Figure 1.
Arterial tissue prolapse between stent struts.
(A) Representative micro-computed tomography (µCT) scan section of stented porcine left coronary artery corrosion cast. (B) Reconstructed surface of arterial lumen negative obtained by µCT of a corrosion cast. The white arrows point to prolapsed regions. (C) Wall shear stress (WSS) distribution in the same region shown in B. Higher WSS is evident in prolapsed regions compared to regions without prolapse. Blood flow is from left to right. (D) Velocity contour plots in prolapsed (top) and prolapse-free inter-strut sections. Regions of low velocity are evident near stent struts in both cases, with larger low-velocity regions in the prolapse-free segment. This segment also shows lower near-wall velocity.
Figure 2.
Figure 2. Radial wall deformation of stented artery.
(A) Representative micro-computed tomography cross-section of a stented porcine left coronary artery corrosion cast. The dotted circle shows the nominal circular cross-section (B) Radial arterial enlargement caused by stenting. The arrows indicate arterial diameter in the stented (left) and stent-free regions (C) Velocity vectors in the mid-longitudinal section plane of the stented artery. The velocity profile along the vessel centerline from Point I to Point II is shown in (D), where the increase in velocity in the stent-free section is visible. The vertical dashed lines mark the end of the stent and the axial locations of Points I and II shown in panel C.
Figure 3.
Axial arterial deformation due to stenting.
(A) Visualization of arterial centerline change in a stented section. The solid line shows the axis of the stent, while the dashed line approximates the centerline of the stent-free artery. (B) Wall shear stress (WSS) distribution in the same stented artery. An extended area of low WSS is seen immediately downstream of the stent at the outer artery wall due to the change in curvature.
Figure 4.
Stent malapposition and its effect on local hemodynamics.
(A) Imprint of malapposed stent end section (arrow) in artery lumen negative (top) and corresponding wall shear stress (WSS) distribution (bottom). Higher WSS can be observed in the vicinity of the malapposed strut due to flow tunneling compared to (B), where a similar fully apposed stent end section is shown. (C) Velocity contour in axial cross-section of the stented artery near a malapposed strut. Changes in velocity and division of blood flow can be seen. (D) Velocity vector plot in the vicinity of the malapposed strut demonstrates the presence of vortices. These influence WSS distribution and may lead to thrombosis.
Figure 5.
Wall shear stress distribution in a porcine left coronary artery with two stents.
The bottom inset shows a magnified view of the stented segments. Wall shear stress (WSS) below 0.5 Pa is reported to correlate with sites of intimal thickening [51]. Such low WSS can be seen here to occur mainly in the vicinity of stent struts and at bifurcations. The left inset shows low and high wall shear stress regions occurring, respectively, at the outer and inner walls of the bifurcation (arrows).
Figure 6.
Oscillatory shear index (OSI) distribution in a porcine left coronary artery with two stents.
The inset shows a magnified view of part of the second stented segment. Elevated values of OSI have been reported to correlate with atheroprone vessel regions [17]. Areas of increased OSI are visible near strut junctions. They contain small focal spots that reach values close close to the maximum of 0.5.
Figure 7.
Velocity contours and secondary flow around individual stent struts in a porcine left coronary artery.
Top: Overview and close-up of reconstructed surface of arterial lumen negative obtained by µCT of a corrosion cast. The labels A to I indicate the location of the cross-sections shown in the bottom panels. Bottom: Velocity contour plots at cross-sections A to I. To visualize secondary flow structures, streamlines are derived from velocity vectors projected onto the respective cross-section.
Figure 8.
Velocity profiles in a porcine left coronary artery with two stents.
Results are shown for cross-sections upstream of the distal stent (A and B), within (C, D E and F) and downstream of the stent (G and H). Top: Velocity contour plots. Bottom: Velocity projections onto axial planes. The vertical axes are normalized to a common diameter.
Figure 9.
Distribution of relative vessel wall area exposed to different levels of shear stress.
Results are shown in the bottom panel as percentage of the respective segment’s surface area in a porcine left coronary artery with two stents. Low wall shear stress: <0.5 Pa. Moderate: 0.5<WSS<2.5). High: >2.5 Pa. Top: Corresponding reconstructed surface of the arterial lumen negative.