The EVAR Landscape in 2013: Noteworthy Developments in the AAA Field

Vascular Disease Management last addressed the current state of endovascular aneurysm repair in its June 2012 issue.¹ A number of significant evolutions and new developments occurring since then warrant an update. The following areas deserve focused attention.

Historical Evolution of EVAR Techniques

It is well established that the history-making pioneering work of Parodi (with Palmaz and Barone) in the late 1980s and early 1990s proved profoundly transformational² and in many ways became the main catalyst for the “endovascular revolution” soon to follow. None of that has changed, but in the high interest of historical accuracy we must now recognize that Ukrainian surgeon Nikolay Volodos – working literally behind the iron curtain – created the first endovascular grafts in the culmination of a remarkable process of conception, development and preclinical testing that preceded human implantation.^3,4

FDA-Approved Devices

The US Food and Drug Administration (FDA) recently approved several significant products for endovascular AAA repair (Table 1): 

• Heli-FX Aortic Securement System (endostaples) (Aptus Endosystems)
• Zenith Flex AAA Endovascular Graft, Zenith Spiral-Z AAA iliac leg graft, Zenith Fenestrated AAA Endovascular Graft (with the adjunctive Zenith Alignment Stent) (Cook Medical)
• Powerlink AFX Endovascular AAA System and IntuiTrak System, with FDA-approved on-label percutaneous indications (Endologix, Inc.)
• Excluder AAA Endoprosthesis with C3 Delivery System (W.L. Gore & Associates, Inc.)
• Aorfix Endovascular Stent Graft (Lombard Medical Technologies, PLC)
• Endurant II AAA Stent Graft System (Medtronic, Inc.)
• Ovation Prime Abdominal Stent Graft System (TriVascular)

The relatively recent approval of the Aptus Endosystems Heli-FX endostaple qualifies as a noteworthy development because these devices will likely find a relevant place in the endovascular toolbox (Figure 1). But clinical information to date is limited and we are therefore unable to discern the best application for the technology at present. More data to help define various aspects surrounding the clinical use of endostaples will be forthcoming from the ongoing international ANCHOR Post-Market Registry.

Cook Medical’s Zenith family of endovascular grafts continued their growth and evolution with the addition of a highly flexible iliac-limb design (Spiral-Z), and the 2012 approval of the customized fenestrated abdominal stent-graft (Figure 2) – representing the culmination of a long process of development and international clinical experience.⁵ 

Recent technological achievements by Endologix have been impressive indeed, and they are now further enhanced by the milestone achievement of a first-ever percutaneous AAA indication for the Powerlink AFX EVAR system (with IntuiTrak). FDA approval was based on the excellent clinical results obtained during the PEVAR trial (cosponsored by Abbott). Moreover, ongoing US trials with the Nellix endovascular aneurysm seal (EVAS) system (Figure 3) and the fenestrated Ventana device⁶ round up a remarkable resurgence for this manufacturer. The Ventana clinical project, however, is currently on hold because of issues related to the renal-artery branch component and the perceived need for a redesign.

W.L. Gore & Associates’ Excluder with the new C3 delivery system has been well received by the aortic endovascular community. The construct allows repositioning of the device during the EVAR procedure, a feature felt to be highly desirable and effective.

AorFix by Lombard Medical Technologies (Figure 4) achieved a first-of-its-kind regulatory approval as it was cleared by the FDA for on-label repair of aneurysms with a proximal-neck angulation up to 90 degrees. This is truly remarkable, but its impact in the EVAR landscape remains unclear at this time.

Medtronic marches on as the EVAR market leader in the US and worldwide thanks to the Endurant stent-graft that has proven highly versatile, effective, and user friendly. Lending further strength to their cause were the 3-year results of the US pivotal trial presented at the 2013 Vascular Annual Meeting of the Society for Vascular Surgery.⁷ The report showed superb durability of the excellent early results, with 100% freedom from aneurysm-related mortality, 0% postimplantation aneurysm rupture, 0% stent graft migration, and 0% conversion to open repair for the 107 patients who were followed to 3 years. The latest iteration of the device, Endurant II, is now available (Figure 5): it features longer iliac limbs, improved radiopacity of the contralateral gate, and main-body diameters up to 28 mm with a delivery system profile of only 18 Fr outer diameter (OD) – graft diameters of 32 mm and 36 mm still feature a 20 Fr OD profile (Figure 5). 

Lastly, TriVascular was granted FDA approval of the Ovation stent-graft that features a 14 Fr OD main-body introducer (Figure 6), the lowest profile EVAR system on the market. The trimodular construct features polymer-fillable rings used to achieve proximal and distal seals. A similar general design (with trimodularity) will likely characterize other low-profile systems undergoing clinical trials or in development. 

Evolving EVAR Technologies and New Designs

The Cordis Incraft 14 Fr AAA stent-graft was initially tested in a phase I-type European study (INNOVATION) with favorable early patient outcomes. The pivotal multicenter US INSPIRATION clinical trial is under way. 

Bolton Medical is currently planning a pivotal clinical trial for their abdominal Treovance device (with a likely start in early Fall 2013). The stent-graft has received CE Mark approval in Europe.

As mentioned above, Endologix’s fenestrated Ventana device is being tested in a clinical trial but the study was recently suspended because of issues related to the performance of the renal-artery branch component. A redesign will be necessary with anticipated restart of the trial at the end of this year or early 2014.

The Nellix EVAS system continues to attract much attention because it represents a truly innovative conception with game-changing potential. The system received CE Mark approval in September 2012, and is now being tested in an ongoing US pivotal trial. It is conceivable the Nellix sac-sealing approach, if successful and durable, might have profound impact and prove game-changing. 

Other noteworthy developments 

Follow-up and surveillance of patients with small AAA is an important subject. New evidence points to the fact that most current practices are unnecessarily aggressive as they relate to the frequency of imaging scans. It would appear that in most cases a 1-year interval should be the minimum, and even longer (2-3 years) for very small aneurysms.^8,9

Dangas et al published in 2012 a meta-analysis of randomized trials that compared EVAR with open repair (OR), confirming the now well-established and evidence-based view that EVAR’s greatest advantage resides in its significantly lower 30-day (“operative”) mortality rate but at the cost of more reinterventions and the mandate to keep patients under (relatively) intense surveillance for life.¹⁰ Predictably, long-term survival of EVAR and OR patients converges and becomes identical over time.

A sobering fact is that in approximately 30% of “real-world” EVAR cases the operator performs endovascular repair using an approved device off-label, that is, outside the confines of the Instructions for Use – particularly as it relates to the anatomy of the proximal neck. Such off-label use can have major impact on outcomes as illustrated in dramatic fashion by Schanzer et al.¹¹ The salient take-home message is that “pushing the envelope” to expand EVAR indications in anatomies and situations well outside the confines of approved uses carries a hefty price as it can lead to sac enlargement and rupture, and a higher-than-expected reintervention rate. It is time perhaps to revisit the wisdom of pushing EVAR in such extreme situations and reconsider whether OR may not be a better option for many if not most such patients. 

FDA approval of the Zenith Fenestrated AAA Endovascular Graft (and the adjunctive Zenith Alignment Stent) in April 2012 added a new dimension to EVAR. The device features fenestrations (windows) or scallops (semicircular openings) that allow the proximal edge of the material to be placed above the renal arteries while still permitting blood flow to vessels accommodated by the scallop or through tubular grafts (covered stents) across the fenestrations (Figure 2). In order to account for anatomical variation, each proximal body graft is custom made for a specific patient. The manufacturer has been deliberate in implementing a slow and very careful commercial launch of the new device, which – quite clearly – is not for everyone. The implicit technical complexity and customized nature of the technology, as well as its considerable cost, require the high level of technical skill, commitment, and case volume only found at large referral centers. But at the same time, it must be recognized that availability and increasing use of fenestrated grafts may well bring gradual abandonment of other “compromise” treatment approaches for aneurysms with disadvantaged or absent proximal necks. 

The evolution and current proliferation of chimney and parallel-graft techniques cannot be ignored.^12-14 They are being reported to be surprisingly competitive with fenestrated grafts when used to repair juxtarenal and pararenal aneurysms,¹⁵ but not everyone is embracing them. However, it cannot be denied they have gradually become reasonable technical options for cases where a more standard approach is not available, and for aortic branch rescue in bail-out situations. 

The heritable nature of AAA disease was confirmed in 2011 with the publication of a paper that described the
herculean effort by an international team of scientists led by Matt Bown from University of Leicester in the United Kingdom leading to the discovery of a single gene associated with the development of AAAs.¹⁶ Remarkably the LRP1 gene appears to be quite specific to AAA and not associated with any other form of cardiovascular disease. This discovery is likely to lead to a host of new possibilities in the areas of prevention and management of abdominal aneurysms. 

Conclusion

It is undeniable the EVAR field has become evermore dynamic, with continued expectations of endless breakthroughs and innovation. But amid all the marketing “noise” generated by unsupported claims and promises, a few things truly stand out as most exciting and potentially transformational as we move forward into 2014 and beyond: the enhancing appeal of percutaneous EVAR (PEVAR) with availability of lower profile and highly flexible systems, and the impressive and rapidly expanding capability to achieve successful endovascular repair of a good number of juxtarenal and pararenal aneurysms. These capabilities can only strengthen the currently dominant role of EVAR, now used for approximately 65% of all AAA procedures in the United States where the number of repairs overall continues to grow.¹⁷ Most refreshingly, the focus on stent-graft integrity and durability of EVAR repair remains undiminished.

Editor’s Note: Disclosure: The author has completed and returned the ICMJE Form for Disclosure of Potential Conflicts of Interest. Dr. Criado reports consultancy, honoraria, and educational grants from Medtronic. 

Manuscript received July 2, 2013, final version accepted July 2, 2013.

Address for correspondence: Frank J. Criado, MD, FACS, FSVM, MedStar Union Memorial Hospital, 3333 N. Calvert St. Suite 560, Baltimore, Maryland 21218, USA.

References

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