In Vitro Flow Visualization in Stented Arterial Segments

Since the early 1980’s, several intravascular stent designs have been introduced in an attempt to improve arterial patency rates following balloon angioplasty. Results in clinical trials have shown that, although patency rates following angioplasty have improved when used in conjunction with stents, thrombosis and neointimal hyperplasia within the stent continue to compromise the potential utility of these devices. Previous studies have implicated certain blood flow patterns as being favorable to the development of thrombosis and neointimal hyperplasia. Detailed information on how vascular stents alter arterial blood flow patterns is not well known. To gain a better understanding of the hemodynamic influence of these devices, an in vitro flow model was constructed simulating a stent within a compliant arterial segment. Flow disturbances were observed qualitatively by dye visualization in two different configurations of a balloon expandable stent. The first configuration was such that the stent inner diameter and vessel inner diameter were approximately equal. The second configuration allowed for the stent inner diameter to be 10% greater than the vessel inner diameter. Results of this study indicated that flow stagnation and flow reversal occurred in both conditions. It was observed, however, that the more expanded stent created greater fluid stagnation times and more focal disturbances than the less expanded stent.