Active stent-graft fixation below the renal arteries may have the least effect on aortic neck degeneration, study finds

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Lillian Malach

Stent grafts with active fixation below the renal arteries as well as oversizing by less than 10% seem to have the least effect on aortic neck degeneration over time, according to a research team who conducted a retrospective review of all endovascular aneurysm repairs (EVARs) for abdominal aortic aneurysms (AAAs) carried out at their parent institution over a 10-year period.

A review of three types of graft fixation—infrarenal active, suprarenal active and suprarenal passive—showed that the suprarenal active fixation method led to greater diameter in both suprarenal and infrarenal aortic neck measurements. Additionally, graft oversizing greater than 15%, and grafts larger than 28mm, also led to larger increases in suprarenal neck measurements. At four years, the change in aortic neck diameter was statistically significant among those with oversizing greater than 15% compared to two other groups: those with oversizing between 10–15% and those with less than 10%.

The results were part of a study led by Carlos F. Bechara, MD, co-director of Loyola University’s Center for Aortic Disease, in Maywood, Illinois, that looked into the effect of stent graft active fixation and oversizing on aortic neck degeneration after EVAR. Lillian Malach, BS, a fourth-year medical student at Loyola Medicine, delivered the findings during the Midwestern Vascular Surgical Society (MVSS) annual meeting (Sept. 9–12).

Aortic neck degeneration post-EVAR has been implicated in the long-term development of endoleaks and subsequent reintervention, Malach explained. “Optimal endograft sizing is a vital aspect to successful repair; however, outside of manufacturer recommendations, there really is no consensus regarding the optimal oversizing of a graft.”

A total of 400 patients who underwent EVAR at Loyola between 2006 and 2015 were analyzed, from which 154 were included after exclusions.

The team measured the largest aortic diameter on axial images 1cm above and below the renal arteries. Change in suprarenal and infrarenal aortic measurements were evaluated by calculating the millimeter difference from each scan compared with the preoperative scan.

The suprarenal active fixation demonstrated the greatest change in aortic neck measurement out to four years, Malach said. “Similar to what we found with the infrarenal aortic neck measurement, the average change in infrarenal aortic neck measurement also demonstrated that the EVAR performed [with a] suprarenal active fixation graft resulted in the greatest change, and we saw an average at four years of 5.31mm change for the suprarenal plus active, and 2.8mm for the graft with infrarenal plus active fixation.”

Meanwhile, the effect of oversizing on suprarenal and infrarenal aortic neck showed that at four years, the greater than 15% group had a statistically larger neck diameter compared to the less than 10% oversizing group: 3.26mm for <15% compared to a 0.41mm average change for >10%.

“Similarly, with the infrarenal neck measurement, the less than 10% group were statistically smaller than either of the other two groups at four years,” continued Malach. “We saw an average of 3.01mm in the less than 10% group compared to 5.95mm and 5.05mm in the other two groups.”

The researchers further concluded that increased degeneration may lead to increased rates of endoleaks, reintervention and aneurysm-related mortality—seen previously in the literature.

“These findings may influence device selection and degree of oversizing when performing EVARs,” Malach added. “In general, these findings may provide additional information for surgeons to make the best decision when evaluating patients for AAA whether with EVAR or open repair. And, [the study] also emphasizes the importance of long-term follow-up surveillance.

“In future, we’re hoping to categorize the clinical significance of suprarenal and infrarenal degeneration, evaluate the endoleak and reintervention rates based on the factors that we looked at in this study, and evaluate iliac sizing to see if they have significant degeneration over time.”

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