Clinical Practice Guidelines for Endovascular Abdominal Aortic Aneurysm Repair: Written by the Standards of Practice Committee for the Society of Interventional Radiology and Endorsed by the Cardiovascular and Interventional Radiological Society of Europe and the Canadian Interventional Radiology Association

Abstract

PreambleTHE membership of the Society of Interventional Radiology (SIR) Standards of Practice Committee represents experts in a broad spectrum of interventional procedures from both the private and academic sectors of medicine. Generally, Standards of Practice Committee members dedicate the vast majority of their professional time to performing interventional procedures; as such they represent a valid broad expert constituency of the subject matter under consideration for standards production.SIR DisclaimerThe clinical practice guidelines of the Society of Interventional Radiology attempt to define practice principles that generally should assist in producing high quality medical care. These guidelines are voluntary and are not rules. A physician may deviate from these guidelines, as necessitated by the individual patient and available resources. These practice guidelines should not be deemed inclusive of all proper methods of care or exclusive of other methods of care that are reasonably directed towards the same result. Other sources of information may be used in conjunction with these principles to produce a process leading to high quality medical care. The ultimate judgment regarding the conduct of any specific procedure or course of management must be made by the physician, who should consider all circumstances relevant to the individual clinical situation. Adherence to the SIR Quality Improvement Program will not assure a successful outcome in every situation. It is prudent to document the rationale for any deviation from the suggested practice guidelines in the department policies and procedure manual or in the patient's medical record.Technical documents specifying the exact consensus and literature review methodologies as well as the institutional affiliations and professional credentials of the authors of this document are available upon request from SIR, 3975 Fair Ridge Dr., Suite 400 N., Fairfax, VA 22033.MethodologySIR produces its Standards of Practice documents using the following process. Standards documents of relevance and timeliness are conceptualized by the Standards of Practice Committee members. A recognized expert is identified to serve as the principal author for the standard. Additional authors may be assigned dependent upon the magnitude of the project.An in-depth literature search is performed using electronic medical literature databases. Then, a critical review of peer-reviewed articles is performed with regard to the study methodology, results, and conclusions. The qualitative weight of these articles is assembled into an evidence table, which is used to write the document such that it contains evidence-based data with respect to content, rates, and thresholds.When the evidence of literature is weak, conflicting, or contradictory, consensus for the parameter is reached by a minimum of 12 Standards of Practice Committee members using a Modified Delphi Consensus Method (Appendix A) (1Fink A. Kosecoff J. Chassin M. Brook R.H. Consensus methods: characteristics and guidelines for use.Am J Public Health. 1984; 74: 979-983Crossref PubMed Google Scholar). For purposes of these documents, consensus is defined as 80% Delphi participant agreement on a value or parameter.The draft document is critically reviewed by the Standards of Practice Committee members, either by telephone conference calling or face-to-face meeting. The finalized draft from the Committee is sent to the SIR membership for further input/criticism during a 30-day comment period. These comments are discussed by the Standards of Practice Committee, and appropriate revisions made to create the finished standards document. Prior to its publication the document is endorsed by the SIR Executive Council.The current guidelines are written to help determine appropriate preprocedural, intraprocedural, and postprocedural management of patients with abdominal aortic aneurysms (AAAs) who are treated with endovascular aneurysm repair (EVAR). Although practicing physicians should strive to achieve perfect outcomes, in practice all physicians will fall short of ideal outcomes to a variable extent. Therefore, in addition to quality improvement case reviews conducted after individual complications, outcome measure thresholds should be used to assess treatment safety and efficacy in ongoing quality improvement programs. For the purpose of these guidelines, a threshold is a specific level of an indicator that, when reached or crossed, should prompt a review of departmental policies and procedures to determine causes and to implement changes if necessary. Thresholds may vary from those listed here; for example, patient referral patterns and selection factors may dictate a different threshold value for a particular indicator at a particular institution. Therefore, setting universal thresholds is difficult and each department is urged to adjust its thresholds as needed to meet its specific quality improvement program situation.SIR is committed to the basic principles of outcomes-focused, evidence-based medicine. Ideally, every Standards of Practice Committee recommendation would be based on evidence derived from multiple prospective randomized trials of adequate statistical power. SIR recognizes the potential pitfalls of developing evidence-based standards for EVAR and of making recommendations regarding EVAR based solely on literature studies. However, these difficulties are far outweighed by the potential improvements in safety and treatment efficacy that may be gained by implementing the key lessons learned from the existing peer-reviewed scientific literature that has evaluated outcomes of EVAR procedures. The recommendations presented in this document are intended to guide clinical practice rather than to mandate the use of specific algorithms. The authors fully anticipate that these guidelines will be appropriately revised when future studies are available.IntroductionAAAs are a leading cause of death worldwide, with increasing incidence and prevalence. In the United States, AAAs occur in an estimated 5%–7% of the population older than 60 years of age, often as an unrecognized disease (2Gillum R.F. Epidemiology of aortic aneurysm in the united states.J Clin Epidemiol. 1995; 48: 1289-1298Abstract Full Text PDF PubMed Scopus (160) Google Scholar). With a high propensity for rupture, AAAs are the 15th leading cause of death overall in the United States (3Silverberg E. Boring C.C. Squires T.S. Cancer statistics, 1990.CA Cancer J Clin. 1990; 4: 9-26Crossref Google Scholar) and the 10th leading cause of death in men older than age 55, with approximately 9,000 AAA-related deaths occurring annually (2Gillum R.F. Epidemiology of aortic aneurysm in the united states.J Clin Epidemiol. 1995; 48: 1289-1298Abstract Full Text PDF PubMed Scopus (160) Google Scholar, 3Silverberg E. Boring C.C. Squires T.S. Cancer statistics, 1990.CA Cancer J Clin. 1990; 4: 9-26Crossref Google Scholar). EVAR for AAA represents an advance in patient care, serving as an effective alternative to traditional open surgical AAA repair, and is now the most common treatment method for AAA repair in the United States. Continued technologic refinements have occurred since the first documented EVAR in 1991, with multiple United States Food and Drug Administration (FDA)–approved devices now available. The reported technical and clinical outcomes of EVAR now parallel or exceed the same outcome parameters for open surgical repair (4Matsumura J.S. Brewster D.C. Makaroun M.S. Naftel D.C. A multicenter controlled clinical trial of open versus endovascular treatment of abdominal aortic aneurysm.J Vasc Surg. 2003; 37: 262-271Abstract Full Text PDF PubMed Scopus (229) Google Scholar). The procedure has resulted in reduced operative times, decreased intraoperative blood loss and transfusion requirements, decreased perioperative morbidity and mortality, and reduced intensive care unit and hospital lengths of stay. Although these reductions, together with the improved patient recovery time, may decrease the immediate costs of AAA repair, this initial financial advantage may be offset by the costly lifelong follow-up imaging that is recommended after EVAR (5Geller S.C. Society of Interventional Radiology Device ForumImaging guidelines for abdominal aortic aneurysm repair with endovascular stent grafts.J Vasc Interv Radiol. 2003; 14: S263-S264PubMed Google Scholar). The Dutch Randomized Endovascular Aneurysm Management trial (6Prinssen M. Verhoeven E.L. Buth J. et al.A randomized trial comparing conventional and endovascular repair of abdominal aortic aneurysms.N Engl J Med. 2004; 351: 1607-1618Crossref PubMed Scopus (918) Google Scholar, 7Prinssen M. Buskens E. de Jong S.E. et al.Cost-effectiveness of conventional and endovascular repair of abdominal aortic aneurysms: results of a randomized trial.J Vasc Surg. 2007; 46: 883-890Abstract Full Text Full Text PDF PubMed Scopus (44) Google Scholar, 8Blankensteijn J.D. de Jong S.E. Prinssen M. et al.Two-year outcomes after conventional or endovascular repair of abdominal aortic aneurysms.N Engl J Med. 2005; 352: 2398-2405Crossref PubMed Scopus (550) Google Scholar) concluded that EVAR provides only a marginal overall survival benefit, and is associated with a substantial, if not prohibitive, cost increase. Additionally, although EVAR has been shown to reduce death and complication rates in the first month after the procedure compared with open repair (7Prinssen M. Buskens E. de Jong S.E. et al.Cost-effectiveness of conventional and endovascular repair of abdominal aortic aneurysms: results of a randomized trial.J Vasc Surg. 2007; 46: 883-890Abstract Full Text Full Text PDF PubMed Scopus (44) Google Scholar, 9Greenhalgh R.M. Brown L.C. Kwong G.P. Powell J.T. Thompson S.G. EVAR trial participantsComparison of endovascular aneurysm repair with open repair in patients with abdominal aortic aneurysm (EVAR trial 1), 30-day operative mortality results: randomised controlled trial.Lancet. 2004; 364: 843-848Abstract Full Text Full Text PDF PubMed Scopus (864) Google Scholar), subsequent longer-term analysis of these randomized trials showed a sustained benefit in terms of aneurysm-related mortality up to 4 years, but the overall survival difference did not persist beyond the first two postoperative years (8Blankensteijn J.D. de Jong S.E. Prinssen M. et al.Two-year outcomes after conventional or endovascular repair of abdominal aortic aneurysms.N Engl J Med. 2005; 352: 2398-2405Crossref PubMed Scopus (550) Google Scholar, 10EVAR Trial ParticipantsEndovascular aneurysm repair versus open repair in patients with abdominal aortic aneurysm (EVAR trial 1): randomised controlled trial.Lancet. 2005; 365: 2179-2186Abstract Full Text Full Text PDF PubMed Scopus (771) Google Scholar, 11Prinssen M. Wixon C.L. Buskens E. Blankensteijn J.D. Surveillance after endovascular aneurysm repair: diagnostics, complications, and associated costs.Ann Vasc Surg. 2004; 18: 421-427Abstract Full Text Full Text PDF PubMed Google Scholar).EVAR outcomes are strongly dependent on appropriate patient and device selection; physician factors such as training, experience, and procedure volume; and various institutional factors (12De Centa I. Coggia M. Cochennec F. Alfonsi P. Javerliat I. Goeau-Brissonniere O. Laparoscopic abdominal aortic aneurysm repair in octogenarians.J Vasc Surg. 2009; 49: 1135-1139Abstract Full Text Full Text PDF PubMed Scopus (3) Google Scholar). EVAR procedures can be extremely challenging and thus require operators who have substantial endovascular experience and refined technical skills. Successful outcomes further depend on meticulous assessment of the pertinent vascular anatomy and proper preprocedure planning. These guidelines are intended for use in assessing the standard of care expected from all physicians who perform EVAR procedures. The most important processes of care are: (i) preprocedural imaging and planning, (ii) appropriate graft and patient selection, (iii) performance of the procedure, (iv) postprocedural surveillance, and (v) management of EVAR-related complications. The outcome measures or indicators for these processes are indications, success rates, and complication rates, and are assigned threshold levels.DefinitionsAbdominal Aortic AneurysmAbdominal Aortic Aneurysm is a permanent pathologic dilation of the abdominal aorta. Currently, intervention is indicated when (i) the diameter reaches 5.5 cm or is 2.5 times the normal aortic diameter or (ii) there is aneurysm growth at a rate exceeding 1 cm per year (13Lederle FA, Johnson GR, Wilson SE, et al. Rupture rate of large abdominal aortic aneurysms in patients refusing or unfit for elective repair. JAMA 200212; 287:2968–2972.Google Scholar, 14Brady A.R. Thompson S.G. Fowkes F.G. Greenhalgh R.M. Powell J.T. UK Small Aneurysm Trial ParticipantsAbdominal aortic aneurysm expansion: risk factors and time intervals for surveillance.Circulation. 2004; 110: 16-21Crossref PubMed Scopus (264) Google Scholar, 15Hirsch A.T. Haskal Z.J. Hertzer N.R. et al.ACC/AHA 2005 Practice Guidelines for the Management of Patients with Peripheral Arterial Disease (Lower Extremity, Renal, Mesenteric, and Abdominal Aortic): a collaborative report from the American Association for Vascular Surgery/Society for Vascular Surgery, Society for Cardiovascular Angiography and Interventions, Society for Vascular Medicine and Biology, Society of Interventional Radiology, and the ACC/AHA Task Force on Practice Guidelines (writing committee to develop guidelines for the management of patients with peripheral arterial disease): Endorsed by the American Association of Cardiovascular and Pulmonary Rehabilitation; National Heart, Lung, and Blood institute; Society for Vascular Nursing; TransAtlantic Inter-society Consensus; and Vascular Disease Foundation.Circulation. 2006; 113: e463-e654Crossref PubMed Google Scholar, 16Peterson B.G. Matsumura J.S. Brewster D.C. Makaroun M.S. Excluder Bifurcated Endoprosthesis InvestigatorsFive-year report of a multicenter controlled clinical trial of open versus endovascular treatment of abdominal aortic aneurysms.J Vasc Surg. 2007; 45: 885-890Abstract Full Text Full Text PDF PubMed Scopus (54) Google Scholar, 17Cho J.S. Dillavou E.D. Rhee R.Y. Makaroun M.S. Late abdominal aortic aneurysm enlargement after endovascular repair with the excluder device.J Vasc Surg. 2004; 39: 1236-1241Abstract Full Text Full Text PDF PubMed Scopus (83) Google Scholar). Repair is always indicated for AAA rupture or when there is a symptomatic aneurysm (eg, back pain), which may be a sign of impending rupture (18Assar A.N. Zarins C.K. Ruptured abdominal aortic aneurysm: a surgical emergency with many clinical presentations.Postgrad Med J. 2009; 85: 268-273Crossref PubMed Scopus (10) Google Scholar). AAAs are classified according to their anatomic relationship to the renal arteries, as this significantly affects treatment. An infrarenal AAA has an intervening normal aortic segment (proximal neck) of at least 10 mm between the renal arteries and the most cephalad extent of the aneurysm, whereas a juxtarenal aneurysm extends to the renal artery level, with a normal-caliber aorta above. A suprarenal AAA not only involves the renal arteries, but extends cephalad so that the superior mesenteric artery and celiac artery arise from the aneurysmal aorta. AAAs may also extend distally beyond the aortic bifurcation to involve the common iliac arteries and occasionally the internal and/or external iliac arteries. A common iliac artery aneurysm has a diameter that reaches or exceeds 2 cm. Iliac artery involvement may significantly affect EVAR, as ancillary procedures may be necessary to ensure a successful outcome. AAAs may also be categorized by configuration: a fusiform AAA typically involves the entire circumference of an extended section of the aorta, and is a “true” aneurysm involving all three layers of the aortic wall. Saccular AAAs are more focal and localized and may be asymmetric or may occur as pseudoaneurysms that do not involve all mural layers.Endovascular Aneurysm RepairEndovascular abdominal aortic aneurysm repair is defined as treatment of an AAA through image-guided placement of a stent-graft device (endoprosthesis) within the native abdominal aorta, securing device fixation to the vascular wall proximal and distal to the diseased aneurysmal segment(s), thus eliminating AAA sac pressurization.EVAR stent-graft devices or endoprostheses have three components, consisting of (i) a delivery system for graft introduction and deployment; (ii) a high radial force, self-expanding metallic stent framework that supports the endoprosthesis and allows for vascular attachment; and (iii) graft fabric that excludes the aneurysm and serves as a new conduit for blood flow. Successful EVAR requires suitable proximal and distal landing zones for stable fixation and complete sealing of the endoprosthesis to the vascular wall. Various devices have different methods of fixation to the vascular wall. The methodology for graft attachment above the AAA (ie, proximal fixation) may be divided into suprarenal and infrarenal fixation. Suprarenal fixation devices employ a bare metallic stent component that extends proximally above the fabric-covered stent-graft, with the latter positioned immediately below the most inferiorly located renal artery, so that apposition is to the vascular tissue in the neck located between the renal arteries and the AAA. The bare metallic stent of such a device extends cephalad, anchoring the graft to vascular tissue adjacent to and above the renal arteries. This has been proposed as a more effective means of ensuring proximal fixation in the presence of unfavorable anatomy (eg, short infrarenal neck length, circumferential thrombus or calcification, severe angulation, conical neck configuration) (19Robbins M. Kritpracha B. Beebe H.G. Criado F.J. Daoud Y. Comerota A.J. Suprarenal endograft fixation avoids adverse outcomes associated with aortic neck angulation.Ann Vasc Surg. 2005; 19: 172-177Abstract Full Text Full Text PDF PubMed Scopus (43) Google Scholar). Because there is no fabric attached to the stent, the mesenteric and renal arteries remain perfused, although concerns have been raised regarding the potential risks of embolization to or occlusion of the renal and/or mesenteric arteries by the suprarenal components (20Alric P. Hinchliffe R.J. Picot M.C. et al.Long-term renal function following endovascular aneurysm repair with infrarenal and suprarenal aortic stent-grafts.J Endovasc Ther. 2003; 10: 397-405Crossref PubMed Scopus (56) Google Scholar). Several studies have reported the safety and efficacy of suprarenal fixation (21Lobato A.C. Quick R.C. Vaughn P.L. Rodriguez-Lopez J. Douglas M. Diethrich E.B. Transrenal fixation of aortic endografts: intermediate follow-up of a single-center experience.J Endovasc Ther. 2000; 7: 273-278Crossref PubMed Google Scholar, 22Malina M. Veith F. Ivancev K. Sonesson B. Balloon occlusion of the aorta during endovascular repair of ruptured abdominal aortic aneurysm.J Endovasc Ther. 2005; 12: 556-559Crossref PubMed Scopus (48) Google Scholar, 23Marin M.L. Parsons R.E. Hollier L.H. et al.Impact of transrenal aortic endograft placement on endovascular graft repair of abdominal aortic aneurysms.J Vasc Surg. 1998; 28: 638-646Abstract Full Text Full Text PDF PubMed Scopus (106) Google Scholar, 24Cayne N.S. Rhee S.J. Veith F.J. et al.Does transrenal fixation of aortic endografts impair renal function?.J Vasc Surg. 2003; 38: 639-644Abstract Full Text Full Text PDF PubMed Scopus (42) Google Scholar, 25O'Donnell M.E. Sun Z. Winder R.J. Ellis P.K. Lau L.L. Blair P.H. Suprarenal fixation of endovascular aortic stent grafts: assessment of medium-term to long-term renal function by analysis of juxtarenal stent morphology.J Vasc Surg. 2007; 45: 694-700Abstract Full Text Full Text PDF PubMed Scopus (21) Google Scholar), with similar rates of renal dysfunction in EVAR performed with suprarenal and infrarenal fixation (24Cayne N.S. Rhee S.J. Veith F.J. et al.Does transrenal fixation of aortic endografts impair renal function?.J Vasc Surg. 2003; 38: 639-644Abstract Full Text Full Text PDF PubMed Scopus (42) Google Scholar). However, there are reports of renal infarction and renal artery occlusions in patients with preexisting renal arterial disease (26Kramer S.C. Seifarth H. Pamler R. et al.Renal infarction following endovascular aortic aneurysm repair: incidence and clinical consequences.J Endovasc Ther. 2002; 9: 98-102Crossref PubMed Scopus (50) Google Scholar, 27Lau L.L. Hakaim A.G. Oldenburg W.A. et al.Effect of suprarenal versus infrarenal aortic endograft fixation on renal function and renal artery patency: a comparative study with intermediate follow-up.J Vasc Surg. 2003; 37: 1162-1168Abstract Full Text Full Text PDF PubMed Scopus (58) Google Scholar), as well as of visceral compromise and arterial occlusion (28Burks Jr, J.A. Faries P.L. Gravereaux E.C. Hollier L.H. Marin M.L. Endovascular repair of abdominal aortic aneurysms: stent-graft fixation across the visceral arteries.J Vasc Surg. 2002; 35: 109-113PubMed Scopus (0) Google Scholar, 29Choke E. Munneke G. Morgan R. et al.Visceral and renal artery complications of suprarenal fixation during endovascular aneurysm repair.Cardiovasc Intervent Radiol. 2007; 30: 619-627Crossref PubMed Scopus (5) Google Scholar) with the use of suprarenal fixation.Infrarenal fixation devices do not have any components that extend above the renal arteries; the proximal margin of the endoprosthesis is positioned immediately below the most inferiorly located renal artery. Fixation is achieved through the radial force of the metallic stent framework of the device, where it is in apposition to the vascular tissue located between the renal arteries and the AAA. Some infrarenal fixation devices also have small “barbs” or retention hooks to further ensure fixation.Stent-graft design allows for customization to an individual patient's vascular anatomy. All current FDA-approved devices have a modular design that permits the combination of various graft components into a composite conduit that is patient-specific for the particular AAA morphology that is to be treated. There are three basic graft configurations: (i) a completely modular stent-graft design that is composed of a graft body and unilateral limb extension that is paired with a contralateral docking limb to achieve a bifurcated graft that simulates the native aortic anatomy; (ii) a one-piece, fully supported, unibody self-expanding endoprosthesis that is positioned on the aortic bifurcation and to which another modular component is added and is extended cephalad to attach immediately distal to the lowest renal artery (this latter component is available with suprarenal or infrarenal fixation); and (iii) an aortouniiliac graft that requires the addition of a surgically created femoral artery–to–femoral artery crossover bypass conduit to provide perfusion of the contralateral lower extremity. This graft configuration is a modification of a bifurcated endoprosthesis and is used when iliac stenotic or occlusive disease does not permit bilateral introduction of graft components. It is also frequently used when EVAR is performed for AAA rupture, as the potentially time consuming placement of a contralateral docking limb is avoided.Endoleaks are defined as continued perfusion of the residual aneurysm sac after EVAR (30Golzarian J. Valenti D. Endoleakage after endovascular treatment of abdominal aortic aneurysms: diagnosis, significance and treatment.Eur Radiol. 2006; 16: 2849-2857Crossref PubMed Scopus (22) Google Scholar). Endoleaks, along with graft migration, represent the most common threat to EVAR durability as an alternative therapy to open surgical aneurysm repair and are the most commonly occurring complication following EVAR (31Veith F.J. Baum R.A. Ohki T. et al.Nature and significance of endoleaks and endotension: summary of opinions expressed at an international conference.J Vasc Surg. 2002; 35: 1029-1035Abstract Full Text Full Text PDF PubMed Scopus (314) Google Scholar). Endoleaks are classified according to the source of continued sac perfusion (30Golzarian J. Valenti D. Endoleakage after endovascular treatment of abdominal aortic aneurysms: diagnosis, significance and treatment.Eur Radiol. 2006; 16: 2849-2857Crossref PubMed Scopus (22) Google Scholar, 31Veith F.J. Baum R.A. Ohki T. et al.Nature and significance of endoleaks and endotension: summary of opinions expressed at an international conference.J Vasc Surg. 2002; 35: 1029-1035Abstract Full Text Full Text PDF PubMed Scopus (314) Google Scholar). Type I endoleak occurs when there is continued sac perfusion as a result of inadequate fixation at the proximal (type IA endoleak) or distal (type IB endoleak) attachment sites of the endoprosthesis. The lack of graft fixation allows arterial blood to enter the aneurysm sac through the space between the stent-graft and the vascular endothelium. These endoleaks invariably require further intervention, as they rarely resolve spontaneously; when identified during or after EVAR, every effort should be made to correct this endoleak, as the continued arterial perfusion places the patient at risk for aneurysm rupture. If this endoleak cannot be corrected, open surgical conversion may be necessary. Type II endoleak, the most common type, allows perfusion of the residual AAA sac through patent branch vessels that normally arise from the abdominal aorta (eg, lumbar artery and inferior mesenteric artery [IMA]). Reversal of arterial flow through a branch vessel arising from the aneurysm provides inflow to the residual AAA sac while another patent arterial branch serves as the outflow vessel. Although the majority of these resolve spontaneously, persistent type II endoleaks that result in continued expansion of the residual AAA sac require intervention. Type III endoleaks occur when there is a functional problem with the device such as a defect in the graft fabric or separation (ie, disarticulation) of one or more modular components of the stent-graft, allowing residual AAA sac perfusion. This type does not spontaneously resolve and requires additional intervention, as this places the patient at significant risk for aneurysm rupture. Type IV endoleaks result from excessive graft porosity that allows continued residual sac perfusion; noncellular elements (eg, serum) may predominate as a transudate and may cause continued sac expansion. This endoleak type is significantly less common than it has been in the past as a result of manufacturer improvements in fabric composition. A type V endoleak (also termed endotension) is one in which there is continued post-EVAR expansion of the residual AAA sac without a demonstrable source of sac perfusion by imaging. Some investigators believe this actually represents one of the previous four types and that there has merely been a failure in demonstrating the endoleak type and source (31Veith F.J. Baum R.A. Ohki T. et al.Nature and significance of endoleaks and endotension: summary of opinions expressed at an international conference.J Vasc Surg. 2002; 35: 1029-1035Abstract Full Text Full Text PDF PubMed Scopus (314) Google Scholar). Thus, one cause for continued pressurization of the aneurysm may be blood flow that is beyond the detection capabilities of currently available imaging technology (32Gilling-Smith G. Brennan J. Harris P. Bakran A. Gould D. McWilliams R. Endotension after endovascular aneurysm repair: definition, classification, and strategies for surveillance and intervention.J Endovasc Surg. 1999; 6: 305-307Crossref PubMed Google Scholar, 33van Sambeek M.R. Hendriks J.M. Tseng L. van Dijk L.C. van Urk H. Sac enlargement without endoleak: when and how to convert and technical considerations.Semin Vasc Surg. 2004; 17: 284-287Abstract Full Text Full Text PDF PubMed Scopus (19) Google Scholar). Other explanations include transgraft passage of serous fluid ultrafiltrate into the aneurysm sac through microporous fabric (16Peterson B.G. Matsumura J.S. Brewster D.C. Makaroun M.S. Excluder Bifurcated Endoprosthesis InvestigatorsFive-year report of a multicenter controlled clinical trial of open versus endovascular treatment of abdominal aortic aneurysms.J Vasc Surg. 2007; 45: 885-890Abstract Full Text Full Text PDF PubMed Scopus (54) Google Scholar, 17Cho J.S. Dillavou E.D. Rhee R.Y. Makaroun M.S. Late abdominal aortic aneurysm enlargement after endovascular repair with the excluder device.J Vasc Surg. 2004; 39: 1236-1241Abstract Full Text Full Text PDF PubMed Scopus (83) Google Scholar). The treatment of endotension must be individualized based on the suspected cause of continued sac expansion.Indications and Contraindications for EVARDespite advances in elective open surgical AAA repair, there is still considerable associated morbidity and mortality. Excellent outcomes are generally achieved in high-volume referral centers but there are still reported mortality rates as high as 7% and morbidity rates that approach 50% in some centers (34Hertzer N.R. Current status of endovascular repair of infrarenal abdominal aortic aneurysms in the context of 50 years of conventional repair.Ann N Y Acad Sci. 2006; 1085: 175-186Crossref PubMed Scopus (9) Google Scholar). Although open surgical repair has been the standard of care for the treatment of AAA, there are associated well recognized disadvantages, including lengthy operative, anesthesia, and recovery times, as well as a potentially prolonged hospitalization that involves use of the critical care unit. Additionally many patients are poorly suited for open repair because of coexisting medical conditions such as cardiac, pulmonary, or renal dysfunction, which present a high operative and/or anesthesia risk, and thus unacceptably high potential complica