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January 2011 Supplement
Treatment Strategies for Complex Iliac Artery Disease
Tips for treating this challenging presentation with endovascular techniques.
By Jean Bismuth, MD, and Alan B. Lumsden, MD
In recent years, the number of aortobifemoral procedures for occlusive disease performed by vascular surgery trainees has, surprisingly, not declined1 despite a significant increase in total procedures performed for aortoiliac disease, the majority of which are endovascular cases. This is, of course, to a great extent driven by improved device performance and likely a greater number of vascular surgeons who are well-trained interventionists.
BACKGROUND
Aortobifemoral bypass remains an efficacious and
durable operation and is the procedure against which all
other iliac procedures are benchmarked. It has been
shown that primary patency rates are better for bypass at
1, 3, and 5 years when compared to iliac stenting.2 This
trend may be more pronounced as interventionists push
the envelope further and not only treat iliac lesions of
TransAtlantic Inter-Society Consensus (TASC) B and C,
but also D.3 However, if one thinks of an open procedure
like an endovascular procedure, consisting of both a
delivery system and a therapeutic component, the delivery
system for aortobifemoral bypass remains unappealing.
Consequently, endovascular management of aortoiliac
disease has moved to the front line of the treatment
algorithm. Although the durability of the therapeutic
component may be more compromised, the appeal of
the delivery system more than compensates. A catheterbased
approach is recommended as first-line therapy for
TASC A and B lesions and is likely the preferred option
for initial revascularization of C lesions. Whether a
patient undergoes an endovascular procedure or an
operation for a TASC D lesion depends in great part on
the treating clinician's experience, expertise, and comfort
in either open procedures or advanced endovascular
techniques. One question that remains unclear is
whether one can maintain a standpoint that all lesions
should be treated based on plain old balloon angioplasty
(POBA) first with iliac stenting only being used as a rescue
procedure or whether primary stenting is indicated.
One of the main reasons for the confusion is that earlier
studies did not define stenoses by accepted classifications
such as TASC. Indeed, a recent article showed that, as
one might expect, there is no difference in long-term
patency between TASC A and B lesions treated with
POBA or stenting. This is not the case for TASC C and D
lesions, for which primary stenting seems to fare significantly
better than POBA.4
There are multiple potential predictors of failure for endovascular procedures involving the aortoiliac segment, which can include a stenotic ipsilateral superficial femoral artery, ulcer/gangrene, smoking history, and chronic renal failure with hemodialysis. There is some indication that patients with these risk factors who do undergo endovascular procedures in the aortoiliac segment should be considered for primary stenting.5,6
We believe that there are also a variety of technical elements of aortoiliac stenting that can improve outcomes and success rates, particularly in the more complex lesions. One of the tools we use is intravascular ultrasound (IVUS). IVUS allows for accurate measurement/sizing, identification of lesion length, and also evaluation of plaque characteristics, particularly with respect to calcification and dissections. It also provides a better idea of the appropriateness of the therapy delivered and allows for accurate evaluation of lesions posttreatment. In a recent study evaluating stent deployment by IVUS, it was found that 40% of patients had underdeployed stents, although they appeared adequately expanded by arteriography. In the group of patients who were evaluated by IVUS in addition to arteriography, no stenoses or occlusions were noted at follow-up, whereas in the group evaluated by arteriography alone, 25% had stenoses or occlusions at followup.
Of course, there are a number of stents on the market that have substantially varying results depending on the clinical scenario in which they are used. One can essentially separate stents initially into two groups, self-expanding and balloon expandable, and can be further subdivided into covered and uncovered stents. There is some suggestion that covered stents may, at least in the short-term, provide better patency rates,7 but whether this holds true long-term remains unclear. More recently, the MELODIE study showed 2-year patency rates of almost 88% for the uncovered Express® LD balloon- expandable stent.8 There are many variables that may impact stent efficacy, which include but are not limited to: (1) stent construction (laser-cut or etched, woven, knitted, coiled, or welded); (2) flexibility, radial strength, hoop strength, radiopacity, and foreshortening; (3) resistance to kinking; (4) metal thickness; (5) trackability or pushability of the device; and (6) in case of balloon-expandable stents, does the device stay on the balloon, or is it at significant risk of dislodging during delivery? All of these factors, as well as the source of the metal, corrosion resistance, and the amount of open area-to-metal surface ratio, may all affect the biocompatibility of the stent, and ultimately, long-term patency rates.
Generally, our preference has been to use uncovered balloon- expandable stents in aortoiliac interventions due to their precise placement, ease of delivery, good radial force in calcified lesions, adequate flexibility, and “what you see is what you get” qualities that include minimal foreshortening and superior positioning when extending stents into the aorta using the kissing stent technique. We generally reserve covered stents for complications or what we consider highrisk lesions (embolization, exophytic calcification) and, consequently, only rarely use them as our primary device.
FAILED AORTOILIAC STENTING
Before embarking on endovascular interventions in the
aortoiliac segments, it is imperative that the operator
understands the pathophysiology and the severity of
inflow and/or outflow compromise. If there is inadequate
flow in the infrainguinal segment, then early failure
may occur. Similarly, if all proximal disease is left
untreated, then the stent is more likely to be compromised.
It has been shown in a 10-year follow-up that if
one fails to extend treatment into the aorta for lesions
that are at the aortic bifurcation, outcomes are generally
inferior.9 In the case presented (Figure 1), a patient had
been seen and treated initially with balloon angioplasty,
followed up by covered stents placed in both common
iliac arteries (CIA) extending into the external iliac arteries.
The patient was referred to our hospital with early
stent occlusion and failed previous endovascular treatments,
which was found to be due to an aortic stenosis
(Figure 1, solid black arrow) and poor outflow. The
patient underwent an aortobifemoral bypass and a
simultaneous femoral-popliteal bypass. As the patient
was a young working woman, who very much needed to
remain active and maintain her quality of life (with a
background of already failed multiple endovascular interventions), it was felt that a bypass would give her
the best long-term result.
TREATMENT OF ILIAC LESIONS
TO SUPPORT A BYPASS
Another example is of an 83-year-old woman who
presented with severe rest pain having had two prior
femoral-femoral crossover bypasses performed by separate
surgeons over an 8-month period, which both failed.
Basic principles dictate that inflow should always be corrected
before performing a downstream bypass. Figure 2
shows a flush occlusion at the left CIA. Previous surgeons
failed to identify a high-grade stenosis in the distal CIA,
as well as diffuse severe disease extending up into the distal
aorta based on IVUS. The approach for this patient,
who actually had adequate outflow, was to attempt
recanalization of the left side and then treat the right side
with a balloon-expandable stent primarily. Despite a reentry
device recanalization of the left side that was not
fruitful, adequate treatment of the common iliacs (Figure 3)
on the right side with a new femoral-femoral bypass was
sufficient to provide the patient with adequate lower
extremity reperfusion.
TREATMENT OF SEVERELY CALCIFIED
LESIONS
We find that patients with severely calcified lesions of the
CIA that extend up to the aortic bifurcation are best managed
by kissing stents. Generally, these lesions do not
respond well to balloon angioplasty because they are
extremely resistant to dilation, and the hoop strength of
balloon-expandable stents is a great advantage.
Additionally, as previously discussed, it is important to have
a stent that will deploy precisely and be able to travel
through the tight lesion, which in this case did not respond
very well to predilation. In Figure 4, the solid arrow identifies
a large calcium shelf, which after deployment of kissing
stents, is effectively displaced to improve flow distally. The
near occlusion could not be traversed from the ipsilateral
side, and a snare was used to snag a wire introduced from
the contralateral side. For the stents to be deployed simultaneously
into the aorta, access through the lesions needs
to be obtained bilaterally in the femoral arteries.
CONCLUSION
In this short review of endovascular interventions for
aortoiliac occlusive disease, we have discussed some of
the available evidence supporting management of this
arterial segment. Additionally, we have shared several
cases identifying some fundamental aspects of this management.
The data support the use of stents primarily,
particularly in this era of aggressive endovascular management
of both TASC C and D lesions. Of note, it is
important that patients who are treated are followed
closely by physical examination and noninvasive testing,
as this will help in the treatment of failing stents.
Jean Bismuth, MD, is with Cardiovascular Associates, Debakey Heart & Vascular Center, The Methodist Hospital in Houston, Texas. He has received no financial compensation for participation in this supplement. Dr. Bismuth may be reached at jbismuth@tmhs.org.
Alan B. Lumsden, MD, is with Cardiovascular Associates, Debakey Heart & Vascular Center, The Methodist Hospital in Houston, Texas. He has disclosed that he has served as a speaker for Boston Scientific Corporation. He has received no financial compensation for participation in this supplement.
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