Endovascular aortic aneurysm repair (EVAR) with the Endurant stent graft appears to be similarly successful and safe across the spectrum of aortic neck morphologies, according to a registry study published online May 1, 2015, ahead of print in the Journal of Vascular Surgery. Patients with challenging anatomy are no more likely than those with normal anatomy to require reintervention, despite increased risk of type I endoleak.  

Nonetheless, “[e]xtensive surveillance with annual imaging is recommended to detect and to treat stent graft-related complications, especially in patients with challenging anatomy,” advise Joep A.W. Teijink, MD, PhD, of Catharina Hospital (Eindhoven, the Netherlands), and colleagues.

The investigators analyzed data on 1,218 patients electively treated for AAA with the Endurant stent graft system (Medtronic Vascular) at 79 international sites between March 2009 and April 2011. Patients were enrolled in the Endurant Stent Graft Natural Selection Global Postmarket Registry (ENGAGE).

Proximal aortic neck anatomy in each patient was characterized as:

• Regular: proximal neck ≥ 15 mm with a suprarenal angulation ≤ 45 degrees and an infrarenal angulation ≤ 60 degrees
• Intermediate: proximal neck of 10-15 mm with the same suprarenal and infrarenal angulations, or a proximal neck > 15 mm with 1) a suprarenal angulation ≤ 60 degrees and an infrarenal angulation of 60-75 degrees or 2) a suprarenal angulation of 45-60 degrees and an infrarenal angulation ≤ 75 degrees
• Challenging: infrarenal necks that exceeded at least 1 of the 3 defining metrics

Anatomy was regular in 75.9% of patients, intermediate in 15.5%, and challenging in 8.5%. The last group did not meet criteria set forth in Endurant’s Instructions for Use.

Demographic and risk factors were mostly similar among the anatomical groups, although women were more prominent in the challenging and intermediate categories compared with the regular category (20.2% and 13.2% vs 9.1%; P = .01). On average, the group with challenging anatomy had larger maximum AAA diameters, and suprarenal and infrarenal neck angles differed for all group comparisons (all P < .01).

Operation time was longer and contrast volume was greater in patients with challenging compared with regular anatomy. Fluoroscopy time was also longer in the challenging vs regular group (all adjusted P < .01). However, there were no differences in length of postoperative stay or ICU admission.

Technical Success, Early Outcomes Not Compromised

Technical success was similar among the anatomic categories, ranging from 99.1% in the regular group to 97.1% in the challenging group.

Overall, 4 patients required immediate conversion to open surgery; only 1 was from the challenging group, and the reason for conversion was inability to remove the delivery device when a suprarenal strut became entrapped in the delivery system. Cases of type I and type III endoleak were equally distributed among the groups, although more proximal extension cuff placements were required to correct perioperative type Ia leaks in the challenging group than in the regular group. No patients died during the procedure.

By 30 days, 12 patients with regular anatomy, 1 with intermediate anatomy, and 3 with challenging anatomy had died, but there was no difference in adjusted mortality risk among the groups. One rupture occurred, in a patient with regular anatomy. Two patients with regular anatomy and 1 with challenging anatomy were converted to open surgery, yielding no difference between those groups. Likewise, the odds of needing secondary procedures were similar among all groups (table 1).

One year after implantation, all-cause and AAA-related mortality were similar among the groups, as were rates of secondary procedures, conversion to surgery, and types I and III endoleak. Stent graft stenosis was less prevalent in patients with regular vs challenging anatomy (adjusted OR 0.22; 95% CI 0.05-0.92).

Difficult Anatomy Now Less of a Bar to EVAR

“Advances in technology, imaging, and operator experience have led to an extension of the use of EVAR beyond initial manufacturers’ guidelines,” the authors observe. “Nowadays, an increasing number of patients with more challenging anatomies of the proximal infrarenal neck are treated with conventional EVAR.”

The current findings are in accord with previous small, retrospective studies, the investigators note. Though type I endoleaks were more common in patients with challenging anatomy, a conservative approach to treating less severe cases may be justified by the fact that more than three-quarters of the leaks seen at final angiography resolved spontaneously within 30 days, they add.

Longer operative time and greater use of contrast material in challenging patients may imply more complicated procedures, Dr. Teijink and colleagues acknowledge. Moreover, a previous study of the ENGAGE database reported neck length to be an independent risk factor for neck-related adverse events, they observe, and thus “preoperative planning with adequate sizing is of utmost importance. High image quality and optimal alignment of the C-arm in the cranial-caudal position are crucial to obtain maximum sealing in short necks.”

Evidence from this and an earlier study also suggest that “challenging anatomy of the infrarenal neck involves aneurysm size and probably the iliac axis,” the authors write.

Endurant May Overcome Disadvantages of Earlier Devices

While previous research indicates that women are at increased risk for postoperative complications, in the current study sex had no impact on technical outcomes or major adverse events within 1 year, the authors note. “This can be explained by the use of the Endurant stent graft, which may be better suited to overcome challenging aortoiliac anatomy in women compared with previous devices,” they assert. 

Neck length and angulation have also been reported to be risk factors for device migration, Dr. Teijink and colleagues write, but that finding was based on experience with first-generation endografts, which—unlike Endurant—have no active suprarenal fixation.

The authors acknowledge several study limitations:

• Registry data did not permit evaluation of the effect of neck thrombus and calcification
• Longer follow-up is required to assess the durability of the endograft in challenging anatomies
• The number of patients with challenging anatomy was insufficient to yield firm conclusions

However, they report, the Endurant for Challenging Anatomy: Global Experience (EAGLE) registry is now enrolling patients to assess whether the current guidelines for anatomic eligibility for EVAR with this stent graft system are still applicable.

Broos PPHL, Stokmans RA, van Sterkenburg SMM, et al. Performance of the Endurant stent graft in challenging anatomy. J Vasc Surg. 2015;Epub ahead of print.

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