A novel design of a noncylindric stent with beneficial effects on flow characteristics: an experimental and numerical flow study in an axisymmetric arterial model with sequential mild stenoses.

The objective of this study was to investigate whether a novel noncylindric "stent," implanted upstream of one or more mild arterial stenoses could be beneficial, by increasing in-stent wall shear stresses (WSS) and by limiting the flow recirculation zones in the vicinity of the stenoses. An in vitro model employing flow visualization, and computational fluid dynamics were used for the study of steady and unsteady flow fields in a model of a coronary artery with two sequential 50% stenoses. Two different tube-entrance geometries (a cylindric and a convergent nozzle), modeling an ostial stented arterial segment, were studied regarding their effect on flow patterns and WSS at various Reynolds numbers (Re = 200-800). In this preliminary study, the internal walls of these tube entrance geometries were smooth, not taking into account the roughness of the actual stent's strut. "In-stent" WSS was significantly increased at the noncylindric configuration compared to that in the regular cylindric geometry. The difference of the spatially averaged "in-stent" WSS between the two designs gradually increased with the increase in Re, reaching a peak value up to 50% in the case of the noncylindric endovascular device, for the examined Re range. For the same configuration, both the experimental and numerical analyses indicated a decrease in flow recirculation region at the vicinity distally to a sequential stenosis up to 6%, and the mean flow velocity was increased for both steady and pulsatile flow. These effects of the new "stent" configuration could be important for the delay of restenosis processes and should be further investigated in vivo.