Infective endocarditis is an infection of the heart valves or endocardium. It occurs at a rate of 10,000-20,000 cases per year in the US. Staphylococcus aureus is the most common cause. Diagnosis is made using the Modified Duke Criteria which considers blood culture results, echocardiogram findings, and clinical features. Treatment involves prolonged antibiotic therapy for 4-6 weeks depending on the causative organism. Surgery may be required for complications or refractory infection. Prophylaxis with antibiotics is recommended for certain high risk dental and surgical procedures to prevent bacteremia and seeding of valves.

1. Infective Endocarditis

2. Epidemiology
• 10-20,000 cases per year in the US
• Male:Female ratio 1.7:1
• New trends
– Mean age was 30 in 1926, now > 50% of
patients are over 60
– Decline in incidence of rheumatic fever
– More prosthetic valves
– More nosocomial cases, injected drug use
– More staphylococcal infection

3. Epidemiology
• Mitral valve alone 28-45%
• Aortic valve alone 5-36% (bicuspid
valve in 20% of all native valve IE)
• Both mitral and aortic valves 0-36%
• Tricuspid valve 0-6%
• Pulmonic valve <1%
• Right and left sided 0-4%

4. Classification
• OLD
– Subacute Bacterial Endocarditis
• Death in 3-6 months
– Acute Bacterial Endocarditis
• Death in < 6 weeks
• NEW
– Native Valve Endocarditis
– Prosthetic Valve Endocarditis

5. Pathogenesis
• Alteration of the valvular endothelial
surface leading to deposition of
platelets and fibrin
• Bacteremia with seeding of non-
bacterial thrombotic vegetation (NBTE)
• Adherence and growth, further platelet
and fibrin deposition
• Extension to adjacent structures
– Papillary muscle, aortic valve ring abscess,
conduction system

6. Pathogenesis
• Low pressure side of structural lesion
– Atrial side of mitral valve (MR)
– Ventricular side of aortic valve (AR, AS with R)
– Congenital abnormality (MV prolapse, bicuspid AV)
– Scarring from rheumatic heart disease or sclerosis
as a consequence of aging
– Prosthetic valves
• Other turbulence, high-velocity jets
– Ventricular septal defect
– Stenotic valve
• Direct mechanical damage from catheters,
pacemaker leads

7. Pathogenesis
• Transient bacteremia
– Traumatization of mucosal surface
colonized with bacteria (oral, GI)
– Low grade, cleared in 15-30 minutes
– Susceptibility to complement-mediated
bacterial killing
• Leads to concept of prophylaxis

9. Microbiology
• Staphylococcus aureus (30-40%)
• Viridans group streptococci (18%)
• Enterococci (11%)
• Coagulase-negative staphylococci (11%)
• Streptococcus bovis (7%)
• Other streptococci (5%)
• Non-HACEK Gram negatives (2%)
• HACEK Organisms (2%)
• Fungi (2%)
• “Culture negative” (2-20%)

10. Characteristics of Causative Organisms
• Adherence factors critical for growth in the
vegetation
– Can adhere to damaged valves (Staph, Strep and
Enterococci have adhesins that mediate
attachment)
– Staph adhesin binds fibrinogen and fibronectin
– Bacteria trigger tissue-factor production from local
monocytes and induce platelet aggregation so the
organisms become enveloped in the vegetation
– Protection from immune clearance leads to large
numbers of bacteria (109
-1010
per g of tissue)

11. Risk Factors
• Structural heart disease
– Rheumatic, congenital, aging
– Prosthetic heart valves
• Injected drug use
• Invasive procedures (?)
• Indwelling vascular devices
• Other infection with bacteremia (e.g.
pneumonia, meningitis)
• History of infective endocarditis

12. Clinical Manifestations
• Symptoms
– Fever, sweats, chills
– Anorexia, malaise, weight loss
• Signs
– Anemia (normochromic, normocytic)
– Splenomegaly
– Microscopic hematuria, proteinuria
– New or changing heart murmur, CHF
– Embolic or immunologic dermatologic signs
– Hypergammaglobulinemia, elevated ESR, CRP,
RF

14. Cardiac Pathologic Changes
• Vegetations on valve closure lines
• Destruction and perforation of valve
leaflet
• Rupture of chordae tendinae,
intraventricular septum, papillary muscles
• Valve ring abscess
• Myocardial abscess
• Conduction abnormalities

15. S. Aureus mitral valve vegetation, anterior
leaflet

17. Pathologic Changes
• Kidney
– Immune complex glomerulonephritis
– Emboli with infarction, abscess
• Aortic mycotic aneurysms
• Cerebral embolism
– Infarction, abscess, mycotic aneurysms
– Purulent meningitis is rare

19. Pathologic Changes
• Splenic enlargement, infarction
• Septic or bland pulmonary embolism
• Skin
– Petechiae
– Osler nodes: diffuse infiltrate of neutrophils, and
monocytes in the dermal vessels with immune
complex deposition. Tender and erythematous
– Janeway lesions: septic emboli with bacteria,
neutrophils and SQ hemorrhage and necrosis.
Blanching and non-tender. Palms and soles

24. Case Definition
• 1977 Pelletier and Petersdorf criteria
• 1981 von Reyn criteria
• 1994 Duke criteria
• 2000 Modified Duke criteria

25. Modified Duke Criteria
• Major Criteria
–Positive blood cultures with typical
organisms
–Persistently positive blood cultures
–Evidence of Endocardial involvement
• Positive Echocardiogram
– Oscillating intracardiac mass
– Abscess
– Dehiscence of prosthetic valve
• New Valvular regurgitation

26. Modified Duke Criteria
• Minor Criteria
– Predisposition (valvular disease or IDU)
– Fever
– Vascular phenomena (Arterial emboli,
septic pulmonary infarcts, intracranial
hemorrhage, Osler, Janeway)
– Immunologic phenomena (GN, Osler, Roth
spots, Rheumatoid Factor)

27. Modified Duke Criteria
• Definite IE
– Pathologic criteria
– Clinical criteria
• 2 Major Criteria OR
• 1 Major and 3 minor Criteria OR
• 5 Minor Criteria
• Possible IE
• 1 Major and 1 Minor OR
• 3 Minor
• Rejected IE

28. Blood Cultures
• MULTIPLE BLOOD CULTURES
BEFORE EMPIRIC THERAPY
• If not critically ill
– 3 blood cultures over 12-24 hour period
– ? Delay therapy until diagnosis confirmed
• If critically ill
– 3 blood cultures over one hour
• No more than 2 from same venipuncture
• Relatively constant bacteremia

29. “Culture Negative” IE
• Less common with improved blood
culture methods
• Special media required
– Brucella, Mycoplasma, Chlamydia,
Histoplasma, Legionella, Bartonella
• Longer incubation may be required
– HACEK
• Coxiella burnetii (Q Fever), Trophyrema
whipplei will not grow in cell-free media

30. HACEK
• Haemophilus aphrophilus, H.
paraphrophilus, parainfluenzae
• Actinobacillus actinomycetemcomitans
• Cardiobacterium hominis
• Eikenella corrodens
• Kingella kingae

31. Other microbiologic methods
• PCR
– Coxiella burnetii
– Tropheryma whipplei
– Bartonella henselae
• Serology
– Coxiella burnetii
– Bartonella
– Brucella
– Legionella
– Chlamydophila psittaci

32. Echocardiography
• Transthoracic
– Relatively low sensitivity
– Good specificity
• Transesophageal
– Detection of valve ring abscess (87% vs.
28% sensitivity for TTE)
– Detection of prosthetic valve IE

33. When to go to TEE first?
• Limited thoracic windows = TTE low
sensitivity
• Prosthetic valves
• Prior valvular abnormality
• S. aureus bacteremia and suspected IE
• Bacteremia with organisms likely to
cause IE
= high prior probability of IE

34. Other tests
• Electrocardiogram
– Conduction delays
– Ischemia or infarction
• Chest X-ray
– Septic emboli in right-sided IE
– Valve calcification
– CHF

35. Treatment of IE
• Native vs. Prosthetic Valve
• Bactericidal therapy is necessary
• Eradication of bacteria in the vegetation
– May be metabolically inactive (stationary
phase)
– May need higher concentrations of
antimicrobial agents

36. Antimicrobial Therapy
• Most patients are afebrile in 3-5 days
• Long duration of therapy (4-6 weeks or
more)
• Combination therapy most important for
– Shorter course regimens
– Enterococcal endocarditis
– Prosthetic valve infections

37. Native Valve IE
• Viridans Streptococci and S. bovis
– Aqueous Penicillin G 12-20 million
units/day continuously or divided q4 or q6
for 4 weeks
– If intermediate susceptibility to penicillin,
aqueous penicillin G 24 million units or
ceftriaxone 2 g q24 PLUS aminoglycoside
for the first 2 weeks

38. Native Valve IE
• Aminoglycosides for synergy
– Low concentrations are adequate (1-3
mcg/ml)
– Gentamicin 3 mg/kg divided q12 or q8
– Little data for q24 dosing

39. Native Valve IE
• Enterococci, ampicillin sensitive
– High rates of failure
– β-lactams are bacteriostatic, must combine with
aminoglycoside for optimal therapy
– High-level gentamicin resistance occurs in 35%
• High-dose ampicillin for 8-12 weeks
• Enterococci, ampicillin resistant
– Vancomycin plus gentamicin
• Enterococci, vancomycin resistant
– Linezolid or daptomycin
– Penicillin + vancomycin + gentamicin ?

40. Native Valve IE
• S. aureus
– Penicillinase-resistant semi-synthetic
penicillin (oxacillin or nafcillin) 1.5-2 g IV q4
or cephalosporin (cefazolin 1-2 g IV q8) for
4-6 weeks
– Aminoglycoside synergistic but does not
affect survival, not recommended
– Short course in right-sided IE
• 2 weeks of semi-synthetic penicillin and
aminoglycoside

41. Native Valve IE
• Methicillin-resistant S. aureus
– Vancomycin is bacteriostatic
– Vancomycin plus aminoglycoside or
rifampin
– Daptomycin
– Linezolid

42. Native Valve IE
• HACEK
– Ceftriaxone 2 g IV q 24 x 4-6 weeks
• Fungal
– Amphotericin
– Fluconazole
– Caspofungin, little data
– Surgery usually necessary 1-2 weeks into
treatment

43. Native Valve IE
• Indications for surgery
– Refractory CHF
– More than one systemic embolic event
– Uncontrolled infection
– Physiologically significant valvular
dysfunction
– Ineffective antimicrobial therapy (e.g.
fungal)
– Local suppurative complications
– Mycotic aneurysm

44. Prosthetic Valve IE
• Staphylococci most common
– Coagulase negative staphylococci
• Enterococcus
• Nutritonally variant streptococci
• Fungi

45. Prosthetic Valve IE
• Risk is greatest in the first 3 months
and first year (early PV IE)
– Coagulase-negative staphylococci in early
endocarditis, S. aureus
– Late-onset more similar to native valve
disease in microbiology but more
coagulase-negative staphylococci. Valve is
endothelialized

46. Prosthetic Valve IE
• TEE should be used first
• Staphylococci
– Vancomycin or oxacillin plus rifampin for at
least six weeks, gentamicin for the first two
weeks (3 mg/kg q24)
– Rifampin started at least 2 days after 2
other agents to avoid resistance

49. Prophylaxis of IE
• Uncertainty and controversy
• No randomized trials
• Indirect evidence (uncontrolled clinical
series, case-control studies)
• Decision analysis