Biomechanics of human common carotid artery and design of novel hybrid textile compliant vascular grafts

Abstract

The mechanical properties and structure of a human common carotid artery were studied in order to develop criteria for designing and manufacturing compliant textile vascular grafts. The arterial wall comprised a composite of elastin and collagen fibers with the collagen fibers crimped. This structure led to a unique pressure-circumferential stretch ratio curve, the slope of which increased with an increase in strain. The increase in slope was particularly rapid at a stretch ratio above 1.4 or pressure above 120 mmHg. Based on the knowledge gained, a criteria for the design of biomechanically compliant arterial grafts was developed. An elastomeric prestretched polyurethane monofilament yarn with a low modulus of elasticity and a bulked polyester multifilament yarn with a high modulus of elasticity were combined and used as threads in the manufacture of grafts. Tubular structures of diameters in the range 4-6 mm were made by weaving. Transverse compliance and morphological and permeability properties of these grafts were determined and compared with those of a currently available woven commercial grafts and human carotid arteries. Results indicated that the compliance values of the hybrid grafts were comparable with those of the human carotid artery. Preliminary in vivo studies in dogs showed promising results: a thin, stable neointima developed within 6 months of implantation on the flow surface.