This document discusses the use of arterial duplex testing to evaluate lower extremity arterial disease. It provides details on: 1) How duplex testing uses Doppler ultrasound to assess blood flow via velocity spectra and anatomy via B-mode imaging to classify occlusive and aneurysm disease. 2) The characteristic features of normal versus abnormal velocity spectra that indicate things like stenosis or occlusion. Parameters like peak systolic velocity and pulsatility index are used to interpret test results. 3) How duplex testing can map the arterial tree and detect changes after interventions like bypass grafting or angioplasty through identifying stenosis. Accurate interpretation of velocity spectra is important for diagnostic evaluation.

1. www.elsevier.com/locate/semvascsurg
Available online at www.sciencedirect.com
Interpretation of arterial duplex testing of lower-
extremity arteries and interventions
Kelley D. Hodgkiss-Harlowa
, and Dennis F. Bandykb,n
a
Division of Vascular Surgery, Kaiser Permanente Foundation, San Diego, CA
b
Division of Vascular and Endovascular Surgery, University of California, San Diego School of Medicine, Sulpizio
Cardiovascular Center, 7404 Medical Center Drive, Mail Code 7403, La Jolla, CA 92037
a b s t r a c t
Arterial duplex testing is used to evaluate patients with lower-limb arterial occlusive or
aneurysmal disease to provide clinicians with detailed information on location, extent, and
severity of disease. It is possible to detect disease from the visceral aorta to the tibial
arteries. Duplex testing is interpreted in conjunction with limb-pressure measurements to
accurately categorize arterial hemodynamics and functional impairment. Understanding
the features of duplex-acquired velocity spectra recordings is fundamental to accurate
diagnostic testing, including the characteristic spectral features of “normal” versus
“abnormal” lower-limb arterial flow, hemodynamic changes associated with stenosis or
occlusion, and the status of distal limb or foot perfusion. Scanning can provide an arterial
map of occlusive or aneurysm lesions analogous to an angiogram. Testing is accurate
before and after intervention for the detection of stenosis; a common failure mode after
bypass grafting or peripheral angioplasty. The detection of high-grade stenosis in an
arterial repair allows for pre-emptive treatment before thrombosis occurs and improves
long-term patency.
& 2013 Elsevier Inc. All rights reserved.
1. Introduction
Duplex ultrasound is an integral component of diagnostic
testing for the evaluation of lower-extremity arterial disease,
including after intervention (bypass grafting and angioplasty)
[1,2]. Testing provides objective information about blood flow
(pulsed Doppler spectral analysis) and anatomy (B-mode and
color Doppler imaging) for the accurate classification of
occlusive and aneurysm disease. Modern ultrasound instru-
mentation affords assessment of blood flow using one of
several techniques (eg, color Doppler imaging, pulsed Doppler
spectral analysis, power Doppler imaging, or B-flow imaging)
and high-resolution B-mode imaging of artery anatomy,
including three-dimensional vessel reconstruction and eval-
uation of atherosclerotic plaque morphology. Test
interpretation ranges from normal to clinically relevant dis-
ease categories of mild, moderate, or severe ischemia, and
should be performed in conjunction with indirect physiologic
testing (eg, systolic blood pressure measurement and pulse
volume plethysmography) to accurately categorize arterial
hemodynamics and functional impairment. When peripheral
arterial disease (PAD) is identified, duplex imaging can be
used to map the arterial tree for occlusive or aneurysm
lesions, analogous to an angiogram [3]. After intervention,
duplex testing can detect changes in functional patency of a
bypass graft, arterial repair, or angioplasty sites by identi-
fication of stenosis. Accurate interpretation of velocity spec-
tra recordings obtained by duplex scanning is fundamental to
successful application of this diagnostic technique. This
review details the characteristic features of normal and
0895-7967/$ - see front matter & 2013 Elsevier Inc. All rights reserved.
http://dx.doi.org/10.1053/j.semvascsurg.2013.11.002
n
Corresponding author.
E-mail address: dbandyk@ucsd.edu (D.F. Bandyk).
S E M I N A R S I N V A S C U L A R S U R G E R Y 2 6 ( 2 0 1 4 ) 9 5 – 1 0 4

2. abnormal duplex-acquired velocity spectra necessary for test
interpretation and disease classification.
2. Lower-extremity duplex testing
To perform detailed arterial mapping, duplex ultrasound
instrumentation for peripheral testing requires the use of
curved and linear array transducers with 3.5- to 7-MHz
imaging frequencies for appropriate depth penetration and
high-resolution imaging of the abdominal and extremity
arteries. A 90-degree imaging angle should be used to meas-
ure vessel diameter, identifying intima-medial thickening,
and assessing atherosclerotic plaque composition. There are
two types of Doppler ultrasound displays: a color flow
Doppler image showing mean flow velocity distribution dis-
played as a color-encoded map superimposed on the gray-
scale B-mode tissue image; and a spectral Doppler image
showing the time-varying flow velocity distribution within a
selected sample volume. The latter display provides quanti-
tative information as to the peak velocity during the pulse
cycle and the spectral content, that is, the range of velocities
at each point in time. To obtain reproducible information
from pulsed spectral Doppler recordings, a Doppler beam
angle of r60 degrees relative to the transducer insonation
beam and the artery wall should be used.
The normal pulsed Doppler velocity spectra recorded from
a peripheral lower- or upper-extremity artery has the features
of multiphasic or triphasic waveform with a narrow spectral
width (range of velocities) throughout the pulse cycle, indi-
cating red blood cells are moving at a similar speed and
direction in a nondisturbed or laminar flow pattern (Fig. 1).
The velocity spectra waveform with each cardiac pulse
reflects blood acceleration during systolic, an early diastolic
flow reversal caused by the propagated pressure pulse wave
and its reflection from a higher downstream resistance,
followed by late antegrade diastolic flow. There might be
atherosclerotic plaque imaged, but lumen reduction at the
recording site and proximal is o50% diameter reducing (DR).
Spectral broadening with peak systolic velocity (PSV) increase
in the pulsed Doppler signal indicates “disturbed” flow or
turbulence and can be recorded centerstream at bifurcations,
regions of focal diameter change, and sites of stenosis.
For interpretation of PAD severity, the duplex-acquired
velocity spectra parameters of acceleration time, pulsatility
index (PI), and maximum spectra velocity measured at PSV
and end-diastole are used (Table 1). Changes in these wave-
form parameters allow detection of segmental, hemody-
namic significant occlusive disease. The PSV measurement
is reproducible and the most common velocity spectra
parameter used in the interpretation of normal artery flow,
critical limb ischemia, and for the grading of arterial stenosis.
Normal PSV in lower-limb arteries is in the range of 55 cm/s
at the tibial artery to 110 cm/s at the common femoral artery
(Table 2). The end-diastole velocity measurement is used in
conjunction with PSV for evaluating high-grade stenosis
(>70% DR) with values >40 cm/s indicating a pressure-
reducing stenosis.
The PI is calculated by dividing the peak-to-peak velocity
spectra shift by the mean velocity. The PI of normal periph-
eral arteries is >4.0 (femoral artery, >6; popliteal artery >8). PI
values r4 reflect proximal inflow or occlusive disease, and
Fig. 1 – Duplex image with normal, multiphasic velocity
spectra recorded from the common femoral artery (top)
and superficial femoral artery. Recording made using a
60-degree Doppler beam angle and pulsed Doppler
sample volume is positioned in the flow centerstream
where color flow pixels indicate highest mean velocity.
Table 1 – Velocity spectra waveform parameters used for duplex test interpretation.
Testing area PSV EDV AT PI Mean flow velocity
Peripheral artery X X X X
Bypass graft surveillance X X X X
Peripheral angioplasty X X X
AT, systolic acceleration time; EDV, end-diastolic velocity; PI, pulsatility index; PSV, peak systolic velocity.
S E M I N A R S I N V A S C U L A R S U R G E R Y 2 6 ( 2 0 1 4 ) 9 5 – 1 0 496

3. changes in PI or spectral waveform damping are diagnostic of
multilevel occlusive disease (Fig. 2). Division of the distal
artery PI by the proximal artery PI calculates the “damping
factor” with the normal value of Z0.9 and a value o0.9
diagnostic of occlusive disease.
The systolic acceleration time during systole can also be
used to diagnose occlusive disease proximal to pulsed Dop-
pler recording site. A normal value is o133 ms [4]. As the
systolic acceleration time increases to >200 ms, spectra
waveform develops a rounded upslope (termed tardus parvas)
configuration due to the prolonged time to PSV. The presence
of damped, low-velocity blood flow in an extremity artery or
bypass graft indicates a proximal pressure-reducing lesion
with regional systolic blood pressure o60% of normal (Fig. 3).
The diagnostic accuracy of systolic acceleration time can be
influenced by cardiac conditions (eg, cardiomyopathy, aortic
valve disease), but downstream occlusive disease has mini-
mal influence on diagnostic sensitivity.
Arterial stenosis is recognized with color flow imaging by a
reduction in the color-encoded flow lumen, imaging a high-
velocity flow region with color bar aliasing and development
of a mosaic flow pattern in the lumen signifying turbulent
flow. At the site of a high-grade (>75% DR) stenosis, the real-
time color Doppler flow will appear as a whitened, color-
desaturated “flow jet” with mosaic color flow extending for
several vessels diameters downstream, corresponding to
post-stenotic turbulence.
The definition of a significant or “critical” arterial stenosis is
a lesion that is associated with a resting systolic pressure
gradient of >15 mm Hg and reduces resting volume flow. In
peripheral arterial circulation, this correlates with Z50% DR
stenosis or >75% cross-sectional area reduction. Assessing the
PSV changes that occur from proximal to, within, and distal to
an arterial stenosis, duplex testing can estimate hemodynamic
significance and predict the degree of lumen DR with specified
ranges, eg, o50% DR, >50% DR, and >70% to 75% DR (Fig. 4,
Table 3). Velocity spectra characteristics of a >50% DR arterial
stenosis include an elevated PSV >180 cm/s, systolic spectral
broadening indicating highly disturbed flow, ie, post-stenotic
turbulence, with simultaneous forward and retrograde velocity
spectra during systole. The ratio of PSV (Vr) across a stenosis is
a useful parameter to grade stenosis severity, with a Vr >2
indicating >50% DR and a VR >4 correlating with >70% DR.
Typically, a pressure-, and flow-reducing arterial stenosis is
associated with monophasic waveform with PSV >250 to 300
cm/s, a Vr across the stenosis >3.5, and end-diastolic velocity
>40 cm/s. Downstream of a significant pressure-reducing
arterial stenosis, the spectral waveform should appear
damped and monophasic, with prolongation of acceleration
time and a decrease in PSV to below normal levels. As stenosis
severity increases to >90% DR, the volume flow through the
stenosis trends toward zero, which can produce a PSV at the
stenosis in a minimally elevated range (100 to 200 cm/s) and
low velocity (o10 cm/s) “trickle” flow downstream. Athero-
sclerotic plaque associated with >50% stenosis might be
calcified and produce an acoustic shadow that interferes with
measurement of residual artery diameter or cross-section area
reduction on transverse imaging. Correlation studies between
duplex testing and angiogram measurements have found
measurement of PSV and Vr are the best predictors of
peripheral arterial stenosis severity when expressed as %DR.
3. Lower limb arterial duplex testing
The extent of duplex mapping can be individualized based on
the indication for arterial testing. Screening for aneurysm and
or imaging to identify tibial artery calcification are appropriate
test indications in selected patients. Evaluation of the patient
with exertional leg pain, ie, diagnosis of claudication, and/or
signs of PAD, such as absent pulses, dependent rubor, and
nonhealing ulcer, can localize site(s) of arterial occlusive
disease. Lower-limb testing should include imaging of the
abdominal aorta and iliac arteries for aneurysm and the
common femoral arteries interrogated for the presence of
normal, ie, triphasic, velocity spectra. Incomplete vessel imag-
ing can occur due to bowel gas, obesity, poor patient cooper-
ation, or acoustic shadowing caused by plaque calcification.
The findings of duplex mapping are recorded in a sche-
matic of the extremity arterial tree, analogous to an
Table 2 – Mean (7standard deviation) artery diameters
and peak systolic velocities in healthy subjects.
Artery Diameter (cm) Velocity (cm/s)
Infrarenal aorta 2 7 0.2 55 7 12
Common iliac 1.5 7 0.18 70 7 18
External iliac 0.8 7 0.13 115 7 21
Common femoral 0.8 7 0.14 114 7 24
Superior femoral 0.6 7 11 90 7 14
Popliteal 0.5 7 0.1 68 7 14
Tibial arteries 0.3 7 0.4 55 7 10
Fig. 2 – Segmental duplex-acquired velocity spectra recorded
from a patient with multilevel femoropopliteal and tibial
artery occlusive disease. The multiphasic common femoral
artery flow indicates no significant proximal occlusive
disease. Abnormal monophasic velocity spectra recorded
from the popliteal and tibial artery signify segmental
occlusive lesions. Progressive damping of the popliteal and
tibial artery spectral waveforms establishes the diagnosis of
multilevel infrainguinal disease. Note the decrease in peak
systolic velocity (PSV) and low pulsatility index (PI) at the
ankle level.
S E M I N A R S I N V A S C U L A R S U R G E R Y 2 6 ( 2 0 1 4 ) 9 5 – 1 0 4 97

4. arteriogram, with notation of site(s) of aneurysm or occlusive
disease and measurements of velocity spectra at nondiseased
arterial segments (common femoral, superficial femoral,
popliteal, and tibial arteries) and at sites of stenosis. The
length of an arterial occlusion can be estimated based on the
location of exit and re-entry collaterals. Duplex mapping
allows classification of atherosclerotic occlusive disease in
the aortoiliac, femoral-popliteal, and popliteal-tibial arterial
segments based on TransAtlantic InterSociety Consensus
guidelines for grading lesions from A through D based on
lesion length and morphology. Endovascular therapy is rec-
ommended for TransAtlantic InterSociety Consensus A (sin-
gle lesion o3 cm) and B (single lesion 3 to 5 cm or tandem
lesions o3 cm) lesions because clinical results are equivalent
to surgical intervention with less morbidity. More advanced
TransAtlantic InterSociety Consensus C and D lesions, such
as long-segment (>5 to 10 cm) occlusions or multiple
stenoses, might also be amenable to endovascular therapy,
but the patency and re-intervention rates are not superior to
surgical revascularization; causing most surgeons to indi-
vidualize intervention based on patient risk factors predictive
of procedural morbidity.
Duplex-acquired velocity spectra recorded from nonstenotic
artery segments should be correlated with segmental or
ankle-brachial index (ABI) systolic pressure measurements.
Changes in spectral waveform, PI, and PSV develop as the ABI
deceases from normal (>0.9), to moderate ischemia (0.5 to
0.85), to severe ischemia levels (o0.5) (Fig 3). Severe limb
ischemia is present when the peripheral artery spectral wave-
form is damped, the pulsatility index is o1.5, and PSV is low
(o20 to 30 cm/s). The correlation of velocity spectra with ABI
is useful in estimating regional systolic pressure based on the
PSV and PI of segmental duplex spectra waveform recorded
from nonstenotic artery segments in diabetic or renal
Fig. 3 – Normal (left) and abnormal (right) velocity spectra recording from tibial artery at ankle. Multiphasic, normal peak
systolic velocity (PSV) (>50 cm/s) predicts normal ankle systolic pressure. Monophasic, low PSV tibial artery flow predicts
resting ankle-brachial index of o0.6.
Fig. 4 – Duplex categories (normal, o50%, >50%, 70% to 75%) of peripheral artery stenosis based on velocity spectra waveform
interpretation. PSV, peak systolic velocity.
S E M I N A R S I N V A S C U L A R S U R G E R Y 2 6 ( 2 0 1 4 ) 9 5 – 1 0 498

5. transplantation patients with heavily calcified, incompressi-
ble arteries precluding cuff-derived systolic pressure measure-
ment. In patients with mild claudication (ABI >0.8), tibial
artery velocity spectra can be triphasic, but after exercise
treadmill testing, a monophasic, damped waveform develops,
corresponding to the decrease in ankle systolic pressure.
The overall accuracy of peripheral duplex testing compared
with contrast angiography in grading PAD lesions is >80%, but
varies relative to arterial segment scanned, and is decreased
in limbs with multilevel disease. In blinded comparisons,
duplex grading of atherosclerotic occlusive disease (o50%
DR, >50% DR, occlusion) in the aorto-iliac segment had a
diagnostic sensitivity of 81% to 91% and specificity of 90% to
99%; for the femoropopliteal segment, sensitivity ranged from
67% to 91% and specificity 94% to 99% [4,5]. Multilevel disease
reduces diagnostic accuracy primarily in interpretation of
percent DR for the distal tandem stenosis with overall accu-
racy decreasing from >90% to 63% in the aortoiliac segment
and from 93% to 83% in the femoropopliteal tract. Distal to an
occlusion or high-grade stenosis, a stenosis identified by color
Doppler imaging should have a Vr >2.5 for interpretation of
>50% DR. The diagnostic accuracy of arterial duplex is suffi-
cient that several vascular groups have performed infraingui-
nal revascularization based solely on duplex arterial mapping,
which identified suitable proximal and distal anastomotic
sites, confirmed a patent artery to the foot as well as an
adequate diameter saphenous vein as a bypass conduit [6].
3.1. Femoral artery duplex scan after cannulation
Duplex scanning is the preferred diagnostic modality for
identification of pseudoaneurysm and arteriovenous fistula
development after catheter-based interventions. Test
indications can include pain, pulsatile mass, or bruit at an
arterial access site. Duplex features of femoral false aneurysm
include flow outside the artery, presence of a track or “stalk”
from the puncture site to the aneurysm sac, and a character-
istic “to and fro” flow pattern in the stalk corresponding to
blood flow into the aneurysm during systole and sac emptying
during diastole. Imaging of a false aneurysm stalk indicates
suitable anatomy for ultrasound-guided thrombin injection to
cause thrombus. Using B-mode and color Doppler imaging, a
needle is positioned within the sac and thrombin slowly
injected. Confirmation of sac thrombosis as well as normal
arterial and venous flow at the arterial puncture site com-
pletes the procedure. If an arteriovenous fistula is present at
the access site, a high-velocity flow jet (PSV >300 cm/s)
between the artery and vein will be identified and the external
iliac artery velocity spectra will have elevated PSVs, a low-
resistance flow signal proximal to the arteriovenous fistula,
and a triphasic (high resistance) signal distal.
3.2. Duplex testing after arterial intervention
A surveillance program after lower-limb arterial intervention
is recommended, but the extent of testing, including the
frequency of duplex testing, remains controversial. After
lower-limb open arterial repair (bypass graft, endarterectomy)
or endovascular therapy, duplex imaging can be a useful
component of clinical assessment that should also include
patient query for new symptoms of limb ischemia and
measurement of ABI. The frequency of testing should be
individualized to the patient, type of arterial intervention,
and initial post-repair duplex scan findings. An appropriate
surveillance schedule would be within 2 weeks of the proce-
dure and, if normal, 3 to 6 months later. Patients treated for
Fig. 5 – Duplex images of normal, multiphasic velocity spectra recording from a polytetrafluoroethylene prosthetic
femoropopliteal bypass graft (left) and superficial femoral artery stent (right). Peak systolic velocity is in normal
(450 cm/s) range.
Table 3 – Duplex classification of peripheral artery occlusive disease.
Stenosis category Peak systolic velocity (cm/s) Velocity ratio Distal artery spectral waveform
o20% o150 o1.5 Triphasic, normal PSV
20% to 49% 150À200 1.5À2 Triphasic, normal PSV
50% to 75% 200À300 2À4 Monophasic, reduced PSV
>75% >300 End-diastolic velocity >40 >4 Damped, monophasic, reduced PSV
Occlusion No flow, length of occlusion estimated based on distance from exit and
re-entry collaterals
Damped, monophasic reduced PSV
PSV, peak systolic velocity.
S E M I N A R S I N V A S C U L A R S U R G E R Y 2 6 ( 2 0 1 4 ) 9 5 – 1 0 4 99

6. critical limb should have testing every 3 months during the
first year. Color Doppler imaging of the arterial repair,
including adjacent inflow and outflow arteries, is performed
with the hemodynamics characterized by duplex-derived PSV
measurements along the reconstruction. The presence of
multiphasic, normal PSV flow at the ankle correlates with a
normal ABI and indicates the absence of angioplasty or
bypass graft stenosis (Fig. 5). The focus of duplex surveillance
is on the identification and repair of critical stenosis defined
by duplex velocity spectra criteria of PSV >300 cm/s and PSV
ratio across the stenosis >3.5—correlating with >70% DR
stenosis (Fig. 6) [7]. In some instances, the only indication of
a “failing” bypass is the identification of a low (o40 cm/s)
graft PSV. Low graft flow velocity predicts thrombosis and
requires a detailed search for an occlusive lesion, including
the use of angiographic imaging if duplex did not detection a
graft stenosis. When conducted appropriately, a duplex
surveillance program should result in an intervention graft
for detected stenosis of approximately 20% within the first
year and a failure rate of o5% per year.
Interpretation of initial duplex scan is based on color flow
mapping for occlusive or aneurysm lesions and velocity
spectra changes associated with stenosis. Sites of stenosis
(PSV >180/cm/s, Vr >2) are interpreted as abnormal, and
predict the arterial repair is prone to development of myoin-
timal hyperplasia and more likely to require revision than if
the duplex testing is normal. Residual repair-site abnormal-
ities should be scanned more frequently (at 6- to 8-week
intervals) to detect stenosis progression, which can occur in
the absence of symptoms, especially in patients treated for
critical limb ischemia. In patients with lower-limb arterial
bypass grafts, the measurement of mean graft flow velocity,
calculated as the mean PSV recorded from two to three
nonstenotic graft sites, correlates with volume flow and,
when low (o40 cm/s), signifies a graft at risk for thrombosis.
A >30 cm/s reduction of mean graft velocity (MGV) on serial
scans indicates development of a hemodynamically signifi-
cant stenosis that should be repaired. Graft flow velocity
might be o40 cm/s in large-caliber (>6 mm diameter) grafts
or bypasses to a pedal or isolated tibial artery.
Fig. 6 – Surveillance algorithm after bypass grafting and endovascular therapy. ABI, ankle-brachial index; PSV, peak systolic
velocity; Vr, velocity ratio.
Table 4 – Risk stratification for graft thrombosis based on vascular laboratory testing data, including peak systolic velocity
at stenosis, velocity ratio at stenosis, graft flow velocity, and change in ankle-brachial index.
Category High-velocity criteria, PSV
(cm/s)
Velocity
ratio
Low-velocity criteria, GFV
(cm/s)
ABI
change
I Highest riska
(>70% stenosis with low graft flow) >300 >3.5 o45 or staccato graft flow >0.15
II High riska
(>70% stenosis without change or normal
graft flow)
>300 >3.5 >45 o0.15
III Moderate riskb
(50% to 70% stenosis with normal graft
flow)
180À300 >2.0 >45 o0.15
IV Low risk (normal bypass or o50% stenosis with
normal graft flow)
o80 o2.0 >45 o0.15
ABI, ankle-brachial index; GFV, graft flow velocity; PSV, peak systolic velocity.
a
40% to 50% likelihood of stenosis progression or graft thrombosis within 3À6 months
b
20% to 30% of early (o 3 months) lesions regress, 10%À20% of lesions remain stable, 40% to 50% progress to >70% stenosis.
S E M I N A R S I N V A S C U L A R S U R G E R Y 2 6 ( 2 0 1 4 ) 9 5 – 1 0 4100

7. If color Doppler imaging identifies a stenosis, measure-
ments of PSV and Vr are performed, as well as recording
lesion length and graft/vessel diameter. Lesions with duplex-
derived velocity spectra of a high-grade stenosis (PSV >300
cm/s, end-diastolic velocity >20 cm/s, Vr across the stenosis
>3.5) correlate with a >70% DR stenosis and should be
repaired [8]. The application of these threshold criteria has
been shown to correctly identify arterial repairs (bypass
grafts, angioplasty sites) at risk for thrombosis. If a policy of
no intervention is followed, the incidence of thrombosis is in
the range of 25% during the subsequent 6-month interval
[9,10].
The risk of infrainguinal bypass thrombosis is predicted by
using the combination of high- and low-velocity duplex
criteria and decreases in ABI (Table 4) [11]. In the highest-
risk group (category I), development of a pressure-reducing
stenosis has produced low flow in the graft, which, if it
decreases below the “thrombotic threshold velocity,” will
result in thrombosis. Prompt repair of category I lesions is
recommended and category II lesions can be scheduled for
elective repair within 1 to 2 weeks. A category III stenosis
(PSV of 150 to 300 cm/s, Vr o3.5) is not pressure or flow
reducing in the resting limb. Serial scans at 4- to 6-week
intervals are recommended to determine the hemodynamic
progression course of these lesions [12,13]. An important
feature of the “graft-threatening” stenosis is its propensity
to progress in severity, reduce graft flow, and form surface
thrombus; events that can precipitate thrombosis. Using
serial duplex scans, a category III stenosis that does not
progress can be distinguished from the progressive lesion
that needs to be repaired. The majority (approximately 80%)
of bypass grafts will have no stenosis identified, ie, a category
I scan. For these patients, surveillance at 6-month intervals is
recommended. Category I scan but graft flow velocity o40
cm/s indicates a “low-flow” bypass and increased risk for
thrombosis, based on the concept of “thrombotic threshold
velocity,” which is lower in autologous vein than prosthetic
bypasses. Prescribing an anticoagulation regimen of sodium
warfarin to maintain the prothrombin time at an interna-
tional normalized ratio of 1.6 to 2 and antiplatelet therapy
(aspirin, 81 mg/d or clopidogrel bisulfate, 75 mg/d) can reduce
the incidence of low-flow vein or prosthetic polytetrafluoro-
ethylene (MGV o 60 cm/s) bypass graft thrombosis [14].
Using duplex ultrasound surveillance, it can be anticipated
that approximately 20% to 30% of infrainguinal bypass graft
and peripheral angioplasty sites will have a >70% stenosis
identified within the first year. The likelihood of stenosis
developing is influenced by a number of factors; but the most
predictive is the presence of a residual stenosis (PSV >180 cm/
s, Vr >20) in the repair. An arterial intervention with residual
stenosis should be monitored at 1- to 2-month intervals for
stenosis progression. After lower-limb vein bypass grafting,
risk factors for graft stenosis include small vein caliber (4
mm), presence of venovenous anastomosis (spliced vein), use
of alternative venous conduits (eg, arm vein, lesser saphe-
nous vein, greater saphenous vein remnants), prior intra-
operative graft revision, or a history of early graft
thrombectomy. The majority of stenosic lesions producing
bypass graft or angioplasty failure are focal (o2 cm in length)
and suitable for endovascular treatment. More extensive, ie,
longer segment, stenosis or early-appearing (o3 months)
lesions might require surgical repair (bypass graft) or stent
angioplasty (balloon angioplasty, atherectomy). Timely inter-
vention for repair-site stenosis is associated with improved
stenosis-free patency in the range of 70% to 80% at 1 year
[7,13]. For infrainguinal vein bypass, patency at 2 years was
identical for surgical (63%) and endovascular (63%) repair of
duplex-detected stenosis, and overall assisted graft patency
by life-table analysis was 91% at 1 year and 80% at 3 years.
Based on the costs of duplex surveillance, the salvage of 10%
of arterial intervention, ie, thrombosis prevented, is cost
effective. Many vascular groups believe duplex surveillance
should be “part of the service” after infrainguinal vein bypass
grafting. It should be emphasized that the benefit of surveil-
lance is highly dependent on the durability and morbidity of
procedures used to correct “graft stenosis.” Importantly,
duplex surveillance with intervention for >70% stenosis is
safe, with mortality rate o0.5%, early failure rate o1%, and
intermediate (3-month) failure rate o15%.
4. Summary
Arterial duplex scanning is a versatile and accurate diagnos-
tic method for the diagnosis, screening, and management of
lower-limb vascular disease. Although resolution of com-
puted tomography angiography continues to improve, pro-
viding detailed artery anatomy and three-dimensional vessel
reconstruction, these advancements cannot replace duplex
ultrasound because of its noninasive nature, lower cost, and
portability. Also, an important advantage of duplex ultra-
sound is the hemodynamic information afforded to assess
limb perfusion before and after intervention. The interpreta-
tion of arterial duplex testing requires knowledge of anatomy,
hemodynamics, and the spectrum of artrerial interventions
used to treat occlusive and aneurysmal disease. This exper-
tise can be demonstrated by obtaining certification from the
American Registry for Diagnostic Medical Sonography (www.
ARDMS.org) as a registered physician in vascular laboratory
interpretation.
S E M I N A R S I N V A S C U L A R S U R G E R Y 2 6 ( 2 0 1 4 ) 9 5 – 1 0 4 101

8. Questions regarding arterial duplex test interpretation
1. The duplex scan image of the right groin after a cardiac catheterization procedure demonstrates:
A. Femoral artery stenosis
B. Femoral false aneurysm
C. Arteriovenous fistula
D. Femoral artery dissection
Answer:
2. The duplex scan of the right femoral artery demonstrates:
A. false aneurysm
B. arteriovenous fistula
C. cavernous venous aneurysm
D. femoral aneurysm rupture
Answer:
3. The duplex scan image of the external iliac artery stent demonstrates:
S E M I N A R S I N V A S C U L A R S U R G E R Y 2 6 ( 2 0 1 4 ) 9 5 – 1 0 4102

9. A. o50% stenosis
B. 50% to 70% stenosis
C. o70% stenosis
D. o90% stenosis
Answer:
4. The duplex scan images of a femoral-popliteal vein bypass show the graft is:
A. Low risk for failure
B. Moderate risk for failure
C. High risk for failure
D. Cannot determine failure risk without an angiogram
Answer:
5. The duplex scan images of the superficial femoral artery indicate:
A. Stenosis with exit collateral artery
B. Focal arterial dissection
C. Arteriovenous fistula
D. False aneurysm
Answer:
Answers to questions:
1. C
2. A
3. C
4. C
5. C
S E M I N A R S I N V A S C U L A R S U R G E R Y 2 6 ( 2 0 1 4 ) 9 5 – 1 0 4 103

10. r e f e r e n c e s
[1] Strandness DE Jr. Duplex Scanning in Vascular Surgery.
Philadelphia: Lippincott Williams & Wilkins; 2002. (A com-
prehensive review of clinical applications for duplex
scanning.)
[2] Zwiebel WJ, Pellerito JS, Introduction to Vascular Ultrasonog-
raphy, 5th ed. Philadelphia: Elsevier Saunders; 2005. (An
introductory textbook for vascular technologists that pro-
vides background physics, hemodynamics, and testing pro-
cedures for duplex scanning.)
[3] Cossman DV, Ellison JE, Wagner WH, et al. Comparison of
contrast arteriography to arterial mapping with color-flow
duplex imaging in the lower extremities. J Vasc Surg
1989;10:522–9.
[4] Moneta GL, Yeager RA, Antonovic R, et al. Accuracy of
lower extremity arterial duplex mapping. J Vasc Surg 1992;15:
275–84.
[5] Moneta GL, Yeager RA, Lee RW, Porter JM. Noninvasive
localization of arterial occlusive disease: a comparison of
segmental Doppler pressures and arterial duplex mapping. J
Vasc Surg 1993;17:578–82.
[6] Hatsukami TS, Primozich JF, Zierler RE, et al. Color Doppler
imaging of infrainguinal arterial occlusive disease. J Vasc
Surg 1992;16:527–33.
[7] Gonsalves C, Bandyk DF, Avino A, Johnson BL. Duplex features
of vein graft stenosis and the success of percutaneous trans-
luminal angioplasty. J Endovasc Surg 1999;6:66–72.
[8] Ascher E, Marks NA, Hingorani AP, et al. Duplex-guided
endovascular treatment of occlusive and stenotic lesions of
the femoral popliteal arterial segment: a comparative study
in the first 253 cases. J Vasc Surg 2006;38:251–8.
[9] Caps MT, Cantwell-Gab K, Bergelin RO, Strandness DE Jr. Vein
graft lesions: time of onset and rate of progression. J Vasc
Surg 1995;22:466–75.
[10] Bandyk DF, Johnson BL, Gupta AK, Esses GE. Nature and mana-
gement of duplex abnormalities encountered during infraingui-
nal vein bypass grafting. J Vasc Surg 1996;24:430–8.
[11] Gupta AK, Bandyk DF, Cheanvechai D, Johnson BL. Natural
history of infrainguinal vein graft stenosis relative to bypass
grafting technique. J Vasc Surg 1997;25:211–25.
[12] Westerband A, Mills JL, Kistler S, et al. Prospective validation of
threshold criteria for intervention in infrainguinal vein grafts
undergoing duplex surveillance. Ann Vasc Surg 1997;11:44–8.
[13] Armstrong PA, Bandyk DF, Wilson JS, Shames ML, Johnson
BL, Back MR. Optimizing infrainguinal arm vein bypass
patency with duplex ultrasound surveillance and endovas-
cular therapy. J Vasc Surg 2004:724–31.
[14] Brumberg SR, Back MR, Armstrong PA, et al. The relative
importance of graft surveillance and warfarin therapy in infrain-
guinal prosthetic bypass failure. J Vasc Surg 2007;46:1160–6.
S E M I N A R S I N V A S C U L A R S U R G E R Y 2 6 ( 2 0 1 4 ) 9 5 – 1 0 4104