Experimental characterization and modeling of the passive and active properties of coronary and carotid arteries

Abstract

Atherosclerosis of the coronary or carotid arteries is the leading cause of mortality and disability in industrialized nations. Both arteries are of great biomedical and clinical interest because they are prone to atherosclerosis and are often treated with balloon angioplasty, stenting or carotid endarterectomy to prevent myocardial infarction and stroke. 

Our hypothesis is that detailed knowledge of their mechanical behavior can greatly improve the preoperative planning of these therapies, e.g., patient-specific finite element analysis can be used to simulate the balloon angioplasty and stenting procedure and optimize the choice of balloon and stent geometry. In addition, stresses and strains on cells and tissues have been shown to influence the development of atherosclerotic lesions.

Three-dimensional mechanical models of the artery are therefore required to analyze the distribution of stresses and strains in the vessel wall. However, most biomechanical studies and constitutive models consider only the passive and not the active behavior of arteries in their computer simulations. Our approach involves a holistic experimental investigation of the passive and active behavior of coronary and carotid arteries obtained in this first phase of the proposal from pigs. In a second, future phase, once the methods have been established, the approach will be extended to human tissue. This is achieved by passive and active uniaxial and biaxial extension tests on intact and sectioned specimens, as well as extension-inflation tests on intact arterial segments. Second, the underlying microstructure responsible for the mechanical properties of the tested arterial tissues will be characterized by histological studies of collagen, elastin, and smooth muscle cells. Third, based on these data, a three-dimensional model capable of describing and predicting the active muscle contraction behavior in addition to the passive behavior of these important arteries will be developed, calibrated, and validated against the extensive data set. 

Existing experimental data and an appropriate material model that considers smooth muscle activation in these arteries are very scarce and limited to a single location in these arteries and only to strip tests. In addition, most biomechanical studies and constitutive models consider only the passive and not the active behavior of the arteries in their computer simulations. 

The combination of the expertise of both applicants in passive and active experiments and modeling of soft biological tissues at the Graz University of Technology (Austria) and the Technical University of Braunschweig (Germany) is firstly necessary to address all the tasks in the proposed project, and secondly will allow the development of a unique three-dimensional active material model of these two important arteries, which is currently not possible with the data available in the literature.