Visualization of blood flow in carotid artery stenting with endovascular Doppler optical coherence tomography imaging and computational fluid dynamic modeling

Carotid artery stenting (CAS) is currently the standard of care for carotid atherosclerotic lesions. The goal of CAS is to provide support for the arterial wall and attempt to restore normal blood flow; however, placement of a stent causes significant alterations to the treated artery’s vascular morphology and hemodynamics. The presence of stagnant or recirculation zones around the stent struts could promote thrombogenesis, leading to post-procedural complications such as stroke. The risk of post-procedural complications can further be increased when the stent is malappositioned. Alternatively, the treated arterial wall could revert back to its narrower state (restenosis). Currently, the factors that cause post-procedural complications are not well understood. Furthermore, clinical imaging modalities lack the resolution to measure the local hemodynamics in diseased arteries. In this study, we utilized an emerging high resolution (1 to 10 μm) and minimally invasive optical imaging system known as endovascular optical coherence tomography (EV-OCT). EV-OCT imaging is analogous to ultrasound; however backscattered light is measured instead of sound. Fiber optic catheters were inserted into the subclavian artery (SA) and common carotid artery (CCA) of porcine models following carotid stent deployment. Cross-sectional velocity profiles were acquired through a function variant of EV-OCT termed endovascular Doppler optical coherence tomography (EV-DOCT). EV-DOCT images visualized velocity contours around the stent struts within the SA or CCA. Computational fluid dynamic (CFD) models were employed to provide further insight into the local hemodynamics. The dimensions of the artery and virtual stent CFD model were measured and constructed based on EV-OCT images. A time-dependent velocity profile of a human internal carotid artery was used as the inlet parameter. Correlation between hemodynamic events from EV-DOCT images and CFD models were observed. More specifically, low to stagnant regions of flow were resolved around stent struts. These regions have been suggested to promote thrombogenesis. EV-DOCT has the potential to provide real-time monitoring of the stent placement, as well as to determine improper stent placement and malapposition more accurately than carotid angiography. Characterization of hemodynamic events could provide insight into the cause of post-procedural complications.