**5.1.2 Outlet: Pressure**

312 Biomedical Science, Engineering and Technology

This problem can be approached in one of two ways, do you a) want to compare the mass transport capabilities between different stent designs or b) want to analyse arterial mass transport for a single stent design under various stenting and artery wall conditions. The latter of which is of more initial interest because a comprehensive understanding of a multifaceted mass transport study with a generic stent design will give a greater understanding of the interactions between drug/polymer characteristics and the arterial condition. Once these interactions are better understood the researcher can revert to

The main goal of a DES is to prevent the onslaught of arterial restenosis, which occurs in part due to damage inflicted on the artery during stent deployment. However, researchers to date have generally neglected the artery wall damage induced and its influence on mass transport. An exploratory DES mass transport computational study, even if it is only 2D modelling, should consider both cause and effect. A stent should not just be placed flush with the artery wall, there is going to be some wall indentation and intimal damage, the extent of which is a study onto itself. To this end the resulting artery wall compression will alter the effect that is the transport of the anti-restenotic drugs throughout the artery wall. Stent design and drug/polymer properties, although of significant importance, should be a

Once the governing equations have been applied to the model domain the boundary conditions need to be allocated. Often with biological modelling it is necessary to make assumptions when applying boundary conditions. For example treating the artery wall as rigid (Mongrain et al., 2007; Devereux, 2005; Kaazempur-Mofrad and Ethier, 2001) or assuming that mass transport within the wall is modulated solely by diffusion (Balakrishnan et al., 2008, 2007, 2005; Mongrain et al., 2007, 2005) are two examples of ways commonly employed to simplify what is in reality a very complex problem. However, as previously mentioned the fundamental *in vivo* issues should be taken into account as much

The heart is a muscular organ that undergoes repetitive contraction and relaxation of its walls in order to propel blood through the circulatory system. Coupled with the complex geometry of the coronary arteries, the pulsating blood velocity profile is an integral part in the mass transport behaviour of blood borne species. However, when considering the transport of drugs from a DES a common assumption to make is the presence of a steady fully developed flow profile within the lumen (Balakrishnan et al., 2008, 2007, 2005; Mongrain et al., 2007, 2005). When modelling BSMT it may be necessary to incorporate the time-dependent pulsatile nature of blood flow. However, the transient nature of blood side drug transport enables the assumption of a steady flow inlet boundary condition that in most cases will not have a considerable impact on WSMT. Arterial flow can be replicated by

comparing stent designs for a predetermined deployment configuration.

secondary consideration until these fundamental issues have been addressed.

**5. Typical computational boundary conditions for DES models** 

as possible when applying such simplifications.

**5.1.1 Inlet: Velocity** 

**5.1 Application of momentum boundary conditions** 

applying a pulsatile parabolic velocity profile at the vessels inlet.

**4.4 DES problem design and deployment** 

A pressure of zero can be applied to the outlet of DES computational models which reduces the likelihood of encountering backflow through the outlet. The application of such a boundary condition is prevalent in mass transport studies of this nature (Kolachalama et al., 2009; Balakrishnan et al., 2008, 2007, 2005; Rajamohan et al., 2006).
