In-stent restenosis and coronary curvature: Translational approach to computational fluid dynamics

Coronary in-stent restenosis (ISR) is a pathology afflicting the stented coronary following the procedure due to neointimal hyperplasia and re-occlusion. Hypotheses relating to ISR include fluid mechanical influences (e.g. wall shear stress (WSS), flow patterns) and geometric changes due to stent placement, in conjunction with species involvement (e.g. hypoxic conditions). The present study has been performed to investigate hemodynamic parameters (e.g. WSS, etc.) and/or oxygen mass transport in a realistic configuration of the stented coronary vessel, which is characterized by asymmetries and non-uniform geometry. To this end, stented porcine right coronary arteries have been analyzed, whose in vivo geometry was reconstructed by combining data from micro-CT (stent) and by finite element analysis (vascular wall). The availability of corresponding histological images allows a direct observation with CFD and mass transport results. Additional histomorphometric measurements were performed where necessary. From the first application study, regarding coronary curvature and injury, it was found that the greater radius of curvature greatly influenced the WSS at the entry region of the stent due to skewing of the velocity profile; yet the localization was notable throughout the entire stent with the additional of a physiological curvature. This impact may be pertinent when considering implant conditions; in addition, the injury was identified as an independent factor of ISR. Following the second application study, regarding coronary curvature and oxygen mass transport, results display the complex stented coronary geometry has a great effect on convection dominated mass transport of species, such as oxygen, especially in the presence of a curved geometry. These evaluations are instrumental in characterizing the localization of NIH due to the presence of the device within coronary artery through CFD simulations; Better elucidation of the overall effects of the fluid environment, especially in relation to geometry curvature, on the effective delivery of renewed flow and oxygen to the arterial wall following stent placement may lead to improved options to reduce ISR through arterial patency and device longevity.