In their search for an effective vascular graft to replace a segment of a natural, biological blood vessel, a team of scientists in New Hampshire, USA, has designed a device that mimics the structure of the natural artery (US Patent 6 042 666).

The implantable prosthesis is formed from

layers or tubes of material. It is made by radially nesting a first, second and third layer of material, either as tubes, wound sheets or a wrap. These are then heated to make them coalesce into a continuous wall body. Through the thickness, each region retains the structure of the starting material. The entire structure is made from polytetrafluoroethylene (PTFE) or PTFE with another fluoropolymer.

Native arteries and veins have a common pattern of organization made up of three layers: an internal intima is surrounded by a media and then an external adventitia. Each of these layers has a predominant structure and cell type. The walls of arteries are built of elastin, collagen, a non-fibrous glucosaminoglycan-rich matrix and smooth muscle cells. The microscopic structure of the artery wall correlates with the function of the various wall-layers and components.

Studies seem to show that there is a net transport of macromolecules across the arterial wall, say the scientists. They argue there is a need for an in vivo implantable material device, and in particular a vascular graft, which is formed as a lamellate structure that mimics the natural artery with differential cross-section permeability acceptable to the surrounding tissue.

The graft they have devised improves surgical handling and has enhanced healing properties because of the arrangement of variable porosity regions of PTFE.

There are a number of vascular grafts that are stronger, the scientists admit, but these do not generally have the differential permeability necessary for enhanced healing and tissue ingrowth, nor do they offer improved surgical handling.

The material has other applications, such as heart-valve leaflets, sutures and vascular-access devices. It can also be used for patches or supports for tissue repair or reinforcement.

For further information, contact: patent assignee, Atrium Medical Corp, 5 Wentworth Drive, Hudson, NH 03051-4929, USA; tel: +1-603-880-1433.