Engineering in-plane mechanics of electrospun polyurethane scaffolds for cardiovascular tissue applications

Effective cardiovascular tissue surrogates require high control of scaffold structural and mechanical features to match native tissue properties, which are dependent on tissue-specific mechanics, function heterogenicity, and morphology. Bridging scaffold processing variables with native tissue properties is recognized as a priority for advancing biomechanical performance of biomedical materials and, when translated to the clinical practice, their efficacy. Accordingly, this study selected electrospinning on a rotating cylindrical target as an apparatus of broad application and mapped the relationship between key processing variables and scaffold mechanics and structure. This information was…

In Vivo Strain Analysis of Dilated Ascending Thoracic Aorta by ECG-Gated CT Angiographic Imaging

Accurate assessment of aortic extensibility is a requisite first step for elucidating the pathophysiology of an ascending thoracic aortic aneurysm (ATAA). This study aimed to develop a framework for the in vivo evaluation of the full-field distribution of the aortic wall strain by imaging analysis of electrocardiographic- (ECG) gated thoracic data of 34 patients with ATAA. Seven healthy controls (i.e., non-aneurysmal aorta) from patients who underwent ECG-gated CT angiography for coronary artery diseases were included for comparison. To evaluate the systolic function, ECG-gated computed tomography (CT) angiography was used to generate patient-specific geometric meshes of the ascending aorta…

On the severity of aortic stenosis in ascending aortic aneurysm: A computational tool to examine ventricular-arterial interaction and aortic wall stress

Abstract An ascending thoracic aortic aneurysm (ATAA) is a life-threatening cardiovascular consequence of vessel dilatation that portends adverse events and death. From a clinical perspective, ATAA should not be treated as an isolated disease, and surgery is often carried out in the presence of AS, aortic insufficiency or a calcified valve leaflet. Aortic stenosis (AS) is common in ATAAs and leads to both vessel rigidity and left ventricular (LV) impairment. In this study, lumped-parameter modeling and computational analysis were used to assess the change in the wall shear stress (WSS) and intramural wall stress of patient-specific ATAA models with different degrees of AS (i.e., mild to sev…

Comparison of hemodynamic and structural indices of ascending thoracic aortic aneurysm as predicted by 2-way FSI, CFD rigid wall simulation and patient-specific displacement-based FEA

Patient-specific computational modeling is increasingly being used to predict structural and hemodynamic parameters, especially when current clinical tools are not accessible. Indeed, pathophysiology of ascending thoracic aortic aneurysm (ATAA) has been simulated to quantify the risk of complications by novel prognostic parameters and thus to improve the clinical decision-making process related to the intervention of ATAAs. In this study, the relevance of aneurysmal wall elasticity in determining parameters of clinical importance, such as the wall shear stress (WSS), is discussed together with the significance of applying realistic boundary conditions to consider the aortic stretch and twis…

Hereditariness of Aortic Tissue: In-Vitro Time-Dependent Failure of Human and Porcine Specimens

This study aims to investigate the time dependent failure of aortic tissues for pathological and healthy samples by biomechanical testing. The experimental campaign has involved human pathological tissue and healthy swine tissue as preliminary study towards the development of novel failure criteria.

A Non-Local Mode-I Cohesive Model for Ascending Thoracic Aorta Dissections (ATAD)

This paper presents a non-local interface mechanical model to describe aortic dissection. In this regard, the mode-I debonding problem based on a cohesive zone modeling is endowed with non-local terms to include long-range interactions that are present in multi-layered biological tissue. Such non-local effects are related to the collagen fibers that transmit forces between non-adjacent elements. Numerical simulations are provided with different values of the non-local parameters in order to show the effect of the non-locality during the debonding processes.

Shear Stress and Aortic Strain Associations With Biomarkers of Ascending Thoracic Aortic Aneurysm

This study aims to investigate the association of wall shear stress (WSS) and aortic strain with circulating biomarkers including matrix metalloproteinases (MMP), tissue inhibitors of metalloproteinase (TIMP), and exosomal level of microRNA (miRNA) in ascending aortic aneurysms of patients with bicuspid or tricuspid aortic valve.A total of 76 variables from 125 patients with ascending aortic aneurysms were collected from (1) blood plasma to measure plasma levels of miRNAs and protein activity; (2) computational flow analysis to estimate peak systolic WSS and time-average WSS (TAWSS); and (3) imaging analysis of computed tomography angiography to determine aortic wall strain. Principal compo…

Identification of circumferential regional heterogeneity of ascending thoracic aneurysmal aorta by biaxial mechanical testing

Abstract Ascending thoracic aortic aneurysm (ATAA) in patients with bicuspid aortic valve (BAV) can present an asymmetrical aortic dilatation compared with patients with tricuspid aortic valve (TAV). This pattern of aneurysm dilatation led us to hypothesize that biomechanical differences likely induced by regional heterogeneity of material properties can underlie the observed asymmetric enlargement discrepancies between BAV ATAA and TAV ATAA. This study aimed to characterize the mechanical properties and associated aortic tissue stiffness changes along the circumferential direction of aortic rings collected from surgically-repaired patients with ATAA. Biaxial material testing was performed …

Patient-specific computational evaluation of stiffness distribution in ascending thoracic aortic aneurysm

Quantifying local aortic stiffness properties in vivo is acknowledged as essential to assess the severity of an ascending thoracic aortic aneurysm (ATAA). Recently, the LESI (local extensional stiffness identification) methodology has been established to quantify non-invasively local stiffness properties of ATAAs using electrocardiographic-gated computed tomography (ECG-gated CT) scans. The aim of the current study was to determine the most sensitive markers of local ATAA stiffness estimation with the hypothesis that direct measures of local ATAA stiffness could better detect the high-risk patients. A cohort of 30 patients (12 BAV and 18 TAV) referred for aortic size evaluation by ECG-gated…

Micromechanical Modeling of Aortic Pathologies

Simulation study of transcatheter heart valve implantation in patients with stenotic bicuspid aortic valve

Bicuspid aortic valve (BAV) anatomy has routinely been considered an exclusion in the setting of transcatheter aortic valve implantation (TAVI) because of the large dimension of the aortic annulus having a more calcified, bulky, and irregular shape. The study aims to develop a patient-specific computational framework to virtually simulate TAVI in stenotic BAV patients using the Edwards SAPIEN 3 valve (S3) and its improved version SAPIEN 3 Ultra and quantify stent frame deformity as well as the severity of paravalvular leakage (PVL). Specifically, the aortic root anatomy of n.9 BAV patients who underwent TAVI was reconstructed from pre-operative CT imaging. Crimping and deployment of S3 fram…