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"Subacute Bacterial Endocarditis
And
Antimicrobial Prophylaxis"

By:  LCDR Marc Arena

Infective Endocarditis

Subacute bacterial endocarditis (SBE)

• Microbial infection of the heart valves or endocardium
• Congenital or acquired cardiac defects
• Infective endarteritis, an analogous disease of the vasculature

Incidence

• General population
• 10 to 60 cases per million people per year
• People with predisposing conditions account for 80% of cases

Characteristics

• Onset from rapid to insidious
  
• Causes:
• Rapid - Staphylococcus aureus
• Insidious- Streptococcus viridans

• Symptoms:
• Weakness
• Fatigue
• Weight loss
• Fever
• Chills
• Night sweats
• Anorexia
• Arthralgia

• Signs:
• Petechial hemorrhages (skin or mucosa)
• Linear hemorrhages under the nails (10% of cases)
• Osler nodes- small red/ purple subcutaneous nodules (10-20% of cases)
• Janeway lesions- flat, non-tender, blanching spots on the palms and soles
• Retinal hemorrhages (10-25% of cases)
• Heart murmur (almost all cases)

• Outcome:
• Prior to antibiotics- always fatal
• Now- still fatal in 10-70% of cases

• Complications:
• Reinfection
• Congestive heart failure
• Renal disease
• Cerebral vascular accident

Infective endocarditis and Dentistry

Dental procedures induce a transient bacteremia

Relationship between dental procedures and SBE

• Invitro studies
• Anecdotal evidence
• Definitive proof needs double blind placebo study involving 6000 at risk patients (not likely)
• Streptococcus Viridans predominant cause of endocarditis following dental procedures

Need for antimicrobial prophylaxis

• Benefits outweigh risks
• Antibiotic in the blood prior to bacterial dissemination
• A loading dose should be employed
• Antibiotic should be specifically effective against the organism
• Antibiotic should be continued only as long as the bacteremia persists
• Antibiotic should be inexpensive and easy to use

Indications for Prophylaxis

• Cardiac conditions (Table 1)
• History of Rheumatic heart disease
• Systemic lupus erythematosus (Libman-Sacks endocarditis)
• Marfan's Syndrome
• Prior history of drugs to treat obesity
• Fenfluramine (Pondimin)
• Phentermine (Adipex, Fastin)
• Dex-fenfluramine (Redux)

Conditions where prophylaxis is not recommended

• Cardiac conditions (Table 1)
• Neutropenic patient (coordinate all treatment with physician)
• Diabetic patient (if properly controlled)
• Asplenic patient (consult physician)
• End stage renal disease patient (consult physician)

• Transplant patient (coordinate all treatment with physician)
• HIV infected patient
• Total joint replacement (two years after placement see table 4)

• Other implanted devices (consult physician)
• Cerebrospinal fluid shunts (ventriculoatrial/ yes; ventriculoperitoneal/ no)
• Intravascular access device
• Penile implant
• Intraocular implants (not recommended)
• Breast Implants (not recommended)

Causes of bacteremia

• Dental/ professional (see table 2)
• Dental/ daily functions (estimated at 1000 times greater than risk from dental treatment)

Prophylaxis regimen recommended by the AHA/ADA (June 1997) (Table3)

Prophylaxis regimen recommended by the ADA/AAOS (July 1997) (Table 4)

Recommendations for all patients requiring antimicrobial prophylaxis

1. Adequately screen all patients to establish need for antimicrobial prophylaxis prior to any treatment.
2. Home care must be excellent to minimize the chance of creating a bacteremia
3. Routine dental care should be performed only after the patient has demonstrated excellent oral home care
4. Perform all dental treatment as expeditiously as possible to reduce exposure to antibiotic. This reduces the risk of overgrowth by antibiotic-resistant strains of bacteria.
5. When treating a patient over a few consecutive days extend the antimicrobial coverage for the entire period.
6. Allow at least 7 days between appointments to reduce the risk of creating an overgrowth of resistant strains if bacteria.
7. Patients on antibiotics for any other reason should be prophylaxed with an antimicrobial different than the one they are presently taking.
8. Having the patient rinse with an antimicrobial mouth rinse (chlorhexidine or povidone iodine for 30 sec.) prior to dental treatment may be a useful adjunct to prophylaxis. (not required by the ADA)
9. Edentulous patients may develop ulcers from ill fitting dentures. New dentures should be evaluated closely. All denture wearers should be encouraged to have periodic exams.
10. When unanticipated bleeding occurs while performing procedures not associated with bacteremia, institution of the antimicrobial prophylaxis is recommended and effective.

TABLE 1 - CARDIAC CONDITIONS ASSOCIATED WITH ENDOCARDITIS.

Endocarditis Prophylaxis Recommended

High-risk category

Most other congenital cardiac malformations (other than above and below)

Acquired valvar dysfunction (e.g., rheumatic heart disease)

Hypertrophic cardiomyopathy.

Mitral valve prolapse with valvar regurgitation and/or thickened leaflets

Endocarditis Prophylaxis Not Recommended