Biomechanlcal considerations of the design of endovascular stents: effect of coil-pitch on intraluminal flow movement

摘要

The proliferation of the vascular cells is affected by the intravascular hemodynamics, which fact seems to be partly responsible for the restenosis after indwelling endovascular stents. To analyze the changes in detailed flow pattern caused by indwelling endovascular stents, the flow was visualized in an in vitro mock perfusion circuit. Single-coil endovascular stent (wire diameter - 0.5 mm, coil diameter = 4 mm; coil-pitch = 2.5, 5, or 10 mm) was inserted within a glass tube placed within a mock circulation circuit, and a physiological saline solution containing rat erythrocytes chosen for tracer particles was perfused at 30-90 ml/min. The behavior of the erythrocytes within the glass tube was video-recorded under a microscope and was subjected to off-line analysis. A complex and three-dimensional spiral flow pattern due to the secondary flows superimposed on the main stream was observed near the wall of the glass tube in the vicinity of the stent wire. The flow velocity near the wall significantly decreased with the decrease in the coil-pitch of the stents, particularly at higher volumetric flow rates. In conclusion, the flow velocity near the vessel wall was affected by the coil-pitch of the endovascuiar stents, which suggests a possibility to improve stent design.