Epidemiology of infectious endocarditis (IE)

  • 20% of cases have definitive infective endocarditis (very difficult to diagnose)
  • Most common in people in their 70s

Pathophysiology of IE

  • Most patients develop endocarditis through one of three routes:  rheumatic heart disease, degenerative valve lesions (may occur secondary to arteriosclerosis or a thrombus), congenital valvular lesions (mainly in kids due to an artificial valve)
  • Hemodynamic factors lead to valvular insufficiency, lesions result in a high degree of turbulence & create conditions leading to bacterial colonization
    • The endothelial surface must be altered (ex. stenotic/insufficient valves) to become a suitable site for the adherence of bacteria
      • Staph, enterococci, pseudomonas aeruginosa & viridians strept are the bacteria most likely to adhere well
      • Staph & strept account for 80-90% of cases
        • 40% mortality in staph infected IE
          • Coagulase negative staph (mostly MRSA) is mainly associated w/ prosthetic valves
        • Enterococci are is the 3rd most common form of endocarditis & should be treated w/ a combo regimen including a beta-lactam
    • platelets & fibrin adhere & result in nonbacterial thrombotic endocarditis (NBTE).  Bacteria adhere & colonize, the bacteria will continue to aggregate & eventually form a vegetation.
  • Gram negative bacilli are responsible for less than 5% of cases but have over 75% mortality
    • HACEK group:  Haemophilus spp., Actinobacillus actinomycetemcomitans, Cardiobacterium hominis, Eikenella spp. and Kingella kingae.
    • Pts. At risk for gram negative IE:  narcotic addicts, prosthetic valve recipients, pts w/ cirrhosis   (pts are typically 40-50)

Signs and symptoms of IE

fever < 103


diffuse myalgias (19%)

embolic episodes

+ heart murmur (>85%)

  • Especially if the murmur is new or gets louder

weight loss

night sweats (acute)

low back pain (23%)




splenomegaly (25-60%)

sensory loss



petechiae (20-40%)

monoarticular arthralgias

LE arthritis (38%)

hemiplegia (20-40%)


  • Areas of the body may show ischemic areas resulting from infected embolic events
  • Blood cultures are the most important lab test used to diagnose endocarditis b/c they will show the agent >90% of the time.  Usually obtain 2 blood cultures prior to starting antibiotics & then 2 more cultures w/in 36-48 hours after the start of therapy
  • Patients may or may not show elevated WBCs (leukocytosis–20-30%)
  • ESR is very common (90-100%) but is nonspecific so this test isn’t usually ordered
  • Rheumatoid factor is positive in about half of patients w/ endocarditis but is also nonspecific is therefore rarely used
  • Treatment of IE
    • Generally speaking parenteral (IV) antibiotics are favored over oral b/c bioavailability concerns
      • Also generally want to use combo therapy in order to achieve rapid bacteriocidal effect (bacteriostatic are less effective)
    • Antibiotics have poor penetration into infected vegetations in part due to their difficulty penetrating fibrin plates as well as the fact that there is usually a lack of a cellular response from the host & the bacteria have altered metabolic states w/in the vegetation
    • Penicillin-susceptible Strept  (native valve endocarditis)
      • penicillin G  or ceftriaxone are first line therapies for most pts > 65  or who have renal or cranial nerve impairment
        • Vanco is the alternative therapy
    • Penicillin-susceptible Strept (prosthetic valve endocarditis)
      • penicillin G or ceftriaxone +/- gentamicin are first line therapies
        • Vanco is the alternative therapy
    • Penicillin-resistant Strept (native valve endocarditis)
      • Use a higher dose of penicillin G  or ceftriaxone + gentamicin
        • Vanco  is the alternative therapy
    • Penicillin-resistant Strept (prosthetic valve endocarditis)
      • Use a higher dose of penicillin G  or ceftriaxone + gentamicin
        • Vanco is the alternative therapy
  • Staph aureus is the leading cause of nosocomial bacteremia & endocarditis in the world
    • MSSA in the absence of a prosthetic valve
      • Naficillin +/- gentamicin or oxacillin +/- gentamicin
        • For pts w/ a nonanaphyalactoid rx to penicillin use cefazolin +/- gentamicin
    • MSSA with a prosthetic valve
      • Naficillin + Rifampin + gentamicin or oxacillin + Rifampin + gentamicin
    • MRSA in the absence of a prosthetic valve
      • Vanco
    • MRSA with a prosthetic valve
      • Vanco + Rifampin + Gentamicin
    • Enterococcus (native or prosthetic valve)
      • Ampicillin or Penicillin G + Gentamicin
        • When using the Pen G + Gentamicin therapy, you must watch out for nephro & ototoxicity as you are using both drugs for 4-6 weeks (only w/ enterococcus are you using gent this long) & gentamicin is known for these adverse SE
      • Vanco + Gentamicin is a second line therapy but see the above comments concerning Gent as you are using it here for 6 weeks
    • Empiric therapy for endocarditis:  IV Vanco 15 mg/kg q 12 h  +  gentamicin 1mg/kg IV q 8 h
      • Vanco = gram +             Gentamicin = gram –
  • May consider surgery for IE in patients w/ any of the following:  refractory CHF, more than 1 systemic embolic event, an uncontrolled infection, if antimicrobial therapy is ineffective, if the pt has a prosthetic valve, if there are myocardial abscesses or other local complications
  • Daptomycin is indicated for right sided endocarditis (telavancin & dalbavancin haven’t been approved yet for endocarditis)
  • Giving prophylactic antibiotics for infective endocarditis (IE) is NOT recommended generally especially not for patients undergoing GU or GI tract procedures due to the SE outweighing the benefits
Regimens for a Dental Procedure






Regimen—Single Dose (30-60 min before procedure)








2 grams

50 mg/kg

Unable to take oral medications


2 grams IM or IV

50 mg/kg IM or IV


Cefazolin or Ceftriaxone

1 gram IM or IV

50 mg/kg IM or IV

Allergic to pencillins or Ampicillin (oral)


2 grams

50 mg/kg



600 mg

20 mg/kg


Azithromycin or Clarithomycin

500 mg

15 mg/kg

Alllergic to penicillins or ampicillin (unable to take oral meds)

Cefazolin or Ceftriaxone

1 gram IM or IV

50 mg/kg IM or IV



600 mg IM or IV

20 mg/kg IM or IV

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