Experimental study of blood laminar flow through a stented artery

Abstract

Abstract-The objective of this research is to study the blood flow close to the wall of a stented artery. Indeed, previous works have showed that the restenosis phenomenon is induced by the endothelial cells stimulation due to the wall shear stress values. The coronary angioplasty is responsible of wall shear stress modification, mainly between the stent struts, at the inlet and the outlet of the endoprothesis. That is why, to study the flow disturbances through a stented section, we built an in vitro model reproducing the struts shapes of a marketed endoprothesis. The experimental artery is composed of a seethrough square section vein, which reproduce the struts design with a magnitude of 100. A programmable pump provide a steady or a pulsatile flow. By using the velocimetry per imagery of particle (PIV) optical method we have explored the flow between and over the stent branches, in order to assess and to quantify the wall shear stress and to locate the interesting zones.Keywords-Stent, endoprothesis, coronary artery, restenose, wall shear stress, endothelium cell. I.INTRODUCTIONFor several years the leading cause of morbidity and mortality in the developed countries has been the whole of the disorders of the cardiovascular system and mainly the phenomenon of stenosis in coronary arteries. Since the 80's, there is an alternative to the usual balloon angioplasty. Indeed, the use of tiny metallic scaffolds (named coronary endoprothesis or stent) has surpassed all expectations. Now, the use of the technique of stent is generalized in practical clinic (representing 60-90 percent of procedures), approximately 1,000,000 patients worldwide undergo a non surgical coronary artery interventional procedure yearly. A coronary stent is a small, slotted, stainless steel or nickel tube mounted on a balloon catheter, which remains in the artery. The procedure is the following one: the coronary stent is placed over the angioplasty balloon and moved to the site of lesion. The stent expands with the balloon and remains in place after the balloon is deflated and removed, thereby serving as a mechanical scaffold to prevent restenosis.Unfortunately, there is still a very important disadvantage. Indeed the rate of restenosis, response to stent implantation, still occurs frequently (in 20% or 40% of cases). In-stent restenosis occurs mainly at the area of the injury vascular induced by the implantation of the endoprothesis but not exclusively. It also frequently appears in all the zones where the flow can be disturbed , in particular between the branches of stent. The composition of in-stent restenosis includes vascular smooth muscle cell and endothelium cell i.e. it consists predominantly of neointimal growth. Previous study showed that the areas of endothelium exposed to a low and oscillating stress correspond to the places where the restenosis develops preferentially [1], indeed, endothelium cells are an interface extremely active, able to bring an answer differentiated according to the stresses physics of its environment [2]. The...

Materials, fluid dynamics, and solid mechanics aspects of coronary artery stents: A state‐of‐the‐art review

“…The techniques/equipment that have been used are dye injection flow visualization,191, 192 transit‐time and Doppler flow probes,193 ultrasonic segment‐length transducers,193 particle image velocimetry,194 and time‐resolved digital particle image velocimetry (TRDPIV) 195. Measurements were made in a model of a coronary artery,191 the left reduced anterior descending coronary in adult mongrel dogs,193 and a synthetic model of a compliant artery (straight tube of Silicone, 300 mm long, 12 mm inside diameter, and 0.5 mm wall thickness) 195.…”

Experimental Research on Balloon-expandable Endovascular Stent Expansion

“…S. Natarajan et al [9] studied the consequences of the presence of a stent on the flow of blood from a fluid dynamics point of view by the visualization experiments. N. Benard et al [10] studied the flow disturbances to quantify the wall shear through an experimental stented artery which is an in vitro model reproducing the struts shapes of a marketed endoprothesis. However, all the experimental achievements above did not or partly consider the entire in vivo environment in which the stent supports the clogged artery.…”