Implantation of Polyimide Vascular Grafts in Small-Diameter Blood Vessels

Objective. To study the biocompatibility, ease of implantation, and mechanical properties of polyimide vascular grafts under experimental conditions on Wistar rats. Materials and methods. We performed nine experiments. Polyimide vascular grafts obtained using electroforming were implanted into the abdominal aorta of rats. Postoperatively, motor activity, temperature, and skin color of the hind limbs of the experimental animals were assessed. After one, three, and six months, the animals were removed from the experiment. A macroscopic assessment of the implantation site was performed to assess capsule formation and expansion at the graft site. A morphological examination of the conduit was then performed, assessing connective tissue capsule growth, neointimal formation, and the severity of the inflammatory response. Results. During surgery, the graft proved easy to suture (no cutting through, optimal suture tightening), and the anastomoses were leak-tight. In all nine cases, motor activity, temperature, and skin color of the lower limbs of the experimental animals were consistent with those of healthy rats. Morphological examination revealed neointimal formation in all cases. The implanted grafts remained patent throughout the observation period, and no aneurysmal dilation was observed. One animal, withdrawn after one month, and two animals, withdrawn after three months, showed the appearance of calcifications at the border of the prosthesis and neointima, which may indicate a low rate of native aortic tissue ingrowth into the graft wall. A moderate immune reaction to implantation was observed. A connective tissue capsule consisting of collagen fibers formed outside the graft, within which blood vessels were visible. Conclusion. Polyimide grafts appear promising and warrant further investigation.

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