resulting in IE.

2. How often does routine tooth brushing and flossing cause transient bacteremia?

    Transient bacteremia occurs 20% to 68% of the time with routine tooth brushing and flossing. It occurs 20% to 40% of the time with use of wooden toothpicks, and 7% to 71% of the time with chewing food. This is part of the rationale of the latest AHA guidelines deemphasizing antibiotic prophylaxis during certain dental and other procedures—namely, that the vast majority of the time bacteremia is due to daily activities and not to the occasional or rare dental or other procedure. The emphasis now is more on maintaining good oral hygiene and access to routine dental care.

3. True or false: Prospective randomized placebo-controlled trials have demonstrated that antibiotic prophylaxis before a dental or other procedure reduces the risk of IE?

    False. Despite the fact that for 50 years antibiotic prophylaxis has been recommended, there has never been a prospective randomized placebo-controlled trial to support this recommendation. In fact, the data on whether antibiotic prophylaxis even significantly affects bacteremia is contradictory, with some studies showing some reduction and others showing no reduction.

4. What are the four conditions identified as having the highest risk of adverse outcome from endocarditis for which prophylaxis with dental procedures is still recommended?

5. Which of the above AHA criteria for endocarditis prophylaxis is not recommended for prophylaxis in the 2009 European Society of Cardiology (ESC) guidelines?

    Cardiac transplant recipients with valvulopathy. The 2009 ESC guidelines take an approach that is generally similar to that of the 2007 AHA guidelines on which conditions and which procedures should be considered for endocarditis prophylaxis. However, the ESC guidelines do not list cardiac transplant recipients with valvulopathy as a population that should receive prophylaxis, noting that prophylaxis in this group is not supported by strong evidence, and that the probability of IE from dental origin is extremely low in such patients.

6. In the new AHA guidelines, for those patients with conditions listed in Question 4, which dental procedures carry a recommendation of endocarditis prophylaxis?

    The guidelines emphasize that all dental procedures that involve the manipulation of gingival tissue or the periapical region of teeth or perforation of the oral mucosa should receive endocarditis prophylaxis. Procedures that do not require prophylaxis include routine anesthetic injections through noninfected tissue, dental radiographs, placement of removable prosthodontic or orthodontic appliances, bleeding from trauma to the lips or oral mucosa, and select other procedures and manipulations. The guidelines emphasize that prophylaxis for the former mentioned procedures “may be reasonable for these patients,” although “its effectiveness is unknown” (and this prophylaxis recommendation is given a class IIb recommendation, with level of evidence C). New changes in the AHA guidelines on IE are summarized in Box 33-1.

Box 33-1   SUMMARY OF THE MAJOR CHANGES IN THE UPDATED AMERICAN HEART ASSOCIATION’S SCIENTIFIC STATEMENT ON INFECTIVE ENDOCARDITIS PROPHYLAXIS

image Bacteremia resulting from daily activities is much more likely to cause infective endocarditis (IE) than bacteremia associated with a dental procedure.

image Only an extremely small number of cases of IE might be prevented by antibiotic prophylaxis, even if prophylaxis is 100% effective.

image Antibiotic prophylaxis is not recommended based solely on an increased lifetime risk of acquisition of IE.

image Recommendations for IE prophylaxis are limited to only the four conditions identified as having the highest risk of adverse outcome from endocarditis (see text).

image Antibiotic prophylaxis is no longer recommended for any other form of congenital heart disease, except for the conditions listed in the text.

image Antibiotic prophylaxis is recommended for all dental procedures that involve manipulation of gingival tissues or periapical region of teeth or perforation of oral mucosa only for patients with underlying cardiac conditions associated with the highest risk of adverse outcome from IE (see text).

image Antibiotic prophylaxis is recommended for procedures on respiratory tract or infected skin, skin structures, or musculoskeletal tissue only for patients with underlying cardiac conditions associated with the highest risk of adverse outcome from IE (see text).

image Antibiotic prophylaxis solely to prevent IE is not recommended for genitourinary (GU) or gastrointestinal (GI) tract procedures.

Modified from Wilson W, Taubert KA, Gewitz M, et al: Prevention of infective endocarditis guidelines from the American Heart Association. Circulation 116:1736-1754, 2007.

7. For those patients with conditions for which antibiotic prophylaxis is recommended, undergoing dental procedures for which prophylaxis is recommended, what regimens are recommended?

    Antibiotic treatment should be administered as a single dose before the procedure, with antimicrobial therapy directed against viridians group streptococci. Amoxicillin (2 g orally [PO]), administered 30 to 60 minutes before the procedure, is the first-line recommendation. Those unable to take oral medication can be treated with ampicillin (2 g intramuscularly [IM] or intravenously [IV]) or cefazolin or ceftriaxone (1 g IM or IV). For those allergic to the penicillins or ampicillin, potential agents to use include cephalexin, clindamycin, azithromycin, clarithromycin, cefazolin, and ceftriaxone.

8. For what other procedures may prophylaxis be considered in patients with high-risk lesions?

    The new AHA guidelines deemphasize prophylaxis for most other procedures. Antibiotic prophylaxis solely to prevent IE is not recommended for genitourinary (GU) or gastrointestinal (GI) tract procedures. Among those procedures where prophylaxis may be considered (class IIb, level of evidence C) are:

9. Is endocarditis prophylaxis recommended in patients treated with coronary stents, pacemakers, or defibrillators, those undergoing transesophageal echocardiography (TEE), or those who have undergone coronary artery bypass grafting (CABG) (without valve replacement)?

    No. Note, however, that some electrophysiologists will pretreat or post-treat patients undergoing pacemaker or defibrillator implantation with antibiotics to prevent local infection (but not endocarditis).

10. What factors (discussed in detail in the ESC guidelines on endocarditis) should raise the suspicion for endocarditis?

image Bacteremia or sepsis of unknown cause

image Fever

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