How does juxtaluminal calcium affect critical mechanical conditions in carotid atherosclerotic plaque? an exploratory study
Zhongzhao Teng, Jing He, Umar Sadat, John R. Mercer, Xiaoyan Wang, Nasim S. Bahaei, Owen M. Thomas, Jonathan H. Gillard
University of Cambridge, School of Clinical Medicine
Volume 61, Issue 1, Page: 35-40
Most studies investigating carotid atherosclerotic plaque vulnerability focus on three plaque components namely fibrous cap, lipid-rich necrotic core and plaque hemorrhage. Calcification within the plaque is often overlooked. Traditionally, calcium has been recognized as a plaque stabilizing role. But whether large overall calcium content in a carotid plaque makes it vulnerable or not remains inconclusive. This study suggests that juxtaluminal calcium (JLCa), a calcium nodule located on the lumen surface, might be one of the high risk compositional features responsible for ischaemic cerebrovascular events. In this study, the local mechanical stress concentration modulated by the presence of JLCa was assessed as high stress concentration might damage the local tissue leading the calcium abscission. Results indicated that presence of JLCa increased local stressescompared to when calcification was artificially covered with a 0.2mm-thickness FC (107.87kPa [76.99, 129.14] vs. 63.17kPa [34.55, 75.13]; Median, [inter quartile range]; p<0.0001]. Stress variation during one cardiac cycle changed from 32.32kPa [20.65, 48.84] to 22.99kPa [8.40, 25.59] (p=0.0002) and stretch ratio decreased from 1.18 [1.07, 1.27] to 1.13 [1.10, 1.18] (p=0.03). The presence of JLCa only had a very limit impact on the local fluid shear stress conditions. The appearance of high stress concentration around the region with JLCa might be due to the mismatch of material properties between calcium and adjacent soft tissues as calcium is a much stronger constituent. Together with studies focusing on other aspects of calcium, such as size (micro calcium), this study highlights that a general description of calcium may be insufficient. The nature of its risk depends upon on its location within a plaque, at times it may stabilise the lesion while at other times it may increase plaque instability.