CONSTITUTIVE DESCRIPTION OF HUMAN FEMOROPOPLITEAL ARTERY AGEING

Introduction: Femoropopliteal artery (FPA) mechanics play a paramount role in pathophysiology and the artery’s response to therapeutic interventions, but data on mechanical FPA properties are scarce. Our goal was to... [ view full abstract ]

Introduction: Femoropopliteal artery (FPA) mechanics play a paramount role in pathophysiology and the artery’s response to therapeutic interventions, but data on mechanical FPA properties are scarce. Our goal was to characterize human FPAs over a wide population to derive a constitutive description of the FPA ageing that can be used for computational modeling.

Methods: Fresh human FPA specimens (n=579) were obtained from n=351 predominantly male (80%) donors 54±15 years old (range 13-82 years). Morphometric characteristics including radius, wall thickness, opening angle, and longitudinal pre-stretch were recorded. Arteries were subjected to multi-ratio planar biaxial extension to determine constitutive parameters for an invariant-based model accounting for the passive contributions of ground substance, elastin, collagen and smooth muscle. Non-parametric bootstrapping was used to determine unique sets of material parameters which were used to derive age-group-specific characteristics. Physiologic stress-stretch state was calculated to capture changes with ageing.

Results: Morphometric and constitutive parameters were derived for seven age groups. Vessel radius, wall thickness, and circumferential opening angle increased, while longitudinal pre-stretch decreased with ageing (p<0.01). Age-group-specific constitutive parameters accurately portrayed orthotropic FPA stiffening with greater longitudinal changes due to degradation and fragmentation of longitudinal intramural elastin, and adaptive remodeling with reduction in physiologic longitudinal and circumferential stretches and stresses with age.

Conclusions: Constitutive description of FPA ageing, based on ex vivo human FPA analysis, may allow better understanding of pathophysiology and for the development of computational models of FPA function and behavior. These models may be useful for device development and in personalized medicine approaches.