Abstract 16957: Ascending Thoracic Aortic Aneurysm Wall Stresses Evolve in Parallel With Diameter Growth

Abstract

Introduction: Guidelines for ascending thoracic aortic aneurysm (ATAA) repair use ATAA diameter, with repair recommended at ≥5.5cm, but ATAA biomechanics may better predict acute type A dissection (ATAD) risk. However, little is known regarding changes in wall stresses among clinically followed patients with <5.5cm ATAA over time. This information is important for patient risk stratification. Hypothesis: We hypothesized that peak ATAA wall stresses would change over time in a patient-specific fashion alongside diameter. Methods: 31 nonsurgical ATAA patients (<5.5cm and growth <0.5cm/year) with computed tomography angiography (CTA) scans taken 3 to 5 years apart were identified. Images were used to construct patient specific three-dimensional ATAA models. Peak diastolic circumferential stresses were determined along the ascending aorta (AA), sinotubular junction (STJ), and aortic sinuses using finite element analysis. Diameters at both time points were measured from CTA scans by a single radiologist blinded to stress results. Stress and diameter distributions were compared using paired t-tests. Results: In the overall population, ATAA diameter increased over time (4.39±0.4 cm vs. 4.43±0.4 cm, p=0.02), while diastolic circumferential stresses along the aorta did not significantly change. However, we found two distinct patient groups: one where wall stresses increased and one where stresses decreased over time. Separate analysis of these groups showed significant changes in circumferential stress in all three aortic regions (488 ± 120 vs. 340 ± 63 kPa for the sinuses, 472 ± 127 vs 345 ± 76 kPa for the STJ and 337 ± 54 vs 277 ± 28 kPa for AA, p<0.001), and significant increase in diameter in the group with increasing stresses (p=0.02). Conclusions: In this nonsurgical group, there is no statically significant change of peak ATAA wall stresses at diastole over 3-5 years. The patients with increased stress were found to be associated with increases in diameter during the corresponding time period. More patient specific data is required to investigate the interaction between wall biomechanics and aortic remodeling. Our results lay the foundation for developing patient-specific ATAD risk predictors for ATAD using patient-specific wall stress changes.