On Estimation of the Artery Injury by a Stent

Shmuhel Rivkin,
Department of Solid Mechanics, Materials and Systems,
Faculty of Engineering, Tel Aviv University

The goal of the research was to develop a convenient approach for estimating of artery injury caused by an interaction with a coronary stent. This interaction is characterized by a damage factor defined as a ratio of the interface contact stress to the average blood pressure. Routine way of deriving the contact stresses evaluation is to employ a 3D finite element model based on discretization of the stent and the artery. Using such a model is very computationally expensive and the problem of parametric study in a broad range of parameters for different stent types becomes unrealistic.

A new numerically efficient method for the damage factor evaluation was developed. The method hinges on the reducing of a 3D problem to a 2D one by some plausible simplifying assumptions. The suggested approach was justified by the comparison with the routine 3D model. The calculations were carried out for the SciMED stent. It appeared that for the existing stents of this type with radii 3.25mm and 4.25mm the difference for the 1mm stent-artery radial mismatch does not exceed 4\% and increases to maximum value of 8\% for the mismatch of 0.5mm. The comparison was carried out for several types of sick artery wall models. Namely, the case of linear elastic homogeneous material and the case of two-layered wall consisting of the materials with non-linear elastic properties were addressed.

The suggested method is rather general and can be applied for each stent possessing rotational symmetry if its radial compliance is known. The calculations carried out for the different stent types have shown that that for the same radial mismatch the difference in the damage factors can be very significant. This points out on the necessity of the preliminary damage factor evaluation in order to take a proper therapeutic solution.

For the Cardiocoil stent possessing helical symmetry the suggested approach is inapplicable. The damage factor for this stent was obtained analytically. This result was submitted as a scientific paper to the Journal of Biomechanical Engineering and got a positive reviews.

The paper includes acknowledgments to the Nicholas and Elisa:beth Slezak Super Center.