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Aortic Neck Dilation after EndovascularAbdominal Aortic Aneurysm Repair: ShouldOversizing Be Blamed?
Sergio M. Sampaio, MD,1 Jean M. Panneton, MD,1 Geza Mozes, MD, PhD,1
James C. Andrews, MD,2 Audra A. Noel, MD,1 Manju Kalra, MB, BS,1
Thomas C. Bower, MD,1 Kenneth J. Cherry, MD,1 Timothy M. Sullivan, MD,1 and
Peter Gloviczki, MD,1 Rochester, Minnesota
Long-term durability after endovascular abdominal aortic aneurysm repair (EVAR) is dependentupon the maintenance of an effective seal between the endograft and the proximal landing zone.Continuous neck dilation might lead to the loss of such a seal. This study aims at evaluating theincidence, risk factors, and clinical consequences of post-EVAR aneurysm neck dilation inpatients treated with two types of endografts: AneuRx� and Ancure�. We reviewed data con-cerning all consecutive patients submitted to primary EVAR using the AneuRx and Ancuredevices. Preoperative neck anatomic characteristics (diameter, calcification, and thrombus load)were evaluated, and device oversize percentage was calculated. Postoperative same-level neckdiameter was measured on all postoperative computed tomographic (CT) scans. Probabilities ofneck dilation (‡10% and ‡15%) relative to preoperative diameter and first postoperative diam-eter were estimated with the Kaplan-Meier method and compared between patients using bothtypes of endograft. The impact of anatomic characteristics on neck dilation incidence wasevaluated using Cox proportional hazards models. Mean neck dilation was compared betweenpatients with and without device migration and proximal type I endoleak. Both groups had similarprobabilities of dilating >10% relative to preoperative diameter and to first postoperative diam-eter. Proximal necks in AneuRx-treated patients had higher probabilities of dilating ‡15% relativeto preoperative diameter than Ancure-treated patients (45.5% vs. 18.7% at 1.5 years,p = 0.025), but the probability of such dilation relative to the first postoperative diameter was notdifferent between the two groups (12.4% vs. 9.1% at 1.5 years, p = 0.832). None of the pre-operative neck characteristics was associated with neck dilation risk. Device oversize per-centage was correlated with the percentage of neck dilation at first postoperative CT scanrelative to preoperative diameter in both the AneuRx (correlation coefficient = 0.469, p < 0.0001)and the Ancure (correlation coefficient = 0.464, p < 0.011) groups, but it was not correlated withthe percentage of neck dilation at 1 or 1.5 years relative to first postoperative CT scan in eithergroup. Patients with and without caudad device migration (‡5 mm) had similar percentages ofneck dilation at 1.5 years relative to preoperative diameter, but migrators had higher meanpercentages of dilation at 1.5 years relative to first postoperative neck diameter (11.4% vs. 5.6,p = 0.012). Two phenomena may be differentiated: an immediate postimplant dilation, stronglycorrelated with the percentage of oversize and more likely to reach values ‡15% with an AneuRxdevice than with an Ancure graft, and a subsequent dilation, relative to the first postoperativelymeasured diameter, equally probable with either type of device, not correlated with the per-centage of oversizing but associated with caudad device migration. Our study does not supportany adverse role for the degree of oversize.
1Division of Vascular Surgery, Mayo Clinic, Rochester, MN, USA.2Department of Radiology, Mayo Clinic, Rochester, MN, USA.
Presented at the Twenty-sixth Meeting of the Canadian Society forVascular Surgery, October 22-23, 2004, Quebec City, Quebec, Canada.
J. M. Panneton is currently at Eastern Virginia Medical School andVascular and Transplant Specialists, Norfolk, VA.
Correspondence to: Jean M. Panneton, MD, Vascular and TransplantSpecialists, 250 West Brambleton Avenue, Suite 101, Norfolk, VA,23510, USA, E-mail: jpanneton@vascularandtransplant.com
Ann Vasc Surg 2006; 20: 338-345DOI: 10.1007/s10016-006-9067-2� Annals of Vascular Surgery Inc.Published online: May 19, 2006
338
INTRODUCTION
Since its introduction in 1991,1 endovascular aortic
abdominal aortic aneurysm repair (EVAR) main
outcome analysis has shifted from feasibility and
short-term results to long-term durability. Lasting
effectiveness is dependent upon the maintenance
of a water-tight seal between the device and the
landing zones. One of the key points in keeping
such sealing is the proximal landing zone, or
aneurysm neck: close apposition around the device
is essential in preventing proximal type I endoleaks
and device migration. Aortic neck dilation has been
associated with adverse events such as device
migration and proximal seal failure.2 Reports on
the incidence, risk factors, and consequences of
aortic neck dilation, however, are remarkably
scarce. This study aims at investigating these issues
in two cohorts of patients: one treated with the
AneuRx� (Medtronic, Santa Rosa, CA) and an-
other with the Ancure� (Guidant, Menlo Park, CA)
device.
METHODS
We abstracted information relative to all consecu-
tive patients undergoing primary EVAR at our
institution between December 15, 1999, and May
7, 2003, using the following inclusion criteria:
� Use of either the AneuRx or the Ancure device
� Primary EVAR
� Availability of a preoperative computed tomo-
graphic (CT) scan
� Availability of at least two postoperative CT
scans, performed on two different occasions
Anastomotic aneurysms were excluded. Postopera-
tive surveillance consisted of a visit during the first
month, every 6 months during the first 2 postoper-
ative years, and thereafter yearly. Imaging modali-
ties included a contrast-enhanced CT scan,
ultrasound, and plain abdominal radiographs at each
follow-up visit. CT scans were obtained using GE
Lightspeed� scanners (General Electric, Milwaukee,
WI). Noncontrast images, 5 mm thick with 5 mm
spacing, were obtained through the abdomen and
pelvis. Contrast-enhanced images were then ob-
tained with a single breath-hold during the injection
of 120 mL of non-ionic contrast at 4 mL/sec. Helical
acquisition was performed with reconstruction of
the images into 2.5 mm slices every 2.5 mm.
All CT scan measurements were performed using
electronic calipers, available on the digital image
archive software, allowing for a 300% magnifica-
tion.
Mid-neck level was defined as the CT slice at
mid distance between the more caudad renal
artery and the craniad extremity of the aneurysm
sac. The distance in the CT table position be-
tween this level and the last slice showing the
most caudad main renal artery was recorded and
used as the reference to determine the level for
postoperative neck diameter measurements in
order to ensure that all subsequent measurements
were performed at the same aortic segment.
Adventitia to adventitia distances were evalu-
ated,3 using the minor axis of the cross-sectional
ellipse. Neck dilation was evaluated as a per-
centage of dilation relative to the baseline diam-
eter, according to the formula [(neck diameter at
any postoperative time point) – (baseline diameter)]/
baseline diameter. Two different thresholds for neck
dilation were set (10% and 15%), and their
probability was estimated relative to two different
baselines: preoperative diameter and first postop-
eratively measured diameter.
Mean percentages of neck dilation were calcu-
lated at first postoperative CT scan (relative to
preoperative diameter) and at 12 and 18 months
post-EVAR (relative to the two above-mentioned
baselines).
Proportion of proximal endograft oversizing was
calculated using the following formula: (endograft
diameter - mid-neck diameter)/mid-neck diameter.
Calcification and thrombus presence were
quantified at the mid-neck level (defined above),
aiming at characterizing the planned landing seg-
ment. Calcification was measured as a percentage
of calcified neck perimeter. Thrombus presence was
quantified in three different ways: thrombus max-
imal thickness, percentage of thrombus-lined neck
wall, and percentage of cross-sectional area occu-
pied by thrombus.
Reverse-tapered necks were defined as the ones
in which the difference between the most caudad
and the most cephalad neck diameters was ‡3 mm.
Aneurysm maximal diameter was measured
using adventitia to adventitia distances along the
ellipse minor axis.3 The percentage of the cross-
sectional area occupied by thrombus was also
evaluated at the maximal diameter level.
Endograft position was evaluated, measuring the
distance in the CT table positions between the last
slice showing the most distal renal artery and the
first slice showing evidence of endograft. Endograft
migration was defined as an increase ‡5 mm in this
distance, assuming as baseline the distance mea-
sured in the first available postoperative CT scan.
The 5 mm threshold was chosen according to the
Lifeline Registry guidelines.4
Vol. 20, No. 3, 2006 Aortic neck dilation after EVAR 339
All postoperative CT scans were also reviewed
for the presence of proximal type I endoleaks.
Whenever characterization of the type of endoleak
was not possible based on CT scan, angiography
reports were reviewed.
Statistical Analysis
The probabilities of neck dilation ‡10% and ‡15%
were estimated using the Kaplan-Meier method,
and Wilcoxon�s survival test was used to compare
the two devices. Associations between probability
of neck dilation and preoperative anatomic neck
characteristics were investigated with Cox�s pro-
portional hazards models.
Impact of neck dilation on adverse events was
tested comparing means of percent neck dilation
(at first postoperative CT scan, at 12 and 18 months
post-EVAR) between migrators and nonmigrators
and between patients with and without proximal
type I endoleak. Whenever normality assumptions
were not met, Wilcoxon�s rank sum tests were
used; otherwise, two sample t-tests were per-
formed. p < 0.05 was considered statistically sig-
nificant.
RESULTS
From a total of 144 patients, 112 (77.8%) were
submitted to EVAR using the AneuRx device and
32 (22.2%) using the Ancure endograft. Median
available follow-up was lower in the AneuRx-
treated patients: 257 vs. 629 days.
Neck Dilation
Fifty-four necks in the AneuRx group and 19 necks
in the Ancure group dilated ‡10% relative to the
preoperative diameter. The probability of neck
dilation ‡10% relative to preoperative diameter
was not different between patients treated with the
AneuRx [91.9% at 2 years, standard error
(SE) = 7.2] and Ancure (80% at 2 years, SE = 9.4)
devices, p = 0.53. The median time to neck dilation
‡10% was 290 days in the AneuRx group and 365
days in the Ancure group (Fig. 1).
When we defined neck dilation as an increase
‡15% relative to preoperative neck diameter, such
an event occurred in 30 AneuRx-treated patients
and in seven Ancure-treated patients. AneuRx
patients had a higher probability of such dilation
(45.5%, SE = 8.1 at 1.5 years) than Ancure pa-
tients (18.7%, SE = 8.6 at 1.5 years), p = 0.025.
Median time to neck dilation ‡15% was 585 days
in the AneuRx group and 1,066 days in the Ancure
group (Fig. 2).
Taking the first postoperatively measured neck
diameter as baseline, subsequent neck dilation
‡10% occurred in 21 patients from the AneuRx
group and eight patients from the Ancure group.
Probabilities of these events were not different
among the AneuRx (36.1% at 1.5 years, SE = 9.1)
and Ancure (23.5% at 1.5 years, SE = 9.26) groups,
p = 0.366 (Fig. 3). Using the same baseline, neck
Fig. 1. Freedom from early neck dilation (‡10% relative
to preoperative diameter) after EVAR. Dark line, Ancure;
light line, AneuRx; p = 0.532, Wilcoxon�s test. SE <10%
for the entire curves� length.
Fig. 2. Freedom from early neck dilation (‡15% relative
to preoperative diameter) after EVAR. Dark line, Ancure;
light line, AneuRx; p = 0.025, Wilcoxon�s test. SE <10%
for the entire curves� length.
340 Sampaio et al. Annals of Vascular Surgery
dilation ‡15% was observed in eight AneuRx-
treated patients and two Ancure-treated patients,
both groups having similar probabilities of such an
event (at 1.5 years, AneuRx 12.37%, SE = 5.4;
Ancure 9.1%, SE = 6.2), p = 0.832 (Fig. 4).
Neck Dilation Magnitude
Mean neck dilation at the first postoperative CT
scan was similar between AneuRx [5.7%, standard
error of the mean (SEM) = 0.7] and Ancure (4.5%,
SEM = 1.2) patients, p = 0.226.
At 1 year, AneuRx-treated necks had dilated on
average 5% (SEM = 0.8) and Ancure-treated ones
4.7% (SEM = 1.3) relative to their first postopera-
tively measured diameter, p = 0.863.
At 1.5 years, mean neck dilation was still not
different between the AneuRx (6.5%, SEM = 1) and
the Ancure (6.5%, SEM = 1.3) groups, p = 0.973.
Neck Dilation Determinants
The impact of preoperative anatomic neck charac-
teristics was investigated in the cohort as a whole
and separately for each endograft group. None of
the neck characteristics was significantly associated
with the probability of neck dilation (using either
the 10% or the 15% threshold) relative to the
preoperative neck diameter or the first postopera-
tive diameter (associations tested using Cox pro-
portional hazards). Anatomic characteristic
frequencies for each of the endograft groups are
summarized in Table I.
Percentage of oversizing was correlated with
percentage of neck dilation at first postoperatively
measured neck diameter in both the AneuRx (cor-
relation coefficient = 0.469, p < 0.0001) and the
Ancure (correlation coefficient = 0.464, p = 0.011)
groups. Oversizing, however, was not correlated
with the percentage of neck dilation at 1 or 1.5 years
(Table II) relative to first postoperative diameter, for
either the AneuRx or the Ancure group.
Impact of Neck Dilation
Patients with and without postoperative proximal
type I endoleak (which occurred in six patients)
had similar mean percentages of neck dilation at
the first postoperative CT scan and at 1 and 1.5
years relative to first postoperative CT scan.
Patients with and without caudad device
migration (‡5 mm) had similar mean percentages
of early neck dilation relative to preoperative
diameter at first postoperative CT scan.
Migrators, however, had higher mean percent-
ages of late neck dilation at 1.5 years (11.4%,
SEM = 1.9) compared with nonmigrators (5.6%,
SEM = 0.8%), p = 0.012 (Fig. 5).
These results are summarized on Table III.
DISCUSSION
Ancure and AneuRx devices were chosen by their
characteristics: they were at the same risk of
migration regarding their absence of suprarenal
Fig. 3. Freedom from late neck dilation (‡10% relative
to first postoperative diameter) after EVAR. Dark line,
Ancure; light line, AneuRx; p = 0.366, Wilcoxon�s test. SE
‡10% for the dotted portion of the curve.
Fig. 4. Freedom from late neck dilation (‡15% relative
to first postoperative diameter) after EVAR. Dark line,
Ancure; light line, AneuRx; p = 0.832, Wilcoxon�s test. SE
‡10% for the dotted portion of the curves.
Vol. 20, No. 3, 2006 Aortic neck dilation after EVAR 341
fixation, but their respective theoretical impact on
dilation should be different due to their different
expansion modes. Neck dilation after EVAR ap-
pears to be an almost universal phenomenon. In
fact, almost every patient treated with any kind of
device the neck was dilated by 10% relative to the
preoperative diameter. This high incidence of neck
dilation is in agreement with the findings of
Prinssen et al., who found that all patients had
increased their neck area after Ancure device
implantation.5 Cao et al. estimate a 15% rate of
neck dilation 2 years after AneuRx implantation,
relative to first postoperative diameter,2 but they
had defined neck dilation as a diameter increase ‡3
mm. We believe there might be some advantages in
defining neck dilation according to a relative per-
centage and not an absolute threshold. In fact, 3
mm represents a 10% increase (a trivial finding in
our study) in a 30 mm neck but a 16.6% dilation (a
much more rare event) in an 18 mm diameter
neck. Both situations surely have different signifi-
cances, and their occurrence should not be treated
as a similar event. May et al.,6 on the other hand,
refer to freedom from neck dilation ‡3 mm of
94.4% 7 years after EVAR relative to first postop-
erative diameter, but their sample consisted of only
28 patients, with various devices.
In this study, we opted for serial measurements
at a level defined by native anatomic criteria (dis-
tance to more caudad main renal artery), rather
than using the endograft position as reference level.
We believe this option to be advantageous since
device migration, a phenomenon reported to have
an incidence that may reach 66.7% at 4 years,7
Table I. Baseline characteristics in AneuRx- and Ancure-treated subjects
Variable
Mean value amongAncure subjects(n = 32)
Mean valueamong AneuRxsubjects (n = 112) p
Neck diameter (mm) 24.4 (0.46) 25.4 (0.28) 0.104a
Percentage of calcium-lined neck perimeter (%) 13.7 (2.75) 9.4 (1.02) 0.235b
Percentage of thrombus-occupied
cross-sectional neck area (%)
33.5 (1.51) 32.1 (1.22) 0.531a
Aneurysm maximal diameter (mm) 52.9 (1.27) 55.9 (1.03) 0.142a
Proximal oversizing (%) 5.2 (2.07) 7.9 (1.08) 0.239c
at-test assuming equal variances.bWilcoxon�s rank sum test.ct-test assuming unequal variances.
Table II. Oversizing impact on neck dilation
Ancure AneuRx
Baseline % Neck dilation atCorrelation coefficientwith % of oversize pa
Correlation coefficientwith % of oversize pa
Preoperative CT scan First postoperative CT scan 0.464 0.011 0.469 <0.0001
First postoperative CT scan 1 Year 0.213 0.103 )0.205 0.340
1.5 Years 0.246 0.174 0.274 0.343
aCorrelation p values.
Fig. 5. Mean proportion of neck dilation at 1.5 years
relative to first postoperative diameter among migrators
and nonmigrators. Whiskers represent SEM. p = 0.012,
Wilcoxon�s rank sum test.
342 Sampaio et al. Annals of Vascular Surgery
would imply measuring neck diameters at levels
progressively more distal when using the endograft
position as reference level. Since a significant pro-
portion of necks have a reverse-tapered configu-
ration (reaching proportions as high as 24.2%,8
32.6% in this study�s series), this situation could
easily result in an overestimation of neck dilation
incidence. AneuRx devices increased the probabil-
ity of neck dilation ‡15% relative to preoperative
diameter but not of subsequent dilation. This
finding may result from the existence of two sep-
arate phenomena: a relatively early dilation,
resulting from the aortic neck adaptation to the
immediate radial force of the endograft presence,
and a subsequent dilation, independent of the de-
vice�s expanding forces. Interestingly, in none of
the groups did the occurrence of neck dilation
reach a plateau. As late as 900 days after EVAR,
there were still patients reaching 10% increases in
their neck diameter relative to their first postoper-
ative diameter. This suggests it will not be possible
to define a safe line in postoperative follow-up time
beyond which neck dilation should no longer be
expected.
Cao et al.2 defined the risk factors of aortic neck
dilation as large neck diameter, large aneurysm
diameter, and circumferentially thrombus-lined
neck. We believe their findings might be the result
of defining neck dilation according to an absolute
threshold (3 mm). In fact, it should be expected
that in such a frequent event as neck dilation after
EVAR is proving to be, higher absolute dilations
(but not proportional) would occur preferentially
in wider necks. Therefore, in spite of similar per-
centages of dilation between wide and narrow
necks, one would still be able to document
a higher frequency of dilation beyond a certain
absolute threshold in wider necks. To this fact,
one could add that wider necks are also correlated
with larger aneurysm diameters (correlation
coefficient = 0.174, p = 0.037 in our series), which
could possibly have contributed to the previously
mentioned associations. In our series, none of the
preoperative anatomic characteristics was associ-
ated with the probability of neck dilation (above
10% or 15% relative to preoperative or first
postoperative diameters). This lack of association
concurs with the findings of Matsumura and
Chaikof.9
Oversizing is intuitively associated with neck
dilation, and this association has been reported
several times.7,10 Such reports, however, were
based on dilations in relation to the preoperative
diameter as baseline. Cao et al.,2 evaluating neck
dilation relative to the first postoperative diameter,
failed to find any association with oversizing. We
combined both types of analysis in this study and
confirmed the role of oversizing in early dilation
relative to preoperative diameter, but subsequent
dilation was independent from device oversizing.
Dilation relative to preoperative diameter is more
likely to reach percentages ‡15% among patients
treated with AneuRx devices than among subjects
treated with Ancure grafts; however, such a dif-
ference was not present for dilation relative to first
postoperatively measured diameter, as one would
expect if continued neck dilation resulted from
radial force applied against the aortic wall.
One could hypothesize that later neck dilation,
occurring relative to a postoperative baseline, re-
sults mainly from the continuing degeneration of
the aortic neck segment and not from the
expanding forces of the device. Aortic neck dilation
after aortic aneurysm open repair,11 as well as
similar degrees of neck dilation after EVAR using
supra and infrarenal fixation devices,2 seem to
support the role of aortic wall degeneration as a
primary factor in post-EVAR aortic neck dilation.
Caution needs to be exerted when evaluating
the impact of aortic neck dilation on clinical ad-
verse events, such as proximal type I endoleak and
caudad device migration. In fact, these risk factors
Table III. Comparative mean neck dilation percentages between patients with and without proximal type
I endoleak and with and without caudad device migration
Proximal type I endoleak Migration
Baseline % Neck dilation at na Yes No pb Yes No pb
Preoperative CT scan First postoperative CT scan 144 1.4% 5.6% 0.117 3.7% 5.5% 0.499
1 Year 81 7% 11.2% 0.327 10.1% 11.1% 0.958
1.5 Years 48 16.5% 12.9% 0.336 18.2% 12.3% 0.072
First postoperative CT scan 1 Year 81 4.4% 4.9% 0.992 6% 4.7% 0.304
1.5 Years 48 9.4% 6.3% 0.349 11.4% 5.6% 0.012
aAvailable patients for analysis.bWilcoxon�s rank sum test.
Vol. 20, No. 3, 2006 Aortic neck dilation after EVAR 343
and outcomes are both time-dependent variables,
and by testing for their association in a nonsyn-
chronous cohort,2 one might simply select patients
with longer follow-up times, documenting spurious
associations. For this reason, we compared the
dilation percentages at fixed time points between
migrators and nonmigrators and between patients
with and without proximal type I endoleak. The
only significant difference was found at 18 months,
when migrators had higher mean dilation com-
pared with nonmigrators. Theoretically, one would
expect device migration to be a precursor to prox-
imal type I endoleak.12 This study may have ana-
lyzed sufficient follow-up time to detect differences
associated with migration but not endoleaks. The
method we used to assess distances is not devoid of
caveats either but allows for the direct interpreta-
tion of data from routinely used surveillance
imaging modalities. It has been used before.7,10,13
We quantified migration by reviewing axial cuts of
CT scans. Almost certainly, this methodology led to
an underestimation of the true length of migration
on heavily angulated necks.
Interestingly, a significant difference between
migrators and nonmigrators was found in the
percentage of dilation relative to first postopera-
tive CT scan, suggesting that clinically important
dilation occurs after the initial aortic adaptation to
the endograft. Conners et al.7 established an
association between dilation relative to preopera-
tive diameter and oversize degree, but they failed
to associate oversize and migration. Such an
association has never been documented, and we
hypothesize that it might in fact not exist. Of
course, more oversized necks have dilated more
by 1 or 1.5 years after EVAR, but they had al-
ready dilated more by the first postoperatively
measured diameter. Our study suggests a scenario
where all (or almost all) endograft-treated aortic
necks do adjust to the device presence, resulting
in an obvious and consistently reported associa-
tion between dilation and oversizing; some necks
keep dilating beyond such initial adaptation,
independent of the degree of oversizing, subse-
quently increasing the risk of migration. Alterna-
tively, these data may simply reflect the dilation
of proximal necks exposed to systemic pressures
after endograft slippage. Theoretically, grafts mi-
grate because of low friction forces between them
and the aortic walls. Oversizing could dilate the
aortic neck to a point of equilibrium between
graft expansion and aortic recoil, but why should
it contribute to continuing expansion beyond
such point, allowing for low friction? Less over-
sizing may simply mean that the imbalance is
achieved at the cost of a smaller degree of
expansion.
One of the obvious limitations of this study is its
small sample size. Emphasis should therefore be
put on the positive results and caution exerted
when interpreting the absence of differences across
groups.
CONCLUSIONS
Aneurysm neck dilation is an almost universal
event after EVAR. Two types of phenomena may be
differentiated: an immediate postimplant dilation,
strongly correlated with the percentage of oversiz-
ing and more likely to reach values ‡15% after
usage of an AneuRx device than after an Ancure
graft placement, and a subsequent dilation, relative
to the first postoperatively measured diameter,
equally probable after using either type of device,
not correlated with the percentage of oversizing but
associated with caudad device migration. Our study
does not support any adverse role for the degree of
oversizing.
S. M. S. is the recipient of an Edward S. Rogers Clinical
Research Fellowship in Vascular Surgery.
REFERENCES
1. Parodi JC, Palmaz JC, Barone HD. Transfemoral intralumi-
nal graft implantation for abdominal aortic aneurysm. Ann
Vasc Surg 1991;5:491-499.
2. Cao P, Verzini F, Parlani G, et al. Predictive factors and
clinical consequences of proximal aortic neck dilation in 230
patients undergoing abdominal aorta aneurysm repair with
self-expandable stent-grafts. J Vasc Surg 2003;37:1200-1205.
3. Ad Hoc Committe for Standardized Reporting Practices in
Vascular Surgery of the Society for Vascular Surgery.
Reporting standards for endovascular aortic aneurysm
repair. J Vasc Surg 2002;35:1048-1060.
4. Lifeline Registry of Endovascular Aneurysm Repair Steering
Committee.Lifeline registry: collaborative evaluation of en-
dovascular aneurysm repair. J Vasc Surg 2001;34:1139-1146.
5. Prinssen M, Wever JJ, Willem P, Mali M, Eikelboom BC,
Blankensteijn JD. Concerns for the durability of the proxi-
mal abdominal aortic aneurysm endograft fixation from a
2-year and 3-year longitudinal computed tomography
angiography study. J Vasc Surg 2001;33:S64-S69.
6. May J, White GH, Ly CN JM, Harris JP. Endoluminal repair
of abdominal aortic aneurysm prevents enlargement of the
proximal neck: a 9-year life-table and 5-year longitudinal
study. J Vasc Surg 2003;37:86-90.
7. Conners MS, Sternbergh C, Carter G, Tonnessen BH, Yose-
levitz M, Money SR. Endograft migration one to four years
after endovascular abdominal aortic aneurysm repair with
the AneuRx device: a cautionary note. J Vasc Surg 2002;
36:476-484.
344 Sampaio et al. Annals of Vascular Surgery
8. Dias NV, Resch T, Malina M, Lindblad B, Ivancev K. Intra-
operative proximal endoleaks during AAA stent-graft repair:
evaluation of risk factors and treatment with Palmaz stents.
J Endovasc Ther 2001;8:268-273.
9. Matsumura JS, Chaikof EL. Continued expansion of aortic
necks after endovascular repair of abdominal aortic aneu-
rysm. J Vasc Surg 1998;28:422-431.
10. Badran MF, Gould DA, Raza I, et al. Aneurysm neck
diameter after endovascular repair of abdominal aortic
aneurysms. J Vasc Interv Radiol 2002;13:887-892.
11. Lipsky DA, Ernst CB. Natural history of the residual infra-
renal aorta after infrarenal abdominal aortic aneurysm re-
pair. J Vasc Surg 1998;27:805-812.
12. Sampaio SM, Panneton JM, Mozes GI, et al. AneuRX device
migration: incidence, risk factors and consequences. Ann
Vasc Surg 2005;19:1-8.
13. Cao P, Verzini F, Zannetti S, et al. Device migration after
endoluminal abdominal aortic aneurysm repair: analysis of
113 cases with a minimum follow-up period of 2 years. J
Vasc Surg 2002;31:229-235.
Vol. 20, No. 3, 2006 Aortic neck dilation after EVAR 345
Recommended