The Impact of Calcification on the Biomechanical Stability of Atherosclerotic Plaques

Abstract

Background-Increased biomechanical stresses in the fibrous cap of atherosclerotic plaques contribute to plaque rupture and, consequently, to thrombosis and myocardial infarction. Thin fibrous caps and large lipid pools are important determinants of increased plaque stresses. Although coronary calcification is associated with worse cardiovascular prognosis, the relationship between atheroma calcification and stresses is incompletely described. Methods and Results-To test the hypothesis that calcification impacts biomechanical stresses in human atherosclerotic lesions, we studied 20 human coronary lesions with techniques that have previously been shown to predict plaque rupture locations accurately. Ten ruptured and 10 stable lesions derived from post mortem coronary arteries were studied using large-strain finite element analysis. Maximum stress was not correlated with percentage of calcification, but it was positively correlated with the percentage of lipid (Pϭ0.024). When calcification was eliminated and replaced with fibrous plaque, stress changed insignificantly; the median increase in stress for all specimens was 0.1% (range, 0% to 8%; Pϭ0.85). In contrast, stress decreased by a median of 26% (range, 1% to 78%; Pϭ0.02) when lipid was replaced with fibrous plaque. Conclusions-Calcification does not increase fibrous cap stress in typical ruptured or stable human coronary atherosclerotic lesions. In contrast to lipid pools, which dramatically increase stresses, calcification does not seem to decrease the mechanical stability of the coronary atheroma.

Independent Association Between Obstructive Sleep Apnea and Noncalcified Coronary Plaque Demonstrated by Noninvasive Coronary Computed Tomography Angiography

“…When patients were divided by OSA severity into normal (AHI <10), mild (AHI [10][11][12][13][14][15][16][17][18][19][20], and severe (AHI >20) groups, the odds for any vessel involvement were 9.6 (95% CI: 1.1-85.3) for mild OSA and 42.1 (95% CI: 4.1-428.4) for moderate to severe OSA. These odds were adjusted for age, sex, race, hypercholesterolemia, and smoking history.…”

“…Overnight polysomnography was performed at nationally accredited sleep centers, and final diagnosis with apnea-hypopnea index (AHI; measure of the severity of disease) was available in all patients included in this study. Obstructive sleep apnea was further classified as no OSA (AHI <10), mild OSA (AHI [10][11][12][13][14][15][16][17][18][19][20], and severe OSA (AHI> 20). The number of vessels involved was defined as 0 if there was no stenosis and 1 if any stenosis or plaque was present.…”

Breast Arterial Calcification

“…Intimal, or more precisely neointimal, calcification is associated with atherosclerosis (5) and occurs in the absence of renal failure. Whether it has any clinical significance beyond serving as a marker of advanced atherosclerosis is unclear because calcification may actually stabilize plaques (6,7). Calcification in the medial layer is independent of atherosclerosis or inflammation, occurs in small arteries in addition to large arteries, and is thought to be detrimental by decreasing arterial compliance (8).…”

Mineral Volume and Morphology in Carotid Plaque Specimens Using High-Resolution MRI and CT

“…Huang et al reported that increases in percent area of plaque occupied by calcium in coronary plaques was associated with decreased stress in the plaque, whereas increased plaque lipid content was correlated with increased stress. 40 On the other hand, some investigators argue that certain types of calcifications may increase risk. 32,33 For example, a shearing plane can be created between calcified and noncalcified plaque, predisposing to rupture in response to a stress such as angioplasty.…”