Analysis of Graft Healing in a New Elastomer-Coated Vascular Prosthesis

Abstract

The need for a vascular prosthesis that does not require preclotting is apparent. The use of biological biodegradable coatings may carry the potential disadvantages of undesirable healing, inflammatory or antigenic reactions, and increased thrombogenicity. A graft has been developed to minimize porosity by coating only the outer surface with a bioinert non-absorbable elastomer (mainly Silastic) so as to leave the inner surface unchanged. Thoracoabdominal aortic 8-mm grafts (ten knitted and five woven coated grafts, six uncoated Dacron grafts) 12 cm long were implanted in mongrel dogs for 6 months. Differences in patency and healing in coated and uncoated grafts were observed by angiography, and by scanning electron and light microscopy. Statistical analysis included Fisher's exact test and Student's unpaired t test. Clinically, no ill effects were noted in coated grafts, and the transinterstitial blood loss was similar to that in preclotted uncoated grafts. One graft in each group occluded for technical reasons. One knitted coated graft developed perigraft seroma. The woven coated grafts and control prostheses had similar handling properties; however, needles appeared to pass through the coated graft material more easily and with less suture drag. Scanning electron microscopy was used to demonstrate similar presence of endothelial-like cells in both groups. Comparisons between coated and control grafts using light microscopy were as follows: pseudoendothelium, 0.26 versus 0.31 mm (P not significant): Inflammation. 0.21 versus 0.73 (P < 0.01); giant cell formation, 0.02 versus 0.88 (P < 0.01); fibrosis. 1.31 versus 1.80 (P < 0.03). Tissue ingrowth into and around the Dacron fibers from the outer surface was similar. This study demonstrates that microporous elastomer-coated vascular prostheses can prevent blood loss. They are safe and comparable to controls with respect to healing and tissue ingrowth. They appear to elicit less inflammation and fibrosis, all of which supports the concept that the graft material and not porosity per se ensures better graft healing.