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Vascular 2 > M8: Peripheral Arterial Disease Part 3 > Flashcards

M8: Peripheral Arterial Disease Part 3 Flashcards

1
Q

does trickle flow show reversal

A

no

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2
Q

why dont you often get a staccato waveform is the peripheral arteries

A

b/c of multiple branches which causes a lower resistance system

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3
Q

role of US in assessing bypass grafts

A
  • assess baseline hemodynamics post revascularization
  • provide info to help w/ decisions about alternative treatments
  • identify correctable lesions before graft thrombosis
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4
Q

indication for US of arterial bypass graft and stent

A

post-opt follow up
new symptoms post intervention (claudication, pain, ulcer, etc)
decreased ABI >0.15 compared to previous exam
lack of pulse, rubor, cyanosis
pulsatile mass near anastomotic site/intervention site

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5
Q

most common location of arterial bypass grafts and stents

other common places

A

AO-iliac (abdo AO to unitlaterl or bilateral iliac)

AO-Fem (abdo AO to uni/bilateral FA)
AX-Fem
Fem-Fem

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6
Q

types of LE arterial bypass grafts

A

synthetic - PTFE or Dacron
autogenous - natural materials
modified biological grafts
composite - synthetic graft connected to a vein (part synthetic, part native vein)

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7
Q

describe autogenous LE arterial bypass grafts

A

vein bypass grafts…. 2 types:

In-situ (as is) vein: vein is left in original location w/ valves cut and branches ligated

reversed vein: vein is ligated, reversed and attached to arteries

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8
Q

veins commonly used for autogenous LE arterial bypass grafts

A

GSV
SSV
basilic or cephalic vein

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9
Q

types of modified biological grafts

A

human umbilical vein
cryopreserved saph vein
bovine/cow

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10
Q

3 types of bypass anastamoses

A

end - end
end to side
side to side

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11
Q

which type of bypass anastamosis allows flow to go both ways

A

end to side

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12
Q

describe the mechanisms of early graft failure (<30 days)

A

due to erros in bypass construction (poor choice of inflow or outflow vessel, retained values, clamp injury)

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13
Q

describe the mechanisms of late graft failure

A

1 month - 2 years: most commonly, intimal hyperplasia can cause a stenosis in the graft

older than 2 years: atherosclerotic plaque can cause a stenosis in the graft

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14
Q

general causes of graft failure

A 
hyper coagulable disorder infection
aneurysmal degeneration in older vein grafts due inability to handle high press
trauma leading to thrombus
thromboembolism
idiopathic
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15
Q

describe the mechanisms of early stent failure (<30 days)

describe the mechanisms of late stent failure (> 30 days)

A

early: technical failures
late: re-current stenosis

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16
Q

common sites of graft obstruction

A

valve site for vein grafts
anastomoses
inflow or outflow tract
graft kink

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17
Q

do we obtain bilateral ABIs when assessing grafts and stents

A

yes

18
Q

describe how you assess a bypass graft and stent

A

obtain TRX 2D and colour and SAG colour and spectral of:

inflow/prox native artery
prox anastomosis
prox graft/stent
mid graft/stent
distal graft/stent
distal anastomosis
outflow/distal native artery
19
Q

if you see a stenosis in a graft or stent, in which plane(s) do you measure

A

TRX and SAG

20
Q

describe the waveform see early post opt (first 2 months) in a stent and bypass

why is it like this

A

may not be triphasic and it will be low resistance

reactive hyperemia

21
Q

how should spectral waveforms seen in early stent/graft assessment change with time

A

change from low resistance to high resistance and triphasic.. some may never become triphasic but should become high resistance

22
Q

w/ a graft, what determines the severity of the stenosis

A

graft material

23
Q

how do we assess a stenosis in a graft

A

do an ABI or TBI
PSV and flow direction
Vr
assess waveform patterns and changes

24
Q

what is the velocity ratio

A

ratio of highest PSV in the stenosis (V2) divided by the PSV of a normal proximal segment

25
Q

characteristic US appearance of a synthetic graft

A

double line wall appearance

26
Q

what should the waveform of the inflow artery of a graft look like and what should the Vr be

should the body of the stent/graft appear any different

A

triphasic
Vr < 2.0

no, should be the same unless there was recent placement

27
Q

what should the waveform of the prox anastamosis of a graft look like and what should the Vr be

A

may be disturbed due to bifurcating and branching

Vr < 2.0

28
Q

how will a large inflow artery feeding a small diameter graft affect the Vr

A

it will make it higher

29
Q

norm PSV and VR for the body of a graft

minimum PSV for vein grafts = 4 mm in diameter… what about for larger grafts

A

PSV <180 cm/s
Vr <2.0

smaller: >40-45 cm/s
larger: minimum ~35 cm/s

30
Q

norm PSV and VR for the body of a stent

is there a minimum velocity for stents

A

< 190 cm/s
Vr <1.5

no

31
Q

what should the waveform of the distal anastamosis of a graft look like and what should the Vr be

A

increased velocity, usually due to size change from a wider graft to a narrower artery…. also disturbed flow

Vr <3.0

32
Q

what should the waveform of the outflow artery of a graft look like and what should the Vr be

A

velocities remain unchanged w/ waveform similar to the body of the graft/stent

Vr <2.0

33
Q

significant inflow artery obstruction is indicated by what type of spectral waveform in the graft

significant outflow artery or anastomoses obstruction is indicated by what type of spectral waveform in the graft

A

monophasic (tardus parvus)

high resistance w/ no end-diastolic flow, or staccato

34
Q

The Vr can be up to what value is the graft diameter is much smaller than the inflow vessel

A

up to <3.0

35
Q

what PSV and Vr in the body of a graft indicate >/= 50% stenosis?

> /= 70% stenosis

A

> /= 50%: PSV >180 cm/s and Vr >2.0

> /= 70%: PSV >300 cm/s and Vr >3.5

36
Q

what PSV and Vr in the body of a stent indicate > 50% stenosis?

> 70% stenosis

A

> 50%: PSV >190 cm/s and Vr >1.5

> 70%: PSV >275 cm/s and Vr >/= 3.5

37
Q

a PSV of what value indicates impending vein graft failure

A

PSV < 40-45 cm/s throughout a normally size graft

38
Q

what Vr value indicates >/= 50% stenosis at the distal anastomoses site

A

Vr >3.0

39
Q

describe aneurysmal dilatation of the bypass or stent

A

focal enlargement twice the proximal arterial segment w/ possible intraluminal thrombus in the aneurysm

40
Q

where can entrapment of a graft commonly occur

describe what happens

A

at the knee…

w/ slight leg bend normal flow is seen
w/ leg straight, no flow is detected w/ colour or spectral doppler

Vascular 2 (6 decks)

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