Infective Endocarditis  - Prevention

OUTCOMES

               Factors that affect mortality include the infecting organism (the mortality of endocarditis due to fungi, Pseudomonas aeruginosa, and aerobic enteric gram-negative bacilli > staphylococci > enterococci > viridans streptococci), the site of infection (aortic alone or aortic plus mitral > mitral alone > tricuspid infection), PVE vs. NVE (early onset PVE > late onset PVE > NVE), age (higher in the elderly and very young) and gender (men > women), and the presence of certain complications, such as heart or renal failure, rupture of a mycotic aneurysm, cardiac arrhythmias and conduction abnormalities, perivalvular extension, cerebral emboli, and perhaps severe immunosuppression due to HIV infection. Heart failure remains the leading cause of death. However, with increasing use of prosthetic valve replacement for heart failure, the leading cause of death may shift to neurologic complications due to embolic episodes or mycotic aneurysms, or uncontrolled infection due to antibiotic resistant microorganisms. Mortality is higher for patients with shorter durations of illness before initiation of antibiotic therapy, perhaps by the fact that acute infective endocarditis is frequently due to S. aureus. Following cure of one episode of endocarditis, patients remain at greatly increased risk for reinfection and PVE, and their increasing age contributes to the poor prognosis during the follow-up.

 

PREVENTION

               The effect of infective endocarditis prophylaxis with antimicrobial agents has been estimated to be very modest, i.e., <10% of all cases are preventable by prophylaxis, assuming all patients with cardiac risk factors are given appropriate antibiotic prophylaxis and also assuming that the prophylaxis regimen is 100% effective . For example, only about 1/2 of cases have recognizable predisposing cardiac lesions, most cases of infective endocarditis do not occur following an invasive procedure, and less than about 2/3 of cases are due to microorganisms (viridans streptococci and enterococci) against which prophylactic regimens are directed. However in those patients who are known to have a risky cardiac lesion (Table 9) and are to undergo certain procedures (Table 10), with subsequent disruption of local bacteria that are capable of producing endocarditis and have predictable susceptibility to antibiotics with minimal inconvenience, toxicity and cost, the American Heart Association (AHA) has made recommendations shown in Tables 11a, 11b.The 2007 AHA Guidelines no longer recommend endocarditis prophylaxis for esophagogastroduodenoscopy, colonoscopy, previous CABG, congenital heart disease not listed in Table 9, pacemakers, or routine genitourinary procedures due to the risks of antibiotic therapy outweighing the benefits.  If a patient is already receiving long-term antibiotic therapy with an antibiotic that is also recommended for IE prophylaxis for a dental procedure, it is prudent to select an antibiotic from a different class rather than to increase the dosage of the current antibiotic.

               Additional preventive measures are avoid unnecessary use of intravascular catheters (a major predisposing event for nosocomial endocarditis), aggressively treat focal infections early with appropriate antibiotic therapy and surgical drainage, obtain at least 3 blood cultures for any febrile illness and before initiation of antibiotic therapy, and maintain good dental hygiene in patients at increased risk for infective endocarditis.

  Table 9: Cardiac Conditions Associated with Highest Risk of Adverse Outcome from Endocarditis

               for which Prophylaxis with Dental Procedures is Recommended.

1. Prosthetic cardiac valve

2. Previous endocarditis

3. Congenital heart disease*

  1. Unrepaired cyanotic CHD, including palliative shunts and conduits

  2. 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†

  3. Repaired CHD with residual defects at the site or adjacent to the site of a prosthetic patch or prosthetic device (which inhibit endothelialization)

4.  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.

 

  Table 10:  Procedures for Which Antibiotic Prophylaxis is Recommended for Patients in Table 9.
  • Dental/oral surgery likely to cause bleeding (manipulation of gingival tissue or periapical region of the teeth or perforation of the oral mucosa).
  • Tonsillectomy and/or adenoidectomy
  • Invasive procedure of respiratory tract which involves biopsy or incision of mucosa
  • Surgical procedures involving infected soft tissue or musculoskeletal tissue

 

  Table 11a. Regimens for Dental Procedures (give 30-60 minutes prior to procedure)

  • Oral

    o       Amoxicillin 2 g PO

  • Unable to take PO

    o       Ampicillin 2 g IV/IM

    o       Cefazolin 1 g IV/IM

    o       Ceftriaxone 1 g IV/IM

  • Penicillin allergy-oral

    o       Cephalexin 2 g PO

    o       Clindamycin 600 mg PO or IV/IM

    o       Azithromycin 500 mg PO

  • Penicillin allergy-unable to take PO

    o       Cefazolin 1 g IV/IM

    o       Ceftriaxone 1 g IV/IM

    o       Clindamycin 600 mg IV/IM

 

  Table 11b: Regimens Involving Non-Dental Procedures of Patients Listed in Table 9.

  •         Respiratory Procedures

    o       Antibiotics as recommended in table 5

    o       If Staphylococcal infection is known or suspected, then substitution with an anti-staphylococcal penicillin (Oxacillin, nafcillin) should be utilized

    o       If MRSA infection known or suspected, then substitution with Vancomycin should be utilized.

    ·        Genitourinary Procedures

    o       Antibiotics only indicated if infection is present

    o       Ampicillin, amoxicillin, vancomycin should be considered to ensure enterococcal coverage

    ·        Skin and Soft Tissue Procedures

    o       Prophylactic antibiotics to prevent endocarditis indicated if infection is present

    o       Oxacillin, cefazolin, clindamycin should be considered.  Utilize vancomycin if MRSA known or suspected.