Abdominal Aortic Aneurysm:
`Overview of Stent-Graft Devices
`
`Frank J Criado, MD, FACS, Marcos F Barnatan, MD, RVT, Jane M Lingelbach, MD, James D Mills, MS,
`Brett E Richards, MS, William R Morgan, MS
`
`Intervention for abdominal aortic aneurysm (AAA)
`dates back centuries; amazingly, early approaches were
`endoluminal. In 1684, Moore attempted to induce
`thrombosis of an aneurysm by introducing large masses
`of intraluminal wire.1 Corradi modified this technique
`in 1879 by passing electrical current along the intralu-
`minal wires,1 and in 1915 Colt further developed en-
`doluminal approaches when he introduced a self-
`expanding wire umbrella into an aneurysm using a
`delivery system similar in many ways to the endovascular
`systems in current use.2 Blakemore and King3 revived
`these concepts in 1938 when they proposed electrother-
`mic coagulation of aortic aneurysms through intralumi-
`nal wiring, a technique that was used until graft replace-
`ment was introduced in 1953. The era of operative
`repair dawned early in the 20th century, beginning with
`aortic ligation, which was first performed successfully by
`Matas4 in 1923, and aortic wrapping, which was de-
`scribed by Rea5 in 1948. Resection and homograft re-
`placement was first performed by Dubost and col-
`leagues6
`in 1951. Endoaneurysmorrhaphy with
`intraluminal graft replacement, leaving the aneurysm
`sac in situ, was described by Creech7 in 1966, and this
`remains the standard for conventional operative repair
`today.
`With advances in preoperative evaluation and surgi-
`cal, anesthetic, and critical care management, elective
`repair of AAA with conventional surgical technique has
`become much safer. Well-trained vascular surgeons can
`treat a majority of AAA patients with an operative mor-
`tality of less than 5%.8 In addition, the risk of late com-
`plications and the need for longterm surveillance are
`relatively small. Nonetheless, the drive for less invasive
`
`Frank Criado, MD, FACS, is a consultant to, speaker for, and receives re-
`search funding from Cordis Endovascular, Warren, NJ, and from Medtronic
`AVE, Sunrise, FL. There are no competing interests for any other author.
`
`Received April 20, 2001; Revised August 8, 2001; Accepted August 31, 2001.
`From the Center for Vascular Intervention, Union Memorial Hospital/
`MedStar Health, Baltimore, MD.
`Correspondence address: Frank J Criado, MD, FACS, Center for Vascular
`Intervention, 3333 N Calvert St, Ste 570, Baltimore, MD 21218.
`
`procedures with quicker recuperation and less pain and
`the needs of medically unfit patients who are at high risk
`in major surgery have propelled the development of en-
`dovascular approaches to exclude AAA using catheter-
`based techniques.
`Balko and colleagues9 reported the first experimental
`use of a stent-graft combination for treatment of aneu-
`rysmal disease in 1986. In 1991, Parodi and colleagues10
`reported the first clinical application of transfemoral en-
`dovascular grafting to exclude AAA. During the last de-
`cade, numerous aortic endografts have been developed
`worldwide. Two of them (Ancure by Guidant, Menlo
`Park, CA, and AneuRx by Medtronic AVE, Sunrise, FL)
`received FDA approval in September 1999; several other
`aortic stent-grafts are now commercially available out-
`side of the USA or in clinical trials in this and other
`countries (Table 1).
`
`PATIENT AND DEVICE CONSIDERATIONS
`In any given case, suitability for endovascular stent-graft
`repair depends on device-specific issues and anatomy.
`Successful endovascular repair requires achievement of
`three objectives: transluminal access to the target site,
`secure endograft fixation, and creation of a hemostatic
`seal between graft and native vessel wall and between
`modular graft components. Patient-related consider-
`ations that affect the likelihood of achieving technical
`success are mostly anatomic in nature. These factors in-
`fluence choice of the most appropriate device for an
`individual patient, because endografts differ signifi-
`cantly in design and performance. Fixation is a case in
`point: it can be in an infrarenal or suprarenal location
`and may be provided by friction seal alone or by barbs or
`hooks.
`Aortic stent-grafts have three main components: the
`delivery system, the graft material, and the metal sup-
`port frame. The ideal delivery system should be flexible
`enough to maneuver through tortuous and angulated
`vessels but also rigid enough to resist kinking, low-
`
`© 2002 by the American College of Surgeons
`Published by Elsevier Science Inc.
`
`S88
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`ISSN 1072-7515/02/$21.00
`PII S1072-7515(01)01096-1
`
`MEDTRONIC 1017
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`Table 1. A List of the FDA-Approved and Investigational Endografts Currently Available in the USA
`Device
`Manufacturer
`Ancure
`Guidant, Menlo Park, CA
`AneuRx
`Medtronic AVE, Santa Rosa, CA
`Endologix
`Endologix Inc., Irvine, CA
`EXCLUDER
`WL Gore and Associates, Flagstaff, AZ
`Lifepath
`Edwards LifeSciences, Irvine, CA
`Quantum Lp
`Cordis Endovascular, Warren, NJ
`Talent
`Medtronic AVE, Sunrise, FL
`Vanguard
`Boston Scientific Corp, Natick, MA
`Zenith
`Cook Inc, Bloomington, IN
`
`Status
`FDA approved
`FDA approved
`Phase II trials
`Phase II trials (enrollment closed)
`Phase II trials (halted)
`Phase I trials
`Phase II trials (enrollment closed)
`Not in use
`Phase II trials
`
`profile (with potential to allow eventual percutaneous
`access), hemostatic, and “user-friendly.”
`The graft material should be strong and durable and
`yet reasonably thin and low profile. Available graft ma-
`terials are PTFE and Dacron/polyester (knitted or wo-
`ven). These are available in various thicknesses, balanc-
`ing strength and durability with the need for lower
`profile. The graft material may be connected to the
`metal skeleton with full- or partial-thickness sutures or
`staples, or they may be interwoven (inlaid). The design
`may be unibody or modular, with a straight tube, ta-
`pered aorto-uniiliac, or bifurcated configuration.11
`The metal frame provides column strength, fixation
`of the endograft to the vessel wall, compression/kink-
`resistance from external forces, and radiopacity to facil-
`itate fluoroscopic visualization at the time of implanta-
`tion. The support system may be an endoskeleton,
`exoskeleton, or a combination of the two; continuous or
`discontinuous; and self-expanding or balloon expand-
`able. Exceptionally, some endografts are unsupported
`(Ancure Endograft). Biocompatible metals in common
`use are stainless steel, Elgiloy (Elgiloy Limited Partner-
`ship, Elgin, IL), and nitinol. Nitinol is a nickel titanium
`alloy (55% Ni, 45% Ti) with the ability to return to a
`predetermined shape (shape memory), a long fatigue
`life, and corrosion resistance. Elgiloy is a nickel, cobalt,
`and chromium superalloy (40% Co, 20% Cr, 15% Ni,
`remainder Fe, Mn, Mo, C, and Be) that exhibits high
`strength and ductility, a long fatigue life, and corrosion
`resistance.
`
`THE DEVICES: CHARACTERISTICS AND
`CURRENT STATUS
`Ancure
`The Ancure Endograft12-15 (Guidant, Menlo Park, CA)
`(Fig. 1) is manufactured in two configurations: tube and
`
`bifurcated. Both are a single-piece, flexible, unsupported
`woven polyester graft prosthesis fixed in place at each
`end by hooks that are driven into the vessel wall on
`
`Figure 1. The Ancure device is a unibody polyester prosthesis with
`barbs at the proximal attachment site. (Reprinted with permission
`by Guidant Corp., Indianapolis, IN.)
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`balloon inflation. The tube graft is available with aortic
`diameters from 20 to 26mm (in 2-mm increments) with
`lengths from 9 to 16cm (in 1-cm increments). The bi-
`furcated endograft is manufactured in trunk/limb diam-
`eters (mm) of 20/10, 22/11, 24/12, and 26/13, with
`lengths from 12 to 19cm (in 1-cm increments). Delivery
`and deployment of this device is through a 23.5F deliv-
`ery catheter that is inserted through a 25F access
`sheath.12
`Clinical trial results of the Ancure Endograft system
`were reported to the FDA in 1999.13 In this trial, 268
`patients were treated with the bifurcated endograft and
`153 with the tube endograft; 111 control patients were
`treated with open surgical repair. Clinical utility of the
`tube endograft configuration is very limited, so the fol-
`lowing references to clinical data pertain to the bifur-
`cated endograft prosthesis only. Major complication
`rates, need for ICU stay, total length of stay, and opera-
`tive blood loss were significantly lower for patients
`treated with the Ancure Endograft system as compared
`to the control group. There was no significant difference
`in peroperative mortality or operative time between the
`two groups. The Ancure device did have a statistically
`significant higher
`incidence of graft
`thrombosis/
`occlusion as compared with the open surgical group.
`Twenty-six patients required intraoperative and two pa-
`tients required postoperative conversion to open repair.
`Endoleaks at the attachment site (type I) were reported
`in 5.0% of patients at discharge and in 2.3% of patients
`at 12-month followup. Branch flow endoleak (type II)
`rates were 35.6% at discharge and 26.6% at 12-month
`followup. There were no endograft permeability en-
`doleaks (type IV). Indeterminate sources of perigraft
`flow (type V or endotension) rates were noted as 7.8%
`and 2.3% during these time intervals. Aneurysm size
`decreased in 47.8% of patients at 12 months, increased
`in 2.2%, and showed no change in 50%. Graft migra-
`tion was reported in one patient.
`Guidant received FDA approval for the Ancure En-
`dograft system in 1999. In March 2001, Guidant sus-
`pended production and announced a recall of all existing
`inventory of the Ancure system, citing inconsistent re-
`porting of device malfunction and manufacturing
`changes to the FDA and problems associated with device
`deployment.14 In July 2001, Guidant received an inves-
`tigational device exemption from the FDA allowing re-
`sumption of clinical usage on a limited basis.15
`
`Figure 2. The AneuRx device is a modular device that relies on
`radial force and friction to maintain proximal fixation. (Reprinted with
`permission by Medtronic, Inc., Minneapolis, MN.)
`
`AneuRx
`The AneuRx16,17 stent-graft (Medtronic AVE, Santa
`Rosa, CA) (Fig. 2) is a modular, bifurcated stent-graft
`system. The grafts are composed of a fully supported
`nitinol exoskeleton with diamond-shaped stent rings.
`The thin-walled, noncrimped woven polyester fabric is
`attached to the exoskeleton by braided multifilament
`sutures. The modular system consists primarily of a
`main bifurcated segment and a contralateral iliac leg.
`The main bifurcated segment is available with aortic
`diameters from 20 to 28mm (in 2-mm increments) and
`iliac diameters of 12 to 16mm, with a length of 13.5cm
`on the contralateral side and 16.5cm on the primary
`access side. The contralateral iliac leg is available in di-
`ameters from 12 to 16mm and lengths of 8.5cm or
`11.5cm. Aortic and iliac cuff modular extensions are
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`also available. The aortic cuff is available in the same
`diameters as the main bifurcated segment and is 3.75cm
`in length. The iliac extension cuff is likewise available in
`the same diameters as the contralateral iliac leg and is
`5.5cm in length. The main bifurcated segment and the
`aortic extension are delivered through 21F catheters; the
`contralateral iliac leg and the iliac extension are delivered
`through 16F catheters.
`Phase II clinical trial results of the AneuRx stent-graft
`system were reported in 1999.16 In the trial, 250 patients
`at 12 study centers underwent either endovascular repair
`(n⫽190) or open surgical repair (n⫽60) for treatment
`of AAA. The device was implanted in 185 of the 190
`selected patients (97%), with four access failures and one
`patient who had a myocardial infarction on induction of
`anesthesia. There was no significant difference in the
`peroperative mortality rates, 1-year mortality rates, and
`primary procedural success rates between the two
`groups. Morbidity in the stent-graft group was signifi-
`cantly lower than in the open surgical group. Significant
`differences between the open surgery and stent-graft
`groups were found with regard to primary procedure
`results. Blood loss/transfusion requirements were signif-
`icantly less in the stent-graft group. The number of days
`spent in the ICU, days to ambulation, and days to reg-
`ular diet were all significantly less in the stent-graft
`group than in the open surgery group. Length of stay was
`6 days less for the stent-graft patients. The aneurysm
`exclusion rate at 30days was significantly greater in the
`open surgery group than in the stent-graft group. There
`was no statistical difference in graft patency at 6months.
`Contrast-enhanced CT revealed the presence of an
`endoleak in 39 stent-grafted patients. Ten patients had
`no identifiable source, and these were felt to represent
`transgraft flow (type IV endoleak); all of these had re-
`solved by one month. Twelve patients had lumbar
`artery/internal mammary artery flow (type II endoleak).
`Seven patients had endoleaks at the proximal aortic seal-
`ing point (type I endoleak). Ten patients had endoleaks
`from either the proximal or distal end of the contralat-
`eral iliac limb. Stent-graft migration was identified in
`three patients at 1-year followup, but all were of less than
`1cm.
`The AneuRx graft-stent system received FDA ap-
`proval in September 1999 for endovascular treatment of
`AAA. Complications related to migration, endoleaks,
`suture breaks, fabric tears, and improper placement have
`been reported since its approval. A retrospective study of
`
`Figure 3. The Endologix device uses PTFE as the fabric. The stent is
`internal to the fabric. (Reprinted with permission by Endologix Inc.,
`Irvine, CA.)
`
`the first 1,192 patients enrolled in the USA for AneuRx
`implantation revealed ten ruptured aneurysms. Most
`ruptures occurred in patients treated with an early, stiffer
`version of the stent-graft and were likely associated with
`poor fixation of the device.17
`
`Endologix
`The Endologix device18 (Endologix Inc., Irvine, CA)
`(Fig. 3) is a unibody, bifurcated, thin-wall PTFE en-
`dograft. The graft is available with proximal diameters of
`25mm and 28mm and limb diameter of 16mm; it is
`designed to address a great variety of dimensions with
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`suture holes; the graft is fully supported. There are seven
`pairs of proximal anchors to improve infrarenal fixation.
`The delivery system is flexible and has an external PTFE
`sleeve within which the endograft is contained. The
`trunk-ipsilateral component is introduced through an
`18F sheath; the contralateral
`limb requires a 12F
`sheath.19
`Phase I results have been reported.19 Twenty-seven
`patients were enrolled at three institutions with a mean
`followup of 11months. All attempted deployments were
`successful, and there were no intraoperative conversions.
`Endoleaks were documented in 39% of patients at dis-
`charge, 23% at 3months, 24% at 4months, and 16% at
`12months. Three proximal attachment site endoleaks
`were reported: two resolved, and one persists in a patient
`with a short angulated proximal neck who refused con-
`version. One distal attachment site endoleak was re-
`ported that persisted at 6months. Two other endoleaks
`of indeterminate source resolved without intervention;
`one of these was associated with increase in aneurysm sac
`size. No other aneurysm expansion was noted, and there
`were no aneurysm ruptures, limb occlusions, or device
`migrations. Other reported complications include two
`iliac artery dissections (which required no intervention)
`and one groin incision–associated lymph leak (which
`resolved). Four complications were related to percutane-
`ous access: one femoral arteriovenous fistula (which re-
`solved), one hematoma, one seroma requiring aspira-
`tion, and one lymphocele.
`The phase II multicenter trial has been conducted
`with complete enrollment. Submission to the FDA for
`premarket approval is anticipated in late 2001.19
`
`Lifepath
`The Lifepath endovascular graft20,21 (Edwards Life-
`Sciences, Irvine, CA) (Fig. 5) evolved from the White-Yu
`custom-made endograft,20 which has been in develop-
`ment since 1991. The first-generation device was an
`aortic tube graft, available in 19- to 27-mm diameters
`and 60- or 90-mm lengths. The second-generation de-
`vice is a bifurcated endograft. It is a modular, standard
`thickness (0.03mm), woven polyester graft that is in-
`tended to be a three-piece unit. The graft is available
`with proximal diameters of 21 to 27mm (in 2-mm in-
`crements), distal iliac diameters of 10 to 16mm (in
`2-mm increments), and iliac limb lengths of 43, 80, and
`110mm. The graft trunk is 9.2cm in length, with a
`5-cm proximal straight segment. Both configurations
`
`Figure 4. The EXCLUDER endoprosthesis is an expanded PTFE
`device with a nitinol stent. (Illustration courtesy of WL Gore &
`Associates, Inc. © WL Gore & Associates, Inc.)
`
`fewer device sizes. Proximal cuffs and iliac extensions are
`available. The self-expanding stainless steel endoskele-
`ton is made of a single wire that is fashioned without
`sutures. There is an infrarenal device and a design with
`2cm of open wire proximally for suprarenal fixation.
`The graft is contained within an outer sheath that is
`delivered through a 20 or 21F introducer; a 9F intro-
`ducer is required for contralateral limb deployment.18
`Phase I results have been reported with a 6-month
`followup.18 Nineteen patients were treated at two insti-
`tutions. There were no intraoperative conversions and
`no peroperative deaths. One patient had an endoleak
`requiring proximal cuff implantation. The Endologix
`device is commercially available in Europe. The phase II
`clinical study in the USA began in July 2000.18
`
`Excluder
`The EXCLUDER endoprosthesis19 (WL Gore and As-
`sociates, Flagstaff, AZ) (Fig. 4) is a modular, bifurcated
`endograft made of thin-wall ePTFE. A nitinol exoskel-
`eton is attached with fluoropolymer tape, leaving no
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`there was one intraoperative conversion because of graft
`displacement, and a second displaced graft was ad-
`dressed with placement of an aortic cuff. There was one
`endoleak after implantation of a tube graft, which had
`resolved at 3months.
`The Lifepath endovascular graft system is currently
`available in Europe. A multicenter, international, pro-
`spective, controlled, nonrandomized feasibility study
`has been completed. Clinical trials in the USA have been
`halted to allow for device modifications prompted by
`the finding of wireform fractures.
`
`Quantum Lp
`The Quantum Lp (Cordis Endovascular, Warren, NJ) is
`the first truly percutaneous device. It uses the new Cor-
`dis BRITE MAX Sheath Introducer, which measures
`13F inner diameter (14.5F outer diameter). The graft is
`a three-piece modular design that includes a proximal
`stent gasket made of a nitinol endoskeletal framework
`covered with an open lattice matrix of polyurethane
`foam that is intended to promote endothelialization
`through the foam matrix, stimulating tissue ingrowth
`and stabilizing the device. The stent gasket serves as a
`docking station for two independent aortoiliac stent-
`grafts. It is intended for infrarenal placement and is re-
`capturable and repositionable. The stent-grafts are com-
`posed of a nitinol endoskeleton attached with staples to
`the overlying graft. Modular extensions are available. So
`far, 19 patients have been treated in phase I clinical trials
`worldwide with the first-generation device. A second-
`generation device has been developed incorporating de-
`sign modifications in the gasket and endolimbs, with
`planned restart of clinical trials in the USA at the end of
`2001.
`
`Talent
`The Talent aortic stent-graft22 (Medtronic AVE, Sunrise,
`FL) (Fig. 6) has been implanted in nearly 20,000 pa-
`tients worldwide since December 1995. The first-
`generation device, for which phases I and II results are
`now available,22 has evolved into a newer-generation
`low-profile system (LPS). The Talent LPS differs from
`the first-generation device in that the thinner graft ma-
`terial used allows for a lower-profile delivery system (by
`2F sizes), with a redesigned delivery sheath. The Talent
`LPS is composed of a thin-walled (0.06mm) woven
`polyester graft, which is intended to be a two-piece mod-
`ular bifurcated device. The graft is available with top-
`
`Figure 5. The Lifepath device is currently undergoing early US clin-
`ical trials. (Reprinted with permission by Edwards LifeSciences,
`Irvine, CA.)
`
`are fully supported with discontinuous Elgiloy wire-
`forms integrated into the graft. The tube graft skeleton is
`balloon expandable; the bifurcated graft skeleton is com-
`posed of balloon-expandable wireforms in the iliac limbs
`and self-expanding wireforms in the iliac stumps and a
`combination of self-expanding and balloon-expandable
`wireforms in the proximal trunk of the main body. The
`delivery system includes a 19F introducer sheath (16F
`for the iliac limbs) with a hydrophilic flexible introducer
`tip and a passive, triple-valve hemostasis system. The
`balloon-mounted graft, contained within a loader, is
`pushed through the sheath for deployment.21
`Results have been published for a subset of 16 patients
`treated with 2 tube grafts and 14 bifurcated grafts.21
`Both tube grafts were successfully implanted and have
`required no reinterventions at 2-year followup. Twelve
`of 14 bifurcated grafts were implanted uneventfully;
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`among endovascular surgeons worldwide for AAA pa-
`tients with challenging anatomy and large-diameter
`proximal necks.
`To date, procedural and 30-day results have been re-
`ported for the phase II multicenter trials involving low-
`risk surgical candidates and high-risk nonsurgical candi-
`dates treated with the first-generation device.22 One-year
`results from the multicenter, nonrandomized, prospec-
`tive, controlled study of the second-generation LPS sys-
`tem have recently been compiled (Criado FJ, unpub-
`lished raw data, 2001). Two hundred forty-six patients
`were treated with the Talent LPS endograft; 123 concur-
`rent control patients were treated with conventional op-
`erative repair. Access was successful in 96% of patients,
`and endograft deployment was successful in 99% of
`those. Perioperative mortality was 0.8% in the study
`group; no patient in the control group died in the peri-
`operative period. Mortality at 1 year was 5.3% in the
`study group, versus 4.1% in the controls. There was no
`significant difference in mortality. Aneurysm exclusion
`as documented at implantation was 77%, but 59% of
`the documented endoleaks were type IV (transgraft).
`CT-proved endoleak was identified in 13% of patients at
`1month and in 12% at 6 and 12months.
`A recent development with the Talent AAA stent-
`graft has been the finding of wireform fractures and
`breaks in the connecting bar. So far, these failures have
`not had clinical consequences. Nonemergent Talent im-
`plants have been halted in the USA pending clarification
`of device failure issues. Submission of the Talent LPS
`phase II data (with 1-year clinical results) to the FDA is
`anticipated before the end of 2001.
`
`Vanguard
`The Vanguard stent-graft23,24 (Boston Scientific Corpo-
`ration, Natick, MA) evolved from the Miahle Stentor/
`Mintec device, which was the first commercially pro-
`duced modular design endograft. It has gone through
`various design modifications, with the most recent, Van-
`guard III, representing the last iteration. The device is no
`longer available or in production because of continuing
`concerns about device failure.23,24
`
`Zenith
`The Zenith AAA Endovascular Graft25,26 (Cook Inc.,
`Bloomington, IN) (Fig. 7) evolved from the custom-
`made Hartley/Lawrence-Brown Perth device used in
`Australia since 1994.25 It is a modular, bifurcated (or
`
`Figure 6. The Talent device is made from polyester fabric and
`nitinol wire rings. (Reprinted with permission by Medtronic, Inc.,
`Minneapolis, MN.)
`
`end diameters of 16 to 36mm (in 2-mm increments),
`iliac limb diameters of 8 to 20mm (in 2-mm incre-
`ments), aortic body lengths of 35 to 75mm, and iliac
`limb lengths of 5 to 20cm. Aortic cuffs and straight or
`tapered iliac extensions are available. A straight tube
`graft is also available in 8- to 46-mm diameters. There is
`a self-expanding inlaid nitinol endoskeleton in the main
`body of the device and a self-expanding exoskeleton in
`the iliac limbs and extensions, both composed of a series
`of discontinuous serpentine wireform springs attached
`to the graft with full-thickness sutures. There is also a
`longitudinal nitinol spine (connecting bar) to provide
`column strength. A 1.5-cm length of proximal bare
`spring allows fixation by friction seal in a transor supra-
`renal location. The device is preloaded within a delivery
`catheter, which is further loaded into an introducer
`sheath ranging from 20 to 24F for the main body and
`18F for the iliac limbs. The wide range of available di-
`mensions and customization possibilities offered by the
`manufacturer make the Talent stent-graft a favorite
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`of the graft (except at the points of proximal and distal
`fixation, where they are sutured to the inside of the
`graft). There is a 20-mm length of uncovered stent (with
`small barbs at the apices) at the top end for suprarenal
`fixation. The delivery system is an 18 or 20F introducer
`sheath for the main body and a 14 or 16F introducer for
`the iliac limbs.26
`(mean followup of
`Early and midterm results
`14months) for 528 patients treated with the Zenith en-
`dovascular graft in seven institutions worldwide have
`been published.26 Bifurcated grafts were used in 92% of
`the patients, aorto-uniiliac grafts in 5.5%, and tube
`grafts in 2%. Four procedures were converted intraop-
`eratively to open surgical intervention (three because of
`access vessel–related issues, one because of deployment
`mechanism failure). There were iliac access–related
`complications reported in 13.9% of procedures, techni-
`cal issues in 3.1%, vascular/arterial complications in
`1.0%, deployment system–related complications in
`1.0%, and intraoperative migration in 1.9%. Endoleaks
`were identified in 16.3% of patients on completion of
`the procedure; 5.5% of patients had endoleaks at 1-year
`followup, 1.7% of patients at 2-year followup, and 4%
`at a later, undefined followup interval. Late complica-
`tions reported include death in 48 of 528 patients (two
`because of aneurysm rupture), three aneurysm ruptures
`(two resulting in death, one successfully treated with
`endovascular intervention), eight graft migrations (all
`noted more than 2 years after implantation of early-
`design grafts without proximal barbs, prompting a
`change in device design), three late conversions (two for
`symptomatic endoleaks, one for symptoms in the setting
`of device migration), and five graft limb thromboses.
`The Zenith AAA stent-graft is commercially available
`in Europe and Australia. Phase II clinical trials in the
`USA are underway.26
`
`FUTURE DIRECTIONS
`Several other investigational devices exist for the treat-
`ment of AAA, including the Anaconda (Sulzer Vas-
`cutech Ltd., Inchinnan, UK) and the Stentford devices,
`for which very little, if any, information is available.
`Noteworthy are new developments in branched and fe-
`nestrated endograft technology27-30 by Inoue and col-
`leagues,27 Chuter and colleagues,28 Anderson and col-
`leagues,29 and others.
`
`Figure 7. The Zenith device is composed of stainless steel Z-stents
`and polyester fabric. A suprarenal bare stent with barbs provides proximal
`fixation. (Reprinted with permission by Cook Inc., Minneapolis, MN.)
`
`fixation graft of standard
`aorto-uniiliac) suprarenal
`thickness (0.15 mm), woven, noncrimped polyester.
`The bifurcated graft is intended to be a three-piece mod-
`ular unit. The graft is available with proximal neck di-
`ameters of 22 to 32mm (in 2-mm increments), a variety
`of main body device lengths ranging from 104 to
`162mm, and distal iliac limb diameters of 8 to 24mm,
`with a variety of iliac limb lengths ranging from 37 to
`122mm. The main body is designed with a longer aortic
`component to facilitate cannulation of the contralateral
`stump; this also moves the junction between the con-
`tralateral iliac limb and main body away from the largest
`component of the aneurysm sac, where most of the mor-
`phologic changes will occur over time, minimizing the
`potential for modular dislocations. The graft is fully sup-
`ported with a combined exoskeleton/endoskeleton
`made up of discontinuous, self-expanding, stainless
`steel, modified Gianturco Z-stents sutured to the outside
`
`

`

`S96
`
`Criado et al
`
`Abdominal Aortic Aneurysm
`
`J Am Coll Surg
`
`OVERVIEW AND CONCLUSIONS
`Although impressive results and amazing developments
`have been achieved in the “short” years since the initial
`publication of Parodi and colleagues,10 endograft tech-
`nology is still in its infancy. Current results, doubts, and
`concerns must be viewed within this context, keeping in
`mind the essentially preliminary and transitional nature
`of present-day devices. Much remains to be learned in
`the areas of durability and longterm integrity of stent-
`graft combinations. Refinements in design and im-
`proved materials are a certainty in the near future, prom-
`ising to optimize performance and minimize risks of
`failure. A lower profile is an important goal for this tech-
`nology, especially because of the promise of improved
`deliverability across disadvantaged iliac arteries in female
`patients and others with small or diseased vessels. The
`goals of longterm freedom from aneurysm rupture and
`device integrity must remain foremost if endovascular
`repair is to be competitive with standard surgical treat-
`ment for the majority of AAA patients. Together with
`device failures and questions about longterm results, en-
`doleaks (especially type II) and secondary failures from
`evolving morphologic changes after endoluminal exclu-
`sion constitute the most significant unresolved issues in
`the field of endograft technology. They emphasize the
`critical importance of appropriate case selection and the
`absolute need for lifelong surveillance of patients after
`endovascular repair of aortic aneurysms.
`
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