Duplex/CDI LE

Question 1

capabilities

Answer 1

LE interventions:
f/u by pass graft
localize stenosis prior to balloon angioplasty

presence of aneurysm
determine >50% diameter reduction or occlusions

Question 2

limitations

Answer 2

dressings/ bandages

calcific shadowing

Question 3

explain Dopper equation

Answer 3

doppler frequency =

2 x F0 x V of moving reflector x cos
//////////////////////////////////////////////////////
c

Question 4

what is the speed of sound in soft tissue

Answer 4

1540 m/sec

Question 5

what does the 2 in the Doppler equation represent

Answer 5

round trip — there are 2 Doppler shifts

red blood cell is first stationary observer
then it
acts as a wave source

Question 6

velocity is what ?

Answer 6

the speed of moving reflectors through soft tissue

Question 7

what is the only controllable variable in the velocity equation

Answer 7

Doppler angle

Question 8

what should Doppler angle be ?

Answer 8

60 degrees

Question 9

technique for native arteries

probe
10 aspects of anatomy
3 general image guidelines

Answer 9

5-7 MHz Linear

Distal EIA
CFA  common femoral  a
CFA bifurcation
SFA
DFA 
POP a 
Trifurcation 
PTA 
PER A 
ATA 

greyscale images for plaque / abnormal wall

color flow patterns

PSV from each major vessel ( prox/mid/dist)

Question 10

if a >50% reduction is suspected what 3 things should be documented

Answer 10

PRE PSV
PSV @highest in stenosis
post stenosis turbulence & decreased PSV

Question 11

what 3 things should be documented or asked about a bypass graft before start of exam

Answer 11

type of bypass
location of bypass
age of bypass

Question 12

what are 2 types of synthetic grafts

Answer 12

PTFE

dacron

Question 13

What are some types of autogenous grafts

Answer 13

RSVG reversed saphenous vein graft

in-situ vein graft

Question 14

which vein is most commonly used in autogenous bypass grafts

Answer 14

GSV

Question 15

what happens surgically when a saphenous vein is used as RSVG
4

Answer 15

vein is removed
replaced in reverse

(so small end of SV is prox and the large end is distal )

vein valves stay open due to flow
branches are ligated

Question 16

what happens surgically in IN-situ vein grafts

3

Answer 16

GSV stays in place
(small end is distal - large end is prox)

prior to surgery valves are broken up with special instrument

branches are ligated

Question 17

what is usually combined with bypass graft duplex?

Answer 17

ABI

Question 18

protocol for bypass graft

5

Answer 18

inflow artery 
prox anastamosis 
mid graft 
distal anastamosis 
outflow artery

Question 19

vein grafts are more likely to have nter-vein lesions because

Answer 19

the valves — can create stenosis

*either by being reversed or surgically ligated which may create weakness in vessel wall

Question 20

what sites of the graft are most likely to become stenotic

Answer 20

anastamosis

Question 21

intergraft stenosis in synthetic grafts are common or uncommon

Answer 21

uncommon

Question 22

Interpretation of native arteries

Answer 22

comparison of stenotic PSV to pre stenotic PSV

Question 23

what are the parameters for interpretation of

stenotic PSV : pre-stenotic PSV

Answer 23

2:1 = >50% diameter reduction
4:1 = >75% diameter reduction
or >400 cm/sec

post stenotic turbulence always needs to be present

Question 24

grafts can also become aneurysmal or occluded (T/F)

Answer 24

True

Question 25

describe typical pre stenotic waveform

Answer 25

monophasic and dampened

Question 26

what does the waveform at the stenosis look like

Answer 26

elevated velocities, spectra broadness

highest PSV should be documented

Question 27

what will waveform look like distal to a stenosis

Answer 27

turbulant, with decreased PSV

Question 28

what type of normal flow might be evident at distal anastamosis of RSVG
and at what part ?

Answer 28

bidirectional flow / retrograde flow in the native artery

Question 29

what type of resistance flow pattern can be considered normal in a bypass graft bc it is an abnormal condition

Answer 29

low resistance

Question 30

why does retrograde flow occur in the native artery of a distal anastamosis of RSVG

Answer 30

pressure gradient

and prox occlusion in the native artery

Question 31

when do initial problems occur after graft

Answer 31

3 months

Question 32

what parameters should be considered when comparing previous studies

Answer 32

• 30 cm/sec in any graft segment from previous

reduced PSV in smallest graft diameter from previous

change in phasicitiy

• > 1.5 ABI readiing

Question 33

what post op complications should be looked for in f/u study

Answer 33

AV fistula - will siphon graft flow

valve cusp site complications

Question 34

Synthetic grafts most common complication

Answer 34

stenosis at anastamosis

Question 35

synthetic graft surveys:

previous data to determine whether a _____% stenosis reduction exists as well as ________

Answer 35

50%

graft occlusion

Question 36

anastomotic sites should be evaluated for what 2 conditions

Answer 36

aneurysm

stenosis

Question 37

Post endovascular intervention :

normal stented arteries may have a(an) ______ PSV

Answer 37

elevated

Question 38

as a general rule 2:1 ratio when determining normal velocities in a stented graft determine

Answer 38

hemodynamically significant stenosis

especially with post stenotic turbulence

Question 39

INtraoperative monitoring is used commonly in what vessel ?

what is it used to identify in LE

Answer 39

carotid arteries

used to :

…patient anastomosis
.. valve cusp sites
…suspected tributary branch sites that may form AVF

Question 40

what is the only user controlled variable in the Doppler equation

Answer 40

Cos only the angle can be controlled,

optimal angel in 60 degrees
40-60 degrees is usually acceptable