DRUG ELUTING STENTS

Drug-eluting stent (DES) has been shown to be effective in reducing the rate of restenosis in the treatment of coronary ahterosclerosis, encouraging the development of novel prototypes with more complex drug release strategies and mechanical designs specific to the vascular bed.

As such, understanding of the device for its safety and efficacy is becoming increasingly important. O'Brien et al. (2012) "Analysis of Drug Distribution from a Simulated Drug-Eluting Stent Strut Using an In Vitro Framework" . We use computational and benchtop simulations to model different types of drug eluting stents, including the consideration of the assumptions that may be made in computational models, and the effect of different strut shapes.

Through computational fluid dynamics and experimental simulations (Vijayaratnam et al. (2019) "Flow-Mediated Drug Transport from Drug-Eluting Stents is Negligible: Numerical and In-vitro Investigations"), we evaluated the effects of different simulation assumptions accounting for non-Newtonian properties of blood, near-wall behavior, and pulsatility of the flow. 

The above figure shows the normalized drug concentration distributions after 60 s for 6 different cases of simulation. In every case, drug pools formed within recirculation zones adjacent to the strut. Nevertheless, the concentrations in the recirculation zones are several times lower than the drug concentrations in the tissue directly underneath the strut. This means the overall drug uptake rate is generally insensitive to the pulsatile effects and the different viscosity models implemented. Experimentally, the drug transport model used in CFD was validated using the set up shown below.

In this framework, the stented artery environment was modelled using an acrylic flow rig, a hydrogel and a polydimethylsiloxane (PDMS) strut loaded with a flourescent marker such that the diffusion of a flourescent marker into the hydrogel from PDMS represents the drug transport into arterial tissue. The experimental results are shown in the following. 

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