Abstract
BackgroundAortic dissection (AD) is a common pathology and challenging clinical problem. A better understanding of the biomechanical effects preceding its initiation is essential for predicting adverse events on a patient-specific basis. Moreover, the predictability of patient-specific biomechanics-based computational models is hampered by uncertainty about boundary conditions and material properties.ObjectivePredisposition of thoracic aortic aneurysms (TAA) to ADs can be related to the degradation of biomechanically important constituents in the aortic wall of TAAs. The goal of the present study is to develop a new methodology to measure strain fields in aortic tissues subjected to radial tensile loading, combining optical coherence tomography (OCT) and digital image correlation (DIC).MethodsRadial tensile tests are performed on 5 samples collected from a healthy porcine descending thoracic aorta and 2 samples collected from a human ascending thoracic aortic aneurysm. At each step of the radial tensile test, the OCT technique is used to acquire images of the sample presenting a speckle pattern generated by the optical signature of the tissue. The speckle pattern is used to quantify displacement and strain fields using DIC. Stress-strain data are also measured throughout the analyzed range.ResultsResults show that strain commonly localizes very early during tensile tests, at the location where the crack onset occurs. Aneurysm samples even show a sharper localization than healthy porcine tissues.ConclusionThis suggests the importance of extending the analysis to a larger number of human samples using our new methodology to better identify the conditions predisposing aortas to dissection.
Highlights
Aortic dissection (AD) is an adverse condition of the aorta, which is typically described by a primary intimal tear on the aortic wall [1]
The goal of the present paper is to introduce a new methodology combining digital image correlation (DIC) and optical coherence tomography (OCT) to measure strain fields in aortic tissues subjected to tensile loading along the radial direction
Since all samples had the same thickness, we evaluated the stiffness at a displacement value of 0.04 mm, corresponding to an average strain of 0.01 (1%), starting from the first positive stress point of the curve
Summary
Aortic dissection (AD) is an adverse condition of the aorta, which is typically described by a primary intimal tear on the aortic wall [1]. Arterial dissection is a common pathology and a challenging clinical problem, the underlying biomechanics remain underexplored. Exp Mech (2021) 61:119–130 to separation in a plane parallel to the lumen [6, 7], as elastin fibers, collagen bundles and smooth muscle cells are organized in concentric lamellar units in the media layer [8]. AD is frequent in patients harboring a thoracic aortic aneurysm (TAA). TAA is a life-threatening cardiovascular disease leading to weakening of the aortic wall and permanent dilation [10]. TAA is characterized at the tissue level by extracellular matrix degradation and biomechanical weakening of the aortic wall, leading to dilation and failure by rupture or dissection. Aortic dissection (AD) is a common pathology and challenging clinical problem. The predictability of patient-specific biomechanics-based computational models is hampered by uncertainty about boundary conditions and material properties
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