Outcomes of Covered Kissing Stent Placement
Compared with Bare Metal Stent Placement in
the Treatment of Atherosclerotic Occlusive
Disease at the Aortic Bifurcation
Saher S. Sabri, MD, Asim Choudhri, MD, Gianluigi Orgera, MD, Bulent Arslan, MD, Ulku C. Turba, MD,
Nancy L. Harthun, MD, Klaus D. Hagspiel, MD, Alan H. Matsumoto, MD, and John F. Angle, MD
PURPOSE: To review the outcomes with the use of balloon-expandable covered iliac kissing stents as compared with
bare metal stents in the treatment of atherosclerotic disease at the aortic bifurcation.
MATERIALS AND METHODS: A review of consecutive patients from a single institution with atherosclerotic
occlusive disease at the aortic bifurcation treated with balloon-expandable kissing stents was performed between
January 1, 2002, and September 1, 2007. Fifty-four patients were identified and divided into two groups: those with
bare metal stents and those with covered stents. Technical and clinical success (Fontaine classification), complications,
and patency at follow-up were documented.
RESULTS: Twenty-six patients (17 men, nine women; mean age, 61 years; age range, 39 –79 years) received covered
stents and 28 patients (15 men, 13 women; mean age, 61 years; age range, 38 – 82 years) received bare metal stents.
Technical success was achieved in 100% of patients in both groups. Major complications occurred in three of the 26
(11%) with covered stents (P ⴝ .66) and two of the 28 patients (7%) with bare metal stents. The median follow-up was
21 months (20 months for covered stents vs 25 months for bare metal stents; range, 1– 62 months). Twenty-two of the
26 patients (85%) with covered stents had sustained improvement in clinical symptoms during the follow-up period
compared with 15 of the 28 patients (54%) with bare metal stents (P ⴝ .02). Primary patency rates at 1 and 2 years were
92% and 92%, respectively, for covered stents and 78% and 62% for bare metal stents (P ⴝ .023).
CONCLUSIONS: The use of covered balloon-expandable kissing stents for atherosclerotic aortic bifurcation occlusive
disease provides superior patency at 2 years as compared with bare metal balloon-expandable stents.
J Vasc Interv Radiol 2010; 21:995–1003
Abbreviations: ABI ⫽ ankle-brachial index, CIA ⫽ common iliac artery, DSA ⫽ digital subtraction angiography, EIA ⫽ external iliac artery, PTA ⫽ percutaneous transluminal angioplasty, TASC ⫽ Trans-Atlantic Inter-Society Consensus
ATHEROSCLEROTIC occlusive disease involving the aortic bifurcation
and proximal common iliac artery
(CIA) has been historically treated
From the Division of Angiography, Interventional Radiology, and Special Procedures, Department of Radiology/Box 800170 (S.S.S., A.C., G.O., B.A., U.C.T.,
K.D.H., A.H.M., J.F.A.) and the Division of Cardiovascular and Thoracic Surgery, Department of Surgery
(N.L.H.), University of Virginia Health System, Jefferson Park Ave, Charlottesville, VA 22908. Received August 13, 2009; final revision received January 25, 2010;
accepted February 8, 2010. Address correspondence to
J.F.A.; E-mail: jfa3h@virginia.edu
Inc., and Thoracic Endograft Trials. He is a paid consultant for W.L. Gore, Cook, Bard, Medtronic, Siemens
Medical, Crux Medical, and Boston Scientific. J.F.A.
has research funded by Atrium Medical and is a
paid consultant for Terumo Medical and Siemens
Medical. None of the other authors have identified a
conflict of interest.
A.H.M. has research funded by NIH-HNLBI CORAL
TRial Angio-Corelab PI, W.L. Gore, Medtronic, Cook,
From the 2008 SIR annual meeting.
© SIR, 2010
DOI: 10.1016/j.jvir.2010.02.032
with surgical bypass (1,2). Endovascular treatment with the “kissing stent”
technique has shown early clinical results comparable to the surgical option
(3–7). However, the longer-term patency rates with aortic bifurcation kissing stents have been disappointing
compared with the patency rates of
CIA and external iliac artery (EIA)
stents (8 –14). Early experience with
the use of covered stents in some vascular beds has shown improved patency rates compared with bare metal
stents, particularly in the treatment of
occlusive lesions involving the superficial femoral artery (15–17). Our
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•
Outcomes of Covered Kissing Stents Compared with Bare Metal Stents
study reviews our experience with
the outcomes of percutaneous placement of expanded polytetrafluoroethylene– covered kissing stents compared
with bare metal balloon-expandable
stents in the treatment of atherosclerotic
occlusive disease at the aortic bifurcation.
MATERIALS AND METHODS
A retrospective review of consecutive patients from a single institution
with atherosclerotic occlusive disease
at the aortic bifurcation treated with
kissing balloon-expandable iliac kissing stents was undertaken for procedures performed between January 1,
2002, and September 1, 2007, by using
a procedural database (Hi-IQ; ConexSys, Albion, Rhode Island). Human investigation review board approval
was obtained for this study. Electronic
medical records were reviewed for patient demographics, vascular disease
risk factors, procedural information,
and clinical and imaging follow-up.
All study subjects had clinical and angiographic evidence of atherosclerotic
occlusive disease involving the aortic
bifurcation with unilateral or bilateral
CIA stenosis or occlusion. The patients
were divided into two groups: those
with covered stents and those with
bare metal stents. Bare metal stents
were used exclusively between January 2002 and November 2004. After
November 2004, a commercially available covered stent became available and
was applied almost exclusively, in an
off-label application. Runoff weighting
scores for each limb were recorded on
the basis of the reporting standards recommendation of the Society of Interventional Radiology Technology Assessment Committee (18).
The clinical status of the patient
was assessed with the Fontaine classification (19) at baseline before the procedure, 6 –12 weeks after the procedure, and at the last clinical follow-up.
Change in clinical status was designated as “improved,” “no change,” or
“worse” on the basis of a change by
one or more Fontaine classes. Resting
ankle-brachial indexes (ABIs) were obtained in all patients at baseline and at
the time of discharge after the procedure. Postprocedure clinical follow-up
with ABIs was also performed at 6 –12
weeks after the procedure and then
annually.
Immediate technical success was defined as less than 30% residual stenosis
of the target lesion(s). Initial clinical success was defined as an improvement in
ABI from baseline of at least 0.1. Follow-up imaging with computed tomographic (CT) angiography or digital
subtraction angiography (DSA) was
performed in select patients on the basis
of the preferences of the physician performing the clinical follow-up. Patency
at follow-up was defined as no evidence
of restenosis or occlusion within the
originally treated vessel on the basis of
follow up CT angiography or DSA
and/or the clinical combination of no
target vessel revascularization procedures and no more than a 0.15 decrease
in follow up ABI. Procedural complications were defined according to the Society of Interventional Radiology Clinical Practice Guidelines (20).
Bilateral percutaneous common
femoral artery access was obtained,
followed by insertion of 6-8-F introducer sheaths in both common femoral arteries for the patients with bare
metal stents and 7-F sheaths for patients with covered stents. One patient
required left brachial artery access to
obtain the diagnostic angiogram. A
weight-based bolus of heparin was administrated intravenously or intraarterially to achieve an activated clotting
time of more than 220 seconds. Under
fluoroscopy, a hydrophilic 0.035-inch
guide wire and a 5-F catheter were
advanced through the iliac lesions via
the common femoral artery access
sites. A 5-F multi-sidehole pigtail catheter was advanced proximal to the
aortic bifurcation. DSA of the pelvis
and both lower extremities was performed by using a power injector in an
anteroposterior projection. Oblique
images of the pelvis arterial anatomy
were also obtained. The introducer
sheaths were advanced over the guide
wire through the lesions to facilitate
delivery of the balloon-expandable
stents across the occlusive lesions. Preprocedure dilation with balloon angioplasty was performed as necessary to
facilitate stent delivery. The bilateral
balloon-expandable stents were positioned over the lesions and the introducer sheaths retracted. Simultaneous
stent deployment was performed by
using the kissing balloon/stent technique (Figs 1,2). The same type of stent
was used in both CIAs. The diameters
of the stents selected were usually
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oversized 10%-20% relative to the
treated iliac arteries. If the combined
diameter of the stents was greater than
the diameter of the distal aorta, then
smaller-diameter premounted stents
were used at initial stent deployment
to keep from overdilating the distal
aorta. Postdeployment dilation with
larger balloons was then used to make
sure the stents opposed the wall both
proximally and distally. The artery diameters were measured from the DSA
images by using the intrinsic calibration and the quantitative vascular
analysis measurement program on the
angiographic equipment (Axiom Artis
Imaging System; Siemens Medical,
Malvern, New Jersey).
The proximal ends of the stents
were positioned at or above the aortic
bifurcation to cover the entire stenotic
segment. In patients with unilateral
CIA stenoses or occlusions involving
the ostium of the ipsilateral CIA, a
stent was also placed in the contralateral CIA, and extended a similar distance into the aorta, to ensure its patency. The distance from the proximal
end of the stents to the aortic bifurcation was measured and documented
in a review by the authors.
In the patients with bare metal
stents, the balloon-expandable stents
used included the Palmaz Genesis
(Cordis Endovascular, Warren, New
Jersey) and Express LD (Boston Scientific, Natick, Massachusetts) stents. All
the stents in the covered stent group
were balloon-expandable expanded
polytetrafluoroethylene covered stents
(iCAST; Atrium Medical, Hudson,
New Hampshire). After the procedure, all patients were placed on 81–
325 mg of acetylsalicylic acid a day for
life and 75 mg of clopidogrel a day for
a minimum of 30 days.
The Fisher exact test was used for
discrete variables. The Student t test
and the Mann-Whitney U test were
used for continuous variables evaluation. Ordinal variables analysis was
performed by using the Kruskall-Wallis test (nonparametric analysis of variance). Patency of the stents was analyzed by using survival analysis with
Kaplan-Meier log-rank test. A P value
less than .05 was considered to be indicative of a statistically significant
difference.
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Sabri et al
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Figure 1. (a) Initial left anterior oblique image from DSA of the pelvis shows bilateral proximal common iliac stenoses (arrows) without
involvement of the distal aorta. (b) Bilateral bare metal kissing stents (Express LD) were deployed. (c) Image from DSA performed at
6-month follow-up shows right common iliac in-stent restenosis (arrowheads) secondary to intimal hyperplasia.
RESULTS
Fifty-four consecutive patients were
identified and divided into two groups:
those with covered stents and those
with bare metal stents. Twenty-six patients (17 men, 9 women; mean age, 61
years; age range, 39 –79 years) received
covered stents–-all of which were
placed after November 2004. Twentyeight patients (15 men, 13 women;
mean age, 61 years; age range, 38 – 82
years) received bare metal stents–-all
but four were placed before November 2004 (Table 1). The demographic
data and risk factors were similar for
both groups. The distribution of the
Fontaine classification scores of clinical symptoms were comparable, with
21 of the 26 patients (81%) with covered stents and 21 of the 28 (75%) with
bare metal stents having claudication
(Fontaine classes II) (P ⫽ .747) (Table
2). Two patients in each group had
tissue loss.
Treated lesion characteristics on the
basis of the TASC II classification of
the aortoiliac segments (1) were statistically more advanced in the patients
with covered stents, with 10 of 26 patients (38%) classified as having class
C and D lesions compared with two of
the 28 (7%) with bare metal stents (P ⫽
.0034) (Table 2). Twelve of the 26 patients (46%) with covered stents had
CIA occlusions: All of these CIA occlusions were unilateral, with contralateral stenosis in eight patients and a
normal contralateral CIA in four. The
remaining 14 patients (54%) had bilateral CIA stenoses. Of the 28 patients
with bare metal stents, three (10%) had
CIA occlusions (one bilateral and two
with contralateral stenoses) and 25
(90%) had CIA stenoses (22 bilateral
and three unilateral with a contralateral normal CIA). Runoff weighting
scores for each limb was recorded on
the basis of the reporting standards
recommendation of the Society of
Interventional Radiology Technology
Assessment Committee (19). The distribution of the scores was comparable
between both groups. The mean runoff weighting scores for patients with
covered stents were 2.0 ⫾ 2.1 on the
right and 2.1 ⫾ 1.6 on the left. The
mean runoff weighting scores for patients with bare metal stents were
1.6 ⫾ 1.8 on the right and 1.5 ⫾ 1.7 on
the left (P ⫽ .134) (Table 2).
Immediate technical success was
achieved with stenting in 100% of
patients in both groups. Major complications, which included vascular
dissection requiring additional stent
placement and distal embolism, occurred in three of the 26 patients
(11%) with covered stents and two of
the 28 (7%) with bare metal stents
(P ⫽ .66). There were no proceduralrelated mortalities.
There was no statistically significant difference between the two
groups with regard to stent diameters.
Twelve of the 26 patients (46%) with
covered stents had one or both iliac
stents dilated to only 6 or 7 mm in
diameter; in 14 of the 26 patients
(54%), the smallest stent diameter was
8 –10 mm. In the patients with bare
metal stents, 11 of the 28 patients
(40%) had a 6 –7-mm-diameter stent
used and 17 (60%) had stents dilated
to 8 –10 mm in diameter (P vs patients
with covered stents ⫽ .784). The left
and right stents were the same size or
within 1 mm of each other in every
case in both groups.
The stents extended more than 1 cm
above the aortic bifurcation to cover
distal aortic disease in five of the 26
patients (19%) with covered stents and
eight of the 28 (28%) with bare metal
stents (P ⫽ .53). One patient in the
covered stent group had a distal aortic
stent placed in addition to the CIA
kissing stents.
Additional EIA interventions were
performed in the same procedural setting in 14 of the 26 patients (54%; 12
underwent stent placement and two underwent percutaneous transluminal angioplasty [PTA]) with covered stents
and 12 of the 28 (43%; 10 underwent
stent placement and two underwent
PTA) with bare metal stents (P ⫽ .586).
Additional femoropopliteal revascularization with PTA, stent placement, or
bypass grafting was performed in five
of the 26 patients (19%) with covered
stents and three of the 28 (11%) with
bare metal stents (P ⫽ .46).
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Outcomes of Covered Kissing Stents Compared with Bare Metal Stents
Figure 2. (a– c) Initial anterioposterior images from DSA shows proximal left common
iliac occlusion (a) treated with bilateral covered kissing stents (b,c) (iCAST stents, arrows
in c). (d) CT angiogram obtained at 12-month follow-up shows patency and absence of
intimal hyperplasia.
The ABIs before and after the procedure are summarized in Table 3. At
baseline, there were no statistically
significant differences between the
limbs or the groups (P ⫽ .314). The
ABIs increased in both study groups
after revascularization. ABIs (in the
left and right limb) improved from an
average of 0.74 and 0.61, respectively,
before the procedure to 0.83 and 0.87,
respectively, at discharge for the covered stent group and from 0.77 and
0.70 to 0.92 and 0.91, respectively, for
the bare metal stent group (covered
stent vs bare metal stent groups, P ⫽
.81). Immediate clinical success, based
on an immediate improvement in the
ABI of more than 0.1, was similar between both groups and achieved in 24
of the 26 patients (92%) with covered
stents and 24 of the 28 (86%) with bare
metal stents.
Clinical follow-up with ABIs was
available in all patients. Imaging follow-up was available in 15 of the 26
patients (57%) with covered stents and
19 of the 28 (68%) with bare metal
stents.
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The median follow-up was 21
months (20 months for covered stents
vs 25 months for bare metal stents;
range, 1– 62 months). Twenty-two of
the 26 patients (85%) with covered
stents versus 15 of the 28 (54%) with
bare metal stents (P ⫽ .02) had sustained improvement in clinical symptoms during the follow-up period on
the basis of the Fontaine classification
(Table 4). Two of the 26 patients (8%)
with covered stents had no initial improvement in symptoms but chose not
to undergo any additional procedures
during the follow-up period. Two patients in the covered stent group had
worsening symptoms during followup, and both required revascularization with thrombolysis of the thrombosed stents followed by balloon
angioplasty. Thirteen patients in the
bare metal stent group described
worsening symptoms during the follow-up period. Of these 13 patients, 12
required additional procedures for target vessel revascularization, including
an aortobifemoral bypass graft (n ⫽ 1),
additional stent placement (n ⫽ 4),
and balloon angioplasty alone (n ⫽ 7).
One patient in the bare metal stent
group underwent a major amputation.
Ten of the 26 patients (39%) with
covered stents continued to smoke after stent placement, compared with 13
of the 28 patients (46%) with bare
metal stents (P ⫽ .59).
There was no significant decrease
in ABIs in the covered stent group
during the follow-up period, with the
ABIs showing little change (0.83 and
0.87 after the procedure and 0.80 and
0.88 at latest follow-up for the right
and left limbs, respectively). However,
there was a significant decrease in the
ABIs for the bare metal stent group,
with follow-up ABIs of 0.74 and 0.79
compared with discharge values of
0.92 and 0.91 for the right and left
limbs, respectively (P ⫽ .003).
With use of Kaplan-Meier analysis,
primary patency rates at 1 and 2 years
were 92% and 92% for covered stents
and 78% and 62% for bare metal
stents, respectively (P ⫽ .023) (Fig 3).
Overall patency rates (combing both
groups) were not affected by patient
sex, stent diameter (greater or less
than 8 mm), external iliac and/or
femoropopliteal interventions, or cessation of smoking.
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Table 1
Summary of Demographics
Parameter
Covered Stents
(n ⫽ 26)
Bare Metal Stents
(n ⫽ 28)
61 ⫾ 10.2
61.5 ⫾ 12.8
17
9
25 (96)
13 (50)
13 (50)
3 (12)
15
13
25 (89)
11 (39)
13 (46)
1 (4)
.612
.584
.999
.342
18 (70)
20 (77)
21 (75)
23 (82)
.764
.741
Mean age (y)
Sex
M
F
Hypertension
Diabetes mellitus
Coronary artery disease
Renal impairment (creatinine
level ⬎2 mg/dL)
Hyperlipidemia
Smoking history
P Value
.885
.418
Note.—Numbers in parentheses are percentages.
Table 2
Summary of Clinical and Anatomic Findings
Parameter
Covered Stents
(n ⫽ 26)
Bare Metal Stents
(n ⫽ 28)
21 (81)
5 (19)
21 (75)
7 (25)
7 (27)
9 (35)
6 (23)
4 (15)
13 (46)
13 (46)
2 (7)
0 (0)
0 (0)
8 (31)
1 (4)
2 (7)
4 (15)
0 (0)
14 (54)
0 (0)
22 (78)
3 (11)
2.2 ⫾ 2.1
2.1 ⫾ 1.6
4.3 ⫾ 3.2
1.4 ⫾ 1.7
1.6 ⫾ 1.7
3.1 ⫾ 3.1
Fontaine classification
II
III–IV
TASC II classification
A
B
C
D
CIA disease
Bilateral occlusion
Unilateral occlusion with
contralateral stenosis
Unilateral occlusion with normal
contralateral artery
Bilateral stenosis
Unilateral stenosis with normal
contralateral artery
Runoff weighting
Right
Left
Right ⫹ left
P Value
.747
.034
.134
Note.—Numbers in parentheses are percentages.
DISCUSSION
The management of symptomatic
atherosclerotic occlusive disease of the
iliac arteries has been dramatically altered by the use of permanent metal
endoprostheses (stents). Clinical success rates of 70%–92% at 2 years have
been reported for bare metal stents in
the CIA (21,22). Patients with CIA origin occlusive lesions, with or without
adjacent distal aortic disease, represent a complex subgroup of patients
because of the technical challenges as-
sociated with stent placement and the
variable results with endovascular
therapy reported in the literature
(11,23–25)
Although encouraging results were
seen using the kissing balloon technique in 1991 for aortic bifurcation and
proximal iliac lesions (26), the longterm benefit from iliac artery angioplasty is limited by elastic recoil of the
lesion and arterial dissections. Early
application of stents at the aortic bifurcation revealed that kissing stents are
•
999
often needed to achieve an adequate
angiographic result. Kissing stents are
now commonly applied for aortic bifurcation and iliac origin occlusive lesions. Unfortunately, clinical results
are still discouraging compared with
those seen with focal CIA disease
(8,10,11,13,25,27–30). Primary patency
rates of 58%– 87% at 2 years are typical
of the results reported, which are inferior to the results seen with focal CIA
disease (10,13,27).
The reasons for the inferior results
with the application of kissing stents
at the aortic bifurcation compared
with single CIA stents remain unclear
and are probably multifactorial. The
results associated with the use of iliac
artery kissing stents have been found
to be particularly poor when the stents
extend into the aorta far enough to
overlap at least one-half the width of a
stent (28). A higher incidence of acute
stent thrombosis suggests that flow
disturbance or increased thrombogenicity or lack or neoendothelialization
of the free end of the bare stents within
the aortic lumen may be important
(30). However, the only factors that
have been shown to affect iliac stent
patency are stent size less than 7 mm
and possibly EIA disease (31).
Reconstruction of the aortic bifurcation by using covered stents rather
than bare metal stents may provide
more laminar flow, decreased thrombogenicity, less chance for prolapse of
plaque through the covered stent, and
less ingrowth of hyperplastic tissue–-a
concept easily extrapolated from the
experience with covered iliac stents
(32). Several studies have demonstrated the efficacy of using stentgrafts for aorto-iliac occlusive disease,
with overall primary patency ranging
from 70% to 85% at 1 year (33–37).
However, the use of stent-grafts for
aortic bifurcation occlusive disease has
not been widely adopted mainly due
to the required large introducer sheath
sizes in the face of potentially small
access vessels, costs, and lack of a U.S.
Food and Drug Administration–approved covered stent for this specific
indication. The covered stents used in
this study were balloon-expandable,
unlike the other available stent-grafts,
which are self-expanding. It also provides the advantage of being able to be
delivered through a relatively small
access sheath (7 F).
The results presented herein dem-
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Table 3
Summary of ABIs
Parameter
Covered stents
Before the procedure
After the procedure
At follow-up
Bare metal stents
Before the procedure
After the procedure
At follow-up
Right ABI
Left ABI
0.74 ⫾ 0.21
0.83 ⫾ 0.23
0.80 ⫾ 0.21
0.61 ⫾ 0.18
0.87 ⫾ 0.22
0.88 ⫾ 0.17
0.77 ⫾ 0.28
0.92 ⫾ 0.17
0.74 ⫾ 0.24
0.70 ⫾ 0.20
0.91 ⫾ 0.21
0.79 ⫾ 0.21
Note.—For covered stents, the P values for right ABIs were .028 for comparisons
before and after stent placement and .21 for comparisons after stent placement and
at follow-up; the P values for left ABIs were .001 for comparisons before and after
stent placement and .82 for comparisons after stent placement and at follow-up. For
bare metal stents, the P values for right ABIs were .012 for comparisons before and
after stent placement and .003 for comparisons after stent placement and at followup; the P values for left ABIs were .002 for comparisons before and after stent
placement and .025 for comparisons after stent placement and at follow-up.
Table 4
Findings at Clinical Follow-up
Finding
Covered stents
Clinical improvement
Stable
Clinical worsening
Bare metal stents
Clinical improvement
Stable
Clinical worsening
No. of Patients
Additional Intervention Performed
during Follow-up
22
2
2
None
None
PTA (n ⫽ 1), surgical bypass (n ⫽ 1)
15
0
13
None
NA
PTA (n ⫽ 8), stent placement (n ⫽ 3),
Surgical bypass (n ⫽ 1), major
amputation (n ⫽ 1)
Note.—The median follow-up was 20 months for covered stents and 25 months for
bare metal stents. NA ⫽ not applicable.
onstrate a clinically and statistically
significant difference in the patency
rates of covered versus bare metal balloon-expandable stents employed in
the treatment of atherosclerotic occlusive disease of the aortic bifurcation
and proximal CIAs (Fig 3). This improved patency of covered stents was
identified despite the increased severity in runoff disease and the more adverse TASC II classification of the aortoiliac disease in the patients with
covered stents. A median clinical follow-up of 25 months in the patients
with bare metal stents and 20 months
in the patients with covered stents
suggests that this difference in clinical
and patency results is durable.
Only two of the 24 patients (8.3%)
who experienced immediate benefit in
the covered stent group had stent occlusion during the follow-up period.
Both patients had occluded EIA stents
and ipsilateral internal iliac artery occlusion at follow-up, which may have
contributed to the thrombosis of the
CIA stent. However, it is difficult to
attribute this only to the EIA stents
because approximately half of the patients in both study groups received
EIA stents. It is worth mentioning that
the antiplatelet therapy used in these
two patients (81–325 mg of acetylsalicylic acid a day for life and 75 mg of
clopidogrel a day for a minimum of 30
days) was similar to that used by the
remainder of the covered stent group.
None of the other patients in the covered stent group presented with instent restenosis. In-stent restenosis or
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target vessel occlusion requiring intervention was visible in 38% of the bare
metal stents at 24-month follow-up.
The superior clinical and patency results seen with covered stents compared with bare metal stents in this
patient population is likely due to
the prevention of in-stent intimal hyperplasia and the improved laminar flow
hemodynamics, which is likely due to
a decrease in turbulent flow in the distal aorta (Fig 4).
The patency rates associated with
iliac artery stents have been reported
to be negatively affected by female
sex, small vessel size, presence of distal aortic and external iliac disease,
and smoking continuation after the
procedure (14,24,38,39). With the exception of distal aortic disease, our
study failed to show a negative effect
on patency for any of the above factors
in either group. There was no difference in patency between men and
women in either group, the men in the
covered stent group did statistically
better (P ⫽ .033) than the men in the
bare metal stent group, and the
women in the covered stent group
trended toward better outcomes than
the bare metal stent group (P ⫽ .075).
Within both groups, the patency of
small- (⬍ 8 mm) versus large- (ⱖ 8
mm) diameter stents was not statistically different. The large-diameter
stents had better patency in the covered stent group compared with the
bare metal stent group (P ⫽ .0087).
Small-diameter stents showed a trend
toward improved patency in the covered stent group as compared with the
bare metal stent group (P ⫽ .0894).
Extending the stents proximally
above the aortic bifurcation in a
“crossing” manner to cover distal aortic disease has been reported to have
worse patency rates. Greiner et al (28)
reported that the primary and assisted
primary patency rates at 2 years for
the “noncrossing” group were significantly higher (94.1% and 100%, respectively) than those obtained in the
“crossing” group (33.2% and 45.3%,
respectively). Sharafuddin et al (39)
also reported that the radial mismatch
secondary to proximal extension of the
stents into the abdominal aorta is a
significant determinant of restenosis.
However, stents that extended more
than 1 cm above the aortic bifurcation
remained patent in four of five patients (80%) in the covered stent group
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Figure 3. Kaplan Meier survival curve shows improved patency of the covered stents
versus the bare metal stents at 1 and 2 years (92 and 92% vs 84 and 72%, respectively).
Figure 4. CT angiogram obtained at 12
months in the coronal plane demonstrates
in-stent stenosis in a bare metal stent (arrowheads).
versus only two of eight (25%) in the
bare metal stent group (Figs 2,4). Our
findings do support the previously
published data, which indicate that
both the presence of distal aortic disease and extension of the stents above
the bifurcation tend to produce lower
patency rates with bare metal stents.
Due to the small sample size in our
study (combined, 13 patients), the utility of covered stents in this particular
application can only be inferred.
Additional EIA interventions, which
were performed in 54% of patients in
the covered stent group and 43% of
patients in the bare metal stent group,
had no significant effect on the patency of the stents. However, the two
patients in the covered stent group
who had occlusion at follow-up both
had EIA interventions where the ipsilateral EIA stent was also found to be
occluded at the same time.
Overall patency was not affected by
the cessation of smoking. However, in
a subgroup analysis, the treated vascular segment remained patent in nine
of the 10 patients (90%) with covered
stents who continued to smoke compared with five of 13 patients (38%)
with bare metal stents who continued
to smoke (P ⫽ .029). These findings
likely reflect the overall superiority of
the covered stents.
Aortoiliac artery stent placement
techniques, the clinical indications for
intervention, and the treatment of patients with atherosclerotic aortoiliac
disease have shown little evolution
during the period of this study. The
major change that occurred in endovascular therapy that led to this study
was the new availability of a Food and
Drug Administration–-approved expanded polytetrafluoroethylene– covered, balloon-expandable stent that
was used in an off-label fashion to
•
1001
treat occlusive disease of the aortoiliac
segments. The slightly worse runoff
quality and the increased percentage
of total occlusion treated in the covered stent group may have been related to an inherent bias among the
interventionalists that the covered
stents were more likely to provide a
more durable clinical result. In addition, the four patients receiving bare
metal stents after the date where covered stent usage started were in cases
where the operator believed the anatomy was favorable and the use of covered stents was not necessary. As with
all retrospective studies of procedures
and new technology, substantial biases can alter results and conclusions,
but the use of historical controls provided closely matched populations in
this study, which helps minimize
these biases.
The demographic data and cardiovascular risk factors of the two groups
were also very similar (Table 1). However, the study remains limited by its
nonrandomized, partially retrospective, and single-institution nature.
Risk factors for bare metal kissing
stent stenosis include the distance the
stents extend into the distal aorta,
vessel size, and runoff (28,31). Further
research is needed to explore why bare
metal stents occlude at a higher rate
when used in the kissing-stent configuration compared with use in iliac arteries
and to determine what benefit covered
stents might have in the kissing-stent
configuration. Wall motion at the aortic bifurcation is more complicated
than in the iliac artery, and wall shear
stress may be important to stent outcomes (40). Although the covered
stent used in this study is rigid compared with most bare metal stents, it
may provide protection from wall
shear–induced intimal hyperplasia.
Differences in inflammatory response
have already been demonstrated in
femoral artery stenting compared with
stent placement in the iliac arteries or
carotid arteries (41), and the response
of the aortic bifurcation may be different than that expected in the aorta or
the iliac arteries. However, covered
stents prevent intimal hyperplasia
only in the middle portion of the stent
and do not prevent intimal hyperplasia
at the ends of the stent (42). In a sheep
model study, polytetrafluoroethylenecovered stents had a similar late lumen
loss compared to bare metal stents (43).
1002
•
Outcomes of Covered Kissing Stents Compared with Bare Metal Stents
The most unique aspect of bare
metal kissing stents, compared with
conventional iliac stent placements, is
that there is a free-floating stent in the
distal aorta. Although cause and effect
have not been shown, the free-floating
stent is the most likely culprit for the
inferiority of bare metal stents in this
setting and points to the potential advantage of covered stents. There is a
case report of cytopathology of failed
bare metal kissing stents that demonstrated intimal hyperplasia and thrombus within the stents and the free-floating portions of the stents (30). The
correlation between the distance a
bare metal stent extends into the aorta
and early failure is further evidence
that the amount of free-floating stent
in the distal aorta is an important determinate of patency (28). The data
presented herein suggest that covered
stents may provide some protection
from the effect of having bare metal in
the lumen of the distal aorta.
In summary, the use of covered balloon-expandable iliac kissing stents,
particularly when the stents extend
into the aorta, appears to be superior
to the use of bare metal balloon-expandable stents at 2 years of follow-up
and suggests that employment of this
technology for atherosclerotic aortoiliac occlusive disease, in appropriately selected patients, may be warranted.
6.
7.
8.
9.
10.
11.
12.
13.
Acknowledgment: The authors acknowledge the tireless efforts of Tammy Amos in
the preparation of this manuscript.
14.
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