Abstract 3327: Asymmetrical Distribution of Shear Stress is Related to Positive Remodeling in Coronary Atheroscletosis. : In Vivo Serial Observation with Three-dimensional Intravascular Ultrasound.
Background: Shear stress is one of the important physical factors in the process of atherosclerosis. It has been recognized that the portions of arterial vessel having lower shear stress are likely to be associated with plaque formation and positive arterial remodeling. This study with use of three-dimensional intravascular ultrasound ( 3D-IVUS ) observed the serial change in coronary plaque thickness as well as the pattern of arterial remodeling, compared to the shear stress distribution at the baseline.
Methods: A total of 110 proximal segments of left descending coronary artery from 18 patients were imaged with 3D-IVUS at the baseline and at the follow-up period (mean 17 ± 7 months). Vessel area (VA), plaque area (PA), maximum (Mx) and minimum (Mn) thickness of plaque were measured, and plaque distribution index (Pd=Mx/Mn) was calculated. Then, year-adjusted percent change (%d−/y) of each parameter during the follow-up period was obtained. Shear stress at each cross section at the baseline was calculated by an user-friendly program of color mapping of shear stress which we recently developed IVUS ( J Am Coll Cardiol, 2005 ). On the basis of this image, we calculated our original index of shear stress asymmetricity in a vessel cross section, which was obtained by minimum shear stress in a vessel cross section divided by the value of its counterpart wall.
Result: During the follow-up period, 47% of segments showed a progression in plaque area, while 53% showed a regression in plaque area. Fifty-four percent of segments showed a positive remodeling (a progression in VA), while 46% showed a negative remodeling (a regression in VA). When the asymmetricity index of shear stress is less than 0.25, %d-VA/y was significantly correlated with %d-PA/y (r=0.64, p<0.001) as well as Pd (r=0.56, p<0.001). However, when the index was more than 0.75, such significant relationship was not observed at all.
Conclusion: This serial IVUS study showed that atherosclerotic plaque formation is associated with vessel area expansion especially in the vessels having larger asymmetrical distribution of shear stress. Therefore, patterns of coronary arterial remodeling during plaque formation might be determined in part by the degree of nonuniformity in shear stress distribution.