Velocity Vector Imaging of Longitudinal Mechanical Properties of Upstream and Downstream Shoulders and Fibrous Cap Tops of Human Carotid Atherosclerotic Plaque

Aims: Atherosclerotic plaque rupture is closely related to high regional mechanical stress in the plaque itself. We aimed to explore the longitudinal mechanical properties of upstream and downstream shoulders and fibrous cap tops of human atherosclerotic plaques in vivo by velocity vector imaging (VVI) combined with acoustic densitometry (AD) imaging. Methods and Results: We included 135 patients with carotid atherosclerotic plaque. VVI and AD were used to examine 3 regions of carotid plaque along the longitudinal-axis view. A total of 405 regions were classified with low or high AD values by corrected averages image intensity (AIIc%) < or ≥50, respectively. Peak systolic strain, strain rate (SR), and velocity were significantly greater for upstream than downstream shoulders and fibrous cap tops of carotid plaque (P < 0.05 for both). AIIc% was significantly lower for upstream than downstream plaque shoulders (P < 0.05). Peak systolic SR of the plaque regions was negatively correlated with corresponding AIIc% (R2 = 0.499, P < 0.05). Conclusions: The longitudinal strain of human carotid atherosclerotic plaques as derived by VVI is associated with its corresponding AD but also in part with the internal position of the strain, with values greater for upstream than downstream shoulders and fibrous cap tops.