FLOW TURBULENCE INDUCED BY CORONARY STENTS

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Although metallic intravascular stents have been placed in patients with peripheral and coronary artery disease, there are no data describing fluid mechanics changes which would predict for favorable or adverse clinical responses. We have hypothetical concerns that placement of multiple stents (either in tandem or non-tandem fashion) may affect flow and large side-branches especially in the setting of either proximal or distal disease. To define quantitative parameters examining flow turbulence and wall sheer stress across stented endovascular surfaces would be helpful in predicting future design modifications and in anticipating potential adverse anatomic or clinical stent placement variables. Therefore, an in vitro pulse duplicator system was developed which reproduces coronary flow waveforms using a glycerin and water mixture equivalent to blood viscosity as the test fluid. Hot film probes and laser doppler techniques were used to assess turbulence and wall shear stress in these artificially constructed vascular tree models before and after stent implantation. These studies demonstrated that multiple stents and especially disease in a vessel segment proximal to the site of stent placement results in significance flow instability which might correlate with adverse short-term responses, including increase thrombogenicity and deleterious chronic affects such as intimal proliferation which might result in chronic restenosis. Further modeling techniques are being used to expand upon this design concept such that we can make more definite analyses and predictions of flow turbulence after stent implantation.