Rate-dependent mechanical behavior of human femoropopliteal arteries in biaxial testing.

INTRODUCTION: Arteries, like other soft tissues, exhibit viscoelastic mechanical behavior, meaning their response to stress and strain is time dependent. Loading-rate dependency, i.e., a change in stiffness with the speed of loading, is one aspect of this viscoelasticity. This study investigates the loading-rate dependent stiffening of human femoropopliteal arteries (FPAs) under load-controlled biaxial testing. METHODS: Human FPA specimens were collected from 14 donors, including 7 males and 7 females, aged 45-55 years. A 10 × 10 mm segment was isolated, mounted onto a biaxial testing device, and subjected to varying loading rates (10 to 50 mN/s). Mechanical responses were recorded, and stress-stretch curves were analyzed. Statistical analyses, including mixed-design ANOVA, assessed the impact of sex and loading rates on tissue stiffness. RESULTS: Results indicated significant loading-rate dependency, particularly in the circumferential direction. Stretch decreased with increasing loading rate, with the most consistent effects observed in the circumferential direction. Statistical analyses revealed no significant interaction between sex and loading rate, though male arteries exhibited slightly higher compliance than female arteries. DISCUSSION: The findings demonstrate that the mechanical response of FPAs is dependent on the loading rate, with more pronounced effects observed in the circumferential direction. At higher loading rates, the human FPAs demonstrated a stiffer response in the circumferential direction.