A brief history of abdominal
`aortic endografting
`
`Peter J. Bromley MD, FRCP(C)
`
`Endoluminal grafting is an
`exciting new technology that
`holds the promise of signifi-
`cantly reducing the morbidity
`and mortality associated with
`open repair of abdominal aor-
`tic aneurysms. From primitive
`beginnings with untested ideas
`and homemade prototypes,
`endografting has become a
`clinical reality. This article pro-
`vides an overview of the devel-
`opment of this technology up to
`the present time.
`
`T he placement of an endoluminal
`
`graft under radiological guid-
`ance is the latest advance in the
`treatment of aneurysmal disease of the
`abdominal aorta. Endografting repre-
`sents a logical extension of endoan-
`eurysmorrhaphy, which has been the
`accepted surgical therapy for abdomi-
`nal aortic aneurysms since the 1960s.1
`In this latter procedure, the aneurysm is
`exposed surgically and opened longitu-
`dinally after proximal and distal hemo-
`static control has been obtained by
`surgical clamps (figure 1A). A syn-
`thetic fabric tube is then sutured to
`nondilated segments proximally and
`distally from within the aneurysm, and
`the sac is closed over the prosthesis
`(figure 1B and C). By avoiding resec-
`tion of the aneurysm sac, aneurysm
`
`surgery was simplified significantly and
`the complication rate improved.1
`The technique of endografting
`strives to further this end by means of
`specially designed “endografts,”
`which can be introduced into the
`aneurysm lumen from a remote and
`minimally invasive access site (typi-
`cally the common femoral arteries).
`These devices are positioned and
`deployed with radiological guidance.
`Proximal and distal fixation are
`obtained in nonaneurysmal segments
`by sutureless endoluminal fixation
`devices. The aneurysm sac
`is
`excluded from the circulation by a
`procedure performed from small groin
`incisions with minimal blood loss, no
`exposure of the aneurysm, and no
`need for aortic cross clamping.
`Since
`the first
`radiologically
`guided, endoluminal repair of an
`abdominal aortic aneurysm in a
`human by Parodi and Palmaz2
`in
`1990, there has been an explosion of
`academic and commercial activity in
`this arena. Far more than arterial
`occlusive disease, endografting of
`aneurysmal disease has propelled the
`development of the new field of
`endovascular
`therapy. Continued
`advancement in this field is best
`served by cooperative efforts between
`those with the advanced training and
`expertise in the various radiological,
`
`endoluminal, and open surgical tech-
`niques necessary for procedural suc-
`cess and good patient outcome. This
`article will discuss the historical
`development of endografting and the
`clinical status of current technology
`and will also touch on endografting’s
`future directions.
`
`In the beginning there was wire
`As a remarkable testament to
`human
`ingenuity,
`endoluminal
`approaches to the treatment of aortic
`aneurysms can be found as far back as
`the mid-19th century. The English
`surgeon Moore, in an effort to stimu-
`late thrombosis, inserted 75 feet of
`fine iron wire into a thoracic aortic
`aneurysm in 1864. Unfortunately, the
`patient died from sepsis a few days
`later.3 Wire placement was first used
`to treat an aneurysm in the United
`States in 1866 by Ranoshoff.4 In 1879,
`the Italian physicians Buressi and
`Corradi3
`inserted wire
`into an
`aneurysm and attempted to induce
`coagulation with an electric current.
`In the first half of the 20th century
`Colt,5 in England, and Blakemore,6 in
`the United States, were proponents of
`the “wiring” method. These tech-
`niques, sometimes using up to 900
`feet of wire,3 produced mixed results
`and remained controversial. In cases
`of fusiform infrarenal aneurysms, the
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`A
`
`B
`
`C
`
`FIGURE 1. Endoaneurysmorrhaphy. (A) A longitudinal incision is made in the exposed aneurysm once hemostatic control has been obtained
`by noncrushing clamps. (B) The graft is sewn in place from within the aneurysm lumen. Back-bleeding from patent lumbar arteries is con-
`trolled by oversewing the origins of these vessels from within the aneurysm (not shown). (C) The graft in place. (Reproduced with permiss-
`sion from: Creech O: Endo-aneurysmorrhaphy and treatment of aortic aneurysm. Ann Surg 164(6):935-946, 1966.)
`
`intent appeared to be to “strengthen”
`the aneurysm while maintaining a
`flowing channel through the middle.3,4
`In fact, complete thrombosis was felt
`to be undesirable since it not infre-
`quently led to fatal gangrene of the
`lower
`extremities. Nonetheless,
`reports appeared sporadically until the
`1970s (figure 2).4
`It was not until Dubost reported on
`the successful resection and in-situ
`bypass of an abdominal aortic
`aneurysm in Paris, on March 19,
`1951, that the era of surgical cure of
`abdominal aortic aneurysms was truly
`born.7,8 The initial flurry of enthusiasm
`for this new procedure, however, was
`later tempered by the identification of
`serious late complications resulting
`from degeneration of the cadaveric
`human aortic allografts (homografts)
`used to perform the bypass.8 The
`1950s became a period of intense
`investigation to identify a suitable
`synthetic material that could be han-
`dled easily and cut to length in the
`operating room, sutured to a blood
`vessel, and trusted to withstand the
`stress of the circulation in the patient
`for many years. Many different mate-
`
`rials were investigated, including
`parachute silk, Vinyon-N, Orlon,
`Dacron, and Teflon, with the latter two
`ultimately proving to be quite suitable
`for arterial grafting.8,9 The availability
`of commercially produced synthetic
`grafts allowed surgical abdominal
`aortic aneurysm repair to become
`more widely applied but did nothing
`to reduce the severity of the surgery.
`The first step in this direction came in
`the form of an in-situ bypass without
`resection, attributed to Creech.1 His
`modification of the original endo-
`aneurysmorrhaphy, described by
`Matas in 1902, allowed the bypass
`graft to be placed within the aneurysm
`lumen and ended the need for lengthy
`and difficult
`resection of
`the
`aneurysm sac from the retroperi-
`toneum. This technique has been the
`standard since that time.
`From today’s perspective, it seems
`a logical next step in the progression
`of this therapy to introduce a graft into
`the lumen of the aneurysm from a
`remote access site without the need
`for exposing and opening
`the
`aneurysm. This moment arrived in
`September of 1990 when Parodi and
`
`FIGURE 2. The wiring technique. A lateral
`abdominal radiograph demonstrating the
`large mass of wire in an abdominal aortic
`aneurysm
`treated by
`this
`technique.
`(Reprinted with permission from: Hicks GL,
`Rob C: Abdominal aortic aneurysm wiring:
`An alternative method. Am J Surg 131:664-
`667, 1976.)
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`associates2 performed, in Argentina,
`the first successful transfemoral endo-
`luminal grafting of an abdominal aortic
`aneurysm in a human. The crude but
`innovative device used in this proce-
`dure was born of a melding of synthetic
`graft with catheter, stent, and imaging
`technology pioneered by interventional
`radiologists.
`In 1964, Dotter and Judkins intro-
`duced the concept of catheter-mediated
`minimally invasive therapy for arterial
`disease when they reported a new tech-
`nique for treating arterial stenoses with
`dilating catheters.10 Searching for a
`means to improve on the results of his
`new “transluminal catheter dilatation”
`procedure, Dotter conducted experi-
`ments using tubular endovascular pros-
`theses in the femoral arteries of dogs.
`Although all of the devices made of
`impervious plastic tubing resulted in
`thrombosis, he had encouraging results
`with coilspring prostheses made of
`stainless steel wire (figure 3), and intro-
`duced the concept of percutaneously
`placed endarterial tube grafts in 1969.11
`Little activity occurred in this area for
`nearly 15 years when both Dotter and
`colleagues12 in Oregon, and Cragg et al13
`in Minnesota, published simultaneous
`reports on nitinol-based coilspring
`grafts, again in a dog model. Nitinol is a
`special alloy of nickel and titanium that
`is highly kink-resistant and possesses
`the characteristic of thermal shape
`memory. Exploiting these properties,
`these investigators were able to pass
`nitinol wire through the lumen of a
`catheter and have the wire shift to a
`coiled-tube state in the arterial lumen by
`exposure to body temperature or by
`flushing the delivery catheter with
`heated saline (60° C). The ability to
`pass the device as a straightened form
`(in the catheter lumen) and have it
`revert to a coiled tube of predetermined
`diameter (in the arterial lumen) meant
`that the diameter of the artery treated
`was no longer restricted by the size of
`the introducer catheter, as was the case
`in 1969.
`
`FIGURE 3. Endarterial tube grafts. Dotter’s
`original stainless steel coilspring endopros-
`thesis. (Image courtesy of the Archives of the
`Dotter Interventional Institute, Portland, OR.)
`
`The following year, Maass and
`coworkers14 in Switzerland reported on a
`series of experiments they had begun in
`the early 1980s using a similar spiral-
`spring vascular endoprosthesis made of
`stainless steel. These devices became
`known as stents in a somewhat abstruse
`reference to Charles Stent, an English
`dentist who in the 19th century devised a
`splint to stabilize skin grafts.15 Numerous
`publications followed throughout the
`1980s as a variety of self-expanding and
`balloon-expanded metal endoluminal
`prostheses were developed and utilized
`in the treatment of arterial occlusive dis-
`ease. In 1984, percutaneously introduced
`coiled wire experienced a brief reincar-
`nation as a potential therapy for abdomi-
`nal aortic aneurysms. That year, Cragg
`and associates16 published further work
`on their nitinol coil grafts. In an article
`entitled, “Percutaneous Arterial Graft-
`ing,” they reported the first percutaneous
`treatment of an experimental abdominal
`aortic aneurysm with a stent composed
`of a tightly wound tubular coil of nitinol
`(figure 4).16 It was not long before wire
`and fabric were united and the stent-graft
`was born.
`
`The stent-graft concept
`Who was truly the first to conceptu-
`alize a stent-graft for the treatment of
`an aneurysm may never be known. The
`archives of the U.S. Patent Office con-
`
`FIGURE 4. Nitinol coil graft. A 1.0 x 2.5-
`cm nitinol coil graft as used by Cragg et
`al.16 The short, thick segment at the bot-
`tom of the figure accepted the end of a
`threaded guidewire used to facilitate
`introduction and positioning. (Reprinted
`with permission from: Cragg AH, Lund
`G, Rysavy JA, et al: Percutaneous Arte-
`rial Grafting. Radiology 150:45-49,
`1984.)
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`guidewire was not mentioned. At the
`proximal and distal ends, “convoluted
`expansion rings” containing a “plural-
`ity of radially spaced anchoring pins”
`provided a means for attachment.
`Choudhury felt that “once in place,
`hemodynamic pressure [would] assure
`a continued fluid tight seal between the
`graft and the healthy vessel wall.”
`Juan Parodi, meanwhile, was a resi-
`dent in vascular surgery at the Cleve-
`land Clinic under Alfred Humpheries
`and Edwin Beven. In a retrospective
`article published in 1997, Parodi recal-
`led fondly “the expression on Ed
`Beven’s face when I told him that I fore-
`saw a day when patients with aneu-
`rysms could be treated under local
`anaesthesia in the outpatient depart-
`ment.”18 Parodi apparently conducted
`some experiments in 1979 on a tubular
`polyester device with expandable stain-
`less steel wire rings at the ends, using
`dogs, but abandoned the project because
`of disappointing initial results.18
`In 1986, Balko and associates19 of
`New York were apparently first to
`describe in a scientific paper a device
`having the characteristics of a stent-
`graft for the treatment of an abdominal
`aortic aneurysm. These investigators
`created artificial aneurysms in the
`abdominal aortas of sheep using large
`Dacron patches and then several weeks
`later inserted their prostheses. These
`were composed of a constrainable wire
`metal framework (resembling Gianturco
`Z-stents) with a polyurethane coating.
`Cessation of sac pulsation and absence
`of bleeding when the aneurysm wall
`was lacerated purposefully deter-
`mined successful acute exclusion of
`the aneurysm. Long-term follow-up
`was not obtained. The devices were
`inserted from femoral artery cutdowns,
`but the lack of fluoroscopic equipment
`necessitated they be positioned by
`direct palpation of the aneurysm neck
`during laparotomy. In their discussion,
`the authors mentioned the potential for
`collaboration between angiographers
`and vascular surgeons in the possible
`
`FIGURE 5. Method for performing aneurysm repair. These illustrations are from Choud-
`hury’s patent, which appears to be the first record of an attempt to create a device and
`method for transfemoral endoluminal repair of an abdominal aortic aneurysm.17
`
`tain a document entitled, “Method For
`Performing Aneurysm Repair” that
`describes a device created by M.
`Hasan Choudhury, which was filed in
`1977 and patented in 1979 (figure 5).17
`Choudhury’s device was to be com-
`posed of a single tube of surgical graft
`material, such as Dacron. It would be
`introduced into the body in a collapsed
`
`form on a catheter placed via a periph-
`eral artery, such as the common
`femoral artery, and maneuvered into
`position to span the normal arterial
`segments proximal and distal to the
`aneurysm. This would be performed
`under fluoroscopic guidance. The
`catheter would contain channels to
`inject
`radiographic contrast. A
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`FIGURE 6. Dacron-covered
`Z-Stents. Gianturco’s group
`devised a multisegmented
`metal stent with a Dacron
`graft cover, which they used
`in experimental animals.
`(Reprinted with permission
`from: Lawrence DD, Charn-
`sangavej C, Wright KC, et
`al: Percutaneous endovas-
`cular graft: Experimental
`evaluation. Radiology 163:3
`57-360, 1987.)
`
`clinical application of such technology.
`Ultimately, radiologically guided aortic
`stent-graft placements were reported in
`experimental animals with very encour-
`aging results on long-term follow-up.20-
`22 At about the same time, Palmaz was
`reporting the results of his newly
`designed balloon-expandable stent. Par-
`odi met Palmaz in 1988 and immedi-
`ately realized that this stent was the
`component he needed to achieve
`anchoring and sealing of an endolumi-
`nal graft.18 Their collaboration resulted
`in a series of 62 canine experiments in
`Buenos Aires and culminated in the
`implantation of a device in a patient on
`September 7, 1990.2,18 In another paral-
`lel development, Harrison Lazarus, a
`vascular surgeon from Utah, had begun
`working on an endograft for abdominal
`aortic aneurysms during the mid-
`1980s.23 His early concept would ulti-
`mately evolve into a Food and Drug
`Administration (FDA)-approved device
`(discussed in the following sections).
`
`Device design
`Early devices were constructed
`from a piece of straight surgical tube
`graft, like Dacron, and modified by the
`
`addition of some form of endovascular
`attachment system. Lazarus experi-
`mented with and patented a device
`having an attachment system com-
`posed only of staples, at the proximal
`end, that would be driven into the ves-
`sel wall at the attachment site by a bal-
`loon device built into the delivery
`system.24 Stent technology was pro-
`gressing rapidly during this period,
`however, and soon all devices incorpo-
`rated some form of stent into the
`attachment sites. Lazarus’s attachment
`device evolved into a self-expanding
`metal system similar in design to
`Gianturco Z-stents but with large
`anchors derived from the initial staple
`system. Parodi’s group initially con-
`structed devices with large balloon
`expandable stents for proximal attach-
`ment. The surgical approach was to
`modify the graft so that it could be
`attached from within the vessel. Inter-
`estingly, neither of these prototypes
`had a distal attachment mechanism. In
`fact, the first three patients in the clini-
`cal series that Parodi reported on in
`1991 lacked any form of distal attach-
`ment device.2 Meanwhile Gianturco’s
`group was building Z-stent devices
`
`long enough to span the infrarenal
`aorta and then covering the stents with
`graft material (figure 6).20-22 These
`stents came with or without wire barbs.
`Three separate design dichotomies
`were apparent from the outset and have
`persisted into current devices. One
`involves the method of obtaining
`device attachment within the vessel—
`radial force producing friction versus
`positive attachment with hooks or
`barbs. Another is the issue of structural
`support over the length of the graft
`material with stents. Finally there is
`the issue of utilizing stents that are
`self-expanding or balloon-expanded.
`The superiority of one approach over
`the other has not yet been resolved.
`Furthermore, it quickly became appar-
`ent during the initial clinical applica-
`tion of this technology that few
`patients could be treated successfully
`with a straight tubular graft.
`
`New devices, new challenges
`By 1995, Parodi25 was reporting on
`a series of 50 patients in whom he had
`performed endograft procedures and
`was being referred to as the father of
`transfemoral abdominal aortic endo-
`grafting.26 In Sydney, Australia, White
`et al27 were accumulating a similar
`quantity of patients. By February of
`1993, the EVT device (Endovascular
`Therapeutics, Inc., Menlo Park, CA),
`derived from Lazarus’s work, had
`already entered Phase I FDA clinical
`trials in the United States, and Moore26
`from UCLA was reporting on the first
`10 patients in 1994. Although Parodi
`was able to implant a significant num-
`ber of straight tubular devices in
`Argentina, the experience in the
`United States indicated that <15% of
`patients with
`abdominal
`aortic
`aneurysms would be suitable for such
`grafts.26,28 Parodi’s approach to patients
`without a suitable distal neck was to
`extend a tapered aortomonoiliac device
`into one iliac, embolize the contralat-
`eral side, and perform a femoral-to-
`femoral bypass.25 The Sydney team
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`II
`
`Table 1. Endoleak
`classification
`Type Description
`I
`Inadequate seal at the
`proximal or distal attach-
`ment sites
`Sac perfusion via patent
`branch vessels such as
`the inferior mesenteric
`artery and/or lumbar
`arteries
`Leaks from component
`junctions, component
`disconnections or fabric
`tears
`Fabric porosity
`
`III
`
`IV
`
`also utilized this technique.29 The impe-
`tus for a completely endovascular solu-
`tion was strong, however, and as early
`as 1993, Chuter30 had constructed a
`bifurcated device and delivery system
`and used it successfully in dogs. He
`then made the first report of successful
`use of his device in a human in Febru-
`ary 1994.31 This was followed, in Sep-
`tember, by a report of 5 patients
`successfully treated at the University
`Hospital in Nottingham, United King-
`dom, using Chuter’s bifurcated
`device.32 The Sydney group published
`the preliminary results of their bifur-
`cated device in 1994 as well,27 and EVT
`introduced a bifurcated device late that
`same year.23 Interestingly, the 5 patients
`in the Nottingham series represented
`only 17% of the 29 consecutive patients
`screened for possible treatment.32
`As experience was gained, a problem
`list of challenges to be overcome in the
`development of new devices was devel-
`oping. For all devices, the femoral and
`iliac arteries represented potential obsta-
`cles to the introduction of the bulky
`delivery systems either from atheroscle-
`rotic stenoses or from severe tortuosity.
`The latter could sometimes be overcome
`by stiff guidewires or by surgical traction
`on the arteries. Angioplasty of focal ath-
`erosclerotic lesions could be performed,
`but was of little help in diffuse disease or
`in patients with intrinsically small arter-
`ies (often the case in women). Parodi25
`developed the approach of anastomos-
`ing a graft to the iliac arteries above the
`restrictive segment to provide a conduit
`for device delivery, but this approach is
`somewhat contrary to the minimally
`invasive theme of the endovascular para-
`digm. In 1994, the sheath used to intro-
`duce the EVT device was 28F and the
`Sydney device was 24F. The devices
`themselves needed to become smaller
`and more flexible.
`According to the Sydney group, in
`general, patients requiring bifurcated
`grafts seemed to have larger and more
`complex aneurysms than those suitable
`for straight-tube grafts.27 Early in their
`
`experience, they deployed both limbs
`of a bifurcated device into the ipsilat-
`eral iliac artery on two separate occa-
`sions, necessitating conversion to open
`procedures in both patients.27 Although
`the details behind the “technical errors”
`are not discussed in their report, these
`mishaps highlight the need for accurate
`measurements of parameters never
`before considered in open surgery. Cus-
`tom fitting of devices to individual
`patients required detailed preoperative
`analysis of computed tomography (CT)
`and angiographic data. Devices made
`too short would need to be rescued by
`open surgery or modular extension
`components, and devices made too
`long could result in confinement of the
`contralateral graft limb (as described
`above) or could cover and occlude
`internal iliac arteries.
`Continued perfusion or late “reperfu-
`sion” of the aneurysm sac were also rec-
`ognized quickly and
`led
`to
`the
`characterization of a new entity, the
`endoleak. This is defined as the persis-
`tence of blood flow outside the lumen of
`the endoluminal graft but within the
`aneurysm sac.33 A variety of endoleaks
`can develop and have been classified by
`a fairly uniformly accepted scheme
`(Table 1). However, continued expan-
`sion of aneurysmal sacs after endograft-
`ing in the absence of identifiable
`endoleaks has led to the development of
`an additional concept, endotension.34,35
`Whether this is a separate notion or an
`additional form of endoleak has led to
`some controversy over its definition and
`the endoleak classification system.34,35
`Although most authorities seem to agree
`that Type I and Type III endoleaks
`should be addressed by further endovas-
`cular procedures or conversion to open
`surgery, the question of what to do with
`branch perfusion
`leaks (Type II
`endoleaks) remains controversial.34-36
`The identification of hemodynamic
`pressures in these reperfusion circuits,
`comparable to those in the systemic cir-
`culation, has raised the level of concern,
`particularly among radiologists.
`
`By early 1995, investigators began
`reporting the first instances of device
`deterioration. Hook fractures, and
`later frame breaks, were identified in
`follow-up of the EVT device resulting
`in a halt to enrollment in the FDA
`trial.23 The attachment system and
`hook configuration were redesigned,
`and the second generation of EVT
`grafts was subsequently introduced at
`the end of 1995.23 No new fractures
`have been reported since the design
`change, but other devices have devel-
`oped similar metal fatigue problems,
`as well as disintegration of sutures and
`fabric erosions.37 Device migrations
`have developed particularly in short
`angulated necks as well as late discon-
`nections of modular components.37,38
`Two cases have been described in
`which patient positioning during sub-
`sequent (and unrelated) surgical pro-
`cedures may have contributed to
`separation of modular components.39
`Furthermore, longitudinal shrinkage
`of the aneurysm after successful
`exclusion may contribute to detrimen-
`tal structural distortion of the grafts.38
`Along a similar line, studies have
`demonstrated continued dilation of
`the infrarenal neck in some patients
`following endograft placement, rais-
`ing the concern that Type I endoleaks
`could develop, possibly years after a
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`A
`
`C
`
`B
`
`D
`
`FIGURE 7. The endovascular team approach.
`(A) A team of interventional radiologists and
`vascular surgeons, in conjunction with surgical
`and radiological support staff, performs an
`abdominal aortic endograft procedure in the
`operating room at the Oregon Health Sciences
`University in Portland. (B) At the affiliated
`Veteran’s Administration Hospital, the OR-
`compatible angiographic suite is depicted just
`prior to an endograft procedure. (C) A preoper-
`ative digital subtraction angiogram (DSA) doc-
`umenting an infrarenal abdominal aortic
`aneurysm suitable for endografting in a 55-
`year-old man. (D) DSA, following placement of
`a Zenith endograft (Cook Inc., Bloomington,
`IN) in the same patient as (C).
`
`graft has been implanted.40 Evidence
`has also appeared that little tissue
`incorporation occurs at the attachment
`site with these devices in humans,
`despite evidence to the contrary in
`experimental animals.41 Device migra-
`tions and dilating necks have fostered
`the use of positive fixation devices and
`suprarenal fixation elements in newer
`generation devices. Their value, how-
`ever, remains theoretical until long-
`term follow-up data on their use
`becomes available. So it appears that,
`in the foreseeable future, patients
`implanted with abdominal aortic
`endografts will be subjected to a life-
`time of close surveillance.
`Another unique set of challenges
`that has arisen out of this evolving
`
`field includes the questions of who
`should perform these procedures and
`where they should be performed.
`Since the size of the delivery system
`required to implant an aortic endo-
`graft necessitates surgical exposure at
`the access site, surgical skills have
`been obligatory from the onset and
`remain so. The potential for com-
`pletely percutaneous systems, how-
`ever, is on the horizon (see below) and
`will no doubt significantly alter the
`playing field in the future. Although
`some vascular surgeons choose to
`ignore the unique skills and experi-
`ence of their colleagues in interven-
`tional radiology and set out to
`rediscover basic catheter and wire
`techniques on their own,42 this cannot
`
`be of any benefit to the patient or the
`field of endovascular therapy.43,44 An
`interventional radiologist would not
`be surprised to hear that surgeons
`implanting the large and stiff early
`EVT device in a tortuous aneurysm
`without an over-the-wire technique
`deployed a device into the thrombus
`necessitating open repair.45 Collabora-
`tive teams of experts in vascular sur-
`gical and endoluminal techniques,
`such as the archetypal Miami Vascu-
`lar Institute, are to be applauded. This
`cooperative approach has also been
`fostered at the Dotter Interventional
`Institute where we evaluate endograft
`candidates and perform endograft
`procedures in conjunction with the
`vascular surgeons (figure 7).
`
`July 2001
`
`SUPPLEMENT TO APPLIED RADIOLOGY I 11
`
`Page 7
`
`IPR2014-00100 Pat. Owner Ex. 2015
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`
`

`
`Current devices
`Nearly 50 years ago, pioneers of aortic
`synthetic graft surgery employed a seam-
`stress to construct a suitable fabric tube for a
`patient after the abdomen had been opened
`and measurements obtained in the operating
`room.9 The graft was then autoclaved and
`sewn into place. Similarly, the first stent-
`grafts were handmade for each patient out of
`available materials, although modern cross-
`sectional imaging techniques obviated the
`need to open the patient’s abdomen. As was
`the case with synthetic grafts, it was not long
`before dedicated endografts for the repair of
`abdominal aortic aneurysms were being
`manufactured commercially. In the United
`States, the marketing of these devices is sub-
`ject to regulations enforced by the FDA.
`Endografts are included in the regulations
`for Class III devices and are subject to a pre-
`market approval system that requires clinical
`testing to establish safety and efficacy prior
`to marketing. Two bifurcated devices have
`completed this process and are marketed in
`the United States for the treatment of abdom-
`inal aortic aneurysms. These are the Ancure
`endografting system (previously the EVT
`graft; Guidant Cardiac and Medical Divi-
`sion, Menlo Park, CA) and the Aneurx stent-
`graft (Medtronic Inc., Minneapolis, MN).
`Both of these devices received FDA
`approval in September 1999. There are at
`least nine other devices currently in various
`stages of premarket development. Table 2
`summarizes many of the features of these
`devices.
`Despite that fact that both contain self-
`expanding stent components, the Ancure
`(figure 8) and Aneurx (figure 9) devices are
`products of very different design philoso-
`phies. The unibody design of Ancure mimics
`that of a standard surgical graft, while the
`Aneurx design is modular. The modular
`design permits greater versatility in match-
`ing a patient’s anatomy, as the device is con-
`structed inside the patient, but the junctions
`between individual parts provide potential
`places for early and late graft failures (see
`the discussion of endoleaks above). The
`stent skeleton provides support against com-
`pression over the entire length of the Aneurx
`device but reduces its mechanical flexibility.
`
`Table 2. Commercial endografts currently under development
`
`Introducer
`Size (F)
`
`Concept
`
`Body
`
`Limbs
`
`Method of
`Fixation
`
`Suprarenal
`Fixation
`
`N/A
`Fully supported
`Fully supported
`Fully supported
`
`Fully supported
`Fully supported
`Fully supported
`Fully supported
`
`Friction
`Friction
`Proximal barbs
`Barbs
`
`No
`Available
`Potential‡
`Only
`
`Nitinol
`Nitinol
`Nitinol
`Stainless steel
`
`Polyester
`Polyester/PTFE
`Polyester
`Polyester
`
`*Company names and locations for each product: Ancure, Guidant Inc., Guidant Cardiac and Medical Division, Menlo Park, CA; Aneurx, Medtronic Inc., Minneapolis, MN; Anaconda, Sulzer-Vascutek, Renfrew-
`shire, Scotland; Ariba, Teramed, Inc., Maple Grove, MN; Excluder, W.L. Gore and Assoc., Flagstaff, AZ; PowerLink System, Endologix Inc., Irvine, CA; LifePath AAA, Baxter/Edwards Lifesciencess LLC, Irvine,
`CA; Quantum LP, Cordis Corp./Johnson & Johnson, Warren, NJ; Talent, Medtronic World Medical, Sunrise, FL; Vanguard III, Boston Scientific, Boston, MA; Zenith, Cook Inc., Bloomington, IN.
`†Although the Ancure graft remains FDA approved, Guidant has initiated a voluntary halt to production of the device as of March 16, 2001 while issues regarding the delivery system and communications with
`the FDA are addressed.
`‡Bare stents are present at the proximal fixation site, although they are not specifically intended for suprarenal fixation at this time.
`ePTFE = expanded polytetrafluoroethylene; PTFE = polytetrafluoroethylene; GAD= graft attachment device.
`
`Trade Name*
`
`Ancure
`Aneurx
`Anaconda
`Ariba
`
`FDA Status
`as of April 2001
`
`Approved†
`Approved
`European trials only
`Completed Phase I
`in March 2001
`
`Excluder
`PowerLink System Phase II trials ongoing
`Lifepath AAA
`
`Completed Phase II
`
`Phase II halted
`in April 2000 (see text)
`
`Quantum LP
`Talent
`Vanguard III
`Zenith
`
`Phase I ongoing
`Completed Phase II
`European trials only
`Completed Phase II
`
`24
`21
`18
`20
`
`18
`21
`20
`
`13
`24
`21
`20
`
`Unibody
`Modular
`Modular
`Modular
`
`Modular
`Unibody
`Modular
`
`Modular
`Modular
`Modular
`Modular
`
`Unsupported
`Fully supported
`Partially supported
`Fully supported
`
`Unsupported
`Fully supported
`Fully supported
`Fully supported
`
`Fully supported
`Fully supported
`Fully supported
`
`Fully supported
`Fully supported
`Fully supported
`
`Hooks
`Friction
`Friction
`Barbs
`
`Anchors
`Friction
`GAD
`
`No
`No
`Yes
`Yes
`
`Metal
`
`Elgiloy
`Nitinol
`Nitinol
`Nitinol
`
`Fabric
`
`Polyester
`Polyester
`Polyester
`Polyester
`
`No
`Available
`No
`
`Nitinol
`Stainless steel
`Elgiloy
`
`Ultrathin ePTFE
`PTFE
`Polyester
`
`12 I SUPPLEMENT TO APPLIED RADIOLOGY
`
`July 2001
`
`Page 8
`
`IPR2014-00100 Pat. Owner Ex. 2015
`Medtronic v. Marital Deduction Trust
`
`

`
`FIGURE 8. The Ancure device (Guidant Car-
`diac and Medical Division, Menlo Park, CA).
`
`FIGURE 9. The Aneurx stent-graft
`(Medtronic Inc., Minneapolis, MN).
`
`FIGURE 10. The PowerLink System
`(Endologix Inc., Irvine, CA).
`
`Conversely, although the Ancure
`device boasts greater flexibility, par-
`ticularly in angulated necks, the
`unsupported iliac limbs have been
`subject to a greater number of throm-
`boses. This has been
`improved
`through the liberal use of Wallstents
`(Boston Scientific, Boston, MA) by
`many interventionalists.2 Finally, the
`self-expanding stents at the ends of
`the Ancure device provide a means to
`initiate deployment of the anchoring
`pins, but otherwise do little to hold the
`
`device in place. Once the graft is
`released from the delivery catheter
`and the pins have contacted the wall,
`they are driven into place by the oper-
`ator with a balloon. The pins provide
`the primary means of securing the
`graft. In contrast, the Aneurx device
`relies entirely on the force of friction
`between