An experimental and computational investigation of the material behaviour of discrete homogenous iliofemoral and carotid atherosclerotic plaque constituents

Abstract

An enhanced understanding of the structure and mechanical behavior of atherosclerotic plaque can potentially provide key guidance for clinical intervention and vascular device design. This study presents an investigation of morphological and mechanical properties of iliofemoral (n = 8) and carotid (n = 22) atherosclerotic plaque constituents. μCT analysis is used characterize the content and morphology of calcifications in excised plaques. Calcified particles contribute a significant proportion of the average plaque volume (7.6% carotid; 19.1% iliofemoral), and on average over 50% of this volume (53.7 ± 18.6% carotid; 61.7 ± 15% iliofemoral) is accounted for by the largest individual particle found in the plaque. Fibrous tissue and calcifications were isolated for mechanical testing. Unconfined compression testing of isolated calcifications uncovered viscoelastic behavior. Tensile stress relaxation uncovered viscoelastic behavior in fibrous atherosclerotic samples. Iliofemoral fibrous samples were found to be statistically significantly stiffer (*p < 0.05) than carotid fibrous samples. Results show isolated calcifications are approximately two orders of magnitude stiffer than non-calcified fibrous tissue. The results from this study advance the current understanding of plaque mechanics and suggest that computational simulation of angioplasty procedures should incorporate a discrete representation of atherosclerotic plaque constituents.