The use of
stents has improved results after balloon carotid angioplasty. Some materials have been reported for covering the
metal surface of the
stent to reduce the rate of subacute
thrombosis and restenosis. We have already developed a new
stent graft with thin-walled controlled micropored
polymer covering, and in a previous study we confirmed tissue ingrowth via the micropores at one month in a beagle model. The progress of cell migration was controlled by micropore density using a constant micropore diameter (30mum diameter, 125mum inter-pore distance). In the present study, we applied our newly developed
stent graft impregnated with
heparin for implantation in the rabbit carotid artery, and carried out an angiographic and histological investigation. Our
stent graft was made from a Palmaz-Schatz
stent and a micropored segmental
polyurethane (SPU) thin film with a
heparin coating. Micropores 30mum in diameter and 125mum apart were created on the thin SPU film using an
excimer laser ablation technique. The surface of the micropored film was then impregnated with photosensitive
gelatin that incorporated the
heparin. The
metal stent was rolled up and fixed to this modified SPU film under microscopic observations. These
stent grafts were deployed in the common carotid arteries (CCAs) of rabbits (37 carotid arteries, 20 rabbits). The animals were sacrificed one, two and three months later, and a histological study and scanning electron microscopy study were performed for evaluation of endoluminal endothelialization and intimal thickening at the late stage. CCAs treated with
stent grafts of micropored film showed poor-patency and intimal
hyperplasia compared with those treated with a simple bare
stent or a
heparin-impregnated
stent. In terms of intimal
hyperplasia and patency, the
heparin-impregnated
stent was superior to the bare
stent. Intimal
hyperplasia was prevented by control of tissue ingrowth through the micropores. The antithrombogenicity of the impregnated
heparin improved patency in the early stage. Our new
stent graft with a
heparin-impregnated SPU film thus appears promising for prevention of restenosis due to neointimal
hyperplasia.