Predictive biomechanical analysis of ascending aortic aneurysm rupture potential

Abstract

Aortic aneurysm is a leading cause of death in adults, often taking lives without any premonitory signs or symptoms. Adverse clinical outcomes of aortic aneurysm are preventable by elective surgical repair; however, identifying at-risk individuals is difficult. The objective of this study was to perform a predictive biomechanical analysis of ascending aortic aneurysm (AsAA) tissue to assess rupture risk on a patient-specific level. AsAA tissues, obtained intra-operatively from 50 patients, were subjected to biaxial mechanical and uniaxial failure tests to obtain their passive elastic mechanical properties. A novel analytical method was developed to predict the AsAA pressure-diameter response as well as the aortic wall yield and failure responses. Our results indicated that the mean predicted AsAA diameter at rupture was 5.6 ± 0.7 cm, and the associated blood pressure to induce rupture was 579.4 ± 214.8 mmHg. Statistical analysis showed significant positive correlation between aneurysm tissue compliance and predicted risk of rupture, where patients with a pressure-strain modulus ≥100 kPa may be nearly twice as likely to experience rupture than patients with more compliant aortic tissue. The mechanical analysis of pre-dissection patient tissue properties established in this study could predict the “future” onset of yielding and rupture in AsAA patients. The analysis results implicate decreased tissue compliance as a risk factor for AsAA rupture. The presented methods may serve as a basis for the development of a pre-operative planning tool for AsAA evaluation, a tool currently unavailable.

Patient-specific finite element analysis of ascending aorta aneurysms

“…Thus, in this study, the systolic AsAA meshes were transformed to obtain the unpressurized geometry using the following approach. Treating the AsAA as a thin-walled cylindrical pressure vessel as often done (8,12,18,20,23), the systolic wall tension in the circumferential (systolic hoop tension), t c sys , and axial directions, ta sys , are given by the Law of Laplace:…”

“…Since the wall tension in the circumferential direction is twice of that in the axial direction, the 1:0.5 circumferential to axial biaxial tension protocol data, collected from the dissected AsAA samples (30), mimics the in vivo loading condition. Following the method presented previously (23), the AsAA tissue stress-stretch response for the 1:0.5 biaxial tension protocol was then extrapolated to the physiological tension level. The circumferential and axial tissue stretches at the systolic condition, c sys and a sys , respectively, were then inversely determined (Fig.…”

“…Through this analysis, decreased AsAA tissue compliance in addition to increased wall tension was identified as a potential marker for rupture risk. The main limitation of the analytical method (23) was that an idealized cylindrical AsAA geometry was assumed and thus the effect of the patient's specific AsAA geometry on the vessel wall stress was not taken into account. To address this limitation, in the present study, patient-specific AsAA FE models were constructed for a total of 27 patients studied previously (23,30), for whom cardiac computed tomography (CT) scans were obtained.…”

“…The main limitation of the analytical method (23) was that an idealized cylindrical AsAA geometry was assumed and thus the effect of the patient's specific AsAA geometry on the vessel wall stress was not taken into account. To address this limitation, in the present study, patient-specific AsAA FE models were constructed for a total of 27 patients studied previously (23,30), for whom cardiac computed tomography (CT) scans were obtained. Utilizing this unique matching dataset of individual patient imaging data, and AsAA tissue elastic and failure properties (30), AsAA rupture risk was assessed on a truly patient-specific level using FE.…”

Modelación y simulación de la arteria aorta a partir de datos clínicos utilizando un modelo fraccional viscoelástico y el método del elemento finito

“…Las arterias se encuentran constituidas por tres capas internas, conocidas como la TúnicaÍntima, Túnica Media y Túnica Externa o Adventicia, estas tienen una forma de cilindro semicircular y básicamente se componen de redes de colágeno, elastina y tejido muscular liso [18], Figura 1. En los humanos jóvenes la capaíntima es un capa extremadamente delgada de aproximadamente 80nm, como una membrana separada de la media por una fina capa de elastina, la media está conformada de células musculares lisas sumergidas en una matriz celular de colágeno y elastina, finalmente la externa es una gruesa capa compuesta de colágeno y fibroblastos [19].…”