throbber
Nature, frequency, and predictors of secondary
`procedures after endovascular repair of abdominal
`aortic aneurysm
`
`Ellis S. K. Sampram, MD,a Matthew T. Karafa, MS,b Edward J. Mascha, MS,b Daniel G. Clair, MD,a
`Roy K. Greenberg, MD,a Sean P. Lyden, MD,a Patrick J. O’Hara, MD,a Timur P. Sarac, MD,a
`Sunita D. Srivastava, MD,a Brett Butler, MD,a and Kenneth Ouriel, MD,a Cleveland, Ohio
`
`Objectives: Endovascular stent grafting offers a potentially less invasive option for treatment of abdominal aortic
`aneurysm. Clinical benefit has been demonstrated with respect to early parameters such as blood transfusion, return of
`gastrointestinal function, and length of hospital stay. Endovascular repair, however, has been criticized on the basis of
`inferior long-term outcome. Secondary procedures may be necessary to address durability issues such as migration,
`high-pressure endoleak, graft limb thrombosis, and degeneration of the stent-fabric structure itself, issues that may
`compromise the primary goal of aneurysm repair, protection from rupture.
`Methods: Between 1996 and 2002, 703 patients underwent endovascular treatment of infrarenal abdominal aortic
`aneurysm at The Cleveland Clinic Foundation. During this time, five devices were used: Ancure, AneuRx, Excluder,
`Talent, and Zenith. Outcome was assessed with physical examination, lower extremity arterial studies, plain abdominal
`radiography, and computed tomography at discharge, at 1, 6, and 12 months postoperatively, and annually thereafter.
`Secondary procedures were defined as any procedure, exclusive of diagnostic angiography, performed after stent graft
`implantation, directed at treatment of aneurysm-related events. Multivariable statistical techniques for censored data
`(Cox proportional hazards modeling) were used to determine baseline parameters associated with need for secondary
`procedures over follow-up, with calculation of hazards ratio (HR) and 95% confidence interval (CI).
`Results: Patient follow-up averaged 12.2 ⴞ 11.7 months. Patient survival was 90% ⴞ 1.4% at 1 year, 78% ⴞ 2.6% at 2 years,
`and 70% ⴞ 3.8% at 3 years. Aneurysm rupture occurred in 3 patients (0.4%), accounting for rupture risk of 1.4% over the
`first 2 years of follow-up (Kaplan-Meier method). Overall, 128 secondary procedures were required in 104 patients
`(15%), with a cumulative risk of 12% ⴞ 1.5% at 1 year, 24% ⴞ 2.8% at 2 years, and 35% ⴞ 4.4% at 3 years after stent graft
`implantation. Among the secondary procedures, new stent grafts and extensions were placed in 34 patients (27%),
`embolization of endoleak was performed in 33 patients (26%), and open surgical conversion was undertaken in 11
`patients (9%). Periprocedural mortality of secondary procedures was 8% overall, but was 18% for patients undergoing
`open surgical conversion. Multivariable modeling identified the date the procedure was performed (HR, 1.53 per
`3-month period of study; CI, 1.22-1.92; P < .001) and aneurysm size (HR, 1.35 per centimeter of minor axis; CI,
`1.13-1.60; P < .001) as independent predictors of need for secondary procedures.
`Conclusions: Current endovascular devices are associated with a relatively high rate of complications over mid-term
`follow-up, culminating in frequent need for secondary remedial procedures. With strict follow-up imaging compliance,
`however, risk for rupture and aneurysm-related death remain exceedingly low. Newer technology may achieve improved
`durability and a lower requirement for secondary procedures, while maintaining the minimally invasive nature of
`presently available devices. (J Vasc Surg 2003;37:930-7.)
`
`Endovascular abdominal aortic aneurysm (AAA) repair
`provides substantial clinical benefit for the patient.1 The
`physiologic insult is clearly reduced with endovascular tech-
`niques compared with a traditional approach, culminating
`
`From The Departments of Vascular Surgerya and Biostatistics,b The Cleve-
`land Clinic Foundation.
`Competition of interest: RKG is a consultant for Cook, Inc, and KO is a
`consultant for Medtronic AVE. The Cleveland Clinic received research
`funding from Guidant, Medtronic AVE, WL Gore & Associates, and
`Cook, Inc.
`Presented at the Twenty-sixth Annual Meeting of the Midwestern Vascular
`Surgical Society, Madison, Wis, Sep 12-14, 2002.
`Reprint requests: Kenneth Ouriel, MD, Chairman, Department of Vascular
`Surgery, The Cleveland Clinic Foundation, Desk S40, 9500 Euclid Ave,
`Cleveland, OH 44195 (e-mail: ourielk@ccf.org).
`Copyright © 2003 by The Society for Vascular Surgery and The American
`Association for Vascular Surgery.
`0741-5214/2003/$30.00 ⫹ 0
`doi:10.1067/mva.2003.281
`930
`
`in decreased use of the intensive care unit, diminished
`length of hospital stay, and early return to normal activi-
`ties.2 In contrast, longer term outcome may be inferior in
`patients who receive stent -grafts, with a greater require-
`ment for hospital readmission to treat device-related prob-
`lems.3,4 The need for secondary procedures reached 33%
`within 3 years of endovascular aneurysm repair in patients
`entered into the EUROSTAR registry.5 Persistent en-
`doleak, device migration, and limb thrombosis were com-
`mon causes for these remedial procedures, approximately
`one fourth of which were open surgical procedures and
`three fourths were endovascular procedures.3
`A variety of issues may underlie the low durability of
`present endovascular devices. Some of these issues may
`relate to anatomy of the aorta and iliac vessels, parameters
`best assessed with precise anatomic measurements such as
`those accessible from core laboratory data. Other concerns
`
`TMT 2104
`Medtronic v. TMT
`IPR2021-01532
`
`

`

`JOURNAL OF VASCULAR SURGERY
`Volume 37, Number 5
`
`Sampram et al 931
`
`Table I. Follow-up protocol comprising institutional standard of care
`
`Item
`
`Timing
`
`History and physical examination
`Four-view abdominal plain radiograph films*
`Helical CT scans
`
`Preoperative; at discharge; 1, 6, 12 months; yearly thereafter
`At discharge; 1, 6, 12 months; yearly thereafter
`Within 3 months of repair; at discharge; 1, 6, 12 months; yearly thereafter
`
`*Before 1999, abdominal plain x-ray films were obtained in two planes alone, anteroposterior and lateral.
`
`may derive from clinical variables such as demographic
`parameters, aneurysm size, or brand of device implanted.
`The present investigation was undertaken to characterize
`the nature and frequency of secondary interventions after
`endovascular aneurysm repair, with analysis of baseline
`variables predictive of remedial interventions.
`
`METHODS
`Over 6 years ending in 2002, 703 patients underwent
`endovascular repair of infrarenal AAA. Five devices were
`used over this period: Ancure (Guidant, Menlo Park, Calif),
`AneuRx (Medtronic/AVE, Santa Rosa, Calif), Excluder
`(W. L. Gore, Flagstaff, Ariz), Talent (Medtronic/AVE),
`and Zenith (Cook Inc, Bloomington, Ind). Among the
`703 patients, 555 patients (79%) received treatment in
`investigational device exemption (IDE) trials: 362 (51%) as
`part of multicenter corporate-sponsored clinical evalua-
`tions, and 193 (27%) under single-institution sponsor-
`investigator IDE studies. The Institutional Review Board
`of The Cleveland Clinic Foundation approved the study
`protocols and the informed consent forms. Commercially
`available devices were placed in the remaining 148 patients
`(21%), and informed consent was obtained from each of
`these patients. Patients who received Zenith devices were
`categorized as those in whom devices were placed as part of
`a multicenter clinical trial (pivotal and continuing access
`phases, Zenith-MCT) and those who received treatment as
`part of a sponsor-investigator IDE (Zenith-SIT). This sub-
`division was deemed necessary because of the broadly dif-
`fering anatomic eligibility criteria in the two subgroups.
`The follow-up protocol was similar for patients in IDE
`trials and patients who underwent implantation of com-
`mercially available devices, representing the standard of
`care for patients receiving treatment at the institution (Ta-
`ble I). Preoperative helical computed tomography (CT)
`was performed with 3 mm axial reconstruction. Angiogra-
`phy and intravascular ultrasound studies were also per-
`formed when measurements were deemed inaccurate on
`the basis of CT scans, in the presence of suspected renal or
`iliac occlusive disease, or when the endograft was placed as
`part of a clinical trial that mandated these studies. Except in
`patients with contraindications such as renal insufficiency
`or history of severe allergy to contrast material, postopera-
`tive CT scans included non-contrast-enhanced, contrast-
`enhanced, and 3-minute to 5-minute delayed post-con-
`trast-enhanced images. Delayed scans are included in our
`imaging protocol to improve sensitivity for detecting en-
`doleak, with careful comparison of sac appearance on pre-
`contrast-enhanced scans and delayed scans.
`
`Data were collected from a review of radiology imaging
`reports and physician chart notes. Any significant discrep-
`ancy between these two data sources prompted an interro-
`gation of the source imaging studies. Outcome reporting
`adhered to the standards outlined by the Ad Hoc Commit-
`tee for Standardized Reporting Practices in Vascular Sur-
`gery of The Society for Vascular Surgery/American Asso-
`ciation for Vascular Surgery (SVS/AAVS).4 Late deaths
`were classified as aneurysm-unrelated or aneurysm-related,
`where aneurysm-related deaths included those deaths that
`occurred as a result of aneurysm rupture or after any pri-
`mary or secondary procedure directed at treating the aneu-
`rysm or complications thereof.
`Secondary procedures were defined as any subsequent
`procedure, whether percutaneous or open surgical, related
`to aneurysm repair or complications thereof. While proce-
`dures performed because of wound complications were
`tabulated for descriptive purposes, they were excluded from
`statistical analysis.
`Endoleak was classified on the basis of serial imaging
`studies.5,6 CT findings, although most influential, com-
`posed only one factor. Presumed type I leak observed on
`CT scans was invariably followed up with angiographic
`confirmation. A leak was considered type II when the
`contrast collection was posterior or at the orifice of the
`inferior mesenteric artery. Type II and IV endoleaks noted
`only on an intraoperative or predischarge imaging study
`were excluded from analysis. Leakage through enlarged
`suture holes or fabric tears was classified as type III en-
`doleak, as were defects related to separation of modular
`components.7 An endoleak was suspected to be type III
`when it directly abutted the graft fabric or was associated
`with obvious disunion of components; half of these were
`confirmed at angiography or at open surgical conversion.
`Migration was defined with clinical and radiographic pa-
`rameters, as suggested by the SVS/AAVS document on
`endovascular reporting standards.4 Migration included
`caudal movement of the proximal attachment site or cranial
`movement of a distal attachment site. A device was consid-
`ered to have migrated when at least 10 mm of movement
`was noted relative to anatomic landmarks, when the patient
`experienced symptoms, or when an intervention was un-
`dertaken to treat migration, irrespective of distance. Aneu-
`rysm shrinkage or growth was determined with a preproce-
`dural CT scan performed 3 months or less before the date
`of the procedure as the baseline. A predischarge imaging
`study was used as the reference scan when a preoperative
`study was not available. Size measurements were made on
`the CT scan with the greatest minor sac dimension on any
`
`

`

`932 Sampram et al
`
`JOURNAL OF VASCULAR SURGERY
`May 2003
`
`remaining length of sealing was deemed inadequate, usu-
`ally when reduced to less than 10 mm.
`Statistical analysis was performed with methods appro-
`priate for censored data. Kaplan-Meier survival analysis was
`used to express patient survival, freedom from aneurysm-
`related death, and freedom from secondary procedures.
`Freedom from such sentinel events as endoleak, device
`migration, graft limb occlusion, and post-repair sac shrink-
`age or enlargement were also expressed with Kaplan-Meier
`curves. Cox analysis was used to evaluate time to secondary
`procedure for specific baseline variables including proce-
`dure date, patient demographic parameters, aneurysm size,
`and procedural details such as brand of device implanted
`and use of adjuvant procedures including placement of
`renal or aortic stents, hypogastric embolization, and use of
`iliac conduits for access. Hazard ratio (HR) was calculated,
`as was 95% confidence interval (CI). Multivariable Cox
`proportional hazards modeling was used to define indepen-
`dent predictors of secondary procedures. Values are speci-
`fied as mean ⫾ SD, except for Kaplan-Meier analysis, in
`which data are expressed as mean ⫾ SE. Significance was
`assumed at P ⬍ .05.
`
`RESULTS
`Patient ages ranged from 48 to 100 years (mean, 75 ⫾
`8.1 years); 605 (86%) were men and 98 (14%) were women.
`The diameter of the aneurysm sac averaged 54 ⫾ 10 mm in
`minor dimension and 58 ⫾ 11 mm in major dimension.
`With a 5.5 cm threshold for minor and major sac axis, 283
`aneurysms (40%) and 391 aneurysms (56%), respectively,
`would be considered large. Pperative mortality (⬍30 days)
`was 1.7% overall (12 patients), 1.0% in those undergoing
`elective treatment (7 patients), and 19% in those undergo-
`ing urgent treatment (5 patients). Of the 12 operative
`deaths, 10 (83%) were procedure-related and occurred as a
`result of perioperative medical complications, whereas 2
`(17%) were device-related and occurred as a direct result of
`complications from the device. Mean duration of follow-up
`was 12.2 ⫾ 11.7 months (range, 0-65 months). Patient
`survival was 90% ⫾ 1.4% at 1 year, 78% ⫾ 2.6% at 2 years,
`and 70% ⫾ 3.8% at 3 years (Kaplan-Meier method; Fig 1).
`Aneurysm-related deaths, including deaths related to the
`initial procedure, occurred in 12 patients (1.7%) and ac-
`counted for 16% of 74 deaths. Risk for aneurysm-related
`death was 2.7% ⫾ 0.5% at 1 year and 3.6% ⫾ 1.2% at 2 and
`3 years postoperatively.
`There were 24 graft limb occlusions in 20 patients
`(2.8%). Risk for limb occlusion was 2.7% ⫾ 0.7% at 1 year,
`4.1% ⫾ 1.2% at 2 years, and 5.5% ⫾ 1.9% at 3 years after
`repair (Fig 2). Late limb occlusion was rare; no new limb
`occlusion was observed after 30 months. Migration was
`noted in 25 patients (3.6%) and, unlike limb occlusion,
`appeared to increase in frequency over longitudinal follow-
`up. Examination of the Kaplan-Meier curve revealed low
`risk for migration during the first year after stent graft
`implantation, estimated at 1.0% ⫾ 0.5% at 1 year but rising
`to 12% ⫾ 3.1% after 3 years of follow-up. Endoleak, of any
`type and observed at any point after discharge, was docu-
`
`Fig 1. Patient survival, expressed as all-cause mortality and aneu-
`rysm-related death.
`
`Fig 2. Freedom from migration or graft limb occlusion over
`follow-up.
`
`axial image. Aneurysm shrinkage was defined as decrease of
`5 mm or more in the minor dimension of the sac; enlarge-
`ment was defined as increase of 5 mm or more in this
`dimension.
`The individual clinician responsible for the patient’s
`care determined the need for secondary procedures. Cer-
`tain clinical events mandated intervention, including post-
`implant aneurysm rupture or symptomatic graft limb occlu-
`sion. Most, however, were less catastrophic, and the need
`for secondary intervention was subjective. Basic treatment
`paradigms were, however, standard at the institution.
`Treatment of types I and III endoleaks was always recom-
`mended. Type II endoleak was treated when the aneurysm
`sac was observed to enlarge over time. As well, patients with
`type II leak received treatment when the aneurysm failed to
`contract despite observation for more than 12 months after
`the initial endovascular repair. Type II leak in patients with
`a shrinking sac was not treated. Device migration was
`treated when it was associated with a type I leak or when the
`
`

`

`JOURNAL OF VASCULAR SURGERY
`Volume 37, Number 5
`
`Sampram et al 933
`
`Fig 3. Freedom from endoleak over follow-up.
`
`Fig 4. Freedom from aneurysm sac shrinkage or growth, defined
`by change 5 mm or more in diameter compared with baseline index
`CT scan.
`
`mented in 162 patients (23.0%). At Kaplan-Meier analysis,
`risk for endoleak was 30% ⫾ 2.3% at 1 year, 42% ⫾ 3.4% at
`2 years, and 56% ⫾ 5.5% at 3 years after implantation (Fig
`3). Most endoleaks were type II (35% ⫾ 3.2% at 2 years);
`fewer were device-related (type I or III, 10% ⫾ 2.6% at 2
`years). Sac shrinkage of 5 mm or more occurred in 39% ⫾
`2.7% of patients at 1 year, 60% ⫾ 3.2% of patients at 2 years,
`and 68% ⫾ 3.6% of patients at 3 years after aneurysm repair
`(Fig 4). Sac enlargement was observed in 3.5% ⫾ 1.0% of
`patients at 1 year, 11% ⫾ 2.5% of patients at 2 years, and
`21% ⫾ 4.5% of patients at 3 years after repair.
`Three post-implantation aneurysm ruptures occurred,
`4, 7, and 19 months after implantation, respectively, for a
`rupture-free probability of 98.6% ⫾ 0.9% at 2 years, ac-
`counting for a 0.7% annualized linear risk for rupture.
`Cause of rupture was thought to be displacement of an iliac
`limb from its attachment site and sudden development of a
`distal type I endoleak in 1 patient and disunion of a proxi-
`
`Fig 5. Freedom from secondary procedures over follow-up.
`
`mal extension cuff from the main body in a second patient.
`Cause of rupture remains undefined in the third patient,
`but occurred in an aortic pseudoaneurysm that developed
`at the juxtaposition of the proximal aspect of a stent graft
`and a previously placed renal stent. Among the three pa-
`tients with aneurysm rupture, two underwent conversion
`to open surgery, and 1 of these patients died periopera-
`tively. The third patient underwent successful endovascular
`insertion of a proximal aortic extension cuff.
`Overall, 128 secondary procedures were performed
`in 104 patients (15%). Among secondary procedures, 4
`were directed at treatment of infectious groin wound
`complications and were excluded from subsequent anal-
`yses, leaving 124 procedures performed in a 100- patient
`cohort available for hazard analysis. Cumulative risk for
`secondary procedures was 12% ⫾ 1.5% at 1 year, 24% ⫾
`2.8% at 2 years, and 35% ⫾ 4.4% at 3 years of follow-up
`(Fig 5). Eight deaths occurred as a result of secondary
`intervention, for a periprocedural mortality rate of 6.3%.
`In total, conversion to open surgical repair was required
`in 12 patients (1.9%); 1 was immediate and was excluded
`from further study, and the remainder were tabulated as
`secondary procedures. Among the 11 patients in whom
`the secondary procedure was conversion to open sur-
`gery, 2 patients died (18%). There were six major indi-
`cations for secondary procedures: endoleak (n ⫽ 63),
`endograft migration (n ⫽ 13), graft limb occlusion (n ⫽
`24 in 19 patients), postoperative hemorrhage (n ⫽ 12),
`inadvertent partial or complete renal artery coverage
`(n ⫽ 8), and aneurysm rupture (n ⫽ 3). Interventions for
`each of these indications are listed in Table II. Of note,
`among 34 type II endoleaks treated, 20 (59%) were
`treated because of sac enlargement and 10 (29%) because
`of failure to contract over more than 12 months of
`observation. In the remaining 4 patients (12%), angiog-
`raphy was performed because of suspected device-related
`(type I or III) leak, but type II leak was found at
`angiography and were embolized at that time.
`Univariable analysis identified four baseline variables
`associated with a significantly increased risk for subse-
`
`

`

`934 Sampram et al
`
`JOURNAL OF VASCULAR SURGERY
`May 2003
`
`Table II. Number of complications and nature of interventions performed
`
`Complication
`
`Procedures*
`
`Covered
`stent†
`
`Bare
`stent
`
`Embolization
`(branch/sac)
`
`Bypass or
`thrombectomy
`
`Surgical
`conversion
`
`Other‡
`
`Total
`events
`
`Endoleak
`Type I proximal§
`Type I distal
`Type II
`Type III, disunion
`Type III, microleak
`Migration
`Proximal neck㛳
`Distal attachment site
`Limb occlusion
`Hemorrhage
`Wound infection
`Post-implant sac rupture
`Renal compromise
`Distal embolization
`Total
`
`17
`3
`34
`4
`5
`
`6
`6
`24
`12
`4
`3
`8
`2
`128
`
`10
`3
`1§
`4
`1
`
`4
`6
`
`4
`
`1
`
`3
`
`1
`
`2
`
`8 (2)
`
`33 (1)
`
`19 (1)
`
`4 (1)
`
`4
`
`1
`
`2 (1)
`
`34
`
`14
`
`33
`
`19
`
`11
`
`17
`3
`131
`6
`10
`25
`13
`12
`24
`12
`4
`3
`8
`2
`270
`
`3
`8 (1)
`4 (1)
`
`2
`17
`
`Numbers in parentheses represent periprocedural deaths, when they occurred.
`*Total complications, excluding those that were not treated. Number exceeds number of patients; many patients had more than one complication and more
`than one secondary procedure.
`†Includes placement of aortic extension cuffs (10), iliac extension limbs (18), and new stent grafts (6).
`‡Evacuation of hematoma with (4) or without (4) repair of artery, incision and drainage of groin wound (4), fasciotomy (3), toe amputation (2).
`§Extension limb placed to occlude backflow from hypogastric artery into sac.
`㛳Patients with proximal type I endoleak due to device migration (13) are categorized under endoleak heading and do not appear again under migration.
`
`Table III. Summary of univariable risk in secondary
`procedures after endovascular aneurysm repair
`
`Hazard
`ratio
`
`95% Confidence
`interval
`
`Male
`Age (per year)
`Procedure date (by quarter)
`Minor sac axis
`Major sac axis
`Renal stent
`Aortic stent
`Hypogastric embolization
`Iliac conduit
`Device
`AneuRx (n ⫽ 203)
`Ancure (n ⫽ 63)
`Talent (n ⫽ 39)
`Zenith-MCT (n ⫽ 144)
`Zenith-SIT (n ⫽ 181)
`Other devices (n ⫽ 73)
`
`1.101
`1.001
`1.549
`1.364
`1.373
`0.946
`2.928
`1.243
`1.027
`
`1.000
`1.217
`2.161
`1.824
`1.446
`1.572
`
`(0.60, 2.02)
`(0.98, 1.03)
`(1.24, 1.94)
`(1.15, 1.62)
`(1.16, 1.62)
`(0.38, 2.33)
`(1.35, 6.36)
`(0.66, 2.34)
`(0.32, 3.25)
`
`Reference
`(0.53, 2.78)
`(0.99, 4.73)
`(0.94, 3.54)
`(0.82, 2.56)
`(0.84, 2.96)
`
`P
`
`.76
`.95
`⬍.001
`⬍.001
`⬍.001
`.90
`.007
`.50
`.96
`.32
`
`quent, secondary procedures (Table III). Secondary pro-
`cedures were more common in patients with larger major
`and minor aneurysm sac axes, in patients who received a
`large aortic stent because of proximal endoleak evident at
`initial aneurysm repair, and in patients who received
`treatment later in the course of the review. There were
`no significant differences in risk for secondary proce-
`dures according to brand of device (Fig 6). Multivariable
`analysis identified two independent predictors of second-
`ary procedures: date of primary operation (HR, 1.53;
`95% CI, 1.22-1.92 per quarter; P ⬍ .001) and minor
`
`Fig 6. Freedom from secondary procedures by brand of device
`implanted. Follow-up is truncated at 24 months because of small
`numbers of uncensored patients at this time, with resultant in-
`crease in standard error of the estimate.
`
`aneurysm axis (HR, 1.35; 95% CI, 1.13-1.60 per centi-
`meter; P ⬍ .001).
`
`DISCUSSION
`More than 25 years ago, Dr Juan Parodi first envisaged
`endovascular techniques for repair of AAA after he ob-
`served the morbidity and mortality of traditional open
`surgical repair when performed in patients with compro-
`mised medical status.8 Reasoning that morbidity was di-
`rectly proportional to invasiveness of the intervention, Dr
`Parodi developed a transfemoral technique for aneurysm
`repair. Early on, however, durability was a problem. The
`initial aorto-aortic devices did not include a distal stent.
`
`

`

`JOURNAL OF VASCULAR SURGERY
`Volume 37, Number 5
`
`Sampram et al 935
`
`Distal type I endoleak developed over time, resulting in
`recurrent pressurization of the aneurysm sac.9 Even when
`later iterations used proximal and distal stents to affix the
`stent graft to the aorta, late endoleak ensued in an unac-
`ceptably great proportion of patients who received nonbi-
`furcated devices.10
`Traditional open surgical repair is associated with a
`moderate degree of periprocedural morbidity but sets a
`high standard for long-term durability. While selected re-
`views document graft-related complications in as many as
`10% of patients,11,12 more recent series attest to lower
`long-term risks.13 The Cleveland Clinic 10-year experience
`documented an extremely low risk for graft-related compli-
`cations, approximating 0.4% in more than 1135 consecu-
`tive patients undergoing elective open surgical infrarenal
`aortic aneurysm repair.13 In fairness to endovascular aneu-
`rysm repair, however, studies of traditional aneurysm sur-
`gery may be criticized on the basis of less rigorous long-
`term imaging follow-up.
`In the present analysis of approximately 700 endovas-
`cular procedures performed at a single institution over 6
`years, secondary procedures were deemed necessary in a
`high proportion of patients. With Kaplan-Meier analysis,
`risk for a secondary remedial procedure was 35% within 3
`years of implantation. It must be emphasized, however,
`that most secondary procedures were percutaneous. Open
`surgical conversion was rarely necessary. This feature may in
`part account for the low rate of aneurysm-related death
`after endovascular repair, estimated at 3.6% over a 3-year
`follow-up, inclusive of initial perioperative deaths. More-
`over, death from aneurysm rupture occurred in only 2 of
`703 (0.3%) patients followed up for a mean of 1 year.
`Univariable analysis enabled identification of three vari-
`ables associated with increased risk for asecondary proce-
`dures: date the procedure was performed, use of a large
`aortic stent for proximal endoleak at implantation, and
`aneurysm size (minor and major axes). Although the par-
`ticular brand of device did not achieve statistical signifi-
`cance as a predictor of secondary procedures, confidence
`intervals for several of the devices, particularly the Talent
`and Zenith-MCT, suggest that type II statistical error is
`great. Of interest, only two variables, ie, procedure date and
`aneurysm size, remained significant in the multivariable
`model.
`The subjectivity of secondary procedures is the main
`limitation of our analysis. It is likely that physicians were
`more apt to intervene to treat an endoleak, for instance,
`when the aneurysm was large. Equally likely, however, is
`the association between challenging anatomy and larger
`aneurysm.14 The proximal aortic neck shortens as the an-
`eurysm enlarges,15 increasing potential for migration and
`type I endoleak. As the aneurysm enlarges, longitudinal
`dimensions change concurrently.16 Angulation of the aor-
`tic neck and tortuosity of the iliac arteries would also be
`expected to correlate with aneurysm size. Had these ana-
`tomic parameters been available for analysis in the present
`study, they might have been found to underlie the associ-
`ation between secondary procedures and sac diameter.
`
`However, precise baseline anatomic measurements were
`unavailable for most patients included in the study.
`Increasing risk for endoleak over follow-up was ex-
`pected for device-related endoleak, specifically type I and
`III leaks. By contrast, the observation of increasing risk for
`type II leak was not expected. In part, this finding can be
`explained by the cumulative manner in which we chose to
`express the data. As well, however, a few patients demon-
`strated new type II endoleak that became evident many
`months after endograft implantation. It is quite possible
`that these leaks were present from the start but were of
`sufficiently low flow to remain below the threshold of
`detection with conventional CT technology. Over time,
`some type II leaks may act in a manner reminiscent of
`arteriovenous fistula, ie, flow increases with decreased out-
`flow resistance and dilatation of the inflow channels.
`The second independent predictor of secondary proce-
`dures was related to chronology of the initial endovascular
`repair. Patients who received treatment later in the course
`of the review were at markedly increased risk for secondary
`procedures. There are several potential explanations for this
`finding, each of which relates to practice change over time.
`The most obvious explanation centers on a time-related
`change in the aggressiveness with which clinicians treated
`such events as endoleak, aneurysm enlargement, and device
`migration. As well, clinicians may have begun to treat more
`anatomically challenging cases during the later years of
`study. While it is tempting to ascribe time-related changes
`in the distribution of endograft brands to increased require-
`ment for secondary procedures, the multivariable design of
`the analysis suggests that the effect of variations in other
`practice-associated parameters was stronger than the effect
`of the brand of device.
`Studies of endovascular aneurysm repair have been
`criticized with respect to failure to demonstrate true pro-
`tection from rupture. Collin and Murie17 noted that the
`observed rupture risk of 1% per year after endovascular
`repair was not remarkably different from the natural history
`of most small aneurysms followed up without intervention.
`It is appealing to compare the results of the present study
`with natural history studies to determine whether endovas-
`cular aneurysm repair truly protects against rupture and
`whether the method does so to an extent equivalent to that
`of traditional open surgical repair. While comparisons be-
`tween our own series and the two multicenter randomized
`small aneurysm trials are neither statistically nor scientifi-
`cally robust, some element of protection from rupture and
`aneurysm-associated death appears to be conferred by en-
`dovascular repair. The UK Small Aneurysm Trial docu-
`mented death from rupture in 31 of 563 (5.5%) aneurysms
`in the surveillance group over a mean of 8 years of follow-
`up.18 This finding was apparent in spite of the relatively
`small size of the aneurysms and the fact that in 62% of these
`patients open surgical repair was ultimately necessary. Sim-
`ilar observations were noted in the Aneurysm Detection
`and Management Trial.19 Although 62% of patients in the
`surveillance group also eventually required open repair,
`2.6% risk for aneurysm-related death was evident over mean
`
`

`

`936 Sampram et al
`
`JOURNAL OF VASCULAR SURGERY
`May 2003
`
`follow-up of 4.9 years, with observed 0.6% annual risk for
`rupture. The present endovascular series documents mid-
`term risks comparable with or better than those of the
`randomized trials. Moreover, these results were achieved in
`a population in which approximately half of the patients
`had large aneurysms that would have excluded them from
`the randomized small aneurysm trials. The relatively low
`mid-term survival rate in our series is most likely related to
`our policy of advocating endovascular repair for patients
`with medical comorbid conditions and recommending
`open surgical repair for younger, healthier patients.
`In summary, endovascular aneurysm repair in its present
`state appears to be associated with durability that is inferior to
`that we have become accustomed to with traditional open
`surgical techniques. Unlike open repair, endovascular repair is
`associated with a relatively frequent requirement for secondary
`procedures designed to address problems including endoleak,
`migration, and limb thrombosis. Despite these problems, the
`technology does appear to protect patients from aneurysm
`rupture and aneurysm-associated death. Here is where the
`goals of endovascular repair attain relevance. Above all, endo-
`vascular methods must protect patients from aneurysm rup-
`ture and aneurysm-related death, at least to the extent accom-
`plished with standard surgical repair. As well, these results
`should be achieved with a lesser degree of patient discomfort,
`shorter hospital stay, and more rapid return to normal activi-
`ties. While protection from rupture and death appear to be
`attainable with presently available endovascular technology, a
`high rate of secondary procedures may negatively affect pa-
`tient satisfaction. We expect that introduction of newer, more
`durable devices presently under development might diminish
`the rate of secondary procedures after endovascular aneurysm
`repair. Until then, it seems reasonable to limit use of stent graft
`repair to those patients with compromised medical status and
`inordinate operative risk or to those patients willing to accept
`the follow-up imaging protocols and who acknowledge the
`higher rate of secondary procedures that are part and parcel of
`present technology.
`
`REFERENCES
`
`1. Hill BB, Wolf YG, Lee WA, Arko FR, Olcott C, Schubart PJ, et al. Open
`versus endovascular AAA repair in patients who are morphological
`candidates for endovascular treatment. J Endovasc Ther 2002;9:255-
`61.
`2. Zarins CK, White RA, Schwarten D, Kinney E, Diethrich EB, Hodgson
`KJ, et al. AneuRx stent graft versus open surgical repair of abdominal
`
`aortic aneurysms: multicenter prospective clinical trial. J Vasc Surg
`1999;29:292-305.
`3. Carpenter JP, Baum RA, Barker CF, Golden MA, Velazquez OC,
`Mitchell ME, et al. Durability of benefits of endovascular versus con-
`ventional abdominal aortic aneurysm repair. J Vasc Surg 2002;35:
`222-8.
`4. Chaikof EL, Blankensteijn JD, Harris PL, White GH, Zarins CK,
`Bernhard VM, et al. Reporting standards for endovascular aortic aneu-
`rysm repai

This document is available on Docket Alarm but you must sign up to view it.


Or .

Accessing this document will incur an additional charge of $.

After purchase, you can access this document again without charge.

Accept $ Charge
throbber

Still Working On It

This document is taking longer than usual to download. This can happen if we need to contact the court directly to obtain the document and their servers are running slowly.

Give it another minute or two to complete, and then try the refresh button.

throbber

A few More Minutes ... Still Working

It can take up to 5 minutes for us to download a document if the court servers are running slowly.

Thank you for your continued patience.

This document could not be displayed.

We could not find this document within its docket. Please go back to the docket page and check the link. If that does not work, go back to the docket and refresh it to pull the newest information.

Your account does not support viewing this document.

You need a Paid Account to view this document. Click here to change your account type.

Your account does not support viewing this document.

Set your membership status to view this document.

With a Docket Alarm membership, you'll get a whole lot more, including:

  • Up-to-date information for this case.
  • Email alerts whenever there is an update.
  • Full text search for other cases.
  • Get email alerts whenever a new case matches your search.

Become a Member

One Moment Please

The filing “” is large (MB) and is being downloaded.

Please refresh this page in a few minutes to see if the filing has been downloaded. The filing will also be emailed to you when the download completes.

Your document is on its way!

If you do not receive the document in five minutes, contact support at support@docketalarm.com.

Sealed Document

We are unable to display this document, it may be under a court ordered seal.

If you have proper credentials to access the file, you may proceed directly to the court's system using your government issued username and password.


Access Government Site

We are redirecting you
to a mobile optimized page.





Document Unreadable or Corrupt

Refresh this Document
Go to the Docket

We are unable to display this document.

Refresh this Document
Go to the Docket