Duplex/CDI LE Flashcards
capabilities
LE interventions:
f/u by pass graft
localize stenosis prior to balloon angioplasty
presence of aneurysm
determine >50% diameter reduction or occlusions
limitations
dressings/ bandages
calcific shadowing
explain Dopper equation
doppler frequency =
2 x F0 x V of moving reflector x cos
//////////////////////////////////////////////////////
c
what is the speed of sound in soft tissue
1540 m/sec
what does the 2 in the Doppler equation represent
round trip — there are 2 Doppler shifts
red blood cell is first stationary observer
then it
acts as a wave source
velocity is what ?
the speed of moving reflectors through soft tissue
what is the only controllable variable in the velocity equation
Doppler angle
what should Doppler angle be ?
60 degrees
technique for native arteries
probe
10 aspects of anatomy
3 general image guidelines
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)
if a >50% reduction is suspected what 3 things should be documented
PRE PSV
PSV @highest in stenosis
post stenosis turbulence & decreased PSV
what 3 things should be documented or asked about a bypass graft before start of exam
type of bypass
location of bypass
age of bypass
what are 2 types of synthetic grafts
PTFE
dacron
What are some types of autogenous grafts
RSVG reversed saphenous vein graft
in-situ vein graft
which vein is most commonly used in autogenous bypass grafts
GSV
what happens surgically when a saphenous vein is used as RSVG
4
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
what happens surgically in IN-situ vein grafts
3
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
what is usually combined with bypass graft duplex?
ABI
protocol for bypass graft
5
inflow artery prox anastamosis mid graft distal anastamosis outflow artery
vein grafts are more likely to have nter-vein lesions because
the valves — can create stenosis
*either by being reversed or surgically ligated which may create weakness in vessel wall
what sites of the graft are most likely to become stenotic
anastamosis
intergraft stenosis in synthetic grafts are common or uncommon
uncommon
Interpretation of native arteries
comparison of stenotic PSV to pre stenotic PSV
what are the parameters for interpretation of
stenotic PSV : pre-stenotic PSV
2:1 = >50% diameter reduction
4:1 = >75% diameter reduction
or >400 cm/sec
post stenotic turbulence always needs to be present
grafts can also become aneurysmal or occluded (T/F)
True
describe typical pre stenotic waveform
monophasic and dampened
what does the waveform at the stenosis look like
elevated velocities, spectra broadness
highest PSV should be documented
what will waveform look like distal to a stenosis
turbulant, with decreased PSV
what type of normal flow might be evident at distal anastamosis of RSVG
and at what part ?
bidirectional flow / retrograde flow in the native artery
what type of resistance flow pattern can be considered normal in a bypass graft bc it is an abnormal condition
low resistance
why does retrograde flow occur in the native artery of a distal anastamosis of RSVG
pressure gradient
and prox occlusion in the native artery
when do initial problems occur after graft
3 months
what parameters should be considered when comparing previous studies
- 30 cm/sec in any graft segment from previous
reduced PSV in smallest graft diameter from previous
change in phasicitiy
- > 1.5 ABI readiing
what post op complications should be looked for in f/u study
AV fistula - will siphon graft flow
valve cusp site complications
Synthetic grafts most common complication
stenosis at anastamosis
synthetic graft surveys:
previous data to determine whether a _____% stenosis reduction exists as well as ________
50%
graft occlusion
anastomotic sites should be evaluated for what 2 conditions
aneurysm
stenosis
Post endovascular intervention :
normal stented arteries may have a(an) ______ PSV
elevated
as a general rule 2:1 ratio when determining normal velocities in a stented graft determine
hemodynamically significant stenosis
especially with post stenotic turbulence
INtraoperative monitoring is used commonly in what vessel ?
what is it used to identify in LE
carotid arteries
used to :
…patient anastomosis
.. valve cusp sites
…suspected tributary branch sites that may form AVF
what is the only user controlled variable in the Doppler equation
Cos only the angle can be controlled,
optimal angel in 60 degrees
40-60 degrees is usually acceptable
