Indexing the height of the patient to the thoracic aortic size may help identify thoracic aneurysm patients who do not meet current threshold for surgery. The purpose of this study was to examine the impact of Aortic Sac Size / Height Index (AHI) on mid-term survival after thoracic endovascular aortic repair (TEVAR) for descending thoracic aortic aneurysms.

Using the society for vascular surgery vascular quality initiative (VQI) national database, patients who underwent TEVAR (repair zones 3-5) for intact dTAAs between 2003 and 2020 were stratified by aortic height index (cm/m) into 3 groups. Group-1 (≤3.17-cm/m) mean aortic diameter of 4.7 (4.0-5.2); Group-2 (>3.17-cm/m to ≤4.06-cm/m) mean aortic diameter 6.0 (5.7-6.3).; Group-3 (≥4.06-cm/m) mean aortic diameter 7.3 (6.8-8.0). Cox proportional-hazard regression and survival models were used to estimate AHI impact on all-cause mortality after TEVAR after adjusting for potential confounders. The ROC curve was used to determine the AHI cut-off for 3-year mortality.

Of 1,311 patients who underwent TEVAR for dTAA, 51.3% were men and the median age was 75 (68-80) years. Table shows the main perioperative characteristics at the time of the TEVAR. The most common group that underwent endovascular repair was group 2. Women had significantly smaller aortic diameter in each group compared to men (group 1, 4.5 [3.4-5.0] cm vs. 5.0 [4.3-5.4] cm; group 2, 5.8 [5.5-6.0] cm vs. 6.1 [5.9-6.5] cm, group 3, 7.0 [6.7-7.5] cm vs. 8.0 [7.4-8.6] cm respectively). On Kaplan-Meier survival analysis (Figure), at 3-years, aneurysms >4.06-cm/m had the worst overall survival compared to the other groups and there were no differences between men and women. Aneurysms with aortic height index smaller than 3.17-cm/m at time of TEVAR had the highest survival at 3-years compared to the other size groups. Aortic height index (with group 1 as reference, HR: 1.41 [1.19-1.65], P<.001; for group 2, HR; 2.35 [1.47-3.82], P<.001 for group 3) and age (HR: 1.04 [1.02-1.06], P<.001) were associated with reduced survival on Cox regression analysis. The AHI index cuff-off point for the repair in terms of better survival appears to be ≤3.8-cm/m (0.60 [0.55-0.65], P<.001) in men (median aortic sac diameter 57 [51-61]) and women (median aortic sac diameter 55 [49-58]). About 32% of patients who underwent TEVAR had aneurysms larger than these criteria.

There is a correlation between a higher AHI and decreased mid-term survival following TEVAR for descending thoracic aortic aneurysms. Repair threshold based on AHI is ≤3.8-cm/m. In our study, 68% of patients met this threshold. AHI may be a more reliable index than absolute aortic size alone irrespective of gender. Further studies are needed to determine the threshold for surgical treatment based on AHI.