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Evaluation Of Peak Wall Stresses Across Tubingen Aortic Pathoanatomy (TAIPAN) Score For Aortic Diameter And Length In Ascending Thoracic Aortic Aneurysms
Siavash Zamirpour, Zhongjie Wang, Yue Xuan, Axel Gomez, Michael D. Hope, David Saloner, Julius Guccione, Liang Ge, Elaine E. Tseng.
University of California, San Francisco and San Francisco VA Medical Center, San Francisco, CA, USA.

Objective: Tübingen Aortic Pathoanatomy (TAIPAN) project determined reference values for aortic diameter and length based upon sex, age, height, and weight to improve upon a single diameter parameter for dissection risk. Since dissection can be considered a mechanical failure that can occur when wall stress exceeds wall strength, we sought to evaluate peak wall stresses across TAIPAN scores in ascending thoracic aortic aneurysms (aTAA).Methods: Chest computed tomography was retrospectively reviewed for 209 aTAA patients to determine the centerline aortic length from aortic annulus to brachiocephalic artery. Patient-specific models were developed from patient-specific geometries, accounting for pre-stress geometry. Wall stresses were determined using finite element analysis. TAIPAN score was calculated: 0, 1, and 2 points for diameter <4.5, 4.5-5.4, and ≥5.5cm, respectively, and 0 and 1 points for length <120 and ≥120mm, respectively. Peak wall stresses were compared by Kruskal-Wallis test.Results: Median (IQR) maximal diameter, aortic length, and peak circumferential and longitudinal stresses were 4.6(0.6)cm, 146(25)mm, 503(163), and 304(79)kPa, respectively. N was 9, 72, and 128 for TAIPAN scores 0, 1, and 2+, respectively. Median (IQR) peak circumferential stresses were 425(79), 455(134), and 549(145)kPa for score 0, 1, and 2+(p=7.3×10-10). Pairwise comparisons were significant between scores 0vs2+(p=0.00051) and 1vs2+(p=1.4×10-8). Median (IQR) peak longitudinal stresses were 252(30), 288(57), and 322(78)kPa for score 0, 1, and 2+(p=3×10-7). Pairwise comparisons were significant between scores 0vs2+(p=0.00026) and 1vs2+(p=1.9×10-5). 23/23(100%) patients with diameter ≥5.5cm were captured by the 2+ threshold, as were 105/186(56%) patients with diameter <5.5cm.Conclusions: There were significant differences in peak wall stresses across TAIPAN scores. Nonetheless, substantial overlap in stresses persists. Notably, 56% of nonsurgical(<5.5cm) patients met the 2+ threshold. Despite using well-defined anatomic markers, aortic lengths were substantially longer than in previous work, suggesting inherent population differences (European civilians vs US veterans).



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