Anatomical Evolution of the Descending Thoracic Aorta after Endovascular Treatment of a Degenerative Aneurysm

Abstract

The objective of this work was to describe the anatomical evolution of the descending thoracic aorta (DTA) after the endovascular treatment of a degenerative aneurysm (TEVAR) and to study the risk factors of unfavorable evolution. This was a retrospective multicentric study comparing the pre- and postoperative scanners of patients treated by TEVAR between September 1997 and July 2015. We compared seven diameters (two for each neck, 15 mm upstream and downstream from the stentgraft and the aneurysmal diameter), four lengths (proximal and distal necks, length of the aneurysm and length of DTA) and four angles (two between the healthy upstream and downstream aorta and two between the necks and the aneurysmal aorta). We made the measurements on the OsiriX software according to the central line. Any increase in the aneurysmal sac of more than 5mm or the presence of a type 1 or 3 endoleak, any reintervention, or a death related to the initial aortic disease defined an unfavorable evolution. We analyzed 61 of the 146 patients treated during this period. Mean age was 74 years. With an average CT follow-up of 27 months, we highlighted a global increase in 2 to 3 mm of the diameter at the level of the proximal and distal necks and 15 mm upstream and downstream from the stentgraft (p<0.005). The aneurysmal diameter decreased by 5 mm on average (p<0.001). We observed a 17 mm lengthening of the descending thoracic aorta (p<0.001). This lengthening was an unfavorable risk factor of evolution and it was mainly related to the lengthening of the initial portion of the DTA (10 mm). We observed a 7° acute evolution of the angle between the proximal neck and the aneurysmal axis (p=0.009). No patient having a stable length of DTA evolved unfavorably. The unfavorable risk of evolution is all the more high as the aneurysmal disease is diffuse. There exists a remodeling of DTA after endovascular treatment of a degenerative aneurism proportional to the extent of the aneurysmal disease and correlated to an unfavorable anatomical evolution. We observed the appearance of a plication at the level of the proximal portion of DTA. The parietal mechanical constraints particularly important near the aortic arch could explain this remodeling. The study of the aorta with functional imaging of this zone could make it possible to measure these stresses and to contribute to optimize the selection of the patients.