Multiaxial mechanical characteristics of carotid plaque: analysis by multiarray echotracking system.

BACKGROUND AND PURPOSE Carotid plaque rupture depends on the various types of mechanical stresses. Our objective was to determine the multiaxial mechanical characteristics of atherosclerotic plaque and adjacent segment of the common carotid artery. METHODS A novel noninvasive echotracking system was used to measure intima-media thickness, diameter, pulsatile strain, and distensibility at 128 sites on a 4-cm long common carotid artery segment. The study included 62 patients with recent cerebrovascular ischemic event and either a plaque on the far wall of common carotid artery (n=25) or no plaque (n=37). RESULTS The mechanical characteristics of the carotid segment devoid of plaque did not differ between the two groups. Among patients with plaque, 16 had a larger radial strain at the level of plaque than at the level of adjacent common carotid artery (pattern A: outward-bending strain). The eight patients who had an opposite pattern (inward-bending strain) were more often dyslipidemic (100% versus 56% P=0.03) and type 2 diabetic (63% versus 12%, P=0.04) than pattern A patients. Strain gradient significantly decreased in parallel with the presence of dyslipidemia and/or type 2 diabetes. Longitudinal gradients of distensibility and Young's elastic modulus were consistent with strain gradients. CONCLUSIONS Type 2 diabetes and dyslipidemia were associated with a stiffer carotid at the level of the plaque than in the adjacent common carotid artery leading to an inward-bending stress. The analysis of plaque mechanics along the longitudinal axis may afford useful information, because repetitive bending strain of an atherosclerotic plaque may fatigue the wall material and result in plaque rupture.