J ENDOVASC THER
`2008;15:335–343
`
`¤FELLOWS COMPETITION, SECOND PLACE
`
`335
`
`¤
`
`Lateral Movement of Endografts Within the Aneurysm
`Sac Is an Indicator of Stent-Graft Instability
`
`Benjamin Y. Rafii, BS; Oscar J. Abilez, MD; Peyman Benharash, MD; and
`Christopher K. Zarins, MD
`
`Department of Surgery, Division of Vascular Surgery, Stanford University School of
`Medicine, Stanford, California, USA.
`
`¤
`
`¤
`
`Purpose: To determine if lateral movement of an aortic endograft 1 year following
`endovascular abdominal aortic aneurysm (AAA) repair is an indicator of endograft
`instability and can serve as a predictor of late adverse events.
`Methods: The records of 60 high-risk AAA patients (52 men, 8 women; mean age 74 years)
`who were treated with infrarenal (n538) or suprarenal (n522) endografts and had serial
`computed tomograms (CT) over $12 months were analyzed. Postimplantation and 1-year
`CT scans were compared, and changes in endograft position within the aneurysm sac
`[lateral movement (LM) versus no lateral movement (NM)] were measured using a
`vertebral body reference point. Longitudinal endograft movement was measured with
`respect to the superior mesenteric artery along the aortic centerline axis. Long-term
`adverse event rates (endoleaks, secondary procedures, conversion, rupture, and death)
`were assessed.
`Results: One year after endograft implantation, LM $5 mm was present in 16 (27%)
`patients; 44 (73%) endografts demonstrated no lateral movement. LM patients had larger
`aneurysms (6.561.5 versus 5.660.9 cm, p50.02) and a longer endograft–to–hypogastric
`artery length (p50.01) than NM patients. There were no significant differences between
`patients treated with infrarenal and suprarenal endografts. At 1 year,
`longitudinal
`migration $10 mm occurred in 5 (31%) of the LM patients versus 2 (5%) in the NM cohort
`(p,0.0001). There were no significant differences in adverse event rates between LM and
`NM at 1 year. However, during long-term follow-up (mean 54626 months, range 12–102), 8
`(50%) LM patients developed a type I endoleak versus 8 (18%) NM patients (p50.02), and 12
`(75%) LM patients required a secondary procedure versus 9 (20%) NM patients (p50.0002).
`One (6%) LM patient experienced aneurysm rupture and 2 (13%) other LM patients
`underwent conversion to open repair.
`Conclusion: Lateral endograft movement within the aneurysm sac at 1 year is associated
`with increased risk of late adverse events and was at least as good a predictor of these
`complications as was longitudinal migration.
`
`J Endovasc Ther 2008;15:335–343
`
`Key words: abdominal aortic aneurysm, endovascular aneurysm repair, stent-graft, lateral
`movement, longitudinal movement, adverse events, migration, type I endoleak, secondary
`procedures, rupture, conversion
`¤
`
`¤
`
`The annual ISES Endovascular Fellows Research Awards Competition held on February 12, 2008, at International
`Congress XXI on Endovascular Interventions (Scottsdale, Arizona, USA) evaluated participants on both their oral and
`written presentations. ISES congratulates the 2008 winners.
`
`Christopher Zarins is a consultant to Medtronic Vascular, manufacturer of the endografts used in this study. The other
`authors have no commercial, proprietary, or financial interest in any products or companies described in this article.
`
`Address for correspondence and reprints: Christopher K. Zarins, MD, Stanford University, 318 Campus Drive West,
`Stanford, CA 94305 USA. E-mail: zarins@stanford.edu
`
`ß 2008 by the INTERNATIONAL SOCIETY OF ENDOVASCULAR SPECIALISTS
`
`Available at www.jevt.org
`
`TMT 2115
`Medtronic v. TMT
`IPR2021-01532
`
`

`

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`J ENDOVASC THER
`2008;15:335–343
`
`Positional stability of aortic endografts is
`important
`for
`the long-term durability of
`endovascular
`aortic
`aneurysm repair
`(EVAR).1–3 Longitudinal migration of endo-
`grafts may lead to loss of fixation and the
`development of type I endoleaks, potentially
`exposing the patient to the risk of aneurysm
`rupture.4–6 However, accurate determination
`of endograft migration on routine cross-
`sectional axial computed tomograms (CT)
`can be difficult, and some patients may
`require secondary intervention in the absence
`of obvious migration.7 Changes in endograft
`position in the mid-portion of the aneurysm
`sac can be readily seen on serial cross-
`sectional CT scans or duplex ultrasound. Until
`now, such changes have been briefly de-
`scribed only in geometric analyses8,9 but
`have not been closely studied or monitored
`as part of the routine endograft surveillance.
`Accordingly, the purpose of this study was
`twofold: (1) to design a simple and reproduc-
`ible method to quantitate changes in the
`position of
`the endograft on serial cross-
`sectional CT scans and (2) to test the hypoth-
`esis that lateral movement of the endograft
`within the aneurysm sac is a predictor of
`long-term endograft instability.
`
`METHODS
`
`Patient Population
`
`Patients with abdominal aortic aneurysms
`(AAA) who underwent EVAR at our institution
`from 1997 to 2004 and were prospectively
`followed with serial
`imaging and clinical
`follow-up were considered for this study.
`Informed consent was obtained from each
`patient prior to surgery, and all patient follow-
`up protocols,
`including imaging, were ap-
`proved by the Institutional Review Board.
`This retrospective analysis began with review
`of imaging and clinical data for 60 EVAR
`patients (52 men, 8 women; mean age 74
`years) who had baseline, postoperative, and
`1-year follow-up CT studies performed at our
`institution with online datasets that were
`suitable for quantitative 3-dimensional (3D)
`image analysis. Thirty-eight patients had
`infrarenal endograft
`implantation (AneuRx
`stent-graft; Medtronic Vascular, Santa Rosa,
`
`CA, USA), while 22 patients were treated with
`a suprarenal endograft
`(Talent stent-graft;
`Medtronic Vascular).
`
`Image Analysis
`
`Postimplantation and 1-year follow-up CT
`scans were evaluated using GE Centricity
`software (GE Healthcare, Chalfont St Giles,
`UK). The position of the endograft within the
`aneurysm sac was measured using a verte-
`bral body reference point. The axial CT slice
`corresponding to the maximum aneurysm
`diameter at the midpoint between the inferior
`border of
`the superior mesenteric artery
`(SMA) orifice and the aortic bifurcation was
`selected for image analysis; the same ana-
`tomical
`level was selected on the 1-year
`follow-up CT by matching bony landmarks
`on the vertebral bodies. Lateral endograft
`movement was defined as a $5-mm change
`in the distance between the mid-portion of
`the stent-graft and the anterior portion of the
`vertebral body at 1 year (Fig. 1). All quantita-
`tive imaging measurements were obtained by
`a single investigator who was not involved in
`the clinical care of
`the patients and was
`blinded to their clinical outcomes. Patients
`exhibiting $5-mm lateral endograft move-
`ment were assigned to the ‘‘lateral move-
`ment’’ (LM) patient group; those exhibiting
`,5-mm lateral movement were placed in the
`‘‘no lateral movement’’ (NM) group.
`Preoperative aneurysm characteristics, as
`well as postoperative iliac fixation length and
`the distance from the distal endograft to the
`hypogastric arteries, were measured using
`quantitative 3D image analysis, as described
`previously.7 Downward displacement of the
`proximal portion of the endograft (i.e., longi-
`tudinal migration) referred to any change in
`centerline distance between the inferior SMA
`orifice and the proximal portion of the stent-
`graft at 1 year. Angulation of the device was
`determined by measuring the distance in
`millimeters from the top of the endograft to
`the level of the complete ring (Fig. 1).
`
`Clinical Analysis
`
`Adverse clinical outcomes were recorded in
`all patients at 1 year and at last available
`
`

`

`J ENDOVASC THER
`2008;15:335–343
`
`ENDOGRAFT MOVEMENT AND INSTABILITY
`Rafii et al.
`
`337
`
`Figure 1 ¤ Lateral displacement of
`(A) Post-
`the endograft within the aneurysm sac.
`implantation CT scan showing measurement of the distance from the vertebral body to the
`midpoint of the endograft. (B) In the 1-year CT scan, the vertebra-graft distance increases due
`to lateral movement of the stent-graft. Note the increased angulation of the proximal stent-
`graft with respect to the axis of the aortic neck.
`
`follow-up. Outcome measures included need
`for secondary intervention (including proxi-
`mal or distal extender cuff placement or coil
`embolization of endoleak), type I endoleak
`(defined as persisting at 1 year or necessitat-
`ing a secondary procedure at any point),
`aneurysm rupture, surgical conversion, and
`aneurysm-related death.
`
`Statistical Analysis
`
`Results are expressed as the mean 6
`standard deviation for continuous variables
`
`for binary
`and as counts (percentages)
`variables. Comparison of aneurysm char-
`acteristics, baseline demographics, and
`outcomes for the 2 patient groups was
`performed using Student t tests for con-
`tinuous variables and 2-tailed Fisher exact
`tests for categorical variables. Predictors
`of lateral movement were assessed with
`an analysis of variance (ANOVA). P,0.05
`was considered significant. All statistical
`analyses were performed using JMP 6
`software (2005; SAS Institute Inc., Cary,
`NC, USA).
`
`

`

`338
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`ENDOGRAFT MOVEMENT AND INSTABILITY
`Rafii et al.
`
`J ENDOVASC THER
`2008;15:335–343
`
`Figure 2 ¤ Examples of post-procedure (A1–D1) and 1-year (A2–D2) CT scans. (A) No
`significant movement of the endograft at 1 year in a 5.3-cm aneurysm. (B) Ten-mm movement
`of the endograft at 1 year in a 6.4-cm aneurysm. (C) Sixteen-mm movement at 1 year in a 7.1-
`cm aneurysm. (D) Sixteen-mm movement at 1 year in a 7.8-cm aneurysm.
`
`RESULTS
`
`Of the 60 patients included in the study, 16
`(27%) endografts exhibited $5-mm lateral
`movement
`(LM group, Fig. 2) at 1 year,
`whereas 44 (73%) exhibited ,5-mm lateral
`movement (NM group). There were no sig-
`nificant differences in age, gender distribu-
`tion, preoperative comorbidities, or length of
`follow-up between the groups (Table 1).
`
`Baseline
`
`Preoperative CT scans revealed no signifi-
`cant differences in infrarenal aortic neck
`length or diameter. However, patients in the
`LM group had a larger preoperative aneurysm
`
`diameter compared to NM (6.561.5 ver-
`sus 5.660.9 cm, p50.02). Postimplantation
`CT scans revealed no significant differ-
`ences in proximal aortic or distal iliac endo-
`graft fixation length between LM and NM.
`However, the LM group had a greater dis-
`tance from the distal end of the endograft to
`(1668
`the
`hypogastric
`arteries
`versus
`10610 mm, p50.01). The LM group also had
`slightly greater angulation of the proximal
`portion of the endograft neck on the post-
`implantation CT scan, although this differ-
`ence only approached significance (1164
`versus 964 mm, p50.06). The type of device
`used (infrarenal or suprarenal) did not have
`a significant effect on the development of
`LM.
`
`

`

`J ENDOVASC THER
`2008;15:335–343
`
`¤
`
`ENDOGRAFT MOVEMENT AND INSTABILITY
`Rafii et al.
`
`TABLE 1
`Demographic Data and Preoperative and Post-Implantation CT Data
`
`Demographics
`Age, y
`Women
`Follow-up time, mo
`Preoperative
`Aneurysm size, cm
`Aortic neck length, mm
`Aortic neck diameter, mm
`Post-implantation
`Infrarenal/suprarenal device
`Proximal fixation length, mm
`Iliac fixation length, mm*
`Device–to–hypogastric artery length, mm*
`Proximal device angulation, mm{
`¤
`
`Lateral Movement
`$5 mm (n516)
`
`No Lateral Movement
`(n544)
`
`75.766.6
`1 (6%)
`56629
`
`6.561.5
`1867
`2663
`
`74.067.0
`7 (16%)
`54625
`
`5.660.9
`22613
`2563
`
`11 (69%)/5 (31%)
`1869
`22611
`1669
`1164
`
`27 (61%)/17 (39%)
`1867
`26611
`10610
`964
`
`p
`
`0.21
`0.67
`0.38
`
`0.02
`0.92
`0.16
`
`0.76
`0.55
`0.88
`0.01
`0.06
`
`339
`
`¤
`
`¤
`
`Continuous data presented as means 6 standard deviations; categorical data are given as counts (percentages).
`* Taken as the average between the 2 limbs.
`{ Distance from the top of the device to the complete ring (Fig. 1).
`
`One Year
`
`In the LM group, mean lateral movement of
`the endograft was 964 mm compared to
`261 mm in the NM group (p,0.0001, Ta-
`ble 2). The LM group also had significantly
`more longitudinal endograft migration (866
`versus 463 mm, p50.003). The aneurysm
`sacs decreased equally in both groups at 1
`year, with average aneurysm size remaining
`significantly larger in the LM group. Longitu-
`dinal endograft migration $10 mm was de-
`tected in 5 (31%) of the LM patients but in
`only 3 (7%) of the NM patients (p,0.0001). LM
`was accompanied by a significant increase in
`angulation of the proximal end of the endo-
`graft at 1 year compared to NM patients
`(p50.01). By ANOVA, there was a statistically
`significant correlation between lateral endo-
`graft movement and longitudinal migration
`(r250.26, p,0.0001), proximal endograft an-
`gulation change (r250.11, p50.01), and pre-
`operative aneurysm size (r250.16, p50.002).
`There was no significant correlation between
`lateral movement and change in aneurysm
`size at 1 year (p50.8).
`
`Clinical Outcome
`
`During a mean follow-up of 54626 months
`(range 12–102), a type I endoleak was found in
`
`16 (27%) of 60 patients at some point during
`the observation period (Table 3). Twenty-one
`(35%) patients required a secondary interven-
`tion. There was no significant difference in
`the incidence of type I endoleak or secondary
`intervention between patients with LM and
`NM at 1 year. However, patients with LM were
`significantly more likely to develop an ad-
`verse clinical event during long-term clinical
`follow-up than NM patients. Eight (50%) LM
`patients developed a type I endoleak at some
`time compared to 8 (18%) NM patients
`(p50.02). Secondary procedures were per-
`formed in 12 (75%) LM patients versus 9
`(20%) NM patients (p50.0002). One patient
`with LM experienced aneurysm rupture and 2
`LM patients required conversion to open
`repair. All patients survived, and there were
`no aneurysm-related deaths. There were no
`ruptures or conversions in NM patients.
`
`Lateral Movement Versus
`Longitudinal Migration
`
`Of the 60 patients in this study, 8 (13%)
`were found to have longitudinal migration of
`the proximal endograft $10 mm at 1 year
`(Table 4). None of
`these 8 patients with
`longitudinal migration had a type I endoleak
`or required a secondary intervention at 1 year.
`
`

`

`ENDOGRAFT MOVEMENT AND INSTABILITY
`Rafii et al.
`
`J ENDOVASC THER
`2008;15:335–343
`
`340
`
`¤
`
`¤
`
`¤
`
`p
`
`,0.0001
`0.003
`,0.0001
`0.01
`0.005
`0.4
`
`TABLE 2
`Changes in Aneurysm Size and Endograft Position at 1 Year
`
`Lateral endograft movement, mm
`Longitudinal migration, mm
`Longitudinal migration $10 mm
`Change in angulation of proximal graft, mm
`Aneurysm size, cm
`Change in aneurysm size, mm
`¤
`
`Lateral Movement
`$5 mm (n516)
`
`No Lateral Move-
`ment (n544)
`
`964
`866
`5 (31%)
`463
`6.261.6
`–367
`
`261
`463
`3 (7%)
`262
`5.261.1
`–467
`
`Continuous data presented as means 6 standard deviations; categorical data are given as counts (percentages).
`
`However, over the long term, 5 of these 8
`patients developed a type I endoleak or
`required a secondary intervention, or both.
`These results were comparable to those seen
`in the LM cohort. However, the patient who
`experienced rupture and 1 of the 2 patients
`requiring conversion to open repair were not
`in the longitudinal migration group.
`
`DISCUSSION
`
`Endovascular AAA repair has gained increas-
`ing popularity over
`the traditional open
`approach in recent years, with over 50% of
`patients requiring AAA intervention undergo-
`ing EVAR in some institutions.10–12 However,
`ongoing concern about the long-term dura-
`bility of EVAR necessitates frequent postop-
`erative ultrasound or CT surveillance for
`positional endograft changes.13–15
`Biomechanical analyses of post-EVAR he-
`modynamics confirm the presence of strong
`¤
`
`forces on the endograft that can contribute to
`longitudinal migration.16 Not surprisingly, a
`number of studies have implicated inade-
`quate proximal fixation as a cause of subse-
`quent migration.17,18 However, some endo-
`grafts exhibit significant migration despite
`fixation,19 and others
`adequate proximal
`remain stable in the absence of good proxi-
`mal fixation.7 In line with these findings, our
`study found no significant difference in
`postoperative proximal
`fixation length be-
`tween patients with lateral endograft move-
`ment and those without.
`fixation has been
`Recently, distal
`(iliac)
`implicated as an important factor in deter-
`mining risk for migration.7,20 Although we
`found a greater device–to–hypogastric artery
`distance in LM patients, there was no differ-
`ence in iliac fixation length between the
`groups. Proximal and distal fixation charac-
`teristics are likely to play roles in endograft
`stability; however, they do not tell the whole
`¤
`
`TABLE 3
`Clinical Outcomes in Patients With $5-mm Lateral Endograft Movement at 1 Year
`
`At 1 Year
`
`At Last Follow-up*
`
`Lateral Movement
`(n516)
`
`No Lateral
`Movement (n544)
`
`Type I endoleak
`Secondary
`interventions
`Conversion to
`open repair
`Aneurysm
`rupture
`¤
`
`2 (13%)
`
`5 (31%)
`
`—
`
`—
`
`2 (5%)
`
`5 (11%)
`
`—
`
`—
`
`Data are given as counts (percentages).
`* Mean 4.562.2 years.
`
`p
`
`0.29
`
`0.11
`
`—
`
`—
`
`Lateral Movement
`(n516)
`
`No Lateral
`Movement
`(n544)
`
`8 (50%)
`
`8 (18%)
`
`p
`
`0.02
`
`12 (75%)
`
`9 (20%)
`
`0.0002
`
`2 (13%)
`
`1 (6%)
`
`0 (0%)
`
`0 (0%)
`
`0.07
`
`0.27
`
`¤
`
`

`

`J ENDOVASC THER
`2008;15:335–343
`
`¤
`
`ENDOGRAFT MOVEMENT AND INSTABILITY
`Rafii et al.
`
`341
`
`¤
`
`TABLE 4
`Clinical Outcomes in Patients With Lateral Endograft Movement Compared to
`Patients With Endograft Migration $10 mm at 1 Year
`
`At 1 Year
`
`At Last Follow-up*
`
`Lateral
`Movement
`(n516)
`
`Longitudinal
`Migration $10 mm
`(n58)
`
`Type I endoleak
`Secondary
`interventions
`Conversion to open
`repair
`Aneurysm rupture
`¤
`
`2 (13%)
`
`5 (31%)
`
`—
`—
`
`Data are given as counts (percentages).
`* Mean 4.562.2 years.
`
`0 (0%)
`
`0 (0%)
`
`—
`—
`
`story. Until now, little attention has been paid
`to the mid-portion of the aortic endograft,
`which lies unsupported within the aneurysm
`sac. For this reason, we proposed that lateral
`movement of the mid-portion of the endo-
`graft over time may contribute to migration
`and thus serve as an indicator of long-term
`endograft instability.
`We sought
`to reliably quantitate lateral
`movement in a manner that could be easily
`and rapidly reproduced in the clinical setting.
`Accordingly, measurement of lateral move-
`ment was performed on serial cross-sectional
`CT studies using standard software available
`in most hospital settings. The rostro-caudal
`midpoint of the abdominal aorta (between the
`inferior SMA orifice and the aortic bifurcation
`in our study) was chosen because we be-
`lieved that maximal lateral endograft move-
`ment in subsequent studies could be best
`detected at this level, which was usually the
`point of maximal AAA diameter. Further-
`more, the SMA orifice and the aortic bifurca-
`tion are easily recognizable landmarks that
`may allow reliable reproduction of measure-
`ments from one clinician to the next.
`Once the appropriate CT slice was selected
`in the postprocedure study, an anatomically
`equivalent slice was identified on the 1-year CT
`using the vertebral body as a reference point.
`The vertebral body was selected because, with
`the exception of trauma or significant degen-
`erative disease, it is a stable structure that
`undergoes no positional variation with respi-
`ration. For the same reason, the anterior-most
`
`p
`
`0.54
`
`0.13
`
`—
`—
`
`Lateral
`Movement
`(n516)
`
`Longitudinal
`Migration $10 mm
`(n58)
`
`8 (50%)
`
`4 (50%)
`
`p
`
`1
`
`12 (75%)
`
`4 (50%)
`
`0.36
`
`2 (13%)
`1 (6%)
`
`1 (13%)
`0 (0%)
`
`1
`1
`
`¤
`
`portion of the vertebral body was used as an
`anatomical reference for the measurement of
`lateral positional changes over time.
`Of all pre- and postoperative aneurysm
`characteristics that we recorded, only aneu-
`rysm size and device–to–hypogastric artery
`distance were found to differ between pa-
`tients with lateral movement and no move-
`ment.
`Interestingly, proximal
`fixation was
`similar in the 2 groups, suggesting that it
`played no significant role in preventing lateral
`movement
`in this patient cohort. Further-
`more, there was no difference in the distribu-
`tion of suprarenal and infrarenal devices
`(suprarenal stent-grafts having longer proxi-
`mal fixation). The shorter device–to–hypogas-
`tric artery distance in patients with lateral
`movement suggests that
`instability of
`the
`endograft distally may have contributed to
`this movement, but iliac fixation length was
`equal
`in both groups. The correlation be-
`tween aneurysm size and lateral movement
`suggests that
`larger aneurysms may be
`predisposed to lateral movement, perhaps
`because the mid-portion of the endograft has
`more space in which to move.
`Type I endoleak was detected in 27% of all
`patients during long-term follow-up. Patients
`requiring secondary intervention represented
`35% of the total cohort. These rates are higher
`than those reported in a number of other
`studies with larger patient populations,21–23
`which may be due to two factors. First, the
`total follow-up time in our study was quite
`long, with outcome data available for an
`
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`

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`
`J ENDOVASC THER
`2008;15:335–343
`
`average of 4.5 years. Second, criteria for
`inclusion in this study required that patients
`have serial digital imaging sets available for
`analysis. The 60 patients represent only ,10%
`of the total number of EVAR patients at our
`institution who were followed in our prospec-
`tive database during this timeframe. The very
`long follow-up and the requirement
`for
`multiple serial imaging studies likely selected
`a high-risk population of EVAR patients: those
`with complex anatomy at risk for late endo-
`graft failure, which thus required especially
`close follow-up. This is in line with other
`studies that suggest that patients with favor-
`able anatomy may not require follow-up CT
`scans as frequently.21,24 We routinely follow
`these ‘‘low-risk’’ patients with duplex ultra-
`sound rather than CT.
`Although the presence of lateral movement
`$5 mm at 1 year corresponded to a relatively
`high rate of adverse clinical events, it was not
`perfect at predicting long-term outcome.
`While the LM group included half of the type
`I endoleaks and the majority of patients
`requiring secondary intervention, 18% of
`patients with no lateral movement experi-
`enced a type I endoleak during long-term
`follow-up and 20% required a secondary
`intervention. However, the commonly accept-
`ed standard of caudal longitudinal migration
`$10 mm25,26 was no better at predicting
`adverse long-term outcome in our patient
`group; it correctly identified only a quarter of
`the type I endoleak patients and those
`requiring secondary intervention. If we used
`a more conservative cutoff of $5 mm (n524),
`the result was similar, with 38% of patients
`experiencing endoleak and 50% requiring
`second intervention in long-term follow-up;
`again, 7 patients with endoleak and 9 patients
`requiring secondary intervention were over-
`looked by this categorization. Thus, despite
`missing some patients with subsequent ad-
`verse events, lateral movement was at least
`as sensitive and specific at identifying such
`high-risk patients as was longitudinal migra-
`tion, if not better. Further studies with larger
`patient populations will help to confirm these
`results. The fact that endoleak can occur in
`the absence of lateral movement supports the
`premise that there are multifactorial determi-
`nants of endograft stability.21,27–29 Nonethe-
`
`less, our results strongly suggest that lateral
`movement may be an important and funda-
`mental contributor to stent-graft migration.
`
`Limitations
`
`The patients included in this study were
`only 10% of our
`total endograft patient
`population and represent only a high-risk
`subgroup. The relatively small study popula-
`tion limits the power of our results and may
`not be representative of all EVAR patients.
`
`Conclusion
`
`This study demonstrates that lateral move-
`ment of the endograft within the aneurysm sac
`is a predictor of late adverse events following
`EVAR. Our results suggest that stabilization of
`the mid-portion of the endograft to prevent
`lateral movement may help prevent endograft
`displacement and late adverse events. This
`observation requires further study.
`
`Acknowledgments: The authors wish to thank Kathleen
`Biederman for assistance in clinical data collection, Laura
`Pierce for facilitating image analysis, and Rishi Bhatnagar
`for providing beautiful artistic renderings.
`
`REFERENCES
`
`1. Parra JR, Ayerdi J, McLafferty R, et al. Confor-
`mational changes associated with proximal
`seal zone failure in abdominal aortic endo-
`grafts. J Vasc Surg. 2003;37:106–111.
`2. 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;35:229–235.
`3. Lee JT, Lee J, Aziz I, et al. Stent-graft migration
`following endovascular repair of aneurysms
`with large proximal necks: anatomical risk
`factors and long-term sequelae. J Endovasc
`Ther. 2002;9:652–664.
`4. Cuypers PW, Laheij R, Buth J. Which factors
`increase the risk of conversion to open surgery
`following endovascular abdominal aortic an-
`eurysm repair? Eur J Vasc Endovasc Surg.
`2000;20:183–189.
`5. Resch T, Ivancev K, Brunkwall J, et al. Distal
`migration of stent-grafts after endovascular
`repair of abdominal aortic aneurysms. J Vasc
`Interv Radiol. 1999;10:257–264.
`
`

`

`J ENDOVASC THER
`2008;15:335–343
`
`ENDOGRAFT MOVEMENT AND INSTABILITY
`Rafii et al.
`
`343
`
`6. Zarins CK, Bloch DA, Crabtree T, et al. Stent
`graft migration after endovascular aneurysm
`repair: importance of proximal fixation. J Vasc
`Surg. 2003;38:1264–1272.
`Iliac
`7. Benharash P, Lee JT, Abilez OJ, et al.
`fixation inhibits migration of both suprarenal
`and infrarenal aortic endografts. J Vasc Surg.
`2007;45:250–257.
`8. Umscheid T, Stelter WJ. Time-related alter-
`ations of shape, position, and structure in self-
`expanding modular aortic stent-grafts. J En-
`dovasc Surg. 1999;6:17–32.
`9. Kra¨ mer SC, Seifarth H, Pamler R, et al. Geo-
`metric changes in aortic endografts over a 2-
`year observation period. J Endovasc Ther.
`2001;8:34–38.
`10. Sternbergh WC, Nordness PJ, York JW,
`et al. Endo-exuberance to endo-reality: trends
`in the management of 431 AAA repairs be-
`tween 1996 and 2002. J Endovasc Ther. 2003;
`10:418–423.
`11. Jordan WD, Alcocer F, Wirthlin DJ, et al.
`Abdominal aortic aneurysms in ‘‘high-risk’’
`surgical patients: comparison of open and
`endovascular
`repair. Ann Surg. 2003;237:
`623–629.
`12. Anain PM, Anain JM, Tiso M, et al. Early and
`mid-term results of ruptured abdominal aortic
`aneurysms in the endovascular era in a
`community hospital. J Vasc Surg. 2007;46:
`898–905.
`13. Raman KG, Missig-Carroll N, Richardson T,
`et al. Color-flow duplex ultrasound scan versus
`computed tomographic scan in the surveil-
`lance of endovascular aneurysm repair. J Vasc
`Surg. 2003;38:645–651.
`14. Zarins CK, White RA, Fogarty TJ. Aneurysm
`rupture after endovascular repair using the
`AneuRx stent graft. J Vasc Surg. 2000;31:
`960–970.
`15. Elkouri S, Panneton JM, Andrews JC, et al.
`Computed tomography and ultrasound in
`follow-up of patients after endovascular repair
`of abdominal aortic aneurysm. Ann Vasc Surg.
`2004;18:271–279.
`16. Li Z, Kleinstreuer C. Analysis of biomechanical
`factors affecting stent-graft migration in an
`abdominal aortic aneurysm model. J Biomech.
`2006;39:2264–2273.
`17. Broeders IA, Blankensteijn JD, Wever JJ,
`et al. Mid-term fixation stability of the Endo-
`Vascular Technologies endograft. EVT Investi-
`gators. Eur J Vasc Endovasc Surg. 1999;18:
`300–307.
`
`18. Conners MS, Sternbergh WC, Carter G, et al.
`Endograft migration one to four years after
`endovascular abdominal aortic aneurysm re-
`pair with the AneuRx device: a cautionary note.
`J Vasc Surg. 2002;36:476–484.
`19. White GH, May J, Petrasek P, et al. Endoten-
`sion: an explanation for continued AAA growth
`after successful endoluminal repair. J Endo-
`vasc Surg. 1999;6:308–315.
`20. Heikkinen MA, Alsac JM, Arko FR, et al. The
`importance of iliac fixation in prevention of
`stent graft migration. J Vasc Surg. 2006;43:
`1130–1137.
`21. Zarins CK, Crabtree T, Bloch DA, et al. En-
`dovascular aneurysm repair at 5 years: does
`aneurysm diameter predict outcome? J Vasc
`Surg. 2006;44:920–930.
`22. Hobo R, Buth J. Secondary interventions follow-
`ing endovascular abdominal aortic aneurysm
`repair using current endografts. A EUROSTAR
`report. J Vasc Surg. 2006;43:896–902.
`23. Laheij RJ, Buth J, Harris PL, et al. Need for
`secondary interventions after endovascular
`repair of abdominal aortic aneurysms. Inter-
`mediate-term follow-up results of a European
`collaborative registry (EUROSTAR). Br J Surg.
`2000;87:1666–1673.
`24. Collins JT, Boros MJ, Combs K. Ultrasound
`surveillance of endovascular aneurysm repair:
`a safe modality versus computed tomography.
`Ann Vasc Surg. 2007;21:671–675.
`25. Chaikof EL, Blankensteijn JD, Harris PL, et al.
`Reporting standards for endovascular aortic
`aneurysm repair. J Vasc Surg. 2002;35:
`1048–1060.
`26. Matsumura JS, Brewster DC, Makaroun MS,
`et al. A multicenter controlled clinical trial of
`open versus endovascular treatment of ab-
`dominal aortic aneurysm. J Vasc Surg.
`2003;37:262–271.
`27. Sampaio SM, Panneton JM, Mozes G, et al.
`AneuRx device migration: incidence, risk fac-
`tors, and consequences. Ann Vasc Surg.
`2005;19:178–185.
`28. Velazquez OC, Baum RA, Carpenter JP, et al.
`Relationship between preoperative patency of
`the inferior mesenteric artery and subsequent
`occurrence of
`type II endoleak in patients
`undergoing endovascular repair of abdominal
`aortic aneurysms. J Vasc Surg. 2000;32:777–788.
`29. van Marrewijk C, Buth J, Harris PL, et al.
`Significance of endoleaks after endovascular
`repair of abdominal aortic aneurysm:
`the
`EUROSTAR experience. J Vasc Surg. 2002;35:
`461–473.
`
`