Effect of healing on small internal diameter arterial graft compliance

Porosity is an essential component for long term function of small internal diameter synthetic vascular prostheses. Theoretically, porosity is required for healing by providing a scaffold for ingrowth of periprosthetic tissues. Porosity may be required for transfer of fluids and ions in prostheses even if tissue ingrowth does not occur. Increased permeability of vascular grafts has been shown to enhance tissue incorporation. Implants with pore sizes greater than 10 microns but less than 45 microns become ingrown with fibrohistiocytic tissue and capillaries. Implants with pore sizes greater than 45 microns are ingrown with organized fibrous tissue and minimal histiocytic response. The phenomenon of differential ingrowth may have important functional significance. Prostheses which heal with organized fibrous tissue have the potential for long term contracture, strangulation of vascularity and calcification. Fibrohistiocytic tissue has low mechanical strength and does not appear to contract or calcify. Elastomeric microporous vascular prostheses which are minimally ingrown or ingrown with fibrohistiocytic tissue maintain compliance after months of implantation. This study was designated to determine the effects of healing on the compliance of small internal diameter vascular replacements and to correlate the compliance to patency rates.