[Role of shear stress in atherosclerosis and restenosis after coronary stent implantation].
Explore the source record for details and available documents.
Coronary Artery Disease↗
Biomedical subjects
Rosaire Mongrain
Publications and source records attributed to Rosaire Mongrain.
Three-dimensional trajectory assessment of an IVUS transducer from single-plane cineangiograms: a phantom study.
The recovery of the three-dimensional (3-D) path of the transducer used during an intravascular ultrasound (IVUS) examination is of primary importance to assess the exact 3-D shape of the vessel under study. Traditionally, the reconstruction is done by simply stacking the images during the pullback, or more recently using biplane angiography to recover the vessel curvature. In this paper, we explain, how single-plane angiography can be used with two projection models, to perform this task. Two types of projection geometry are analyzed: weak-perspective and full-perspective. In weak-perspective projection geometry, the catheter path can be reconstructed without prior transducer depth information. With full-perspective projection geometry, precise depth location of reference points are needed in order to minimize the error of the recovered transducer angle of incidence. The transducer angulation reconstruction is based on the foreshortening effect as seen from the X-ray images. By comparing the measured to the true transducer length, we are able to get its incidence angle. The transducer trajectory is reconstructed by stitching together the different estimated angulations obtained from each image in a cineangiogram sequence. The method is described and validated on two helical vessel phantoms, giving on average a reconstructed path that is less than 2 mm distant from the true path when using full-perspective projection.
Catheterization↗
Image based biomechanics of coronary plaque.
In this chapter we present recent developments in the modeling of coronary artery biomechanics. We first introduce the pathology and localization of lesions in the circulatory system. Recent fluid and structural modeling of CAD is presented and discussed. At the end of the chapter, we present recent effort in coupling these two modeling domains using fluid-structure interaction (FSI).
Coronary Artery Disease↗
Numerical modeling of coronary drug eluting stents.
One of the principal therapies considered for the control of in-stent restenosis is the use of drug loaded polymer-coated stents for local delivery. We present two-dimensional and three-dimensional numerical models to study local delivery of drug eluting stents. The impact of various stent and flow parameters on the concentration distribution in the wall are investigated including the effect of the strut size, coating thickness, strut inter-distance and strut embedment in the vascular wall, blood flowing speed and the respective diffusion coefficients in the blood, wall and polymer. We also present criteria to assess the drug delivery efficiency based of the concept of the therapeutic window which aims at an spatial homogeneous concentration distribution and we introduce the variables to assess the amount of drug delivered in the wall. The results suggest that advection have a much stronger effect compared to diffusion in the blood media and that drug diffusivity in the arterial wall and in the polymer coating significantly affects the drug distribution. It is also shown that fully-embedded struts provide better spatial drug concentration uniformity after a short period of time and the half-embedded struts have a better temporal uniformity.
Diffusion↗
Aortic root reconstruction: from principles to numerical modeling.
Reconstructing the aortic root represents a formidable task for modern cardiac surgery. By the time an individual reaches 75 years of age his or her aortic apparatus has been submitted to more than three billion cardiac cycles, leaving no place for engineering flaws or misconception. The rules that have been established through millions of years of evolution are strict and demanding. During the past two decades, the cardiovascular community has manifested a growing interest in this topic, especially in patients with medial degenerative disease. However, the ideal reconstruction is still to be devised. To achieve a physiological root reconstruction that preserves the diastolic and systolic function of the valve as well as prevents premature degeneration, a few principles have to be respected. Neglecting any one of them has consequences on the normal functioning of the aortic valve. Current surgical techniques have limitations due to the limited availability of biomaterial and the lack of useful tools to assess pathophysiological conditions and assist surgeons in designing better custom-made reconstructions of the aortic root. The authors present a review of the principles behind the physiology of the reconstruction of the aortic root, and review the literature on computerized models exploring the biomechanics and kinetics of the ascending aorta.
Aorta↗
Incidence of stent under-deployment as a cause of in-stent restenosis in long stents.
Although stent under-deployment (SU) has been associated with increased risk of in-stent restenosis, little data have been reported on the incidence of SU in patients presenting with clinical in-stent restenosis. In 59 patients referred for vascular brachytherapy and showing angiographic in-stent restenosis, we sought (1) to determine the incidence of SU using standard intravascular ultrasound (IVUS) criteria (2) to evaluate the effects of repeat angioplasty on further stent expansion. Stented length was 32+/-17 mm and diameter stenosis was 75+/-14%. Before re-intervention, the incidence of reduced absolute values of minimal stent cross-sectional area (MSCSA) varied from 69% (< or =8 mm2) to 15% (< or =5 mm2). After re-intervention, the incidence decreased to 24% (< or =8 mm2) (p = 0.0001) and 0% (< or =5 mm2) (p = 0.005). Before re-intervention, SU as assessed by relative criteria varied from 21% (80% mean reference lumen area or 90% minimum distal reference lumen area) to 28% (100% minimum reference lumen area). After re-intervention, the incidence of SU varied from 7% (90% minimum distal reference lumen area) (p = 0.0001 vs. pre) to 24% (55% mean reference EEM area) (p = ns). No change in strut apposition (97% pre vs. 100% post) nor in symmetry index (100% pre vs. post) was noted. From all criteria, the 90 and 100% minimum reference lumen area criteria were the most altered by repeat balloon dilatation, 21% pre vs. 7% post and 28% pre vs. 11% post, respectively. In conclusion, among patients presenting with severe angiographic in-stent restenosis, a significant number showed signs of SU whose incidence varied according to applied criteria. Significant stent re-expansion can be obtained following IVUS-guided repeat angioplasty irrespective of initial SU criteria.
Angioplasty, Balloon↗