Effects of fibrous cap thickness on peak circumferential stress in model atherosclerotic vessels.

Abstract

It is likely that factors other than stenosis severity predispose some atherosclerotic plaques to rupture. Because focal increases in circumferential stress may be an important mechanism of plaque rupture, we examined peak circumferential stress of atherosclerotic lesions by using finite element analysis based on idealized two-dimensional cross sections of diseased vessels similar to intravascular ultrasound images. The study was designed to test the hypothesis that subintimal plaque structural features such as thickness of the fibrous cap are more important factors in the distribution of stress in the plaque than stenosis severity. The analysis incorporated equilibrium biomechanical parameters from normal and diseased vessels and determined the stress distribution within the plaque at a mean luminal internal pressure of 110 mm Hg. With a constant luminal area reduction of 70%, maximum circumferential stress (sigma max) normalized to luminal pressure (sigma max/P) increased from 6.0 to 24.8 as the thickness of the lipid pool was increased from 38% to 54% of the plaque thickness because of the thinner fibrous cap over the lipid pool. When the lipid pool thickness was constant, increasing the stenosis severity from 70% to 91% by increasing the fibrous cap thickness decreased sigma max/P from 24.8 to 4.7. When no lipid pool was present and the stenosis severity was increased from 70% to 99%, sigma max/P decreased from 5.3 to 4.7. Thus, reducing the fibrous cap thickness dramatically increases peak circumferential stress in the plaque, whereas increasing the stenosis severity actually decreases peak stress in the plaque.(ABSTRACT TRUNCATED AT 250 WORDS)

Intravascular Palpography for High-Risk Vulnerable Plaque Assessment

“…The plaque is supposed to be prone to rupture, if the cap is unable to withstand the stress applied on it. All the stress that is applied on the plaque by the blood pressure is concentrated in the cap, since the lipid pool is unable to withstand forces on it [4,5]. As a result, the stress in a thin cap will be higher than the stress in a thicker cap.…”

Study of reproducibility of human arterial plaque reconstruction and its effects on stress analysis based on multispectral in vivo magnetic resonance imaging

“…Components of the plaque, such as a thinner fibrous cap, inflammation, etc., can contribute to plaque rupture (3,4). Furthermore, biomechanical stress is also considered to be a major determinant of plaque vulnerability (5,6). Research on assessing plaque vulnerability has been carried out for many years using noninvasive imaging techniques such as magnetic resonance imaging (MRI) to define plaque size, shape, and components (fibrous cap, lipid core, calcification, etc.)…”

“…Since the stress analysis results are highly sensitive to fibrous cap thickness variations (5), uncertainties in fibrous cap thickness measurement and their impact on stress analysis results need to be quantified. This would then give a level of confidence when applying the procedure to assess plaque stress based on MRI-measured realistic plaque geometry.…”

Localization of Tissue Transglutaminase in Human Carotid and Coronary Artery Atherosclerosis: Implications for Plaque Stability and Progression

“…Disrupted plaques tend to have large lipid cores comprised of soft cholesteryl esters that redistribute the circumferential wall stress to the shoulder regions of the plaque (Davies, 1996;Falk, 1992;Richardson et al, 1989). This mechanical effect is exacerbated in plaques that have a thin fibrous cap (Loree et al, 1992) and in plaques that are only mildly to moderately stenotic because, according to Laplace's law, wall stress is directly proportional to the radius of the vessel (Lee and Kamm, 1994). The thinning of the fibrous cap may result from a reduced content of smooth muscle cells (SMC).…”