Failure of vascular tissue with applications to the aneurysm wall, carotid plaque and myocardial tissue

Sammanfattning: Cardiovascular disease is the leading cause of death in the modern world. Examples are thoracic aortic aneurysm (TAA), abdominal aortic aneurysm (AAA) and stroke due to plaque rupture. Failure in soft tissues caused by medical devices is also a medical challenge. In all these cardiovascular events a better prediction of failure of the tissue and a better understanding about the tissue properties will help in predicament and treatment. For example the diameter-based indication for surgical repair of AAA and TAAs is not sufficient and refined methods are needed. In this thesis failures of some soft vascular tissues, was studied. Experiments have been combined with numerical modeling to understand the elastic and failure properties of AAA, TAA and plaque tissue as well as the ventricular wall. Vascular tissue is anisotropic, time-dependent, nonlinear and shows large deformations. Among others this thesis showed the importance of viscoelasticity which motivates to develop a new continuum mechanical framework. In addition a large part of this thesis dealt with anisotropy of vascular tissue. For the first time the collagen orientation distribution in the AAA wall has been identified. Collagen and its distribution orientation is also an important feature of this tissue. There was a correlation between the strength and stiffness of the AAA samples with the decreasing wall thickness. Increased stiffness was found in the aortic wall of patients with chronic obstructive pulmonary disease (COPD) compared to patients that did not have COPD. As well as difference in stiffness of TAA tissue, in patients with non-pathologic and pathologic aortic valves. Some of the findings in this thesis could have a long-term consequence for management of risk of rupture in AAA, TAA and plaque.