The mechanical properties of aortic wall, both healthy and pathological, are needed in order to develop and improve diagnostic and interventional criteria, and for the development of mechanical models to assess arterial integrity. This study focuses on the mechanical behaviour and rupture conditions of the human ascending aorta and its relationship with age and pathologies. Fresh ascending aortic specimens harvested from 23 healthy donors, 12 patients with bicuspid aortic valve (BAV) and 14 with aneurysm were tensile-tested in vitro under physiological conditions. Tensile strength, stretch at failure and elbow stress were measured. The obtained results showed that age causes a major reduction in the mechanical parameters of healthy ascending aortic tissue, and that no significant differences are found between the mechanical strength of aneurysmal or BAV aortic specimens and the corresponding age-matched control group. The physiological level of the stress in the circumferential direction was also computed to assess the physiological operation range of healthy and diseased ascending aortas. The mean physiological wall stress acting on pathologic aortas was found to be far from rupture, with factors of safety (defined as the ratio of tensile strength to the mean wall stress) larger than six. In contrast, the physiological operation of pathologic vessels lays in the stiff part of the response curve, losing part of its function of damping the pressure waves from the heart.
Abstract-The lack of reliable mechanical data on coronary arteries and, more specifically, on their wall strength hampers the application of numerical models and simulations to vascular problems, and precludes physicians from knowing in advance the response of coronary arteries to the different interventions. Studies of the mechanical properties of coronary arteries have been carried out almost exclusively on animals. Only a few studies have tried to characterize the in vivo behavior of human coronaries through tests under physiological conditions. In this work, the mechanical properties of human coronary arteries have been characterized. Whole samples from human right (RC) and left anterior descending (LAD) coronary arteries aged between 23 and 83 years have been studied by means of in-vitro tensile testing up to failure.
In recent times, significant effort has been made to understand the mechanical behaviour of the arterial wall and how it is affected by the different vascular pathologies. However, to be able to interpret the results correctly, it is essential that the influence of other factors, such as aging or anisotropy, be understood. Knowledge of mechanical behaviour of the aorta has been customarily constrained by lack of data on fresh aortic tissue, especially from healthy young individuals. In addition, information regarding the point of rupture is also very limited. In this study, the mechanical behaviour of the descending thoracic aorta of 28 organ donors with no apparent disease, whose ages vary from 17 to 60 years, is evaluated. Tensile tests up to rupture are carried out to evaluate the influence of age and wall anisotropy. Results reveal that the tensile strength and stretch at failure of healthy descending aortas show a significant reduction with age, falling abruptly beyond the age of 30. This fact places age as a key factor when mechanical properties of descending aorta are considered.
While the situation of tissue donation and transplantation differs between Latin American and European countries, a common problem is tissue deficiency. Hence, at present, there is a pressing need to generate alternatives so as to increase the possibilities of obtaining the requested materials. Consequently, it would be of significant interest to establish an intercontinental network for tissue exchange, to improve international cooperation, and to help patients that need tissue transplantation, and to evaluate the feasibility of using an intercontinental network for the exchange of cryopreserved arteries (cryografts), preserving the arterial distensibility and ensuring a reduced native artery-cryograft biomechanical mismatch. Distensibility was studied in ovine arteries divided into three groups: intact (in vivo tests, conscious animals), fresh control (in vitro tests immediately after the artery excision, Uruguay), and cryografts (in vitro tests of cryopreserved-transported-defrosted arteries, Spain). Histological studies were performed so as to analyze changes in the endothelial layer and elastic components. The comparison between fresh control and cryografts showed that neither the cryopreservation nor the exchange network impaired the distensibility, despite the expected histological changes found in the cryografts. The comparison between intact and cryografts showed that the cryografts would be capable of ensuring a reduced biomechanical mismatch. The cryopreservation and the intercontinental network designed for artery exchange preserved the arterial distensibility. It could be possible to transfer cryografts between Latin America and Europe to be used in cardiovascular surgeries and/or for tissue banking reprocessing, with basic biomechanical properties similar to those of the fresh and/or native arteries.
F. Análisis de imágenes histológicas F-1 G. Resultados de los ajustes al modelo de Yeoh G-1 H. Resultados de los ajustes del modelo anisótropo mixto de Holzapfel/Demiray a los ensayos de tracción uniaxial H-1 I. Programa de ajuste del modelo de material Holzapfel/Demiray a los ensayos experimentales para Matlab I-1 J. Análisis numérico del ensayo presión-diámetro J-1 K. Modelo de material isótropo Yeoh para el inflado de un globo K-1 viii Gracias a. . . Gracias a Gustavo Guinea y José Miguel Atienza por dirigir esta tesis, por las aportaciones, la información, el interés, el tiempo y las correcciones.Gracias a los compañeros del grupo por introducirme en el mundo de los biomateriales.Gracias a los miembros del departamento Ciencia de Materiales, por haberme acogido durante este tiempo, por la ayuda y el interés.Gracias a mis compañeros de despacho Alex y Borja, por las charlas y risas, y por siempre tener tiempo a responder a preguntas del estilo "¿Cómo se escribe . . .? ¿Cómo se dice . . .? ¿. . . es con acento?"
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.