Similarities of arterial collagen pressure-diameter relationship in ovine femoral arteries and PLLA vascular grafts

Introduction: In-vivo implanted vascular grafts fail due to the mechanical mismatch between the native vessel and the implant. The biomechanical characterization of native vessels provides valuable information towards the development of synthetic grafts. Materials and Methods: Five samples of electrospun nanofibrous poly(L-lactic acid)(PLLA) tubular structures were subjected to physiological pulsating pressure using an experimental setup. Four ovine femoral arteries were also tested in the experimental setup under the same conditions. Instantaneous diameter and pressure signals were obtained using gold standard techniques, in order to estimate the dynamic pressure-strain elastic modulus (E_Pε) of both native vessels and grafts. Results: Synthetic grafts showed a significant increase of E_Pε (10.57±0.97 to 17.63±2.61 10⁶ dyn/cm²) when pressure was increased from a range of 50-90 mmHg (elastin-response range) to a range of 100-130 mmHg (collagen-response range). Furthermore, femoral arteries also exhibited a significant increase of E_Pε (1.66±0.30 to 15.76±4.78 10⁶ dyn/cm²) with the same pressure variation, showing that both native vessels and synthetic grafts have a similar behavior in the collagen-acting range. Conclusion: The mechanical behavior of PLLA vascular grafts was characterized In vitro. However, the procedure can be easily extrapolated to In vivo experiences in conscious and chronically instrumented animals.