Characterization of angiogenesis and inflammation surrounding ePTFE implanted on the epicardium

The response of epicardial tissue to the implantation of expanded polytetrafluoroethylene (ePTFE) was evaluated and compared with identical material implanted within subcutaneous and adipose tissues. These two tissue environments were selected for comparison with epicardial implants because they represent tissue often involved in device implantation. Discs of ePTFE (6 mm) were implanted into three different tissue sites in Sprague-Dawley rats. At 5 weeks, polymers and surrounding tissues were harvested and processed for light microscopy. General histology and histochemistry data indicated all polymers to be well incorporated with new tissue. Subcutaneous implants were covered by a dense fibrous capsule (55-70 microm). Epicardial and adipose implants had no fibrous capsule and a significantly greater number of microvessels (arterioles, capillaries, and venules) within the surrounding tissues compared with subcutaneous implants. An increased level of inflammation was also observed around epicardial implants compared with the other implants. Additionally, the new vasculature surrounding epicardially implanted ePTFE revealed an altered microvessel density and vessel type distribution compared with normal (control) epicardium. These results suggest that epicardial tissue responds to implanted ePTFE with a robust inflammatory response that may support the formation of a new microvasculature that is uniquely different from the native epicardial microvasculature.