Reduced strain in abdominal aortic aneurysms after endovascular repair

PURPOSE: To compare in vivo strain in abdominal aortic aneurysms before and after endovascular aneurysm repair (EVAR), thereby obtaining a quantitative measure of changes in mechanical burden on the aneurysm wall. METHOD: Transabdominal ultrasound was acquired from 10 patients (9 men; median age 76 years, range 61-83) 1 day before and 2 days after elective EVAR. Strain was estimated as the relative cyclic elongation and contraction of the wall tissue in a number of connected segments along the aneurysm circumference. For each time instance of the cardiac cycle, the maximum and the average strain values along the circumference were recorded. The temporal maximums of these parameters (defined as the maximum strain and the peak average strain, respectively) were compared before and after EVAR. RESULTS: Both maximum strain and peak average strain were reduced following EVAR by 41% (range 35%-63%) and 68% (range 41%-93%), respectively. Despite the reduction, cyclic strain was still evident after the stent-graft was placed, even when no evidence of endoleak was found. Further, the strain values were inhomogeneous along the circumference, both before and after treatment. In 2 cases, endoleak was proven by routine computed tomography; the relative reduction in maximum strain was slightly less in these cases (35% and 38%) compared to those without endoleak (45%, range 38%-63%). No difference was found in reduction of peak average strain. CONCLUSION: Strain is significantly reduced after EVAR, but there may still be a certain level of strain after the treatment. The strain values are inhomogeneous along the circumference both before and after treatment. These results encourage further investigation to evaluate the potential for using circumferential strain as an additional indicator of outcome after endovascular repair.