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Vascular > Chapter 14: Ultrasound Assessment of Arterial Bypass Grafts > Flashcards

Chapter 14: Ultrasound Assessment of Arterial Bypass Grafts Flashcards

1
Q

a surgically created joining of two vessels that were formerly not connected

A

anastamosis

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2
Q

a connection between an artery and a vein that was created as a result of surgery or by other iatrogenic means

A

arteriovenous fistula

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3
Q

A channel that diverts blood flow from one artery to another, usually done to shunt from one artery to another

A

graft

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4
Q

An increase in blood flow. This can occur following exercise. It can also occur following restoration of blood flow following periods of ischemia.

A

hyperemia

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5
Q

The great saphenous vein is left in place in its normal anatomic position and used to create a diversionary channel for blood flow around an occluded artery

A

in situ bypass

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6
Q

focal increase in diameter either along the bypass or at an anastamosis; thrombus may or may not be present

A

aneurysms and pseudoaneurysms

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7
Q

swirling of color flow into the dilated portion; “yin-yang” appears may be present with color changing from red to blue as flow fills the dilation

A

aneurysms and pseudoaneurysms

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8
Q

low-velocity, turbulent, disturbed flow will be present in the dilated segment; bi-directional flow in neck

A

aneurysms and pseudoaneurysms

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9
Q

A patent venous tributary will be present off the bypass graft; this tributary may be seen to communicate into the deep venous system

A

arteriovenous fistula

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10
Q

Color filling will be seen within the fistula, extending to the deep venous system; aliasing likely to be present

A

arteriovenous fistula

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11
Q

flow may be slightly pulsatile to continuous within the fistula; antegrade diastolic flow will be evident in the bypass proximal to the fistula

A

arteriovenous fistula

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12
Q

linear object seen extending for several centimeters, parallel to bypass walls

A

dissection

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13
Q

turbulent flow; red to blue flow may be seen in either lumen

A

dissection

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14
Q

disturbed flow with increased resistance; flow may be bidirectional

A

dissection

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15
Q

small projection into the vessel lumen usually less than 1 cm, not associated with a valve

A

intimal flap

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16
Q

disturbed flow or aliasing may be present

A

Intimal flap and myointimal hyperplase

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17
Q

occurs within the bypass or along anastamotic areas; focal increase in vessel wall thickness that protrudes into the lumen

A

Myointimal hyperplasia

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18
Q

increased velocities, turbulence, or aliasing may be present

A

myointimal hyperplasia

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19
Q

intraluminal echoes of varying echogenicity examinations

A

thrombus

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20
Q

no flow or reduced color filling of bypass lumen

A

thrombus

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21
Q

absent Doppler signal or, if present, increased resistance

A

Thrombus

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22
Q

Hyperechoic structures seen protruding into bypass lumen; may be partial or complete leaflet

A

valve remnants

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23
Q

may demonstrate disturbed color-flow patterns or aliasing in region of valves

A

valve remnants

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24
Q

may demonstrate elevated velocities in region of valve

A

valve remnants

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25
Q

made of various manufactured materials such as polytetraflurethylene (PTFE) or Dacron (woven composites)

A

prosthetic (synthetic) bypass grafts

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26
Q

preferred bypass graft material

A

autogeneous vein

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27
Q

Veins used for bypass grafts

A

great saphenous vein
small saphenous vein
cephalic veins
basilic veins

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28
Q

Better long-term patency
less thrombogenic
potential for early failure

A

autogenous vein bypass graft

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29
Q

low potential for early technical failure and ultrasound-detected abnormalities; worse long term success rate because of progressive stenoses

A

PTFE grafts

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30
Q

free vein graft where the vein is completely dissected free from natural position

A

orthograde bypass graft

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31
Q

Free vein graft that can be placed in a reversed position

A

retrograde bypass graft

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32
Q

proximal anastamosis of inflow arteries

A

common femoral
superficial femoral
popliteal
profunda femoral

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33
Q
A
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34
Q
A
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35
Q

distal anastamosis of outflow arteries

A

popliteal
tibioperoneal trunk
anterior tibial
posterior tibial
peroneal

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36
Q

Technical problems following a bypass graft procedure in the first 30 days.

A

retained valve or partial valve leaflet
intimal flap
problems at anastamotic sites
possible graft entrapment
bypass may thrombose

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37
Q

Bypass graft failure between months 1 and 24

A

Myointimal hyperplasia

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38
Q

after 24 months following a bypass graft procedure

A

progression of atherosclerotic disease

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39
Q

rare; can result in late bypass graft thrombosis

A

aneurysmal dilation

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40
Q

Indications for surveillance of bypass grafts

A

acute onset of pain
diminished or absent pedal pulses
persistent nonhealing ulcers
recent history of loss of limbing or swelling
ABI falls greater than 0.15
Early postoperative baseline ultrasound

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41
Q

Routine intervals for surveillance of bypass grafts

A

3, 6, 12 months and annually thereafter

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42
Q

minimal required documentation of grayscale, color flow, and spectral Doppler of graft examination

A

inflow artery
proximal anastamosis
mid-graft
distal anastamosis
outflow artery

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43
Q

Required documentation of stenotic areas

A

before stenotic region
area of greatest velocity shift
distal to stenotic region

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44
Q

Spectral analysis angle should be approximately ___ degrees.

A

60

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45
Q

What is “walking through” a stenosis?

A

spectral analysis with greatest Doppler shift as well as proximal and distal to area

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46
Q

End to end anastamosis allows for flow down bypass conduit as well as some flow to be maintained within native distal artery

A

inflow vessel

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46
Q

Typically a change in caliber as one moves from the inflow artery through the anastamosis and into proximal segment of bypass that results in a small disruption of laminar flow profile

A

proximal anastamosis

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46
Q

The _____ anastamosis may exhibit mild turbulence caused by geometry of anastamosis and slight disruption in laminar flow

A

distal

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47
Q

Primary goal bypass graft ultrasound

A

document anatomic and hemodynamic characteristics of the bypass graft and adjacent vessels

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47
Q

clearly visible if bypass graft is perpendicular to ultrasound beam

A

intimal-medial layer

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48
Q

Normal walls of vein graft

A

smooth and uniform

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49
Q

uniform echogenicity plaque

A

homogeneous plaque

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50
Q

mixed level echoes within plaque

A

heterogeneous plaque

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51
Q

bright white echoes that cause acoustic shadowing

A

calcifications

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52
Q

surface characteristics of plaque

A

smooth surfaced
irregularly surfaced

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53
Q

Two most common image abnormalities of graft ultrasounds

A

valves or valve remnants
myointimal hyperplasia

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54
Q

incomplete valve disruption during surgery

A

valve remnants

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55
Q

typically takes place in areas where vein has sustained injury at site of valve sinus

A

myointimal hyperplasia

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56
Q

rapid proliferation of cells into intimal layer of cellwall which can result in stenosis

A

myointimal hyperplasia

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57
Q

small, confined projections into vessel lumen made up of a segment of vessel wall that has separated from the rest of the wall

A

intimal flap

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58
Q

intimal flap that progresses over several centimeters

A

dissection

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59
Q

can occur adjacent to a suture line

A

aneurysmal dilatation

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60
Q

Aneurysmal dilatation requires the vessel to be ___ times greater than caliber of adjacent vessel

A

1.5

61
Q

Pseudoaneurysms most often form at _______.

A

anastamotic sites

62
Q

Common site of pseudoaneurysm

A

CFA in groin at outflow of a prosthetic aortofemoral or femofemoral crossover graft

63
Q

Normal bypass grafts waveforms

A

multiphasic with a sharp upstroke and a narrow systolic peak; reversed flow during diastole

64
Q

A normal bypass graft waveform is indicative of a normal ___ resistance peripheral arterial bed

A

high

65
Q

complication unique to in situ bypass grafts

A

arteriovenous fistula

66
Q

occurs when a tributary of great saphenous vein connects, directly or indirectly, via a perforator with deep venous system and is left unligated after creation of bypas

A

arteriovenous fistula

67
Q

Doppler spectrum bypass graft proximal to level of fistula

A

constant antegrade flow

68
Q

Doppler spectrum bypass graft distal to level of fistula

A

no or little diastolic flow

69
Q

Energy losses across a stenosis will produce _____ velocities distal to a stenosis and result in a broadened peak.

A

lower

70
Q

2 main criteria characterizing a stenosis

A

measurement of PSV
calculation of velocity ratio

71
Q

Normally functioning bypass grafts PSVs

A

less than 150 cm/s

72
Q

PSV cutoff for an abnormality

A

greater than 180 cm/s

73
Q

measured by dividing maximum PSV at stenosis by PSV obtained just proximal stenosis

A

velocity ratio

74
Q

doubling is PSV compared to adjacent more proximal segment

A

50% or greater stenosis

75
Q

Stenosis range

A

180 cm/s - 300 cm/s

76
Q

75% or greater velocity ratio

A

3.5

77
Q

PSV greater than 300 cm/s

A

75% or greater stenosis

78
Q

calculated by taking an average of 3-4 PSV values in nonstenotic segments

A

Mean graft flow velocity (GFV)

79
Q

Normal GFV

A

greater than 40 cm/s

80
Q

A decrease in GFV indicates:

A

bypass in jeopardy of failure

81
Q

Which of the following is NOT considered a method of assessment of a lower extremity infraguinal bypass graft?
a. physical/clinical evaluation
b. ankle to brachial index
c. chemical blood chemistry panel
d. plethysmography

A

c

82
Q

Which vein would typically be used for an in situ bypass in the lower extremeity?

A

the great saphenous vein

83
Q

What is an advantage of synthetic grafts when compared to autogenous vein grafts?

A

low rate of early technical problems

84
Q

Why are in situ infrainguinal bypass grafts using the great saphenous vein a common and preferred technique?

A

there is a better match of vessel size at the inflow and outflow

85
Q

What is the term to describe an autogenous vein graft in which the vein retains its original anatomical direction?

A

orthograde

86
Q

Independent of the type of bypass graft used, where is the distal anastamosis typically located?

A

distal to the disease

87
Q

Which of the following is NOT one of the main causes for early autogeneous vein graft thrombosis (within the first 30 days)?
a. underlying hypercoagulable state
b. myointimal hyperplasia
c. inadequate vein conduit
d. inadequate run-off bed

A

b

88
Q

After 24 months, what is the likely cause of stenosis in the inflow or outflow vessels?

A

progression of atherosclerotic disease

89
Q

At a minimum, which physiologic test should be included when assessing a lower extremity bypass graft?

A

PVR waveformswith thigh high and below knee pressures

90
Q

Which artery is NOT commonly used as inflow for a bypass graft in the lower extremities?
a. common femoral artery
b. profunda femoris
c. geniculate artery
d. popliteal artery

A

c

91
Q

Which transducer would allow optimal near-field imaging for the evaluation of a superficial, in situ vein graft?
a. 2 to 3 MHz
b. 3 to 5 MHz
c. 5 to 7 MHz
d. 10 to 12 MHz

A

d

92
Q

What views can be used for an initial rough scan of a bypass graft, including inflow and outflow, and may be helpful to identify tributaries of an in situ graft?

A

transverse

93
Q

Which of the following is NOT a potential incidental finding related to the perigraft space?
a. retained valve
b. seroma
c. hematoma
d. abscessses

A

a

94
Q

Where will myointimal hyperplasia typically occur in an autogenous vein graft>

A

at the distal anastamosis

95
Q

If an intimal flap or a dissection is present in a bypass graft, what is the typical cause?

A

intraoperative technical problem

96
Q

In synthetic aortofemoral or femoro-femoral grafts, where may pseudoaneurysms, although rare, occur?

A

the distal anastamosis

97
Q

Arteriovenous fistulae, occasionally seen in in situ bypass grafts, result from failure to ligate which of the following?
a. the small saphenous vein
b. a perforating vein
c. a small arterial branch
d. a defect at valve lysis

A

b

98
Q

How is mean graft flow velocity calculated?

A

averaging three or four velocities from nonstenotic segments

99
Q

What is the first modality that hsould be used to examine a bypass graft?

A

B-mode

100
Q

On a follow-up of a bypass graft done 4 years ago, what may a Doppler spectrum displaying delay in systole indicate?

A

atherosclerotic stenosis at the inflow

101
Q

Duplex ultrasound has been shown to be reliable in the detection of significant pathology in infrainguinal bypass grafts in ______ patients, before measurable changes in physiologic testing.

A

asymptomatic

102
Q

Combining physiologic study data with duplex ultrasound for the assessment of an infrainguinal bypass graft is important for the detection of significant pathology and the evaluation of _____.

A

global limb perfusion

103
Q

Types of bypass grafts can be categorized based on the material used for the graft and ______ employed.

A

surgical technique

104
Q

Vein grafts have a longer patency rate than synthetic grafts (independently of the location) because vein grafts are less _______.

A

thrombogenic

105
Q

Types of materials used for infrainguinal bypass grafts include autogenous veins, synthetic materials, and _______.

A

cryopreserved

106
Q

Within the first 30 days of the perioperative period following the implantation of a bypass graft, the most common problems are ______.

A

technical

107
Q

In the 1 to 24 month postoperative period, 75% of graft revisions are done for stenoses at the proximal or distal ______.

A

anastamosis

108
Q

To document a stenosis within a bypass graft most completely, the PSV and EDV proximal, within, and distal to the stenosis should be noted as well as poststenotic _____.

A

turbulence

109
Q

To ensure accurate documentation during a follow up for a bypass graft, it is important for the sonographer to be familiar with the type and location of the bypass and, therefore, refer to _____.

A

surgical notes

110
Q

Twenty four months after a bypass graft has been performed, the main cause of failure will be _______, primarily in the inflow and outflow arteries.

A

progressive atherosclerosis

111
Q

During follow-up exams of bypass graft using comparison of flow velocities for diagnostic purposes, an effort should be made to obtain the velocities in the same location, as well as with the same _____ as previously employed.

A

angles

112
Q

When evaluating the distal anastamosis and outflow artery of a bypass graft, a(n) ______ in peak systolic velocity (PSV) in the outflow artery can be encountered because the artery may have a smaller caliber.

A

increase

113
Q

Within the vein conduit, the two most common image abnormalities that are observed are _____ and ____.

A

valves
myointimal hyperplasia

114
Q

Color Doppler can be useful in the evaluation of a bypass for defects; however, care must be taken because color can also _____ small wall defects or other pathology.

A

mask

115
Q

Although located in the lower extremities, Doppler spectra in a bypass graft can display ____ resistance characteristics, often owing to hyperemia or arteriovenous fistula.

A

low

116
Q

A blunted, monophasic spectral Doppler pattern with zero diastolic flow typically indicates ______.

A

stenosis

117
Q

A decrease of mean graft flow velocity of more than _____ from previous exam is indicative of potential failure of the graft.

A

30 cm/s

118
Q

A velocity ratio of 3.5 and a PSV >300 cm/s is consistent with a ____ stenosis.

A

> 75%

119
Q

A tunnel PTFE femoral to popliteal graft will be _____ than an in situ graft.

A

deeper

120
Q

To examine the distal anastamosis and outflow of a femoral to dorsalis pedis bypass graft, one may opt to select a transducer with ____ frequency.

A

higher

121
Q

An in situ graft vein refers to:

A

a vein left in its natural anatomic bed

122
Q

The distal anastamosis of a bypass is generally constructed:

A

below the level of the most distal site of arterial disease

123
Q

A patient presents with right foot pain following a right lower extremity in situ bypass 2 weeks ago. Which of the following is least likely to be observed during a duplex ultrasound scan?
a. anastomotic stricture due to suture placement
b. thrombosis
c. a partial valve remnant
d. progression of atherosclerotic plaque

A

d

124
Q

All of the following statements concerning myointimal hyperplasia are true except:
a. will have a different ultrasound appearance than plaque
b. can become evident on ultrasound between 1 and 24 months
c. is not atherosclerotic plaque
d. only occurs at valve sites

A

d

125
Q

Which of the following transducers should be selected to examine a tunneled synthetic graft?
a. 7-10 MHz linear array
b. 5-7 MHz linear array
c. 10-15 MHz hockey stick type transducer
d. 10-12 MHz linear array

A

b

126
Q

You are asked to examine a patient who has a common femoral to below knee popliteal artery bypass graft. Which of the following lists some of the segments that must be included in the examination?
a. the common femoral, distal popliteal, and distal posterior tibial arteries
b. the common femoral, proximal superficial femoral, and proximal profunda femoral arteries
c. The common femoral, distal anastamosis, and mid to distal posterior tibial arteries
d. the common femoral, proximal anastamosis, distal popliteal arteries

A

d

127
Q

Proximity to the bypass graft is particularly important to note for which of the following incidental pathology?
a. abscess
b. dilated lymph nodes
c. venous thrombosis
d. none

A

a

128
Q

An intimal flap is a complication that can be seen with bypass grafts. It should appear as:

A

a small piece of the vessel wall which projects into the lumen of the

129
Q

Which of the following anastamotic sites is the most common location for pseudoaneurysm formation?
a. a common femoral to saphenous vein in situ bypass graft
b. A saphenous vein in situ bypassgraft to mid posterior tibial artery
c. a common femoral artery to prosthetic graft
d. a vein-vein interposition graft

A

c

130
Q

During a 6 month postoperative ultrasound examination of an in situ bypass, you observe the spectrumin the proximal bypass as having a sharp rise to peak systole and continuous antegrade flow throughout diastole. The most likely cause for this waveform includes:

A

a

131
Q

A 50% stenosis within a bypass is most likely associated with which of the following?
a. a verlocity ratio of >2.0
b. an end diastolic velocity of > 20 cm/s
c. A peak systolic velocity os >125 cm/s
D. A velocity ratio of >1.5

A

a

132
Q

Which of the following correclty desribes the calculation of mean graft flow velocity
a. average the volume flow meausmrents, taken at the prroximal and distal portions of the bypass graft
b. average 3 to 4 peak systolic velocity measurements in nonstenotic segments of a bypass graft
c. average 3 to 4 peak systolic velocity measurements taken within a stenotic segmentof the bypass graft \
d. average the volume flow measurements taken at 3 to 4 different segments of the bypass graft

A

b

133
Q

As compared to a previous examination, which statement is correct concerning mean graft flow velocity?
a. a decrease greater than 30 cm/s indicates a bypass may by in jeopardy of failure
b. cannot be used to compare bypass status between visits
c. A decrease greater than 0.15 indicates a bypass may be in jeopardy of failur
d. An increase greater than 2.0 indicates a 50% stenosis is likely present

A

a

134
Q

What finding is observed in all bypass stenoses?

A

poststenotic turbulence

135
Q

You are examining a patient who is 3 years postop with a superficial femoral to peroneal artery in situ bypass. The patient is cocmplainging of calf pain when walking. Which of the following is most likely the cause of this patient’s symtptoms.
a. graft entrapment
b. poor graft flow due to an arteriovenous fistula
c. progression of atherosclerotic disease within the inflow or outflow arteries
d. A stenosist due to suture placement

A

c

136
Q

made of various manufactured materials; associated with poor long-term patency rates

A

prosthetic (synthetic) bypass grafts

137
Q

preferred graft material; better long-term patency rates

A

autogenous vein

138
Q

Most common vein used for bypass grafts

A

great saphenous

139
Q

During the first 30 days, _____ problems are more likely to occur

A

technical

140
Q

Between 1 and 24 months, _____ can developing creating stenosis and usually occurs at ______.

A

myointimal hyperplasia
valve site

141
Q

Most common cause of graft revision between 1 and 24 months

A

myointimal hyperplasia

142
Q

Routine surveillance protocol bypass graft

A

early first postoperative ultrasound, first year 3, 6, 12 months and annually thereafter

143
Q

Normal walls of vein graft should appea:

A

smooth and uniform

144
Q

_____ grafts have a distinctive double line appearance of graft wall.

A

PTFE

145
Q

valve or valve remnants that remain due to incomplete valve disruption during surgery; appear as bright echoes within graft lumen

A

retained valves

146
Q

rapid proliferation of cells into intimal layer; can occur at any point along bypass conduit; typically occurs in areas where vein has sustained injury or valve sinus; can result in stenosis

A

myointimal hyperplasia

147
Q

A normal bypass should demonstrate _____ waveforms with ____ upstroke and _____ systolic peak

A

multiphasic
sharp
narrow

148
Q

abnormal connection between artery and vein

A

arteriovenous fistula

149
Q

Energy losses across stenosis produce lower velocities ____ to stenosis.

A

distal

150
Q

Normal velocities are typically below _____ cm/s

A

150

151
Q

PSV >___ cm/s considered abnormal

A

180

152
Q

calculated by taking average of three to four PSV values in nonstenotic grafts segments at various levels

A

mean graft flow velocity

153
Q

Normal GFV is greater than ___ cm/s

A

45

154
Q
A

Vascular (33 decks)

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