Plaque Morphology in High Versus Low Shear Stress Regions of Human Carotid Stenosis

Background: A role for high shear stress in plaque destabilization has been postulated. We investigate this potential effect by correlating carotid plaque morphology directly with in vivo wall shear stress measurements. Materials and Methods: Carotid endarterectomy patients were enrolled in an IRB approved study using magnetic resonance angiography (MRA) to measure in vivo wall shear stress. After endarterectomy, the specimen was oriented, cross sectioned for histology at 2 mm intervals, and photographed. The shear stress correlating with each histologic segment of vessel was calculated from presurgical MRA using Navier‐Stokes finite element analysis. The plaque regions were evaluated quantitatively for area of necrosis, calcification, hemorrhage and inflammation; fibrous cap and intimal thickness, plaque erosion, rupture or thrombosis. Results: Complete analysis with shear stress correlation has been performed on twenty fields of plaque. No erosion, rupture or thrombosis was noted. Low shear stress areas had a thinner plaque (142 vs 230)and thinner fibrous cap (11 vs 35). Intraplaque hemorrhage was significantly more prevalent in high shear stress (p=0.001, as was calcification (p=0.04), but inflammation and necrosis were not. Conclusion: We can correlate quantitative and qualitative morphologic features and eventually proteomic and genomic alterations within areas of low and high shear stress in atherosclerotic plaques. Our quantitative data supports the concept that high shear stress leads to destabilization of the plaque indicated predominantly by more intraplaque hemorrhage.