Cardiovascular Block: Week 6 > Infective Endocarditis > Flashcards

Infective Endocarditis Flashcards

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1
Q

How common is infective endocarditis?

A

Infective endocarditis is uncommon
1-6% of prosthetic valves become infected
BUT
It is still important because it has a high morbidity and mortality

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2
Q

Why is infective endocarditis difficult to diagnose?

A

Clinical presentation varies widely, making it difficult to diagnose

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3
Q

What are some of the clinical signs of IE?

A
  • Petechiae (common, nonspecific)
  • Splinter hemorrhages (8%)
  • Osler Nodes
  • Roth’s Spots (5%)
  • Janeway’s Lesions (5%)
  • Conjunctival hemorrhages (5%)
  • Hematuria (25%)
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4
Q

What are the two broad classifications of infective endocarditis?

A
  1. Native Valve Endocarditis

2. Prosthetic Valve Endocarditis

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5
Q

Why is it important to distinguish between native valve and prosthetic valve endocarditis?

A
  • Determines possible etiologic microbial pathogens
  • Guides choice of antimicrobial agents that can be used for empiric therapy
  • Guides further management options where necessary
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6
Q

Apart from distinguishing between native valve and prosthetic valve endocarditis, what else should be considered when choosing an empiric antimicrobial agent?

A
  • IE in IV drug users (IVDU)

- IE associated with a nosocomial infection

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7
Q

What are some of the risk factors fro the development of infective endocarditis?

A
  • Structural abnormalities of the heart
  • Prosthetic valves
  • IVDU
  • Nosocomial infections
  • Presence of indwelling intravascular devices
  • Hemodialysis
  • Prior episode of IE
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8
Q

Why is the epidemiology of infective endocarditis changing?

A

Differences in epidemiology between developed vs. developing countries

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9
Q

What contributes to the epidemiology of infective endocarditis in low-income countries?

A
  • Rheumatic heart disease is the main risk factor

- STREPTOCOCCI is the most frequent cause

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10
Q

What contributes to the epidemiology of infective endocarditis in high-income countries?

A
  • Increase in life expectancy
  • Degenerative valvulopathies
  • Prosthetic valves
  • Cardiovascular implantable electronic devices
  • Nosocomial infections
  • Right sided endocarditis related to IV drug users
  • STAPHYLOCOCCI as a cause becoming more frequent
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11
Q

What is the definition of infective endocarditis?

A

Infection of the endocardial surface of the heart

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12
Q

What is the definition of a vegetation?

A

Accumulation of bacteria, fibrin and platelets (implies the physical presence of micro-organusm within the lesion)

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13
Q

What are the two main types of prosthetic valves?

A
  1. Mechanical

2. Bioprosthetic valves (tissue)

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14
Q

What are mechanical prosthetic valves and where does infection of these valves usually occur?

A
  • Metal or carbon alloys
  • Not well suited for microbial adherence
  • Infection at interface of sewing cuff and native tissue
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15
Q

What are complications with mechanical prosthetic valve infective endocarditis?

A
  • Periprosthetic / paravalvular leaks and abscesses
  • Ring abscesses
  • Annular abscesses
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16
Q

What are bioprosthetic valves and where does infection of these valves usually occur?

A
  • Homografts (preserved human aortic valves); or heterografts (bovine pericardial or porcine valve tissue mounted on a metal support)
  • Infection restricted to the cusps
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17
Q

What are complications with bioprosthetic prosthetic valve infective endocarditis?

A
  • cusp rupture, perforation, leaks

- sewing cuffs (similar to mechanical)

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18
Q

Pathogenesis of prosthetic valve endocarditis: what parts of the prosthesis are highly thrombogenic?

A
  • sewing cuff fabric of valve prosthesis
  • sutures
  • annular and periannular mechanical and inflammatory lesions may be present
  • ageing prosthesis
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19
Q

What are the 3 modes of infection in prosthetic valve endocarditis?

A
  1. Contamination at the time of insertion
  2. Hematogenous spread of infection from another site
  3. Contiguous spread of infection from surrounding tissue = secondary infection of indwelling cardiovascular device
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20
Q

What complications are associated with infective endocarditis?

A
  1. Aneurysms, valvular incompetence
  2. Congestive cardiac failure (common)
  3. Embolization of vegetations - multi-organ infection and sepsis
  4. Loosening of sutures = peri-prosthetic leaks or ring abscesses (PVE)
  5. Ruptured ring abscesses = fistulous tracks into surrounding tissues, intracardiac shunting (PVE)
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21
Q

What are the 4 most common bacterial causes of infective endocarditis?

Study These Flashcards
A
  1. Viridans streptococci
  2. Enterococci
  3. Staphylococcus Aureus
  4. Staphylococcus Epidermidis
22
Q

What are other relatively uncommon bacterial causes of infective endocarditis (may be common in nosocomial infections)?

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A
  1. Gram negative bacilli
  2. HACEK organisms
  3. Other unusual organisms
23
Q

What are uncommon organisms that cause culture negative endocarditis?

Study These Flashcards
A
  1. Brucella spp.
  2. Coxiella burnetti
  3. Bartonella spp.
  4. Chlamydia spp.
  5. Mycoplasma spp.
  6. Fungi
    (uncommon but does depend on environment and where a patient works / what they do etc.)
24
Q

What are the most common causes of native valve endocarditis?

Study These Flashcards
A
  1. Viridans streptococci (50-70%)
  2. Staphylococcus Aureus (25%)
  3. Enterococci
25
What are less common causes of native valve endocarditis?
1. Gram negative bacilli including HACEK group organisms | 2. Fungi
26
What are the most common causes of prosthetic valve endocarditis?
1. Staphylococcus epidermidis 2. Staphylococcus aureus 3. Streptococci 4. Enterococci
27
What are less common causes of prosthetic valve endocarditis?
1. Fungi | 2. Gram negative organisms including HACEK
28
What is the most common cause of culture negative endocarditis?
Prior antibiotic use. | - Blood cultures are negative in up to 20% of patients with IE
29
What are the most common causes of infective endocarditis in IV drug users?
1. Staphylococcus Aureus | 2. Pseudomonas Spp.
30
What side of the heart is affected in infective endocarditis in IV drug users?
Right sided endocarditis
31
How is diagnosis of infective endocarditis made?
Suggested by history and physical examination findings - risk factor profile, recent surgical history - CVS exam - systemic manifestations of vasculitis, emboli, immunologic phenomena Supported by echocardiography Confirmed by positive blood cultures
32
What is important regarding the diagnosis of infective endocarditis?
It is difficult to diagnose and often typical clinical criteria are not present. If high index of suspicion and have done echo (even if negative) + have done cultures = TREAT If you strongly believe it is infective endocarditis treat it even if you don't have solid evidence
33
What valve is more commonly affected in native valve endocarditis?
Mitral > Aortic
34
What valve is more commonly affected in prosthetic valve endocarditis?
Mechanical > Tissue (xenograft / homograft)
35
What valve is more commonly affected in IVDU endocarditis?
Tricuspid >> Mitral, Aortic
36
What criteria is used in the diagnosis of Infective Endocarditis?
Modified Duke Criteria
37
Modified Duke Criteria: what are the major criteria?
1. Positive blood culture 2. Serology for Coxiella Burnetii (IgG Titre > 1:800) 3. Evidence of endocardial involvement (echocardiogram)
38
Modified Duke Criteria: what is considered to be a positive blood culture (as part of the major criteria)?
- Typical microorganisms from two separate cultures - Persistently positive blood culture defined as recovery of organism consistent with infective endocarditis from: blood cultures drawn more than 12 hours apart / all of three or a majority of four or more separate blood cultures with the first and last drawn at least 1 hour apart
39
Modified Duke Criteria: what is considered to be a evidence of endocardial involvement on echocardiogram (as part of the major criteria)?
1. Oscillating intracardiac mass on valve supporting structures 2. Peri-valvular ring abscess 3. New partial dehiscence of prosthetic valve or new valvular regurgitation
40
Modified Duke Criteria: what are the minor criteria?
1. Predisposition (heart lesion, IVDU) 2. Fever >38C 3. Vascular phenomena (major arterial emboli, mycotic aneurysms, conjunctival lesions, Janeway lesions 4. Immunologic phenomena (glomerulonephritis, Osler's nodes, Roth spots, RF) 5. Microbiological evidence (positive blood culture, not meeting major criteria) 6. Echocardiogram consistent but not meeting major criteria
41
What is considered to be DEFINITE ENDOCARDITIS using the modified Duke criteria?
- Histological and/or microbiologic evidence of infection at surgery or autopsy OR - 2 major criteria OR - 1 major + 3 minor criteria OR - 5 minor criteria
42
What is considered to be POSSIBLE ENDOCARDITIS using the modified Duke criteria?
- 1 major + 1 minor criteria OR | - 3 major criteria
43
What is the single most important laboratory test in the diagnostic workup of infective endocarditis?
Blood Cultures
44
Describe the usual bacteraemia in infective endocarditis?
Bacteraemia is usually CONTINUOUS and low grade
45
What are important points regarding the procedure of blood collection in infective endocarditis culture samples?
- at least 3 sets of positive blood cultures with the first and last drawn at least 1 hour apart - blood volume for each set: 20-30mls - proper skin disinfection prior to collection!! - cultures must be taken before antibiotic administration - ALWAYS inform the microbiology laboratory when infective endocarditis is suspected (diagnosis on requisition form)
46
What is echocardiography used for in the diagnosis of infective endocarditis?
- To confirm diagnosis | - Vegetations seen on valve
47
How should echo be taken when being used for the diagnosis of infective endocarditis?
Transthoracic or transoesophageal (for improved resolution - detects lesions 1-1.5mm in size)
48
What other laboratory tests can be used in the diagnosis of infective endocarditis?
ESR
49
What are some of the causes of culture negative endocarditis?
- Prior antibiotic therapy (major cause) - Inadequate blood volume collection - Fastidious Organisms (HACEK group, nutritionally variant streptococci, Coxiella burnetti, Mycobacteria, Brucella, Legionella, Bartonella, Anaerobes, Fungi, Viruses) - Non-infectious endocarditis
50
What are causes of non-infectious endocarditis?
1. Marantic endocarditis (NBTE) | 2. Libman-Sacks endocarditis (SLE)
Cardiovascular Block: Week 6
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