Predissection-derived geometric and distensibility indices reveal increased peak longitudinal stress and stiffness in patients sustaining acute type A aortic dissection: Implications for predicting dissection

OBJECTIVE: To assess ascending aortic distensibility and build geometry and distensibility-based patient-specific stress distribution maps in patients sustaining type A aortic dissection (TAAD) using pre-dissection non-invasive imaging. METHODS: Review of charts from patients undergoing surgical repair of TAAD (n=351) led to the selection of a subset population (n=7) with two or more pre-dissection CTAs and echocardiograms at least one year prior to dissection. Ascending aortic wall biomechanical properties (aortic strain, distensibility and stiffness) were compared to age and size matched non-dissected non-aneurysmal controls. Patient-specific aortic strain served as an input in aortic geometry-based simulated three-dimensional reconstructions to generate longitudinal and circumferential wall stress maps. Inspection of peri-operative dissection scans and intraoperative visual examination confirmed primary tear locations. RESULTS: Pre-dissection echocardiography revealed ascending aortas of patients sustaining TAAD to exhibit decreased aortic wall strain (14.50 ± 1.13% vs 8.49 ± 1.08%; p < 0.01), decreased distensibility (4.26 ± 0.44 vs 2.39 ± 0.33 10(−6)cm(2)dyne(−1); p < 0.01), increased stiffness (3.84 ± 0.24 vs 7.48 ± 1.05; p < 0.001), and increased longitudinal wall stress (246 ± 22 vs 172 ± 37 kPa; p < 0.01). There was no significant difference in circumferential wall stress. Pre-dissection CTA models revealed overlap between regions of increased longitudinal wall stress and primary tear sites. CONCLUSIONS: Using pre-dissection imaging, we identified increased stiffness and longitudinal wall stress in ascending aortas of dissection patients. Patient-specific imaging-derived biomechanical property maps like these may be instrumental toward designing better prediction models of aortic dissection potential.