Infective Endocarditis

Question 1

Pathophysiology of IE: What are the steps in the development of IE lesions?

Answer 1

1. Endothelial injury
2. Platelet deposition
3. Adherence of microbials to platelets which occurs via MSCRAMMS
4. Incorporation of microbials into vegetation which then multiplies

Question 2

Clinical criteria for definite IE?

Answer 2

• 2 major criteria; OR
• 1 major criterion and 3 minor criteria; OR
• 5 minor criteria

Question 3

What are the major criteria for IE?

Answer 3

1. Blood culture positive for IE
2. Echo positive for IE
3. New valvular regurgitation

Question 4

What are the minor criteria for IE?

Answer 4

1. Predisposition for IE (e.g. pre-existing heart condition, IV drug use)
2. Fever
3. Valvular phenomena (e.g. major arterial emboli, septic pulmonary infarcts, mycotic aneurysm, intracranial hemorrhage, conjunctival hemorrhages and Janeway lesions)
4. Immunological phenomena (e.g. Osler nodes, Roth spots, and rheumatoid factor)
5. Micro or serological evidence (e.g. positive blood culture that does not meet major criterion, or serological evidence of active infection with an organism consistent with IE)

Question 5

Clinical criteria for possible IE?

Answer 5

• 1 major criterion and 1 minor criterion; OR

- 3 minor criteria

Question 6

When is the possibility of IE rejected?

Answer 6

• Firm alternate diagnosis explaining evidence of IE; OR
• Resolution of IE syndrome with antibiotic therapy for < 4 days; OR
• No pathologic evidence of IE at surgery or autopsy, with antibiotic therapy for < 4 days; OR
• Does not meet criteria for possible IE

Question 7

What are Roth Spots?

Answer 7

• Oral retinal haemorrhages with pale centers
• Infrequent findings
• Also noted in patients with collagen vascular disease and haematologic disorders

Question 8

What are Osler Nodes?

Answer 8

• Small painful reddish nodules

- Most common on pads of fingers and toes

Question 9

What are Janeway Lesions?

Answer 9

• Non-tender, reddish nodular lesions

- Most commonly found on palms of hands and soles of feet

Question 10

What are Splinter Haemorhages?

Answer 10

Small, linear haemorhages under the finger and/or toenails (resemble splinters of wood under the nails)

Question 11

What are Petechiae?

Answer 11

Reddish-brown, pinpoint, haemorrhagic spots on the skin, conjunctivae, or oral mucosa

Question 12

What are the three echo positive signs of IE?

Answer 12

1. Oscillating mass (vegetation)
2. Abscess
3. New partial dehiscence with prosthetic valve

Question 13

Where can vegetations occur?

Answer 13

• Form at sites of endothelial injury located upstream of infected valve: eg. atrial surface of atrio-ventricular valves, ventricular surface of semilunar valves
• Satellite vegetations or jet lesions present along infected flow path: eg. IE of MV with MR => MR might hit LA wall and a vegetation can occur at this site // IE of AV with AR => infected AR jet may hit amvl resulting in jet lesion on MV leaflet

Question 14

What is an abscess?

Answer 14

• Complication of IE
• Extension and penetration of infection into surrounding tissues
• Contain phlegmon (puss)
• DO NOT communicate with circulation (no flow within abscess cavity)
• Most common with PrV and AV IE (in paravalvular region); abscesses may form in anterior aortic root or mitral-aortic intravalvular fossa (MAIF)

Question 15

What is new partial dehiscence of PrV due to IE?

Answer 15

• Dehiscence = rocking of PrV at an angle far in excess of normal excursion
• Clue to dehiscence: paravalvular regurgitation
• In IE: due to weakening of infected valve annulus
• Partial separation of prosthetic sewing ring from native annulus (“pulling away” of PrV from annulus)

Question 16

TTE vs TOE in IE

Answer 16

• TOE has a higher sensitivity and specificity in diagnosis of vegetations and abscess cavities in native and prosthetic valves
• Sensitivity of TTE in detecting abscesses is very low

Question 17

TTE vs TOE in Prosthetic AVR

Answer 17

• Anterior aortic annulus: best seen with TTE (acoustic shadow present with TOE - anterior annulus obscured by AVR artifact)
• Posterior aortic annulus: best seen with TOE (in TTE, AVR shadows posterior aortic annulus)

Question 18

In what clinical contexts is there zero probability of IE?

Answer 18

Zero probability of IE in the absence of:

1. Vasculitic/embolic phenomena
2. Central venous access of pacing wires
3. Recent IV drug use
4. Prosthetic Valve
5. Positive blood cultures

Question 19

Texture of a likely vegetation vs an unlikely vegetation?

Answer 19

• Likely vegetation: reflectance of myocardium (grey)

- Unlikely vegetation: hyper-reflective (white or echo-bright)

Question 20

Location of a likely vegetation vs an unlikely vegetation?

Answer 20

• Likely vegetation: upstream side of valves; along jet pathway; on prosthetic material
• Unlikely vegetation: downstream side of valves

Question 21

Motion of a likely vegetation vs an unlikely vegetation?

Answer 21

• Likely vegetation: independently mobile, high frequency motion
• Unlikely vegetation: fixed and immobile

Question 22

Shape of a likely vegetation vs an unlikely vegetation?

Answer 22

• Likely vegetation: irregular and lobulated, may be multiple
• Unlikely vegetation: filamentous or ‘stringy’; discrete nodule

Question 23

Accompanying abnormalities of a likely vegetation vs an unlikely vegetation?

Answer 23

• Likely vegetation: regurgitation, abscess, pseudoaneurysm, fistula, PrV dehiscence, valve aneurysm
• Unlikely vegetation: none

Question 24

What are other clues to the presence of IE?

Answer 24

1. Perivalvular complications (eg. pseudoaneurysms, fistulas)
2. Leaflet perforation
3. Chordal ruputre
4. Valve aneurysms
5. Significant valve dysfunction (eg. regurgitation and/or obstruction)

Question 25

What are pseudoaneurysms?

Answer 25

Perivalvular cavity (abscess) that communicates with the cardiovascular lumen

Question 26

Abscess vs Pesudoaneurysm

Answer 26

Abscess: 1. Non-pulsatile 2. No communication with circulation Pseudoaneurysm: 1. Pulsatile 2. Communicates with circulation

Question 27

What are fistulas?

Answer 27

- Communication between two neighbouring cavities through a perforation - Occur when weakened and necrotic tissue breaks through valve annulus resulting in a direct communication between 2 cardiac chambers OR a cardiac chamber and a great vessel - Eg. abnormal flow from aorta to RA (flow is continuous over cardiac cycle)

Question 28

What is leaflet perforation?

Answer 28

- Complication of valve aneurysm | - Interruption of leaflet tissue continuity => essentially a hole in the leaflet itself

Question 29

What are valve aneurysms?

Answer 29

- Occur as a consequence of valvular infection => saccular out-pouching of valvular tissue - IE = weakening of valve tissue, loss of elastic components

Question 30

When to refer for TOE in native valve IE?

Answer 30

- TOE recommended; proven higher diagnostic yield | - Exception: negative TTE and exceptional TTE images and low probability

Question 31

When to refer for TOE in prosthetic valve IE?

Answer 31

- TOE mandatory (if no contrary indications); marked diagnostic superiority - Consider CMR; if TOE equivocal (ambiguous) or if periaortic abscess suspected

Question 32

When to refer for TOE in right sided IE?

Answer 32

- TOE recommended in selected cases: clinical complications or left-sided disease

Question 33

When to refer for TOE in cardiac device related IE?

Answer 33

- TOE recommended in selected cases; TTE negative or ambiguous - Consider ICE (intracardiac echo); if TOE negative and high clinical probability

Question 34

What are possible complications of IE?

Answer 34

1. Heart failure 2. Perivalvular extension of infection 3. Embolic events

Question 35

What echo parameters are associated with increased risk of embolism?

Answer 35

1. Large mobile vegetations (>10mm) 2. Located on MV 3. Increased size while on antibiotic therapy 4. Multivalvular infection