Computational stress analysis of atherosclerotic plaques in ApoE knockout mice

The aortic sinus lesions of apolipoprotein E knockout (ApoE KO) mice seldom show any signs of fibrous cap disruption, whereas cap ruptures have been recently reported in the proximal part of their brachiocephalic arteries (BCA). We use histology based finite element analysis to evaluate peak circumferential stresses in aortic and BCA lesions from six 42-56 week-old fat-fed ApoE KO mice. This analysis is able to both explain the greater stability of aortic lesions in mice and provide new insight into the BCA lesion as a model for the stability of human lesions with and without microcalcifications in their fibrous caps. The predicted average peak stress in fibrous caps of aortic lesions of 205.8 kPa is significantly lower than the average value of maximum stresses of 568.8 kPa in BCA caps. The aortic plaque stresses only slightly depend on the cap thickness, while BCA lesions demonstrate an exponential growth of peak cap stresses with decreasing cap thickness similar to human vulnerable plaques. Murine BCA ruptured lesions with mean cap thickness of 2 microm show stresses approximately 1400 kPa, three times higher than human ruptured plaques with a mean cap thickness of 23 microm without microcalcifications in the cap, but nearly identical to the peak stress around an elongated microcalcification with aspect ratio 2 in a human thin cap approximately 50 microm thick. We predict biomechanical stress patterns in mouse BCA close to human vulnerable plaques without microcalcification in the cap, while aortic lesions show stress tendency similar to stable lesions in human.