Endovascular Infections

Question 1

Endovascular infections can fall under 3 categories…

Answer 1

1. Direct infection of blood and its components
2. Infection of endovascular device
3. Direct infection of vasculature and its structures

Question 2

What is infective endocarditis?

Answer 2

Infection of the endocardium (inner lining of the heart).

Question 3

Difference between acute and subacute infective endocarditis

Answer 3

Acute: Sudden and severe illness lasting days to weeks
Subacute (chronic): Gradual, lingering illness with systemic symptoms often lasting more than a few weeks.

Question 4

Overall, the rates of infective endocarditis are … worldwide (increasing/decreasing).

Answer 4

increasing

Question 5

Mean age of infective endocarditis cases has … during the antibiotic era (increased/decreased)

Answer 5

increased

Question 6

Who is more affected by infective endocarditis?
a) men
b) women

Answer 6

a) men

Question 7

T or F: Infective endocarditis is common in children

Answer 7

F: Uncommon in the vast majority of children with no structural cardiac disease or need for CVADs

Question 8

Name 4 reasons why the average age of infective endocarditis patients is shifting upwards

Answer 8

1. Shift from rheumatic to degenerative heart disease in terms of prevalence
2. Aging population (elderly with heart disease survive longer)
3. Use of prosthetic valve replacements in the elderly
4. Increased use of endovascular technologies

Question 9

Native vs prosthetic valve

Answer 9

Native: Valves with which you are born with
Prosthetic: Synthetic valve placed during cardiac surgery

Question 10

What diseases affecting the native valve can be predisposing factors to infective endocarditis? (4)

Answer 10

1. Rheumatic Heart Disease
2. Congenital Heart Disease
3. Degenerative Heart Disease
4. Mitral Valve Prolapse

Question 11

Which poses a bigger risk factor for infective endocarditis?
a) peripheral IV
b) CVAD

Answer 11

b) CVAD (central venous access device)

Question 12

4 predisposing factors to infective endocarditis

Answer 12

1. Native valve disease/defects
2. Prosthetic valves
3. Endovascular device use
4. Persons who inject drugs (PWID)

Question 13

Which valve is most commonly affected by infective endocarditis?

Answer 13

Mitral valve

Question 14

Name the order of valves affected by endocarditis from most to least common

Answer 14

Mitral>Aortic>Tricuspid>Pulmonary

Question 15

Explain the concept of transient bacteremia

Answer 15

Temporary presence of bacteria in the bloodstream after heavily colonized mucosal surfaces (e.g. gums) are disrupted or damaged.
Typically low grade and transient (bloodstream becomes sterilized within 30 min).

Question 16

T or F: A transient bacteremia is not sufficient to infect an NBTE valvular lesion

Answer 16

F: Transient bacteremia IS sufficient to infect an NBTE valvular lesion

Question 17

3 common causes of transient bacteremia

Answer 17

1. Dental extractions
2. Periodontal surgery
3. Chewing candy or paraffin

Question 18

What is dextran?

Answer 18

Sticky coating (polysaccharide/glycocalyx) produced by bacteria.
Plays a role in dental caries.

Question 19

Dextran is commonly produced by…

Answer 19

Streptococcus spp.

Question 20

Dextra promotes…

Answer 20

adherence of bacteria to NBTE

Question 21

Some bacteria adhere to NBTE by expressing adhesion markers that bind…

Answer 21

fibronectin

Question 22

What type of bacteria typically binds fibronectin on NBTEs?

Answer 22

Staphylococcus aureus

Question 23

How do bacteria-platelet aggregates contribute to development of infective endocarditis (2)

Answer 23

1. By decreasing the rate of removal of the organism
2. By increasing adherence and aggregation on vegetations

Question 24

How can we disrupt virulence factors and prophylax people at risk of infective endocarditis?

Answer 24

By using prophylactic antibiotics

Question 25

How do prophylactic antibiotics help prevent IE? (2)

Answer 25

1. They decrease the expression of adhesion factors 2. They kill the bacterial cells directly

Question 26

Within the vegetation itself, what promotes bacterial growth & infection?

Answer 26

1. Minimal phagocyte infiltration 2. The vegetation is protected from circulating immune factors (Abs, complement) 3. The environment favours cell proliferation 4. It is an ideal reservoir for dormant/inert bacteria (so antibiotics have no effect)

Question 27

What bacteria typically cause community-acquired native valve IE? (3)

Answer 27

1. Viridans Streptococcus spp. 2. Viridans Staphylococcus aureus 3. Enterococcus spp. (to a lesser extent)

Question 28

What bacteria typically cause hospital-acquired (nosocomial) native valve IE? (2)

Answer 28

1. Staphylococcus aureus 2. Enterocossus spp. (to a lesser extent)

Question 29

What bacteria typically causes native valve IE in intravenous drug users IVDU)? (1)

Answer 29

Staphylococcus aureus

Question 30

Early post-surgery (<2mo), what bacteria cause prosthetic valve IE? (1)

Answer 30

1. Coagulase negative Staphylococcus spp. > S. aureus 2. Other organisms

Question 31

Intermediate post-surgery (2-12mo) what bacteria cause prosthetic valve IE? (3)

Answer 31

1. Coagulase negative Staphylococcus spp. > S. aureus 2. Enterococcus spp > Streptococcus spp (to a lesser extent)

Question 32

Late post-surgery (>12mo) what bacteria cause prosthetic valve IE?

Answer 32

More similar to native valve (Streptococcus spp/S. aureus)

Question 33

What is culture negative endocarditis?

Answer 33

A type of heart valve infection where standard blood cultures fail to detect the causative microorganisms

Question 34

Culture-negative endocarditis is usually caused by...

Answer 34

HACEK (gram-negative bacteria associated with infective endocarditis)

Question 35

What is HACEK?

Answer 35

Gram-negative bacteria associated with infective endocarditis: Haemophilus Aggregatibacter Cardiobacterium Eikenella Kingella

Question 36

Presentation of IE is quite non-specific. Name 4 main symptoms.

Answer 36

1. Fever (80% of patients) 2. Chills 3. Weakness 4. Dyspnea

Question 37

Signs of infective endocarditis on physical exam (2)

Answer 37

1. Fever 2. Changing heart murmur or new heart murmur

Question 38

Why is cardiac auscultation important in diagnosing IE?

Answer 38

Audible murmurs are present i ~85% of IE cases (esp. left-sided). New or changing murmurs are an important though uncommon sign.

Question 39

Most important diagnostic test for IE

Answer 39

Blood cultures

Question 41

We should avoid giving ... before doing a blood culture so results don't get altered

Answer 41

antibiotics

Question 42

Which type of echocardiogram is more useful for diagnosing IE?

Answer 42

Transesophageal echocardiogram (TEE) is more sensitive than transthoracic echocardiogram (TTE).

Question 43

T or F: Having previous history of IE is a major risk factor for IE

Answer 43

T

Question 44

What are the broad pathologic changes associated with IE

Answer 44

1. Destruction of heart & associated structures 2. Embolism formation 3. Immune activation 4. Abnormal kidney architecture

Question 45

What extravascular organ is always found to have abnormal architecture due to acute IE on biopsy?

Answer 45

Kidney (abscess, infarction, glomerulonephritis)

Question 46

Other than the kidney, another organ in the thoracic cavity that may be affected by an IE

Answer 46

Spleen (enlargement, infarction, abscess, spontaneous rupture)

Question 47

What can happen to the lung as a consequence of IE

Answer 47

1. Pulmonary emboli (septic or bland) 2. Acute pneumonia 3. Pleural effusion 4. Empyema