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									Preprocedural Imaging: New Options
to Reduce Need for Contrast Angiography
Anil Hingorani, MD, Enrico Ascher, MD, and Natalie Marks, MD, RVT

                      In vascular surgery, the gold standard for evaluation of the lower-extremity arterial tree has
                      long been contrast arteriography (CA). Associated risks of CA are well-documented and
                      include severe allergic reactions, arterial injury and/or hemorrhage, and contrast-induced
                      nephropathy. Increasingly, less-invasive techniques, with fewer inherent risks for compli-
                      cation, are being explored as diagnostic alternatives. Magnetic resonance angiography,
                      computed tomography angiography, and duplex arteriography, each offer distinct advan-
                      tages, though are not without limitation. This review explores the indications, advantages,
                      and disadvantages of these newer technologies and provides a comparison to CA as a means
                      for defining the anatomic features of patients undergoing lower-extremity revascularization.
                      This data suggests that noninvasive imaging technologies may, in the future, play an increas-
                      ingly important role in the surgical evaluation of the patient with lower-extremity ischemia.
                      Semin Vasc Surg 20:15-28 © 2007 Elsevier Inc. All rights reserved.




L    ESS-INVASIVE TECHNIQUES are being explored in all
     fields of medicine. Advancements in robotic surgery,
laparoscopic surgery, and percutaneous interventions have
                                                                               went CA, MRA, and DA before undergoing 64 lower-extrem-
                                                                               ity revascularization procedures at Maimonides Medical
                                                                               Center. Patients were excluded from our study protocol if
not been pushed forward by technology only, but by patients’                   their serum creatinine was 2.0 mg/dL after hydration (n
demand for less-invasive methods of treatment. Yet, in vas-                    8). Cases of acute ischemia (n 5) or patients who under-
cular surgery, even though percutaneous revascularization                      went outpatient preoperative evaluation only were excluded
techniques continue to be advanced, the gold standard for                      because MR imaging was not readily available to outpatients
evaluation of the lower-extremity arterial tree, the basic prin-               (n     161) at our institution because of the overwhelming
ciple, techniques, and complications of contrast arteriogra-                   inpatient demand. In fact, the MR imaging machine was in
phy (CA), have remained largely unchanged since Seldinger’s                    such high demand, it could take up to 3 to 7 days to obtain an
article in 1953.1 As a challenge to this widely practiced stan-                MRA for inpatients.
dard, less-invasive imaging technologies actively explored in-                    Reports of these tests, images, and operative findings were
clude magnetic resonance angiography (MRA), computed to-                       collected prospectively and compared to results of CA. Re-
mography angiogram (CTA), and duplex arteriography (DA).2-6                    ports and exams were analyzed by a vascular surgeon blinded
   In an effort to review the potential of these alternatives to CA,           to the identity of the patients, but aware of the clinical infor-
we will initially compare MRA and DA to CA for defining ana-                    mation for each patient. The differences in the three segments
tomic features of lower-extremity occlusive disease in patients                (aortoiliac, femoral-popliteal, and infrapopliteal segments)
undergoing lower-extremity revascularization procedures, and                   were separately documented. Arterial segments were classi-
then include the more-recent use of CTA in the comparison.                     fied as mild disease ( 50%), moderate disease (50% to
                                                                               70%), severe disease (70% to 99%), and occluded by CA,
Comparison of                                                                  MRA, or DA. These imaging studies, and the treatment plans
                                                                               based on their data, were compared.
DA, MRA, and CA
From August 1, 2001 to August 1, 2002, sixty-one consecu-                      Duplex Ultrasonography
tive inpatients with chronic lower-extremity ischemia under-
                                                                               Vascular ultrasonography tests were all performed on either
                                                                               an ATL HDI 3000 or ATL HDI 5000 duplex scanner by two
Division of Vascular Surgery, Maimonides Medical Center, Brooklyn, NY.
Address reprint requests to Anil P. Hingorani, Division of Vascular Surgery,   registered vascular technologists. The arterial segments start-
   Maimonides Medical Center, 4802 10th Avenue, Brooklyn, NY 11219.            ing from mid-abdominal aorta to the pedal arteries were in-
   E-mail: ahingorani@maimonidesmed.org                                        terogated in cross-sectional and longitudinal planes using


0895-7967/07/$-see front matter © 2007 Elsevier Inc. All rights reserved.                                                                    15
doi:10.1053/j.semvascsurg.2007.02.005
16                                                                                           A. Hingorani, E. Ascher, and N. Marks

appropriate scanheads for varying depths, namely 7-4, 10-5,
12-5, 15-2, 5-2, and 3-2 MHz extended operative frequency
range, to obtain high-quality B-mode, color and power
Doppler images as well as velocity spectra. All of these tech-
niques were used to estimate the degree of stenosis and any
discrepancies were communicated to the operating surgeon.
In general, however, color and power Doppler were used
primarily, and B-mode and velocity spectra were used to
supplement these data, especially in the presence of long
lesions or multiple lesions. The arteries were classified as
normal or mildly diseased ( 50%), significantly stenosed
( 50%), occluded or not visualized. Peak systolic velocity
ratios 2 and 3, as compared to the adjacent vessel, were
used to define hemodynamically significant stenoses 50%
and 70%, respectively.2-6 A more-precise evaluation of ar-
terial size, length, and degree of narrowing, as well as plaque
characteristics, were performed for lesions suitable for bal-
loon angioplasty and/or stent placement. At the completion
of the test, a color-coded map of the entire arterial tree was
drawn to help develop the proper revascularization strategy
(Fig 1).


CA
Standard percutaneous retrograde preoperative CA with dig-
ital subtraction angiography (DSA) was obtained. These were
performed by the vascular surgery team in the operating
room as a separate procedure from the revascularization. The
distal aorta to the pedal vessels were visualized. Percutaneous
access was obtained through a hollow-bore single-entry nee-
dle. After a metal guide wire was placed in the external iliac
artery, a 4Fr sheath introducer was inserted. A 4Fr pigtail
catheter was used with a power injector with full-strength
Omnipaque (Sanofi Winthrop Pharmaceuticals, New York,
NY) to obtain angiograms using a OEC 9800 digital mobile
fluoroscopic unit (General Electric, Salt Lake City, UT). Cal-
ipers and multiplanar views were used selectively. Images
were obtained with and without digital subtraction. While
fully appreciating the limitations of CA (in the presence of
multilevel disease, pseudodefects, timing, lack of detail of
the vessel wall, and lack of hemodynamic information)
interventions were made based upon CA.


MRA
MRA was performed using a 1.5-Tesla whole-body scanner
(Magnatom Vision plus, Siemens Medical Systems, Iselin,           Figure 1 Example of duplex arteriography mapping.
NJ). Parameters for the study were a repetition time of 40
milliseconds and an echo time of 1.6 milliseconds. T1-
weighted three-dimensional gadolinium-enhanced imaging
of the aortoiliac system to the level of the ankle was per-       stepping table was not used for this set of data, as it had
formed in a body-array coil with a flip angle of 70 degrees.       not arrived yet. The timing was based upon a 1-cc test
Below the ankle, two-dimensional electrocardiograph trig-         bolus during this phase. Calipers and multiplanar views
gered time-of -flight MRA was performed using a combina-           were used selectively. MRA results were interpreted by MR
tion of the phase-array coil and the head coil with a flip angle   radiologists with extensive experience, who were not
of 30 degrees. Maximum intensity projections and source           aware of the results of other lower-extremity imaging mo-
images were used in the interpretation of the study. Our          dalities (Fig 2).
Preprocedural imaging                                                                                                               17




           Figure 2 Representative magnetic resonance angiography demonstrating patent aortoiliac system with failing popliteal-
           dorsalis due to severe superficial artery and popliteal disease.



Comparison of                                                           undergo MRA and 8 were not able to undergo angiography.
                                                                        The reasons for patients not being able to undergo MRA
DA and MRA versus CA                                                    included: refusal or severely uncooperative (n       9), pace-
Mean SD age of these patients was 76 10 years (range,                   maker (n      10), recent surgery (n       5), acute ischemia
47-97 years). Indications for the proposed revascularization            (n 5), severely contracted knee and hip (n 1), claustro-
procedures included gangrene (43%), ischemic ulcer (28%),               phobia (n 2), and morbid obesity (n 1). Of the total 192
rest pain (19%), severe claudication (9%), and failing bypass           arterial segments of the 64 patients (iliac, femoral-popliteal,
1 (1%). Diabetes, hypertension, and end-stage renal disease             and tibial segments), 17% could not be fully assessed by DA
were present in 86%, 59%, and 15% of the patients, respec-              and 7% by MRA (Table 1). In addition, two patients had to
tively. During the time period of this study, 41 patients were          have repeated MRA study to obtain more information. Even
not able to be entered into the protocol as 33 could not                though there were multiple arteries in each segment, any
18                                                                                                    A. Hingorani, E. Ascher, and N. Marks

Table 1 Causes of Incomplete Exams Comparing MRA, DA,                   terest was fueled by the encouraging results published in the
and CA                                                                  literature.12-24 However, our initial experience, as well as
                                  Cause of Incomplete                   those published from other centers, suggest certain limita-
        Type of Exam                     Exam                     n     tions in this imaging technology in its present state.25-30
MRA                                                                        Because of the variety of reasons listed, a significant por-
 Aortoiliac segment              Timing of dye bolus              1     tion of these elderly patients with multiple comorbid condi-
 Femoral-popliteal               Contracture                      1     tions was not able to undergo MRA. Even with sedation,
   segment                       Knee prosthesis artifact         1     some patients simply refused to have an MRA or literally
 Infrageniculate segment         Venous contamination            10     jumped off the MR table. No one test can be used for all
                                 Movement                         1     patients, and these type of problems still remain at issue.
                                 Contracture                      1        We found that MRA is not yet able to obtain adequate data
DA                                                                      for us on which to decide which intervention to perform
 Aorto iliac segment             Gas interposition                 7    these, at least for the highly selected population at our insti-
                                 Calcified iliac                    1
                                                                        tution. Because have placed over 200 patients into various
     Femoral-popliteal           Calcified                          4
       segment
                                                                        phases of this protocol over the last 3 years and have involved
     Infrageniculate segment     Severe tibial calcification      18     a group of MRA radiologists trained at a leading center for
                                 Gangrene                         1     lower-extremity MRA imaging, we cannot attribute these re-
                                 Noncooperative patient           1     sults to the early phase of a learning curve. The most common
CA                                                                0     problem we encountered with MRA was assessing the degree
Abbreviations: CA, contrast arteriography; DA, duplex arteriography;    of disease and the degree of patency of the distal arteries
   MRA, magnetic resonance angiography.                                 when they were patent and subsequently used for distal anas-
Magnetic resonance angiography        13 patients, duplex arteriogra-   tamosis. Misidentification of the distal superficial femoral ar-
   phy 10 patients.                                                     tery (SFA) as the popliteal artery and identification of mod-
                                                                        erate aortoiliac disease in the face of a normal contrast
                                                                        angiogram and pressure measurements were other difficul-
disagreement in any individual artery was counted as a dis-             ties encountered. These issues have not been resolved, de-
agreement in the entire segment. Disagreements between CA               spite reviewing these data on an ongoing basis with the MRA
and DA were encountered in the iliac, femoral-popliteal, and            radiologists. Problems with low-flow/signal dropout and ve-
tibial segment in 0%, 7%, 14% of the cases, respectively,               nous contamination may be possible causes of the disagree-
and between CA and MRA in 10%, 26%, and 42% (Tables 2                   ments between the studies. Conversely, when severe tibial
and 3). However, because some segments could not be fully               artery calcification is identified, DA may be unreliable and
evaluated with each technique and were excluded from fur-               CA may be necessary. This problem can be recognized by the
ther analysis, the percentage of disagreements may have been            DA technologist, and the vascular surgery team can be ad-
underestimated. Two of the nine differences between DA and              vised to seek alternative imaging modalities. Most of the time,
CA were found to be clinically significant, while 28 of 45               the parts of segments that cannot be visualized well by DA do
differences between MRA and CA were felt to be clinically               not have an impact on the planned procedure, as they are not
significant. Clinical significance was determined if the differ-          the ultimate inflow nor outflow targets, so that the informa-
ence would have resulted in a difference in the revasculariza-          tion obtained is adequate to perform the intended procedure.
tion procedure. The actual procedures performed included a              In this data set, if DA was solely used, we probably would
bypass to an infrapopliteal artery (n 19), bypass to the popli-         have resorted to CA in 16 cases (25%), because not enough
teal artery (n 23), no procedure (n 9), below-knee ampu-                information was obtained by DA alone. However, because we
tation (n 2), percutaneous balloon angioplasty (n 6), axil-             could not identify which segments would not be reliably
lofemoral bypass (n 4), and an ileofemoral bypass (n 1).                assessed by MRA alone, the percent who would have re-
The calculated sensitivity and specificity, positive predictive and      quired CA after MRA had been obtained (and interpreted as
negative value, and accuracy are outlined in Table 4.                   the only imaging tool) could not be estimated.
   On average, the time required for DA, MRA, and CA are 30                This data presented here represent patients with very se-
to 60 minutes (average 46), 20 to 60 minutes, and 40 to 60              vere arterial disease seen at a referral center for limb-threat-
minutes), respectively. Average costs for each are: $300,               ening ischemia. This may partly explain why our results with
$2,100, and $2,200, respectively.

                                                                        Table 2 Disagreements Between DA and CA with Clinical
Limitations of MRA                                                      Significance
This data presented represent a continuing effort by our ser-                 DA                   CA            Clinical Significance
vice to explore alternative imaging techniques. Our previous            AT open       Distal AT disease             Bypass to distal AT
work has demonstrated the use of DA in patients undergoing              Peroneal open Peroneal stenosis             PTA of peroneal
lower-extremity revascularization.7-11 Parallel to this, we             Abbreviations: AT, anterior tibial artery; CA, contrast arteriography;
have been investigating the use of MRA as a preoperative                   DA, duplex arteriography.
imaging tool for lower-extremity revascularization. Our in-             Both noted to have severely calcified tibial vessels.
Preprocedural imaging                                                                                                                    19

Table 3 Disagreements Between MRA and CA with Clinical Significance
            MRA                                                 CA                                         Clinical Significance
CIA moderate disease                             No CIA stenosis                                     CIA, no intervention needed
CFA is OK                                        CFA is diseased                                     Ileofemoral bypass
Pop peroneal stenosis                            Not stenotic                                        Fem pop bypass
Mod disease in Pop tibials                       No pop tibial disease                               Fem pop bypass
Pop, peroneal mod disease                        Open pop per                                        Fem pop bypass
Distal pop diseased                              Open pop                                            Fem pop bypass
Pop very small                                   Open pop                                            Fem pop bypass
Pop is open                                      AK pop closed                                       Bypass to BK pop
AK pop open                                      Ak pop closed                                       Bypass to BK pop
SFA pop open                                     SFA pop stenotic                                    PTA of SFA and pop
Pop open                                         Distal pop closed                                   Bypass to PT
Pop diseased                                     Normal popliteal                                    Fem pop bypass
Mod pop disease                                  Normal pop                                          Fem pop bypass
AK pop open                                      AK pop closed                                       Bypass to BK pop
Mod aortic and pop disease                       No disease aorta and BK pop                         Bypass to BK pop
Stenotic fem pop                                 No stenosis                                         No intervention needed
Pop mod disease                                  Pop open                                            Bypass to pop
TPA open                                         TPA closed                                          Bypass to peroneal
Per mod disease                                  Normal peroneal                                     Bypass to peroneal
Per diseased                                     Peroneal open                                       Fem peroneal bypass
Per closed                                       Per open                                            Fem pop bypass with runoff to per
Per diseased                                     Peroneal open                                       Fem peroneal bypass
Distal PT open                                   Distal PT closed                                    Limited runoff for bypass to PT
AT open                                          Stenotic AT                                         PTA or AT
Per closed                                       Per open                                            Bypass to peroneal
DP diseased                                      DP open                                             Fem DP bypass
DP open                                          DP closed                                           Bypass to AT with no run off
DP closed                                        DP open                                             Bypass to DP
Abbreviations: AK, above knee; AT, anterior tibial artery; BK, below knee; per, peroneal; CFA, common femoral artery; CA, contrast
   arteriography; CIA, common iliac artery; DP, dorsalis pedis artery; EIA, external iliac artery; fem-pop, femoral-popliteal; MRA, magnetic
   resonance angiography; pop, popliteal; PT, posterior tibial artery; SFA, superficial femoral artery; TPA, tibio-peroneal artery.




these imaging modalities are suboptimal. Perhaps if more                 Limitations of DA
outpatients with claudication and SFA disease were included,
the results would have been more favorable. The data, how-               Over the course of 1,020 DA, we have also explored various
ever, do suggest that, while neither DA nor MRA is yet able to           limitation of DA. Poor visualization of vessels with extremely
completely replace CA at our institution, with further ad-               calcified vessel walls, skin-quality problems, such as severe
vances in technology these imaging tools may be able to more             dermatitis, open ulcers, heavy scarring, severe lymphedema,
frequently obtain the necessary information for these com-               and severe hyperkeratosis are some of the problems associ-
plex revascularizations.                                                 ated with DA, as well as rest pain, noncompliant patients and




Table 4 Comparison Magnetic Resonance Angiography or DA versus CA (Excluding Nonvisualized Segments)
                                                                   Positive Predictive        Negative Predictive
                        Sensitivity (%)      Specificity (%)            Value (%)                  Value (%)               Accuracy (%)
MRA
 Aortoiliac                    100                    81                      23                        100                      82
 Femoral-popliteal              86                    53                      82                         60                      74
 Tibial                         61                    51                      30                         79                      54
DA
 Aortoiliac                    100                    96                      67                        100                      96
 Femoral-popliteal              97                    94                      97                         94                      96
 Tibial                         81                   100                     100                         94                      95
Abbreviations: CA, contrast arteriography; DA, duplex arteriography; MRA, magnetic resonance angiography.
20                                                                                                 A. Hingorani, E. Ascher, and N. Marks

                                                                       In very-low flow situations (peak systolic velocity of
                                                                          20 cm/s), such as in the tibial vessels in acute ischemia or
                                                                       cardiogenic shock, setting the pulse repetition frequency at
                                                                       150 to 350 Hz and using the lowest wall filter, the highest
                                                                       persistence and highest sensitivity for the color-flow imaging
                                                                       can be beneficial. At times, distal compression can augment
                                                                       flow and demonstrate patency of tibial vessels.
                                                                          When the tibial vessels are severely calcified, we have
                                                                       found power Doppler and SonoCT to be particularly useful.
                                                                       In addition, examining the vessels in transverse section,
                                                                       changing the color box angle, and increasing the gain can, at
                                                                       times, allow better visualization of the arterial lumen. The
                                                                       depth of the tibioperoneal trunk, origin of the proximal per-
                                                                       oneal and posterior arteries, and the superficial femoral ar-
Figure 3 Severely calcified anterior tibial with lumen not able to be   tery at Hunter’s canal may necessitate use of a lower-fre-
assessed.                                                              quency probe for visualization. However, this tends to
                                                                       sacrifice details resolution and can make images of these areas
                                                                       difficult to interpret. In these cases, velocity spectral analysis
excessive edema (Fig 3). Additionally, we encountered diffi-            can also be a useful adjunct. Manipulation of the leg, using
culty visualizing the iliac arteries due to colostomy, marked          multiple probes and other approaches, may be necessary for
iliac tortuosity, recent abdominal surgery, ascites, morbid            better assessment of difficult arterial segments. For example,
obesity, or gas interposition in a few of our patients.                the medial approach may help visualize the proximal pero-
    To circumvent the problem of severe calcification, we have          neal artery, the medial or posterior approach may assist in
found increasing the gain, persistence, and sensitivity and            visualizing the mid-peroneal artery, and the lateral or posterior
using power Doppler and SonoCT technology quite useful.                approach may facilitate the imaging of the distal peroneal artery
Lack of patient cooperation may be one limitation to accurate          and its branches (Fig 4). Thus, the tibial vessels can be ade-
DA, particularly for the iliac and infrapopliteal segments. In         quately evaluated by using a variety of approaches and angles.
fact, a small percentage of patients are uncooperative because            The most difficult infrapopliteal segments to visualize, in
of altered mental status, inability to position the leg, or severe     our experience, were the most proximal portion of the ante-
ischemic pain. The inclusion of pain medications, sedation,            rior tibial artery and the bifurcation of the tibioperoneal
or having a family member in the laboratory to calm the                trunk. We believe that this difficulty could be explained by
confused patient was also found to be very helpful. In certain         the depth of these arteries. Contrary to the belief that the
instances, we reattempted the exam after a few days of eleva-          peroneal artery in difficult to image, we were able to visualize
tion to decrease the edema and attempted overnight fasting             it using a variety of techniques. Using these techniques made
prior to the exam to reduce bowel gas. Often, with limited             the adequate assessment of the majority of these difficult-to-
visualization of the aortoiliac segment, but with normal com-          visualize arteries possible.
mon femoral artery waveforms, it was elected to proceed to
revascularization, realizing that an intraoperative balloon an-
gioplasty of the inflow arteries may be needed. Nevertheless,
a small number of our patients were not able to have ade-
quate information derived from DA and did require preop-
erative contrast angiography despite these attempts.
    Furthermore, incomplete visualization of the crural and
pedal vessels by DA does not always have a major impact on
the choice of the procedure. For example, if a surgeon prefers
to perform a bypass to the distal anterior tibial artery rather
than to the distal peroneal, and the distal peroneal was too
calcified to insonate, the lack of data on the distal peroneal
may have little impact on the planning of the procedure. In
general, our policy of not performing femoral-distal bypasses
for patients with claudication means that, in the presence of
severe SFA disease or occlusion with at least one vessel run-
off and absence of significant iliac artery disease, a femoral-
popliteal bypass will be planned even if the remaining two
tibial arteries could not be completely evaluated.
    Nevertheless, when difficulties in the evaluation of the
crural and pedal vessels are encountered and the status of             Figure 4 Terminal branches of peroneal artery visualized by duplex
these vessels is necessary, additional techniques can be used.         arteriography.
Preprocedural imaging                                                                                                           21

   The origin of the anterior tibial artery deserves special
attention, as collaterals in this area may be mistaken for a
patent proximal anterior tibial artery. Careful examination of
the origin of the vessels and tracing the vessels distally often
can solve some of these issues. In addition, identification of
the two adjacent veins can help distinguish between a large
collateral and the vessel itself. When patency of vessels that
are not visualized well, despite these techniques is crucial for
the revascularization procedure choice, an angiogram should
be obtained before the procedure is attempted.


Advantages of DA
Invasive contrast angiography remains the gold-standard im-
aging modality in planning these revascularizations, even
though this modality may not detect outflow vessels that may
be more clearly visualized with duplex or MRA as occurs in
very-low flow situations with acute or severe chronic isch-
emia.10,31 Conversely, DA has the capability to detect these
vessels with very low flow ( 20 cm/s). Visualization of these
outflow vessels may result in the performance of lower-ex-
tremity revascularizations that ultimately achieve limb sal-
vage. Moreover, because biplanar arteriography is not the
standard for the entire arterial tree, eccentric lesions, espe-
cially in the iliacs, can go undetected with contrast angiogra-
phy. Finally, while MRA does have certain clear advantages
over CA, we have noted that as many as 25% of patients are
unable to complete their preoperative MRAs due to schedul-
ing difficulties, claustrophobia, metal implants, or pacemak-
ers.
   The advantages of DA as compared to other imaging tools
include the identification of the softest portion of the vessel
wall, which can be marked on the skin before the intended
procedure. Skin marking of the most suitable site for outflow
anastomosis, particularly for infrapopliteal segments, can
limit incision size and eliminate extensive arterial dissection
in search of a soft arterial segment. Information of a noncal-
cified arterial segment is promptly conveyed to the surgeon,
important arterial braches may be spared, and long incision-       Figure 5 Duplex arteriography mapping, skin marking, and comple-
related complications reduced. While a target vessel may be        tion angiogram of bypass to common plantar artery.
patent using luminally based imaging tools, the vessel may be
severely calcified in long segments, as in the diabetic and
end-stage renal disease populations. We have found that pre-       tion, DA has the ability to more accurately assess the chronic
operative localization of the softest portion of the vessel by     nature of an occlusion. Therefore, it is possible to differenti-
DA can accurately identify the most advantageous anasto-           ate between an isolated chronic SFA occlusion and an acute
motic site, thus decreasing the risk of damage to the artery by    embolism with little underlying disease or acute thrombosis
clamping or incomplete proximal control with a tourniquet          with severe underlying atherosclerotic disease. In addition,
due to concomitant severe SFA calcification. Thus, DA can be        aneurysmal vessels with partial thrombosis may have little to
an invaluable aid to the surgeon in determining the anasto-        no luminal dilatation and may be undetectable by CA. Simi-
motic site of choice (Fig 5).                                      larly, ulcerated and irregular plaques that can be a source of
   Because DA is not just a luminal technology, it can be used     embolization are also poorly assessed with CA. High-resolu-
to assess the actual disease of the vessel. High-resolution        tion DA more clearly visualizes these plaques. Consequently,
duplex imaging can assess not only the luminal diameter, but       we have found this imaging modality particularly valuable in
also the thickness of the wall, approximately 1/10th of a          determining patient management as compared to other tech-
millimeter. While a vessel may appear to have a patent lumen       nologies.
with MRA and contrast angiography, the actual thickness of            Furthermore, the hemodynamic information obtained us-
the wall is not evaluated via these techniques. This visualiza-    ing DA may alter patient management. Volume flow and
tion by DA may change the site for the anastomosis. In addi-       velocity measurements can help assess whether the visual-
22                                                                                                A. Hingorani, E. Ascher, and N. Marks




                     Figure 6 Distant arteriography mapping and completion angiogram of bypass to dorsalis pedis.


ized lesion is hemodynamically significant and determine               the surgeon a complete picture of the findings, rather than to
whether repair of the lesion may be beneficial. For example,           have the surgeon merely review the mapping. Thus, the in-
a poorly visualized iliac plaque with little change in the ratio      tricacies and nuances of the actual quality of the arteries and
of peak systolic velocities ( 2) may suggest that the lesion          veins are presented to the surgeon as an adjunct to the map-
may not be of clinical significance. On the other hand, lesions        ping and images taken during the exam. For example, the
that are poorly visualized because of severe calcification with        thickness and characteristics of the target vessels can be more
elevated ratios distal to the obscured lesion suggest a hemo-         effectively communicated by verbal exchange, as compared
dynamically significant lesion. Other luminal imaging mo-              to written details or a drawing. This type of data serves to
dalities do not readily furnish these details.                        further accentuate the advantages of DA over luminally based
   The portability of the duplex machine should be men-               imaging modalities, as this sort of information is not available
tioned. Because DA can be performed at the bedside, in the            otherwise. Areas that are not well-visualized should be iden-
operating room, or in the holding area, time spent transport-         tified as such for the surgeon to decide if this area is crucial.
ing the patient and the personnel required is significantly
reduced. Additionally, obtaining the CA or MRA and their              Role of DA in Renal and Diabetic Patients
interpretation can entail a delay in the definitive treatment of       It has been well-documented that patients with diabetes mel-
a severely ischemic limb in a debilitated patient, as well as         litus and/or chronic renal insufficiency are at increased risk
take a toll on the operative team. With DA, once the patient is       for developing contrast-induced nephropathy when sub-
identified to need urgent revascularization, the machine and           jected to CA, despite use of nonionic contrast media.32-35
technician can be brought to any part of the hospital for an          Although renal function in most patients with contrast-in-
abbreviated directed exam (Fig 6).                                    duced renal failure will return to baseline, a few patients may
                                                                      require hemodialysis, and most will have their proposed ar-
DA Team                                                               terial reconstruction delayed. In modern series, up to 10% of
While prior studies have demonstrated the reliability of              diabetic patients will have contrast-induced renal failure and
DA,13,17,18 it is highly operator-dependent. We require an            up to 12% of patients with chronic renal insufficiency will see
experienced technician whose capabilities are well-known to           their renal function significantly worsen after CA.3,36,37 In
the surgical staff. Our DA technicians are registered vascular        addition, the significant osmotic load associated with dye
technologists, who each undergo a specialized training pro-           injection poses a risk for fluid overload for patients on hemo-
tocol, including examination of the patient by DA and an-             dialysis. Yet, the gold-standard imaging modality for lower-
giography. The variances encountered between both modal-              limb ischemia continues to be invasive CA, even in the pres-
ities are then reviewed. In addition, any differences in DA and       ence of diabetes mellitus and chronic renal failure.
intraoperative completion angiography are analyzed by all of             More recently, several investigators have attempted to
the surgeons and technologists, resulting in a close relation-        validate duplex arterial mapping as a reliable alternative
ship. Prior to each procedure, the case is discussed to afford        to CA.1,14,16,38 Although some of these studies achieved ex-
Preprocedural imaging                                                                                                          23

cellent correlation between DA and CA, few surgeons have           even with severely calcified vessel, such as using multiple
actually performed infrainguinal bypasses without preoper-         projections and using SonoCT.46 Although each individual
ative or prebypass CA.3 In an effort to examine revasculariza-     field of view is limited, we have demonstrated that the vessels
tion without a preoperative dye study, we will focus on our        from the aorta to the pedal vessels can be visualized using DA.
experience with DA in 145 patients who had 180 lower-              While the role of contrast-enhanced DA has not been ex-
limb arterial bypasses and who were at risk for developing         plored, the data on use of contrast-enhanced duplex exams
or worsening their renal failure if given nonionic contrast        for the carotid arteries and aortic endoleaks makes this a
media.                                                             possible future adjunct.47-51 During our experience, we noted
   From January 1998 to November 2000, lower-extremity             that duration of exam became much shorter with increased
DAs were performed in 145 patients with diabetes mellitus          experience. In our initial experience, the entire exam took us
and/or chronic renal failure prior to 180 arterial reconstruc-     as long as 90 minutes. By the end of our experience, the exam
tions. One hundred and twenty-one procedures were per-             could take as little as 25 minutes.
formed on 97 patients with diabetes alone, 41 on 33 patients          These data are based upon our previous experience with
with diabetes and chronic renal insufficiency (CRI), 18 on 15       preoperative DA and represent an extension of our use of
patients with CRI alone. Patient ages ranged from 45 years to      duplex imaging to become an integral part of the interven-
98 years (mean 73 10 years). Indications for surgery were
                                                                   tion itself. In order to perform duplex-guided angioplas-
severe claudication in 20 (15%), rest pain in 28 (21%), non-
                                                                   ties, one needs extensive experience with preoperative DA.
healing ischemic ulcers in 39 (30%), and limb gangrene in 45
                                                                   Furthermore, because duplex imaging is also being used
(34%). Preoperative CA was performed in 16 procedures
                                                                   for duplex-guided thrombin injections of arterial pseudo-
because of extremely poor run-off based on DA and limited
                                                                   aneurysms, endovenous interventions of the greater sa-
visualization of outflow vessels. Adequacy of the inflow was
                                                                   phenous vein, placement of inferior vena cava filters, ca-
confirmed by intraoperative pressure measurements. Postby-
pass CA or duplex imaging was obtained to verify the patency       rotid angioplasties, and lower-extremity angioplasty, we
of the runoff. The DA procedure time averaged 50              12   propose that this new field be termed interventional ultra-
minutes (range 35 to 90 minutes). The distal anastomosis           sonography.52-65
was to the popliteal artery in 65 cases (49%) and to the tibial
and pedal arteries in 67 (51%). Cumulative patency rates at 1
and 3 months were 94% and 83%, respectively. Intraopera-           Comparison of CTA to CA
tive findings confirmed the preoperative DA findings, with            Recent advances in hardware and software have made mul-
the exception of one where the distal anastomosis was placed       tidetector CTA an option for imaging of the lower extremity
proximal to a significant stenosis requiring an extension           in patients undergoing lower-extremity revascularization
graft.                                                             procedures. Prior authors have compared CTA and CA and
   Use of high-quality arterial ultrasonography presents a safe    cite sensitivity and specificity of 93%.46,48 Some of the ad-
and reliable option to preoperative lower-extremity CA for         vances that have led to these advances in CTA over prior CT
many patients with diabetes or impaired kidney function.           technologies include increased volumetric coverage, im-
The ease of use and favorable patient outcomes achieved by         proved z-axis resolution, better separation of different vascu-
this imaging modality may rival use of contrast angiography
                                                                   lar phases and isotropic voxels, and the ability to obtain sin-
for these patients.
                                                                   gle-image acquistion. Furthermore, in contrast to the limited
   This imaging modality can offer results comparable to
                                                                   projection routinely obtained during CA, a wider variety of
those achieved with conventional invasive CA, while at the
                                                                   manipulation of the volumetric data set for image display and
same time reducing associated risks. The advantages of
                                                                   analysis is feasible with CTA. CTA allows more postproce-
avoiding or limiting the use of CA to decrease incidence of
                                                                   dure imaging processing, and one can rotate the three-di-
postprocedure renal insufficiency for the diabetic patient and
those patients with CRI are self-evident. This complication        mensional image to any angle.
also results in substantially increased lengths of stay, addi-        Because CTA is minimally invasive, it offers the potential
tional specialty consults, and higher costs. In addition, it can   to obtain the needed data to plan lower-extremity revascu-
also produce suffering for the patient and their family. More-     larization procedures without the risks of CA. CTA can also
over, an analysis of natural history studies indicates that 23%    offer greater patient comfort and convenience. In comparison
to 63% of patients with diabetes will have progressive renal       to CA, some authors have noted shorter procedure times and
insufficiency, with 10% to 35% winding up on dialysis.39-43         less radiation exposure.49
Of those patients with CRI, up to 28% will require eventual           In a further effort to explore newer alternatives to CA, we
dialysis.44,45 It remains unclear whether administration of in-    compared CTA to CA for defining anatomic features of pa-
traarterial dye can result in additional long-term complica-       tients undergoing lower-extremity revascularizations.
tions in these high-risk patients with peripheral vascular dis-       From November 2003 to March 2004, 36 inpatients with
ease.                                                              chronic lower-extremity ischemia underwent CA and CTA
   Overall, our most common problem with DA has been               before undergoing lower-extremity revascularization proce-
with calcification. However, as we have cited before, some          dures. No patients included in this series had a serum creat-
techniques can be used to obtain the necessary information         inine 1.6 mg/dL.
24                                                                                                     A. Hingorani, E. Ascher, and N. Marks

CTA                                                                      The studies and treatment plans based on these data were
A Siemens 16-slice multiplanar CT (SOMATOM Sensation                     compared.
16) with bolus tracking and care dosing was used for these                  Both observers of the CTA and the CA were blinded to
exams. The specifications of the CTA protocol were a rate                 results of each study. Two patients were not able to have CTA
of dye injection 4 cc/s, to program length 1,024 mm (AP),                due to severely contracted lower extremities and inability to
slice thickness 3 mm, pitch 1.5 mm, KV 120, MA 180, rotation             remain still. One patient had poor opacification of vessels,
time 0.75 seconds, scan time 70 seconds, and dye bolus of                severe dense calcification of femoral and popliteal vessels and
Visapaque (320) 130 to 150 cc (Amersham Health, Bucking-                 knee prosthesis not allowing adequate imaging of the femo-
hamshire, UK). The angio runoff reconstruction was performed             ral-popliteal and tibial vessels. These three patients were not
with 2-mm slices every 1 mm.                                             included in the series.
                                                                            Mean age       SD was 76       12 years. Indications for the
CA                                                                       procedures included gangrene (45%), ischemic ulcer (32%),
Standard percutaneous retrograde preoperative CA with DSA                rest pain (19%), and severe claudication (3%). Sixty-nine
was obtained. These were performed by the vascular surgery               percent were diabetics. No complications were noted from
team in the operating room as a separate procedure from the              CTA of CA in this series.
revascularization. Visualization of the distal aorta to the pedal           Thirteen of eighteen (72%) of these disagreements resulted
vessels was attempted. Percutaneous access was obtained                  in a procedure than that was suggested by CTA (Tables 5 and
through a hollow-bore single-entry needle. After a metal                 6; Fig 7). Prior revascularization had been performed in 14
guide wire was placed in the external iliac artery, a 4Fr sheath         patients (39%). Procedures performed included a bypass to
introducer was inserted. A 4Fr pigtail catheter was used with            infrapopliteal vessels (n 13), angiogram alone (n 11),
a power injector with full-strength Omnipaque (Sanofi                     endovascular treatment (n         6), femoral-popliteal bypass
Winthrop Pharmaceuticals) to obtain the angiograms using a               (n 4), embolectomy (n 1), and major amputation (n 1).
OEC 9800 digital mobile flouroscopic unit (General Elec-                     This experience represents our continuing effort to explore
tric). Calipers and multiplanar views were used selectively.             alternatives to imaging for patients undergoing lower-ex-
Images were obtained with and without digital subtraction.               tremity revascularization. We have found DA to be extremely
While fully appreciating the limitations of CA in the presence           useful in the majority of patients. However, one has to fully
of multilevel disease, pseudodefects, timing, lack of detail of          appreciate that, in addition to the commitment needed to
the vessel wall, and lack of hemodynamic information, inter-             overcome the learning curve, maintain the quality assurance,
ventions were made based upon CA.                                        and establish a DA team, once severe tibial artery calcification
   The reports of these tests and images were compared pro-              is encountered, alternative imaging modalities may be
spectively and the differences in the aortoiliac segment, fem-           needed.
oral-popliteal, and infrapopliteal segments were noted. The                 MRA has also been proposed as an alternative for evalua-
vessels were classified as mild disease ( 50%), moderate                  tion of patients undergoing lower revascularization. With
disease (50% to 70%), severe (71% to 99%), and occluded.                 MRA, the problem is that it is difficult to cover the large


Table 5 Disagreements Between CTA and CA with Clinical Significance
             CTA                                             CA                                         Clinical Significance
CIA diseased                                  Normal CIA                                      CIA does not need intervention
Disease CIA                                   Normal CIA                                      CIA doesn’t need intervention
SFA diseased                                  Normal SFA                                      No impact
Normal popliteal                              Disease in above knee pop                       Bypass to BK pop
Popliteal moderate disease                    Normal popliteal                                Bypass to pop
Popliteal closed                              Popliteal open                                  Fem pop bypass
Popliteal diseased                            Normal pop                                      Fem pop not failing
Popliteal disease                             Normal pop                                      Bypass to pop
Normal tibio-peroneal artery                  Disease tibio-peroneal artery                   Need distal bypass
Tarsal not seen                               Tarsal open                                     Bypass to tarsal
DP not seen                                   DP open                                         No impact
No DP seen                                    DP open                                         Bypass to DP
AT open                                       AT closed                                       Bypass to peroneal
Closed plantar DP                             Open plantar DP                                 Balloon of tibial vessels with good runoff
Closed DP                                     Open DP                                         No impact
AT open                                       AT diseased                                     No impact
Peroneal moderate disease                     Normal peroneal                                 Bypass to peroneal
AT, DP disease                                AT, DP open                                     No impact
Abbreviations: AK, above knee; AT, anterior tibial artery; BK, below knee; per, peroneal; CFA, common femoral artery; CA, contrast
   arteriography; CIA, common iliac artery; CTA, computed tomography angiography; DP, dorsalis pedis artery; EIA, external iliac artery; pop,
   popliteal; PT, posterior tibial artery; SFA, superficial femoral artery.
Preprocedural imaging                                                                                                             25

Table 6 Comparison of CTA and CA
                                                                 Positive Predictive    Negative Predictive
                        Sensitivity (%)    Specificity (%)            Value (%)              Value (%)              Accuracy (%)
Aortoiliac                    –                    100                    –                         –                       100
Femoral-popliteal            100                    25                   80                         –                        81
Infrapopliteal                75                    50                   63                        44                        59
Abbreviations: CA, contrast arteriography; CTA, computed tomography angiography.



volume that needs to be imaged. Multiple protocols have               dency to overestimate disease. Again, none of the prior re-
been set up to solve this issue. However, even with recent            ports have included examination of the pedal vessels (Fig 8).
advancement in MRA, our results have been disappointing                  A review of the data obtained in this series indicated that
because the imaging of the tibial and pedal vessels has had           CTA does not yet seem to be able to obtain adequate data, at
poor sensitivity and specificity. Furthermore, we encoun-              least for this highly selected population at our institution.
tered a large percentage of our patients who were not able to         Prior investigators have suggested that the correlation be-
undergo MRA.                                                          tween CTA and CA was adequate.66-69 However, other larger
   On the other hand, careful examination of prior reports            series have demonstrated poorer result in the infrapopliteal
does reveal that certain areas of difficulty have been encoun-         regions.70-73 These discrepancies may be partially due to dif-
tered with CTA. Even in the article by Catalano et al,66 the          ferences in the technologies being used as rapid advances
most difficult area to visualize was in the tibial area, especially    have been made. Furthermore, there has been little correla-
the peroneal artery. This article stated that CTA had a ten-          tion in prior reports in the types of interventions that would




           Figure 7 Comparison of computed tomography angiography (CTA) and contrast arteriography. CTA suggests severely
           diseased popliteal artery, but angiogram does not.
26                                                                                                             A. Hingorani, E. Ascher, and N. Marks




             Figure 8 Comparison of computed tomography angiography (CTA) and contrast arteriography (CA). CTA fails to
             demonstrate patent nondiseased lateral tarsal artery as demonstrated on CA.



be planned based upon these data. Again because of our                          4. Hingorani A, Ascher E, Markevich N, et al: A comparison of magnetic
referral base, most of our patients were quite elderly, with                       resonance angiography, contrast arteriography, and duplex arteriogra-
                                                                                   phy for patients undergoing lower extremity revascularization. Ann
limb-threatening ischemia in contrast to some of the prior
                                                                                   Vasc Surg 18:294-301, 2004
series were mostly claudicants were evaluated. These data                       5. Hingorani A, Ascher E, Markevich N, et al: Magnetic resonance angiog-
still suggest that because it is not possible to identify in which                 raphy versus duplex arteriography in patients undergoing lower ex-
patients the data is not reliable, it seems that in this selected                  tremity revascularization: which is the best replacement for contrast
population, CTA and MRA do not obtain adequate results to                          arteriography? J Vasc Surg 39:717-722, 2004
base interventions upon. These preliminary data suggest with                    6. Ascher E, Hingorani A, Markevich N, Schutzer R, Kallakuri S: Acute
future advancements, that noninvasive imaging technologies                         lower limb ischemia: the value of duplex ultrasound arterial mapping
                                                                                   (DUAM) as the sole preoperative imaging technique. Ann Vasc Surg
may have an important role in evaluating patients undergo-
                                                                                   17:284-289, 2003
ing lower revascularization.                                                    7. Ascher E, Hingorani A, Markevich N, Costa T, Kallakuri S, Khanimoy Y:
                                                                                   Lower extremity revascularization without preoperative contrast arte-
Acknowledgment                                                                     riography: experience with duplex ultrasound arterial mapping in 485
                                                                                   cases. Ann Vasc Surg 16:108-114, 2002
Special thanks to Anne Ober for editorial assistance.                           8. Mazzariol F, Ascher E, Hingorani A, Gunduz Y, Yorkovich W, Salles-
                                                                                   Cunha S: Lower-extremity revascularisation without preoperative con-
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