Design of biomechanically compliant small diameter vascular grafts and their in vitro and in vivo properties

Abstract

The performances of textile composite vascular grafts, specially designed and constructed in this work were investigated. In developing compliant structures, textile threads of two widely different deformative characteristics, one matching nearly those of the elastin and other of the collagen fibres, were selected. The materials used were a polyurethane monofilament yarn with low modulus of elasticity and a bulked polyester multifilament yarn with high modulus of elasticity. Tubular grafts of diameter in the range 4-6 mm were made by a weaving process utilizing a foil ribbon loom. Two types of woven grafts were developed. In the first type (HVGI1), polyester threads of 9 tex linear density were used as warp, and the same polyester and pre-stretched polyurethane (7.8 tex linear density) were used as the weft. In the second variant (HVG-2), pre-stretched polyurethane thread combined with polyester were used as both the warp and the weft threads. The grafts obtained were stretchable and thus compliant in both the transverse and the longitudinal directions. The hydraulic permeability was assessed at fixed pressure of 120 mmHg. The surface and pore characteristics of grafts were examined using a scanning electron microscope. Eight HVG-I hybrid grafts were also implanted in the carotid and femoral regions of mongrel dogs for periods of up to one year. The form of the pulse wave found in the graft, the healing characteristics of the surface and the changes in the mechanical properties as a result of implantation were examined.