Reducing fibrous cap thickness by increasing the lipid pool from 38% to 54% increased normalized maximum circumferential stress from 6.0 to 24.8, whereas increasing stenosis severity decreased it.
Does fibrous cap thickness affect peak circumferential stress more than stenosis severity in model atherosclerotic vessels?
Reducing fibrous cap thickness dramatically increases peak circumferential stress in atherosclerotic plaques, whereas increasing stenosis severity actually decreases peak stress, suggesting cap thickness is a critical determinant of plaque vulnerability.
Absolute Event Rate: 24.8% vs 6%
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)
Loree et al. (1992) studied Atherosclerotic plaques. Fibrous cap thickness reduction (increased lipid pool) vs. Thicker fibrous cap / increased stenosis severity was evaluated on Maximum circumferential stress normalized to luminal pressure (sigma max/P). Reducing fibrous cap thickness by increasing the lipid pool from 38% to 54% increased normalized maximum circumferential stress from 6.0 to 24.8, whereas increasing stenosis severity decreased it.