COLLAPSE OF DISEASED ARTERIES WITH ECCENTRIC CROSS-SECTION

The mechanism of atherosclerotic plaque rupture is not fully understood. Mechanical stress may be one of the factors contributing to the instability of the fibrous plaque cap. The existence of a severe stenosis may lower the transmural pressure enough to cause the collapse of arteries leading to high concentrated compressive and tensile stresses. This study presents quantitative estimates of the stresses and deformations in the collapsed thick-walled artery. The results of large deformation finite element calculations identify the locations of the high stress concentrations and their magnitudes which cannot be precisely predicted under a thin-wall assumption. The maximum compressive stress calculated reached 80% of the Young's modulus for fairly small negative transmural pressures. Results are useful to predict likely locations of the plaque cap rupture due to compressive stresses. The tube law of area as a function of transmural pressure showed a large discrepancy from a thin-wall calculation. The buckling pressure calculated for the outer-to-inner wall surface radius ratio of 1.60 was nearly 30% lower than that of the elastic thin-wall buckling theory. An increase in eccentricity further reduced this buckling pressure. The results indicate that a thick plaque which is eccentric increases the likelihood of collapse of stenotic arteries.