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Elective repair of bicuspid aortic valve (BAV)-associated ascending thoracic aortic aneurysms (aTAAs) is recommended at lower size limits than tricuspid aortic valve (TAV)-associated aTAAs. Rupture/dissection can occur when wall stress exceeds wall strength. We previously developed a validated computational method for determining aTAA wall stress; however, to date, this method has not applied to a patient-specific BAV aTAA. The goal of this study was to develop a patient-specific BAV aTAA computational model to determine regional wall stress, using the required zero-pressure geometry, wall thickness, material properties, and residual stress.
BAV aTAA specimen was excised intact during elective repair and zero-pressure geometry was generated using micro-computed tomography. Residual stress was determined from aTAA opening angle. ATAA material properties determined using biaxial stretch testing were incorporated into an Ogden hyperelastic model. Finite element analyses (FEA) were performed in LS-DYNA to determine wall stress distribution and magnitudes at systemic pressure.
Left aTAA region had the highest stiffness, followed by the right, and then anterior/posterior walls suggesting regional variability in mechanical properties. During systole, mean principal wall stresses were 108.8kPa (circumferential) and 59.9kPa (longitudinal), while peak wall stresses were 789.4kPa (circumferential) and 618.8kPa (longitudinal). Elevated wall stress pockets were seen in anatomic left aTAA regions.
We developed the first to our knowledge patient-specific BAV aTAA model based upon surgical specimen. Surgical specimens serve as the gold standard for determining wall stress to validate models based on in vivo imaging data alone. Regions of maximal wall stress may indicate sites most prone to rupture and are crucial for evaluating rupture risk based upon the wall stress/strength relationship.
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