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Texas Heart Institute Journal Latest Advances in Endoluminal AAA Repair 19

© 2010 by the Texas Heart ® Institute, Houston

Endoluminal Abdominal Aortic Aneurysm RepairThe Latest Advances in Prevention of Distal Endograft Migration and Type 1 EndoleakEndovascular abdominal aortic aneurysm repair (EVAR) is an attractive alternative to open surgical repair. Distal endograft migration and type 1 endoleak are recognized to be the 2 main complications of EVAR. First-generation endografts had a stronger propensity for dis-tal migration, modular component separation, thrombosis, and loss of structural integrity. Substantial progress has been made in recent years with 2nd- and 3rd-generation devices to prevent these complications. Some of the most common predictors of endograft fail-ure are angulated and short infrarenal necks, large-diameter necks, and thrombus in the aneurysmal sac. The purpose of this study is to describe and review our experience in using innovative techniques and a newer generation of endografts to prevent distal migra-tion and type 1 endoleak in patients with challenging infrarenal neck anatomy. The use of these innovative EVAR techniques and the new generation of endografts in patients with challenging infrarenal neck anatomy has yielded encouraging procedural and intermediate-term results. (Tex Heart Inst J 2010;37(1):19-24)

S ince Parodi and coworkers performed the 1st endovascular abdominal aor-tic aneurysm repair (EVAR) in 1990,1 substantial progress has been made in treating patients with abdominal aortic aneurysms (AAA). Although feasible

in the great majority of patients, EVAR can have a high incidence of postprocedural complications in patients who have challenging infrarenal aortic neck anatomy. Some of the more common sequelae include endoleaks, separation of modular components, aneurysm enlargement, stent or hook fractures, and distal migration of the endograft.2 One major concern is the potential for migration: the incidence has ranged from 9% to 45%.3,4 Type 1 endoleak is also one of the dreaded sequelae of EVAR, because there is a potential for aneurysm rupture.

Factors that Influence Endograft Migration and Type 1 EndoleakDistal migration of the endograft is one of the main recognized complications of EVAR. Migration of the stent-graft is defined as device movement of greater than 10 mm or movement of less than or equal to 10 mm when this last results in secondary interventions, as set forth by the Society for Vascular Surgery and the American Asso-ciation for Vascular Surgery in their reporting standards for endovascular aortic an-eurysm repair.5 Migration is generally believed to be a late-occurring event. Type 1(a or b) endoleak is a persistent perigraft channel of blood flow that is caused by an in-adequate seal at either the proximal (a) or the distal (b) end of the stent-graft. Type 1a endoleak is closely associated with stent-graft migration, and these conditions are com-monly seen in the same patient. Endograft migration and type 1 endoleak are major problems after EVAR that significantly increase the incidence of rupture of abdomi-nal aneurysm and the need for conventional surgical repair. The many factors that affect the success and failure of EVAR are strongly influenced by preprocedural planning, the experience of the operator, the technique employed, and the type and the generation of the endograft. The EUROSTAR Registry collabora-tors have reported that some of the most common predictors of endograft failure—

Review

Maaz Ghouri, MD, MRCSZvonimir Krajcer, MD, FACC

Key words: Aneurysm, dis-secting; aorta, abdominal; aortic aneurysm; aortic diseases; blood vessel prosthesis implantation; foreign-body migration; prosthesis design; stents

This paper is an expansion of an earlier article by the same authors: Krajcer Z, Ghouri M. Advances in dis-tal migration of endografts: innovative techniques to prevent endograft migra-tion and type I endoleak. Endovascular Today 2009; Jan: 61-4.

From: Departments of Cardiovascular Surgery (Dr. Ghouri) and Cardiology (Dr. Krajcer), Texas Heart Institute at St. Luke’s Epis-copal Hospital, Houston, Texas 77030

Address for reprints: Zvonimir Krajcer, MD, 6624 Fannin St., Suite 2780, Houston, TX 77030

E-mail: [email protected]

Dr. Krajcer is a consultant for W.L. Gore & Associates, Inc., and for Endologix, Inc. He is also on the speakers’ bureau for W.L. Gore & Associates, Inc., and for Endologix, Inc., and is a clinical investigator for Aptus Endosys-tems, Inc., and for the Lombard EndoRefix and Aorfix trials. Dr. Ghouri has no financial interest in any product or manufacturer mentioned herein.

Volume 37, Number 1, 201020 Latest Advances in Endoluminal AAA Repair

resulting in type 1 endoleak and stent migration—are angulated and short infrarenal necks, large neck diam-eter, large maximal AAA diameter, neck thrombus, and complex iliac artery anatomy.2,3,6,7 The presence of extensive thrombus or excessive calcium deposition at the arterial implantation sites, specifically at the prox-imal aortic neck or the common iliac artery interface, can prevent satisfactory anchoring of the stent-graft and thereby increase the chance of migration and type 1 endoleak. Calcium or thrombus, or both, can compromise the fixation and sealing of the endograft at the implantation sites. Postprocedural causes for the migration of stent-grafts and for type 1 endoleak include aortic neck dilation, morphologic changes of the aneurysmal sac enclosing the endograft (most notably longitudinal shrinkage), endograft shortening, and stent-graft displacement sec-ondary to proximal external compression.7,8 In addition to these postprocedural factors, the dimensions of the aneurysmal sac at the time of the procedure play an im-portant role in endograft migration. The accepted cri-terion for secure endograft fixation is an infrarenal neck length of greater than 15 mm; but this has been chal-lenged recently, and a minimum neck length of 10 mm has been stipulated as sufficient to produce good seal-ing of the stent-graft.9,10

Similarly, an increased incidence of stent-graft migra-tion has been associated with severe infrarenal neck an-gulation ( 60° angle between the infrarenal aortic neck and the longitudinal axis of the aneurysm). Such se-vere neck angulation increases the incidence of type 1 endo leak by facilitating small leaks through the gaps between the stent and the neck. According to a bench-test study,11 stiffness of the stent also contributes sub-stantially to stent migration in such patients.

Innovative Techniques to Prevent Distal Migration of the EndograftCurrently, 5 endovascular stent-grafts are approved for clinical use in the United States. They include Zenith® (Cook Medical Inc.; Bloomington, Ind), AneuRx® AAAdvantage (Medtronic, Inc.; Minneapolis, Minn), Gore EXCLUDER® AAA Endoprosthesis (W.L. Gore & Associates, Inc.; Flagstaff, Ariz), Powerlink® (Endologix, Inc.; Irvine, Calif ) and Talent (Medtronic). In order to treat patients who have tortuous infrarenal neck anat-omy, several manufacturers have modified their original designs to make the endograft more f lexible. Some of the newer-generation endografts—the Zenith (Fig. 1), the EXCLUDER (Fig. 2), and the Aorf ix (Lombard Medical Technologies; Newton, Mass)—also offer ac-tive f ixation to the aortic wall with the use of barbs, clips, or hooks that are an integral part of the device. Because the anatomic causes of stent migration can-not be changed, success in preventing such migration lies in modifying the deployment technique and the

design of the stent-graft itself. Modifications in tech-nique should begin with how the delivery system is in-troduced.12 When the angulation, for example, is on one side of the coronal plane, introducing the delivery sys-tem from the side opposite the angle will facilitate pas-sage at the top of the bend.

Superstiff-Guidewire TechniqueIt is usually helpful to bench-test the endograft to match the neck anatomy. Maneuvers like bending the guide-wire before introduction, in order to align it with the

Fig. 1 The Zenith® stent-graft uses suprarenal fixation. The barbs secure the stent-graft to the suprarenal wall, which reduces the risk of migration and enhances the endograft–vessel attachment.

Fig. 2 The EXCLUDER® endograft uses 8 pairs of “anchors” for infrarenal attachment (see proximal end of graft).


axes of the aneurysm and the neck, could be helpful12 (Fig. 3). Also of benefit is the use of a superstiff guide-wire, such as the 0.035-inch Lunderquist (Nycomed US Inc.; Melville, NY) or the 0.035-inch Amplatz® (Bos-ton Scientific, Inc.; Natick, Mass), in combination with slow and controlled deployment of the endograft12 (Figs. 4A and 4B). It is not advisable to attempt to reposition the endoprosthesis after deployment has been initiat-ed, because this increases the risk of migration. Several techniques have specifically applied the EXCLUDER en-dograft to the prevention of distal migration and type 1 endoleak in patients who have severe infrarenal neck angulation, short infrarenal necks, or both.13

Combination Technique Using the Palmaz XL Stent with the EXCLUDER Stent-GraftOne of the described techniques, for use in patients who have complicated infrarenal neck anatomy, is the per-manent deployment of the Palmaz® XL stent (Cordis Corporation, a Johnson & Johnson company; Miami Lakes, Fla) in the infrarenal neck before permanent de-ployment of the EXCLUDER endograft. This technique has been shown to offer a reliable mode of EXCLUDER fixation and prevention of distal migration. The com-bination of the use of the Palmaz XL stent after the de-ployment of the EXCLUDER has also been successful in preventing type 1 endoleak and distal migration (Figs. 5A and 5B).

Endowedge Technique with the EXCLUDER Stent-GraftIn patients who have short infrarenal neck anatomy, the “endowedge technique” described by Minion and

coworkers13 also offers satisfactory juxtarenal sealing during EXCLUDER endograft placement (Fig. 6). This

Fig. 3 A 0.035-inch superstiff guidewire is bent to conform the endograft to tortuous infrarenal aortic neck anatomy.

Fig. 4 A) Controlled and modified deployment of the EXCLUDER®

endograft over a 0.035-inch Amplatz ® superstiff wire, demon-strating the initial “flowering” of the endograft. B) Angiogram shows the controlled and modified endograft deployment tech-nique, which facilitates aligning the endograft with the axis of the neck and the body of the aneurysm.

A

B


technique enables the scalloped proximal 4 mm of the EXCLUDER endoprosthesis to be wedged against the renal angioplasty balloons, which are placed via the bra-chial approach. The first 2 to 3 rings of the endograft are slowly deployed (flowering technique), and then the device is advanced upwards against the inflated renal balloons for the completion of deployment.

Kilt Technique with the EXCLUDER Stent-GraftIn patients who have funnel-shaped or reverse-tapered aortic necks, an adjuvant procedure called the “kilt technique” is another possibility. In this technique, an aortic cuff is deployed in the distal infrarenal seal zone before the main body is deployed.13 The proximal end of the EXCLUDER contains barbs, which enable the de-vice to remain above the aortic extension and thereby prevent distal migration. Careful inflation of an angio-plasty balloon of the appropriate size then achieves the proximal seal of the prosthesis.

Anatomic Fixation with the Powerlink Stent-GraftPowerlink is a bifurcated unibody stent-graft system that provides an “anatomic fixation” by straddling the aortoiliac junction (Fig. 7). The endograft is deployed so that its bifurcated component rests on the aortoiliac bifurcation. An additional aortic extension can, if nec-essary, lengthen the endograft to the infrarenal neck. This device helps to create an endoluminal channel sys-tem from the bottom up and prevents distal migration.

Newer-Generation Endografts to Prevent Distal Migration and Type 1 EndoleakThe Aorfix Endovascular AAA Repair System (Lom-bard) is a newer-generation endograft that is designed to overcome problems with infrarenal neck anatomy. This device—currently undergoing clinical trial in the Unit-ed States—is made of polyester material and is partially supported by nitinol frames (Fig. 8). The proximal part of the Aorfix has incorporated nitinol clips for active fixation of the device to the aortic wall. The Aorfix has excellent procedural outcomes in terms of technical suc-cess, mortality rate, and avoidance of endoleak, migra-tion, and stent-graft fracture.11,12 This stent-graft is very flexible and can conform to severely tortuous infrarenal necks (Fig. 8). Due to its unique ring design, the Aorfix resists kinking, tolerates oversizing, and does not trans-fer strain to seal zones. In the study reported by Alberti-ni and colleagues,11 there were no instances of stent-graft migration with Aorfix after a mean follow-up time of 12 months (range, 1–43 mo). Those investigators also

A B

Fig. 5 Abdominal angiograms of a patient with a short and an-gulated infrarenal neck before (A) and after (B) abdominal aortic aneurysm repair, using the combination technique of Palmaz® XL stent deployment in the infrarenal neck and EXCLUDER® endograft deployment.

Fig. 6 Endowedge technique: balloon angioplasty is performed simultaneously with a 32-mm balloon in the aorta and a 6 ! 18-mm balloon-expandable stent in the left renal artery, which enables a satisfactory juxtarenal seal during EXCLUDER® endograft placement.


showed that the incidence of type 1 endoleak was very low with the use of this stent-graft in patients who had severely angulated aortic necks. Lombard Medical (the maker of Aorfix) also offers EndoRefix nitinol clips that can be advanced through a delivery catheter and a 16F sheath to staple the stent-graft to the aortic wall in patients who experience distal migration of the previ-ously placed endograft. The EndoRefix clips are current-ly undergoing clinical trial in the United States for use in patients who have previously placed stent-grafts with distal migration or who have challenging infrarenal neck anatomy that places them at risk of distal migra-tion and type 1 endoleak. Only patients with polyes-ter stent-grafts are candidates for the use of EndoRefix clips. The polytetrafluoroethylene graft material appar-ently is at risk of damage from the use EndoRefix clips. Another innovation in the f ield of AAA repair is the Aptus stent-graft (Aptus Endosystems, Inc.; Sunnyvale, Calif ), which incorporates an endostapling system with the endograft to prevent migration (Fig. 9). The Anaconda (Vascutek, part of TERUMO Cardio-Vascular Systems Corp.; Ann Arbor, Mich) is another device, undergoing clinical trials in the United States, that represents the next generation of stent-graft systems for AAA repair. This is the only graft system that en-ables repositioning of the graft after deployment. The Anaconda’s highly unusual f lexibility and excellent

Fig. 7 Artistic rendering of a Powerlink® stent-graft demon-strates the principle of anatomic fixation of the endograft at the aortoiliac junction to prevent migration.

Fig. 8 Three-dimensional computed tomographic image of the Aorfix® device reveals severe angulation of the infrarenal aortic neck.

Fig. 9 Nitinol stent frame of the Aptus device in the infrarenal aorta. Endostaples can be seen affixing the graft to the vessel wall.


torque control enable accurate deployment and opti-mal placement even in patients with challenging anato-my.14

We have previously shown15 that when EVAR fails to resolve type 1 endoleak, the aortic wrap technique can be an important surgical alternative. In using this technique, the infrarenal retroperitoneum is opened through a 5-cm left-flank incision, and the aneurysmal aorta is exposed. After both renal arteries have been ex-posed, the aorta is dissected circumferentially from the surrounding tissues below the renal arteries. A graft “passer” is then placed around the aorta, which enables a 12-mm Hemashield® graft (Boston Scientific Corpora-tion; Natick, Mass) to be pulled around the aortic neck, encircling it just below both renal arteries. The graft is measured and tightened, and is then secured with 2-0 TICRON sutures (Covidien Syneture; Mansfield, Mass) (Fig. 10). An abdominal aortic angiogram is then per-formed to check for type 1 endoleak. If the results are satisfactory, the omentum is placed between the duode-num and aortic grafts to prevent any erosion of the graft into the intestine, and the abdominal incision is closed in standard fashion.15

ConclusionThe key factors inf luencing the success of the EVAR technique are preprocedural planning, the experience of the operator, the technique used, and the generation of the endograft. Several adjunctive techniques during stent-graft deployment can also achieve successful en-dovascular repair in patients who have challenging in-frarenal neck anatomy. Regular follow-up of patients with complex infrarenal neck anatomy after EVAR is mandatory. When EVAR fails, the aortic wrap is a rea-sonable surgical alternative. Future improvements in device attachment will simplify and improve the re-sults of EVAR.

References 1. Parodi JC, Palmaz JC, Barone HD. Transfemoral intralumi-

nal graft implantation for abdominal aortic aneurysms. Ann Vasc Surg 1991;5(6):491-9.

2. Fulton JJ, Farber MA, Sanchez LA, Godshall CJ, Marston WA, Mendes R, et al. Effect of challenging neck anatomy on mid-term migration rates in AneuRx endografts. J Vasc Surg 2006;44(5):932-7.

3. Albertini J, Kalliafas S, Travis S, Yusuf SW, Macierewicz JA, Whitaker SC, et al. Anatomical risk factors for proximal peri-graft endoleak and graft migration following endovascular repair of abdominal aortic aneurysms. Eur J Vasc Endovasc Surg 2000;19(3):308-12.

4. Harris PL, Vallabhaneni SR, Desgranges P, Becquemin JP, van Marrewijk C, Laheij RJ. Incidence and risk factors of late rup-ture, conversion, and death after endovascular repair of infrare-nal aortic aneurysms: the EUROSTAR experience. European collaborators on stent/graft techniques for aortic aneurysm repair. J Vasc Surg 2000;32(4):739-49.

5. Chaikof EL, Blankensteijn JD, Harris PL, White GH, Zarins CK, Bernhard VM, et al. Reporting standards for endovascu-lar aortic aneurysm repair. J Vasc Surg 2002;35(5):1048-60.

6. Peppelenbosch N, Buth J, Harris PL, van Marrewijk C, Fran-sen G; EUROSTAR Collaborators. Diameter of abdominal aortic aneurysm and outcome of endovascular aneurysm re-pair: does size matter? A report from EUROSTAR. J Vasc Surg 2004;39(2):288-97.

7. Resch T, Ivancev K, Brunkwall J, Nyman U, Malina M, Lind-blad B. Distal migration of stent-grafts after endovascular repair of abdominal aortic aneurysms. J Vasc Interv Radiol 1999;10(3):257-66.

8. Wolf YG, Hill BB, Lee WA, Corcoran CM, Fogarty TJ, Za-rins CK. Eccentric stent graft compression: an indicator of insecure proximal f ixation of aortic stent graft. J Vasc Surg 2001;33(3):481-7.

9. Greenberg R, Fairman R, Srivastava S, Criado F, Green R. Endovascular grafting in patients with short proximal necks: an analysis of short-term results. Cardiovasc Surg 2000;8(5): 350-4.

10. Stanley BM, Semmens JB, Mai Q, Goodman MA, Hartley DE, Wilkinson C, Lawrence-Brown MD. Evaluation of pa-tient selection guidelines for endoluminal AAA repair with the Zenith Stent-Graft: the Australasian experience. J Endo-vasc Ther 2001;8(5):457-64.

11. Albertini JN, DeMasi MA, Macierewicz J, El Idrissi R, Hop-kinson BR, Clement C, et al. Aorfix stent graft for abdominal aortic aneurysms reduces the risk of proximal type 1 endoleak in angulated necks: bench-test study. Vascular 2005;13(6): 321-6.

12. Albertini JN, Perdikides T, Soong CV, Hinchliffe RJ, Tro-janowska M, Yusuf SW. Endovascular repair of abdominal aortic aneurysms in patients with severe angulation of the prox-imal neck using a flexible stent-graft: European Multicenter Experience. J Cardiovasc Surg (Torino) 2006;47(3):245-50.

13. Minion DJ, Yancey A, Patterson DE, Saha S, Endean ED. The endowedge and kilt techniques to achieve additional jux-tarenal seal during deployment of the Gore Excluder endo-prosthesis. Ann Vasc Surg 2006;20(4):472-7.

14. Saratzis N, Melas N, Saratzis A, Lazarides J, Ktenidis K, Tsakiliotis S, Kiskinis D. Anaconda aortic stent-graft: single-center experience of a new commercially available device for abdominal aortic aneurysms. J Endovasc Ther 2008;15(1):33-41.

15. Younis G, Messner G, Gregoric I, Krajcer Z. Aortic wrap as a novel technique of type I endoleak repair. Ann Vasc Surg 2006;20(5):690-5.

Fig. 10 Wrapping technique: photograph of the operative field reveals the location of the two 12-mm-diameter Hemashield® vascular grafts that were wrapped around the infrarenal aortic neck, just distal to the renal arteries.

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