Simulation of mass transfer phenomenon in a CAD drug eluting stent system

Abstract

Coronary Artery Disease (CAD) is one of the diseases frequently occur in human after the age of 40. To treat CAD by catheterization, balloon angioplasty is the simplest surgical method. The main drawback of balloon angioplasty is restenosis which occurs at about 30 – 50% cases of the treatment. One improvement of the balloon angioplasty is Bare Metal Stent (BMS)-based angioplasty where a BMS is left at the treated artery to prevent restenosis. The BMS is indeed found successful to provide long term benefit against arterial restenosis. However it has the shortcoming of causing inflammation at the artery wall where it is placed. To overcome inflammation problem primarily, a drug coating is used over the BMS. A therapeutic drug is encapsulated into the porous polymeric material to form the coating given over the bare stent. This type of stent is known as Drug Eluting Stent (DES) which inhibit the inflammation problem and also several implant centered biological processes causing restenosis thereby prevent or minimize the failure of angioplasty. This DES-based angioplasty is relatively new and the drug mass transfer phenomenon observed in CAD-DES is still not fully understood though it has huge impact on the overall treatment methodology. Therefore the main objective of this thesis is to study the mass transfer phenomenon occurs in a CAD-DES system theoretically by performing simulation. Here a 1D and a 2D unsteady model has been developed which describe the drug release from DES coating and concentration of the drug at the artery wall tissue layer with respect to time and position. A fixation to best fitted value of the drug coating thickness decay parameter has also been performed for standard duration (30 days decay time limit). Besides the effect of coating thickness decay parameter (n and k) and diffusivity coefficient of drug on concentration profile has also been studied here.