Simulation of stent deployment in a realistic human coronary artery

Abstract

Background: The process of restenosis after a stenting procedure is related to local biomechanical environment. Arterial wall stresses caused by the interaction of the stent with the vascular wall and possibly stress induced stent strut fracture are two important parameters. The knowledge of these parameters after stent deployment in a patient derived 3D reconstruction of a diseased coronary artery might give insights in the understanding of the process of restenosis.

Methods: 3D reconstruction of a mildly stenosed coronary artery was carried out based on a combination of biplane angiography and intravascular ultrasound. Finite element method computations were performed to simulate the deployment of a stent inside the reconstructed coronary artery model at inflation pressure of 1.0 MPa. Strut thickness of the stent was varied to investigate stresses in the stent and the vessel wall.

Results: Deformed configurations, pressure-lumen area relationship and stress distribution in the arterial wall and stent struts were studied. The simulations show how the stent pushes the arterial wall towards the outside allowing the expansion of the occluded artery. Higher stresses in the arterial wall are present behind the stent struts and in regions where the arterial wall was thin. Values of 200 MPa for the peak stresses in the stent strut were detected near the connecting parts between the stent struts, and they were only just below the fatigue stress. Decreasing strut thickness might reduce arterial damage without increasing stresses in the struts significantly.

Conclusion: The method presented in this paper can be used to predict stresses in the stent struts and the vessel wall, and thus evaluate whether a specific stent design is optimal for a specific patient.

Figure 1

The intravascular ultrasound images of a mildly stenosed right coronary artery (panel A), the corresponding contrast angiogram (panel B) and the 3D reconstruction (panel C).

Figure 2

Mesh of the vessel with an inset showing the internal lumen (panel A). Geometry and mesh of the stent in its undeformed configuration (Panel B). The model of the right coronary artery with the unexpanded stent is show in panel C. The location of the minimal lumen diameter (MLD) is indicated by the dashed line.

Figure 3

Panel A: Shapes of the lumen at the beginning (green) of the expansion and at the maximum inflation pressure of 1.0 MPa for three different axial locations in the stent (shown in the middle left side). Panel B: The corresponding von Mises contour maps.

Figure 4

Expansion of the lumen area versus the inflation pressure for the three different axial locations in the stent depicted by the dotted red lines.

Figure 5

Von Mises contour maps in the anterior and posterior views of the luminal surface at the maximum inflation pressure of 1.0 MPa.

Figure 6

Von Mises stresses in the stent at the inflation pressure of 1.0 MPa.

Figure 7

Results from the simulation with a strut thickness of 0.14 mm. The top panel shows the expansion versus the inflation pressure location 2. The panels at the bottom show the von Mises stress distribution at the luminal surface (left) and the stresses von Mises stress in the stent (right).