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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_5760_Библиотеки_им_академика_М_И_Перельмана.pdf
Common iliac artery stenosis
)
2.1 · Pelvic andLeg Arteries
63
2
(PTA and stent)
Internal iliac artery stenosis
External iliac artery stenosis (PTA)
Common femoral artery stenosis (TEA
Stenosis at profunda femoris origin
(TEA for stages II, III/no preop.
angiography necessary)
Profunda femoris artery
Superficial femoral artery stenosis
(conservative/( PTA))
Superficial femoral artery occlusion
(bypass for stages (llb), Ill, IV)
Entry site stenosis
Popliteal artery stenosis/occlusion
(PTA, bypass)
Lower leg artery occlusion (cons.)
. Fig. 2.8 Diagram of atherosclerotic stenotic lesions that can be
diagnosed by duplex imaging and initial treatment based on duplex
ndings (dierent therapeutic management may be required based on
the clinical stage or in patients with multilevel involvement)
arteries is not necessary in these cases as the primary surgical
approach is not aected by occlusions distal to the popliteal
artery or trifurcation. Outow to the foot may be evaluated
along with intraoperative completion angiography if this
information is deemed necessary for patients who are likely
to require additional surgical or interventional measures.
In the following two settings, the decision to perform
thromboendarterectomy (TEA)
can also be made without
additional imaging tests: (1) if duplex ultrasound demonstrates stenosis of the common femoral artery or profunda
femoris origin – with occlusion of the supercial femoral
artery– and if the examination also rules out occlusion in the
pelvic territory, or (2) if, in case of occlusion of the supercial
femoral artery, the duplex examination conrms resupply of
the P1 popliteal segment without major popliteal artery narrowing. In these cases, TEA at the inguinal level is the rst
therapeutic step, with further measures depending on the
clinical outcome. is therapeutic approach is independent
of the status of the arteries below the knee, and the benet of
using preoperative anteroposterior angiography to evaluate
collateral circulation in the thigh in cases of supercial femoral artery occlusion is disputed.
Only the main branch of the profunda femoris artery provides relevant collateral ow in patients with an occluded supercial femoral artery. is branch runs almost parallel to the latter
and is the only artery that needs to be evaluated with sonography
as it is only here that a stenosis compromising collateral function
would require surgical repair (see . Fig.2.60 (Atlas)).
e author’s experience in 180 patients conrms that
duplex sonography is a reliable preoperative imaging modality
both for identifying patients with stenosis of the femoral bifurcation or arterial occlusion above the knee who require surgery and for planning the surgical procedure. In this patient
population, the sonographic examination allowed adequate
evaluation of the pelvic arteries in 95% of the patients; in these
cases, ultrasound correctly diagnosed 96% of all pelvic artery
stenoses and occlusions, and the therapeutic approach was
modied accordingly (e.g., pelvic artery PTA). Overall, the
sonographic ndings led to a correct therapeutic decision in
94% of the patients with clinically indicated vascular reconstruction of the iliacofemoropopliteal segment (PTA, TEA,
bypass with preoperative planning) (see
. Table2.19).
A duplex ultrasound examination of the infrapopliteal arteries is time-consuming. Acoustic shadowing produced by calcied plaques or edema can impair detection and grading of
stenosis in small arteries. is is especially problematic if indirect
stenosis criteria (ow prole) do not apply because the patient
has multilevel occlusive disease with proximal obstruction.
Several studies (Grassbaugh et al. 2003; Karacagil et al.
1996; Boström etal. 2002; Mazzariol etal. 2000) show duplex
ultrasound to be highly accurate in localizing and grading
steno-occlusive disease of the calf arteries and to enable reliable planning of the surgical approach and
potential bypass target below the knee
identication of a
, with bypass patency
rates similar to those in patients examined by preoperative
angiography. e choice of the preoperative imaging modality in patients with popliteal occlusion and involvement of the
calf arteries in stage III and IV PAOD depends not only on the
expected diagnostic information but also, and importantly,
on the examiner’s skills and experience with duplex ultrasound, the time available (see 7 Sect. 2.1.8), and the organization and workow in the department (in Germany, most
duplex ultrasound examinations are performed by clinicians,
in particular angiologists and vascular surgeons).
An exception to the restrictive use of diagnostic angiography is the examination of patients with long-standing diabetes mellitus and secondary macro- and microangiopathy.
Medial sclerosis in diabetics may preclude complete sonographic evaluation of the calf arteries, and serial stenoses may
thus be overlooked. Nevertheless, the identication of all
macro- and microangiopathic lesions is still necessary for
initiation of appropriate therapeutic measures.
hemodynamic eect of arterial stenosis is evaluated
e
using hemodynamic parameters. Flow models and in vivo
studies indicate that a reduction in arterial diameter of 50%
or more becomes hemodynamically signicant and will
cause an increase in peak systolic velocity (PSV). In highergrade stenosis, peak end-diastolic velocity (EDV) is increased
as well. e increase in PSV correlates with the degree of stenosis (see . Fig. 5.20).
In contrast to the carotid artery territory, B-mode evaluation of plaque morphology for estimating the risk of embolism has no role in the examination of the leg arteries. is is
obvious given the diculties one faces in assessing the risk of
embolism associated with carotid artery stenoses in B-mode
sonography and the rare occurrence of interdigital artery
64
Chapter 2 · Extremity Arteries
embolism (blue toe). Nevertheless, one must be aware that, as
in the carotid territory, the risk of embolism increases with
the degree of stenosis and plaque thickness.
2
Determining the degree of stenosis from the vessel diameter and the residual perfused lumen using transverse color ow
images is less reliable than hemodynamic grading based on
spectral Doppler velocity measurement. e former is done
only for preliminary orientation and is susceptible to artifacts
caused by calcied plaques. Moreover, physical and technical
limitations necessitate the wider spacing of color scan lines, and
the interpolation which then becomes necessary oen overestimates the patent lumen and underestimates the stenosis.
e hemodynamic degree of stenosis determined by
duplex ultrasound correlates better with its ischemic eects
and with the patient’s clinical symptoms than the morphologic
degree determined by imaging modalities such as angiography or MRI.Morphologic methods have inherent limitations
resulting from the fact that the apparent luminal narrowing
caused by an eccentric plaque changes with the imaging plane.
ese limitations can only be minimized by evaluating all nor-
. Table 2.4 Duplex ultrasound criteria for arterial evaluation
Technique Criteria
B-mode Assessability
Anatomy (course, variants)
Vessel contour (aneurysm, stenosis)
Vessel wall changes (calcication, plaque, cysts)
Pulsation (axial, longitudinal)
Perivascular structures (hematoma, abscess,
tumor, other compressing structures)
Doppler Demonstration of ow
Flow direction
Flow pattern (laminar, turbulent)
Flow prole (monophasic/triphasic)
Flow velocity
mal and diseased arterial segments in two or three planes.
Another drawback of morphologic stenosis grading is the failure to adequately account for plaque conguration and how it
aects the hemodynamic relevance of a stenosis. A concentric
plaque causing the same diameter reduction as an eccentric
2.1.5 Normal Duplex Ultrasound ofPelvic
andLeg Arteries
plaque has more marked hemodynamic eects because the
decrease in cross-sectional area is greater (see
. Fig.2.17d).
Flow in the limb arteries is pulsatile and nearly laminar, due
to the high peripheral resistance, which is reected in the
Doppler waveform by a narrow bandwidth with a clear sys-
2.1.4 Interpretation andDocumentation
tolic window. e typical triphasic waveform is characterized
by a steep systolic upslope and rapid return to baseline, folMinimum documentation of a duplex ultrasound examination of the legs consists of longitudinal B-mode images and
angle-corrected spectral Doppler waveforms from the representative sites, which are the common femoral artery, the
origins of the deep and supercial femoral arteries, and the
popliteal artery (P1 and P3 segments). In patients in whom
the arterial status below the knee is clinically relevant, the
documentation is supplemented by B-mode images and
Doppler waveforms from the anterior and posterior tibial
arteries proximally and at the level of the ankle. If the ndings at these sites are inconclusive or if a specic clinical
question has to be answered, additional images and Doppler
waveforms from the common and external iliac arteries, possibly the below-knee arteries as well, are documented. In
addition, steno-occlusive lesions are documented with longitudinal images and waveforms. Intra- and peristenotic spectral Doppler waveforms are analyzed (
. Table2.9) to estimate
the degree of stenosis based on pre- and intrastenotic peak
systolic velocity (PSV) and the poststenotic ow pattern
(from preserved triphasic prole to monophasic waveform).
An aneurysm must be documented in two planes and its
diameter measured in the transverse plane. Partial thrombosis, if present, should be reported as well. Documentation of
additional color ow images (transverse view of aneurysm,
longitudinal view of stenosis) may be helpful but is optional.
e report should describe the morphologic changes and
Doppler results on which the diagnosis is based (. Table2.4).
lowed by a short early diastolic reversal of ow and subse-
quent diastolic forward ow varying in magnitude and
duration with the body region supplied (. Fig. 1.43). e
brief diastolic ow reversal is due to high peripheral resis-
tance (7 Sect. 1.2.2).
e character of the Doppler waveform varies with the
elasticity of the vessel wall and peripheral resistance and is
inuenced by systemic and local hypercirculatory eects
(fever, hyperthyroidism, phlegmon). e amount of ow persisting during diastole is subject to physiologic factors and
pathologic changes including sympathetic tone, wall elasticity, compliance of the aorta, and heart rate. In addition, the
waveform shape is inuenced by the ratio of skin to muscle
supply, which is why diastolic ow is higher in the profunda
femoris than in the supercial femoral artery (. Fig.2.9).
e main factors inuencing the ow prole (Doppler
waveform) can be summarized as follows:
5 Wall elasticity (atherosclerosis, medial sclerosis)
5 Peripheral resistance:
5 Physiologic:
Ȥ Muscle activity
5 Abnormal:
Ȥ Inammation, phlegmon (stage IV PAOD)
(. Fig.2.9c)
Ȥ Hypercirculation
Ȥ Medications
Ȥ Postocclusive vasodilatation
abc
2.1 · Pelvic andLeg Arteries
65
. Fig. 2.9 a Peak systolic velocity (PSV) in the leg arteries decreases toward the periphery, but the triphasic ow pattern persists. The example
shows normal blood ow in the bular artery with the corresponding triphasic waveform. The artery has a diameter of 2.7mm. b Sonoanatomy
of the anterior tibial artery origin. The popliteal artery gives o the anterior tibial artery, which courses anteriorly to pierce the interosseous membrane, in front of which it descends, initially taking a course close to the bula. The image shows the anterior tibial artery scanned from a posterior
approach (transducer in popliteal fossa), with ow displayed in blue (ow away from transducer), below its origin from the popliteal artery (A.POP)
as it pierces the interosseous membrane (hyperechoic structure between tibia and bula). With the transducer slightly tilted, the anterior tibial vein
comes into view (blue, ow toward transducer) along its course parallel to the artery and as it enters the popliteal vein. c Hyperemia. Peripheral
inammation is another factor that can alter the Doppler waveform besides an increased ow resulting from exercise-induced hyperemia or when
an artery is recruited as a collateral. In the example, a phlegmon of the foot results in a monophasic waveform with reduced pulsatility and a rather
high end-diastolic velocity (EDV) of 22cm/s. An upstream stenosis is ruled out here as the steep systolic upslope is preserved and a PSV of 130cm/s
is measured (which is relatively high for an artery below the knee, see a). The variation in PSV in this patient is attributable to absolute arrhythmia. A
mirror artifact is present (<SA)
2
. Table 2.5 Normal diameters (D) and peak systolic velocities
(PSV) with standard deviations determined in the lower
extremity arteries of 30 healthy subjects
Artery D (cm) PSV (cm/s)
External iliac artery 0.85±0.11 116±29.7
Common femoral artery 0.81±0.17 112.2±22.7
Proximal supercial femoral
artery
Profunda femoris artery 0.55±0.14 95.1±21.5
Popliteal artery 0.58±0.12 71.6±12.4
0.65±0.14 93.95±15.9
Arterial diameters and PSV are subject to wide interindividual variation and decrease toward the periphery (. Table2.5),
while the triphasic ow prole is preserved.
Investigations of
leg arteries
(Jäger etal. 1985; Kohler 1990; Karasch et al.
normal ow velocity in the pelvic and
1990; Polak etal. 1992) have revealed wide variations between
dierent study populations and individual subjects within a
study population. It is therefore somewhat more dicult to
dene an absolute systolic velocity threshold above which a
hemodynamically eective stenosis should be assumed, as is
the case for the diagnosis of carotid and renal artery stenosis.
Given the wide variation in blood ow velocities in the
peripheral arteries, the normal velocities measured by our
group (. Table2.5) are comparable to those reported by oth-
ers (Jäger etal. 1985; Kohler 1990).
In addition to PSV and changes in the normal triphasic
ow prole, the acceleration index has become an estab-
lished parameter for describing occlusive and postocclusive
changes in blood ow. Higher-grade stenosis or occlusion is
associated with a postocclusive decrease in PSV and delayed
systolic upstroke (see . Figs. 6.8 and 1.49). e acceleration
index is the quotient of PSV and the pulse rise time from the
onset of systole to the rst peak.
e pulsatility index (PI) can be used to describe the pulsatility of ow (see formula in . Fig. 1.29). As the poststenotic decrease in PSV (. Fig. 2.10) and increase in EDV
become more pronounced through dilatation of the arterioles and the resulting decrease in peripheral resistance, triphasic ow becomes monophasic, and the magnitude of this
change correlates with the decrease in PI (see . Figs. 1.29,
2.9, and 2.52 (Atlas)).
2.1.6 Abnormal Findings
e following subsections describe the therapy-oriented
sonographic workup of vascular conditions aecting the leg
arteries, including relevant sonographic ndings and parameters, and discuss the role of ultrasound in the diagnostic
management of the respective disease entities.
2.1.6.1 Atherosclerotic Occlusive Disease
Most atherosclerotic lesions occur in the thigh vessels
(approx. 40%), followed by the pelvic and calf vessels, each
accounting for approx. 20–30% (Schoop 1988). More than
20% of patients already have occlusive lesions of more than
one level at the time of diagnosis. Since vascular sclerosis is a
generalized process, it typically involves both legs, but oen,
one side will be aected more severely.
Vascular duplex ultrasound of the leg arteries is pre-
dominantly used for the stepwise diagnostic workup of
patients presenting with typical symptoms of peripheral arterial occlusive disease (PAOD) (. Fig.2.7), treatment planning, and dierentiation of atherosclerosis from other
vascular conditions (. Table2.6).
e duplex ultrasound ndings, in conjunction with the
clinical disease stage, guide the further diagnostic and thera-
66
ab c
Chapter 2 · Extremity Arteries
2
. Fig. 2.10a–c Segmental duplex ultrasound of the lower extremity arterial tree based on spectral Doppler analysis and identication of postocclu-
sive waveform changes to localize occlusive disease. a Normal triphasic Doppler waveforms (no hemodynamically relevant stenosis or occlusion) from
the common femoral artery, popliteal artery, and anterior and posterior tibial arteries. b Pelvic artery occlusion is indicated by postocclusive monophasic waveforms from the common femoral, popliteal, and anterior and posterior tibial arteries. The postocclusive ow pattern is seen in all arteries distal
to the occlusion. c In isolated occlusion of the proximal anterior tibial artery, ow is triphasic in the common femoral, popliteal, and posterior tibial
arteries, while a postocclusive waveform is obtained from the anterior tibial/dorsalis pedis artery
. Table 2.6 Indications for (color) duplex ultrasound of the leg arteries
Indication Diagnostic tasks
Stepwise diagnostic workup of
PAO D
Diagnostic evaluation of aneurysm Localization
Arterial compression Entrapment syndrome
AV stula Localization
Follow-up of surgical or interventional procedures
Localization of ow obstruction (above the knee, below the knee, pelvic level, vessel origin)
Identication of type of ow obstruction (stenosis, occlusion)
Length of ow obstruction (length of occlusion, sequential stenoses)
Stenosis grading (high-grade versus low-grade)
Cause of occlusion (embolism, atherosclerosis, trauma, compression, dissection)
Evaluation of postocclusive outow tract
Therapeutic decision making: medical treatment, radiologic intervention, surgery
Characterization (saccular, spindle- shaped, false)
Extent (infrarenal, aortoiliac, popliteal)
Thrombosis (partial, complete)
Treatment: compression therapy of pseudoaneurysm, thrombin injection
Adventitial cystic disease
Thoracic outlet syndrome
Compression by tumor
Flow volume in stula
Bypass grafting (anastomotic stenosis, suture aneurysm, infection, occlusion, ow velocity inside
bypass graft: prognosis)
PTA (residual stenosis, restenosis, puncture aneurysm, hematoma)
Endovascular stenting (patency, stenosis)
def
2.1 · Pelvic andLeg Arteries
67
abc
. Fig. 2.11a–f Collateral circulation in pelvic artery occlusion. a Occlusion of the external iliac artery (A.I.E) after PTA and stent (S) implantation.
The common iliac artery (A.I.C) is displayed in red. The internal iliac artery (A.I.I) is also patent with ow coded in blue. Flow in the external iliac vein
(V.I.E) posterior to the artery is toward the center (blue); ow in the internal iliac vein (V.I.I) as it ascends from the true pelvis and enters the common iliac vein is displayed in red (toward transducer). b The common femoral artery (A.F.C) with ow toward the periphery (blue, postocclusive
ow signal) is lled via the epigastric artery (EPIGASTR A), where ow is retrograde (blue). The stented external iliac artery (A.I.E) is occluded. c The
femoral circumex artery (A.C.F) with retrograde ow displayed in red lls the proximal profunda femoris artery (A.P.F), resulting in retrograde ow
(red, toward transducer) in a short segment of the profunda femoris directly at the site of entry of the femoral circumex. d In the supercial femoral artery (A.F.S), ow is orthograde with a postocclusive Doppler waveform (monophasic, delayed systolic rise). e Distal to the site of entry of the
femoral circumex artery (A.C.F), there is orthograde ow in the profunda femoris artery as well (A.P.F, blue, ow toward the periphery). f Doppler
waveforms (ow volume, ow direction) reect the changing intravascular pressure at the site of sampling (compare waveforms obtained at the
sampling sites in d and e). While the color duplex image shows retrograde systolic ow toward the center (toward transducer) in the profunda femoris artery (A.P.F>) close to its origin from the common femoral artery (A.F.C), Doppler interrogation demonstrates to-and-fro ow in this segment. In
contrast, the waveform in c shows high retrograde ow because part of the blood ows toward the periphery through the profunda femoris downstream of the sampling site (seen in c to the right of the A.C.F). The to-and-fro ow at the profunda femoris origin is due to the fact that this artery
contributes to relling of the common femoral artery, which receives only insucient collateral ow from epigastric arteries. The Doppler waveform
very accurately reects the hemodynamic situation as a function of local pressure and pressure variation through the cardiac cycle (see . Fig.2.58
(Atlas)). In the absence of collateral ow through the femoral circumex artery, the waveform sampled here would be the same as in c
2
peutic strategy (. Fig.2.7). e overall motto is: No further
(invasive) diagnostic test without therapeutic consequences.
is means that additional diagnostic tests, especially invasive ones, should not be ordered unless they are expected to
provide relevant supplementary information for adequate
treatment planning.
distal aortic anaeurysm), dissection (see
and stenosis due to bromuscular dysplasia.
In patients with occlusion at the pelvic level, collateral
ow mainly occurs through the internal iliac artery systems.
Additional collateral pathways include the inferior mesenteric artery and internal iliac artery in common iliac artery
occlusion and the epigastric arteries (entering just above the
2.1.6.1.1 Pelvic Arteries
Lower extremity steno-occlusive disease aects the pelvic
arteries in 11% of cases. Isolated occlusions at this level occur
in the common iliac artery in approx. 54% of cases, in the
external iliac in 21%, and in the internal iliac in 13% (Schoop
1988). e clinical presentation of pelvic artery occlusion
varies with the presence of collateral pathways and concomitant involvement of distal arteries (40–50% incidence of
combined femoropopliteal obstruction). Reconstruction of
the occluded pelvic artery to improve inow of blood is particularly important in patients with additional supercial
femoral artery occlusion. Moreover, pelvic artery repair has a
good long-term prognosis and patency rate. Important nonatherosclerotic conditions aecting the arteries at the pelvic
level include aneurysmal disease (especially in patients with
groin) in external iliac artery occlusion (
addition to the typical claudication symptoms of the lower
leg, occlusion in this territory is associated with specic claudication pain of the gluteal, hip, and thigh muscles.
When the external iliac artery is occluded and the lateral
circumex artery provides collateral ow, backward ow
occurs in the proximal profunda femoris and common femoral arteries. is is seen in the Doppler examination as
reversed ow with a monophasic character. Additionally, collateral ow through the lateral circumex artery lls the
supercial femoral artery, while the common femoral artery
oen receives collateral ow from epigastric arteries entering
just above the inguinal ligament (see . Fig.2.53i (Atlas)).
If direct evidence in the form of increased blood ow
velocity in the stenotic segment cannot be obtained, especially
7 Sect. 2.1.6.4.7),
. Fig. 2.11a–f). In
68
Chapter 2 · Extremity Arteries
when evaluation is impaired due to overlying bowel gas or
obesity, spectral Doppler imaging of the proximal common
femoral or distal external iliac artery can provide indirect evi-
2
dence of upstream obstruction.
A stenosis of less than 50–60% has no relevant eect on
the poststenotic Doppler waveform. Only higher-grade stenoses produce ow changes including a decrease in PSV, a
less steep systolic rise, and a delayed diastolic drop with persistent ow toward the periphery in the poststenotic segment
(see . Fig.2.52 (Atlas)). e lower PSV and the delayed systolic rise are primarily due to the upstream ow obstruction
while monophasicity indicates peripheral vasodilatation in
response to a mismatch of blood supply and demand. is
peripheral situation in turn also inuences the prestenotic
waveform via the collaterals.
e ankle-brachial index (ABI) decreases aer exercise,
and ow becomes less pulsatile, which may result in a monophasic waveform. In the absence of vascular disease, the ABI
and Doppler waveform will return to normal aer a short
rest. is is why a short
waiting period following positioning
of the patient on the couch (>3min) is necessary to obtain
accurate quantitative measurements and spectral Doppler
information. On the other hand, an additional spectral
Doppler measurement during the recovery phase can help in
dierentiating absence of stenosis from high-grade proximal
stenosis with good collateralization. e latter is characterized by a relatively normal Doppler waveform at rest
(. Fig.2.53 (Atlas)) but a markedly delayed return to normal
aer activity (. Fig.2.12).
. Figs.2.52 and 2.53 (both Atlas)), giving rise to false-
index (
negative results. A pulsatility index with a cuto of 4 was
found to have 94% sensitivity and 82% specicity for identifying isolated aortoiliac obstruction (iele et al. 1983).
Indirect stenosis criteria can be used when the insonation
conditions in the true pelvis are poor. Whenever abnormal
ndings are encountered, however, an attempt should also be
made to identify the stenosis directly. Under normal scanning conditions, state-of-the-art (color) duplex ultrasound
equipment oen allows faster direct localization of stenosis
or occlusion than is possible with use of indirect criteria.
While waveform analysis alone is used in many studies
with a standardized design, one should be aware of potential
pitfalls. Another important parameter, which is especially
relevant in order not to miss moderate stenosis or stenoocclusive disease with very good collateralization, is measurement of peak systolic velocity (PSV) in comparison with
the opposite side (>30% dierence). Audible analysis of the
Doppler signal is another option. Upstream stenosis is suggested when the systolic whipping sound is weaker compared
with the contralateral side. However, to use this criterion, it is
pivotal to perform the Doppler interrogation with a small
(<50°) and identical angle on both sides (Schäberle et al.
2013). For an experienced examiner, the acoustic signal is the
best criterion for ruling out pelvic artery stenosis. While this
acoustic criterion does not lend itself to standardization, the
change in the acoustic signal in the presence of upstream stenosis at the pelvic level is visually reected in the waveform
(damping and less steep systolic rise).
e potential pitfalls discussed above show that wave-
2.1.6.1.2 Time-Ecient Examination Based
onWaveform Analysis
erapeutically relevant stenosis in the pelvis and thigh can
be reliably and eciently ruled out by segmental spectral
Doppler evaluation of blood ow in the common femoral
and popliteal arteries and comparison with the contralateral
leg. Relevant stenosis is unlikely proximally if the waveform
shows normal, triphasic ow. Compared with angiography,
this method has 88–95% sensitivity and 81–98% specicity
in identifying hemodynamically relevant stenosis at the pelvic level (Eiberg et al. 2001; De Morais Filho et al. 2004;
Fontcuberta etal. 2005; Sensier et al. 2000; Cossman etal.
1989; Skaalan etal. 2003). Spronk etal. (2005) report poor
sensitivity of only 56% but good specicity using the criterion of a sharp monophasic waveform for diagnosing aortoiliac obstructive disease. However, this study is limited by
the use of MR angiography as the standard of reference.
Another parameter used to rule out hemodynamically
signicant, higher-grade stenosis is the
(. Fig. 1.28c). A signicant stenosis of the aortoiliac segment
is unlikely if the pulsatility index is greater than 5.5 (Johnson
etal. 1983; Neuerburg etal. 1991). e following pulsatility
indices have been determined: 8.5±3.5in a normal population, 2.8 ± 1.6 in isolated stenosis at the pelvic level,
2.3 ± 1.0 in concomitant pelvic and thigh occlusion, and
6.3±2.6in isolated femoral artery occlusion. Note, though,
that eective collateralization results in a higher pulsatility
pulsatility index
form phasicity alone is not a reliable criterion (e.g., stenosis
of femoral artery bifurcation,
. Fig.2.12f) and this may also
explain the discrepancy of results reported by investigators
using this parameter. To be on the safe side, the examiner
should combine evaluation of waveform phasicity, PSV, and
acceleration time
on the aected side in comparison to the
contralateral side to make allowance for the fact that the pelvis is rich in arteries that can be recruited as collaterals. is
is how the author’s group achieved 95% sensitivity and 98%
specicity in the detection of >60% stenoses in 85 patients
with suspected pelvic artery stenosis (intermittent claudication, pulses, ABI) (Schäberle etal. 1998). Stenosis was conrmed by angiography in 32 of the patients.
As noted, a triphasic waveform merely indictes that there is
adequate peripheral perfusion at rest. To avoid misinterpretation, it is helpful to compare spectral Doppler ndings obtained
aer activity (i.e., immediately aer positioning of the patient
on the couch) with the ndings aer the usual rest of approx.
3–4 min. Muscle activity induces physiological peripheral
vasodilation, reected in the waveform as a larger diastolic
ow component (
. Fig.2.9). In individuals without vascular
pathology, blood ow quickly returns to normal (within
1min), and identical triphasic Doppler waveforms are obtained
from both sides. In patients with moderate stenosis, well collateralized high-grade stenosis (. Figs.2.12 and 2.53 (Atlas)),
or with very well collateralized occlusion, the waveform will
also return to normal but it takes longer. erefore, spectral
ab
cd
ef
2.1 · Pelvic andLeg Arteries
69
2
. Fig. 2.12a–e Pitfalls in grading common iliac artery stenosis. a The Doppler waveform obtained in the left groin (common femoral artery)
shows monophasic ow, consistent with upstream stenosis. The waveform was obtained immediately after positioning of the patient, who had
walked from the waiting room to the examination room. b After 5min of rest, the waveform shows normal triphasic ow with a slightly delayed
systolic upstroke (acceleration time of 182ms, peak systolic velocity (PSV) of 96cm/s). However, the PSV here is markedly dierent from the PSV
measured on the contralateral side (PSV of 170cm/s), which should prompt continuous duplex imaging of the pelvic segment despite the triphasic waveform. c The Doppler spectrum from the contralateral common femoral artery is triphasic with a PSV of 170cm/s. d Monophasic ow
with delayed return to normal and reduced PSV in this patient was found to be caused by a stenosis of the common iliac artery at its origin from
the aorta. The waveform recorded immediately after positioning of the patient for the examination shows criteria of high-grade stenosis (>90%;
PSV>6m/s and end-diastolic velocity (EDV)>1m/s, monophasic ow). e The correct degree of stenosis can be estimated from the Doppler waveform obtained in the stenotic segment after 5min of rest and is approx. 70% (PSV of 380cm/s, triphasic ow). This example illustrates the importance of performing spectral Doppler analysis at rest to ensure accurate stenosis grading by spectral analysis (PSV, indirect criteria). fAnother
pitfall that must be borne in mind is that high-grade obstruction downstream of the spectral Doppler sampling site can mimic steno-occlusive
disease at the pelvic level because it presents with the same changes in the waveform (monophasic ow, reduced PSV). In the example shown, the
waveform from the external iliac artery/common femoral artery (AFC) junction is consistent with upstream obstruction (PSV of 30cm/s, monophasic ow). However, this patient has no iliac artery stenosis and the abnormal waveform is due to high grade-stenosis at the origins of the supercial
and profunda femoris arteries (PSV>300cm/s, not shown), as indicated by aliasing in the color ow image
70
Chapter 2 · Extremity Arteries
Doppler analysis 1min aer activity allows dierentiation of
transient physiologic changes from vascular pathology.
In conclusion, segmental spectral Doppler analysis
2
requires combined bilateral determination of PSV and eval-
uation of waveform phasicity
in order not to overlook
hemodynamically relevant stenosis. Any abnormality
should prompt continuous mapping of the proximal territory to search for steno-occlusive lesions. A triphasic
Doppler waveform alone is not sucient to rule out
upstream stenosis.
Another pitfall to be aware of is that high-grade obstruction downstream of the spectral Doppler sampling site can
mimic iliac steno-occlusive disease, because it causes similar
changes in the waveform (reduced pulsatility and lower PSV)
(. Fig.2.12f). For instance, a patient with profunda femoris
stenosis and supercial femoral artery occlusion or highgrade stenosis at the supercial femoral artery origin will
have a similar waveform as a patient with iliac artery obstruction (except that the steep systolic rise is preserved). In this
situation, the examiner must rule out iliac artery stenosis by
direct evaluation (see direct and indirect criteria in
2.1.6.1.4
).
7 Sect.
velocity in the normal arterial segment upstream of the
stenosis. e intrastenotic PSV increase is typically calculated as the ratio of intrastenotic PSV to prestenotic PSV,
or PSV ratio for short. In general, a PSV ratio>2 is interpreted to indicate >50% stenosis and a ratio>4 to indicate
>75% stenosis. PSV ratios cannot be used when a stenosis
is located in a bifurcation or at the origin of an artery (iliac
artery or profunda femoris origin). At these sites, threshold velocities determined by ROC analysis with angiography as the gold standard can be used instead. Several
studies investigated a PSV cuto of 180cm/s, which was
originally proposed for identication of hemodynamically
relevant profunda femoris artery stenosis (Strauss et al.
1991), and found 71–96% sensitivities and 92–95% specicities (Moneta etal. 1992; Aly et al. 1998; Katsamouris
etal. 2001). A drawback is that absolute PSV is inuenced
by systemic factors, as underlined by the results of a study
using a PSV threshold of 200cm/s, for which the authors
found a high sensitivity of 95%, while specicity was only
55% (de Smet etal. 1996).
e increase in blood ow velocity in a stenotic segment
is associated with a pressure drop. e pressure gradient
across a hemodynamically relevant stenosis results in a
2.1.6.1.3 Stenosis Grading
An intrastenotic peak systolic velocity (PSV) of over 180–
200cm/s and focal doubling of PSV have emerged as criteria
for hemodynamically relevant stenosis in ow models and
invivo. Using these thresholds, investigators reported sensitivities of 71–100% with specicities of 92–100% (Whyman
etal. 1993; Moneta etal. 1992; Aly etal. 1998; Katsamouris
etal. 2001). On the other hand, receiver operating characteristic (ROC) curve analysis identied markedly lower velocity
thresholds of 120cm/s for 50% stenosis and 160 cm/s for
70% stenosis (Sacks etal. 1990), but these turned out to be
unsuitable in the routine clinical setting. e threshold
velocities identied by ROC analysis vary greatly, depending
on the study population investigated (e.g., proportion of
patients with hypertension or diabetes mellitus).
Conventional angiography is limited in the grading of
stenosis at the pelvic level, especially in patients with stenosis
at the common iliac artery origin caused by eccentric posterior wall plaque. Strict lateral views are required for reliable
decrease in peripheral systolic blood pressure and can be
measured by determining the ankle-brachial index (ABI). A
decrease in ABI suggests arterial disease. Strauss etal. (1995)
used the PSV measured by duplex ultrasound in stenotic segments at the pelvic level to calculate the pressure gradient
across the stenosis using the simplied Bernoulli equation
and compared the results with direct intra-arterial pressure
measurement. In this study, the following correlations were
found between angiographic parameters and duplex ultrasound:
5 Cross-sectional area reduction determined densito-
metrically and the hemodynamic degree of stenosis
based on the PSV ratio: R=0.64
5 PSV and densitometrically determined cross-sectional
area reduction: R=0.56
5 Pressure gradient calculated from the ow velocity
determined by color duplex ultrasound using the
Bernoulli equation (
. Fig.2.13) and the pressure
gradient measured by intra-arterial catheter: R=0.86
grading of this type of stenosis. For more distally located pelvic artery stenoses, the standard anteroposterior projection
(oen the only projection available) should ideally be supplemented by le and right anterior oblique views (which are
perpendicular to each other). Lateral projections are required
for exact grading because most stenoses in this territory,
especially in the external iliac artery, are caused by eccentric
plaque on the posterior wall. CT angiography using thin
slices (1mm) is an alternative option, while MR angiography
tends to overestimate stenosis severity.
Hemodynamic stenosis grading by
imaging
is based on the identication of a focal increase
spectral Doppler
in peak systolic velocity (PSV) compared to the blood ow
While this study found the best agreement between invasive
angiography and noninvasive duplex ultrasound for the pressure gradient across the stenosis (. Fig. 2.13), the author’s
experience suggests that the pressure gradient calculated
from PSV using the simplied Bernoulli equation can be
misleading, especially when higher-grade stenosis is present.
e pressure drop expressed in the ABI reects the degree of
stenosis but ignores the eects of collateralization. For a
given degree of stenosis, the ABI is lower in the absence of
collateralization and increases with the magnitude of collateralization. Better collateralization also results in less damping of the poststenotic waveform.
mmHg
Mean Doppler gradient
Mean catheter gradient
2.1 · Pelvic andLeg Arteries
40
30
20
10
0
010203040
. Fig. 2.13 Correlation (R=0.86) of the mean pressure gradient
across a pelvic artery stenosis calculated from color duplex ultrasound
using the simplied Bernoulli equation (p=4×PSV2) and the pressure
gradient measured by intra-arterial catheter (Strauss etal. 1995)
eoretically, one would expect the magnitude of the
pressure gradient across an iliac artery stenosis to also reect
collateralization, meaning that good collateralization should
result in a smaller increase in PSV across the stenotic segment and hence a less steep pressure gradient compared with
a stenosis of the same degree but poorer collateralization
(comparable to the situation in supercial femoral artery stenosis; . Fig.2.16b). In steno-occlusive disease of more central arteries, however, the intrastenotic increase in PSV is less
dependent on collateralization.
Another issue to be borne in mind is that eccentric
plaque
, which is frequent in the iliac and common femoral
arteries, causes less severe stenosis in terms of hemodynamic
relevance than circumferential plaque with the same degree
of angiographic diameter reduction. is is due to the fact
that a 50% diameter reduction reduces the vascular crosssectional area by 75% when caused by circumferential stenosis as opposed to only 50% when caused by eccentric stenosis
(. Fig. 2.17d). Circumferential stenosis thus has more
marked hemodynamic eects, resulting in a greater increase
in intrastenotic PSV and more severe peripheral ischemia.
is explains the discrepancies between morphologic and
hemodynamic methods of stenosis grading and why a hemodynamic method such as duplex ultrasound is oen a better
indicator of the patient’s clinical situation than radiologic
methods based on morphology alone.
2.1.6.1.4 Leg Arteries
Preferred sites of atherosclerotic femoral artery stenosis are
the bifurcation (supercial and profunda femoris origins)
and the adductor canal.
mmHg
71
Isolated stenosis or occlusion of the common femoral
artery is rare (approx. 4%); most patients with common
femoral artery stenosis have concomitant obstructions of
the supercial femoral and below-knee arteries. Occlusion
of the common femoral artery or femoral bifurcation is of
considerable clinical signicance and, whenever possible,
should be treated by surgical repair (TEA); collateralization
here is poor, as all collateral pathways (via the iliac and profunda femoris arteries) comprise the femoral bifurcation,
and auxiliary collaterals have a low capacity. e
femoris artery
supplies the thigh muscles and is the most
profunda
important collateral in all arterial obstructions distal to the
femoral bifurcation. As a phylogenetically old vessel, the
profunda femoris artery is rarely aected by sclerotic
changes distal to its origin. All isolated obstructions of the
profunda femoris are due to embolism or occur in patients
with diabetes mellitus. Stenosis at the origin of the profunda
femoris artery is more common in patients with atherosclerosis of the femoral bifurcation and is clinically relevant due
to the key role of the profunda femoris as a collateral in
obstruction of the femoropopliteal circulation. Surgical
repair of the profunda femoris artery is the treatment of
choice.
e
supercial femoral artery is the preferred site of ath-
erosclerotic lesions and is the most common site of isolated
occlusions, which have an incidence of 27%. Occlusion of
both the femoral and popliteal arteries occurs in 40–45% of
cases. In all cases of isolated popliteal artery occlusion,
thrombosed popliteal aneurysm and nonatherosclerotic vascular disorders (which preferably aect the popliteal artery)
must be ruled out in the dierential diagnosis.
e treatment of femoropopliteal artery occlusion
depends on the clinical presentation, cause, site, and length
of the occluded segments. ese frequently aected and
hence clinically signicant vessels are easily accessible to
duplex scanning as they lie close to the surface and there are
no intervening scatterers. Many studies have conrmed the
diagnostic accuracy of duplex ultrasound in evaluating femoropopliteal occlusive disease (. Table 2.7). e precise
information on the site and length of an occlusion provided
by duplex ultrasound is necessary for therapeutic decision
making; however, treatment is ultimately dictated by what is
required clinically (
B-mode imaging will show atherosclerotic wall lesions as
. Fig.2.8).
irregularities of the wall contour, intimal thickening, or
plaques (. Table2.8). In larger arteries, the B-mode image
already allows a rough estimate of the degree of luminal narrowing when caused by echogenic, noncalcied plaques;
however, the hemodynamic degree of luminal narrowing is
always derived from the Doppler waveform.
An atherosclerotic occlusion is suggested if extensive
intraluminal plaques are depicted and the arterial wall is no
longer visible. e B-mode examination thus allows dierentiation of stenotic lesions caused by atherosclerosis from
luminal narrowing caused by external structures.
2
72
Chapter 2 · Extremity Arteries
. Table 2.7 Sensitivity, specicity, and diagnostic accuracy of duplex ultrasonography compared with angiography in the diagnosis of
hemodynamically relevant stenosis (>50%), occlusion, and aneurysm of the pelvic and leg arteries (see . Table2.20)
2
Author Vascular territory Duplex technique Reference method Sensitivity (%) Specicity (%) Accuracy (%)
Kohler etal.
(1987)
Legemate etal.
(1991)
Allard etal.
(1994)
Cossman etal.
(1989)
Mulligan etal.
(1991)
Moneta etal.
(1992)
Strauss (2001) Iliac
Schäberle
(1998)
Polak etal.
(1990)
Landwehr etal.
(1990)
Koennecke
etal. (1989)
Legemate etal.
(1991)
Ranke etal.
(1992)
Katsamouris
etal. (2001)
Aly etal. (1998) Aortoiliac
Khan etal.
(2011)
Femoropopliteal Conventional Conventional angio 82 92 –
Aortoiliac Conventional IA DSA 89 92 91
Aortoiliac
Femoropopliteal
Iliac
Common femoral
Supercial femoral
Profunda femoris
Popliteal
Femoropopliteal Color Conventional angio 89 91
Iliac
Common femoral
Supercial femoral
Profunda femoris
Popliteal
Common femoral
Supercial femoral
Profunda femoris
Popliteal
Femoropopliteal,
iliac, proximal
segments of crural
arteries
Femoropopliteal Color Angiography or
Femoropopliteal Color Angiography or
Femoropopliteal Color Angiography or
Aortoiliac
Femoropopliteal
Tibial
Femoropopliteal
Crural
Femoropopliteal Color Angiography 94.5 99
Conventional Conventional angio 83
87
Color Conventional angio 81
70
87
71
85
Color Conventional angio
or IA DSA
Color Conventional angio
or IA DSA
Color Conventional angio
or IA DSA; intraoperative
IA DSA
IA DSA
IA DSA
Color Angiography 84 96
Color Angiography 87 94
Color Angiography 86
Color Angiography 89
89
76
87
83
67
87
75
94
79
94
97 98 97
88 95 93
92 99 96
97 97 97
99
80
100
82
96
93
98
97
85
95
97
99
99
98
97
99
73
91
72
96
92
90
94
91
99
99
99
92
90
92
93
87
93
93
83
86
88
86
93
88
96
83
IA DSA intra-arterial digital subtraction angiography