Thoracic Endovascular Aortic Repair Migration and Aortic Elongation Differentiated Using Dual Reference Point Analysis

Abstract

We evaluated patients using two reference points as a means for differentiating stent graft migration from aortic elongation. Conventional standards define migration as an absolute change in the distance from the distal graft ring to a distal landmark ≥10 mm compared with baseline measurement. Aortic elongation occurs over time in both healthy individuals and patients with aortic disease. Aortic elongation in patients with stent grafts may result in increased distal thoracic aortic lengths over time. These patients meet the standard definition for migration even if the stent has not moved in relation to the elongating aorta. This retrospective study evaluated the aortic length of 23 patients who were treated with the conformable Gore TAG thoracic endoprosthesis (W. L. Gore & Associates, Flagstaff, Ariz) in three clinical trials (dissection, traumatic injury, and aneurysm). Patients were selected having met the standard definition for migration. A standardized protocol was used to measure aortic centerline lengths, including the innominate artery (IA) to the most distal device ring, the IA to the celiac artery (CA), and the distal ring to the CA (Fig). Baseline lengths obtained from the first postoperative image were compared with length measurements obtained from the first interval at which they met standard definition for migration. The conventional standards for migration using a single reference point were compared with the use of dual reference points. Twenty of the 23 patients with endograft changes were deemed to have aortic elongation rather than true migration. The remaining three patients were deemed to have migration based on the IA to distal ring position compared with the IA to CA length change. The IA to CA interval length change was markedly greater in those with elongation than migration (Table). The distal ring to CA interval length change can be found in the Table. The IA to distal ring length was similar for elongation and migration (Table). These results highlight the dynamic changes that can occur in the aorta as a natural consequence of age. Employing two landmarks can account for these changes and proves to be an important factor, among others, in the differentiation of aortic elongation from true stent graft migration.TableInterval changes in aortic distancesMigration (n = 4)Elongation (n = 16)IA – CA change, mm−3.5 ± 5.423.8 ± 8.4IA – Distal ring change, mm2.5 ± 3.24.7 ± 5.5Distal ring – CA change, mm−9.8 ± 5.418.5 ± 6.6IA-CA and distal ring-CA lengths increased substantially in patients with elongation compared to those with migration. There was no apparent difference in length change between the IA – distal ring measurements. Open table in a new tab