Does shear stress modulate both plaque progression and regression in the thoracic aorta?
Human study using serial magnetic resonance imaging
Jolanda J. Wentzel, PhD*,||,
Roberto Corti, MD*, ,
Zahi A. Fayad, PhD ,
Paul Wisdom, Bsc,
Frank Macaluso, Bsc,
Mark O. Winkelman, Msc ,
Valentin Fuster, MD, PhD and
Juan J. Badimon, PhD,*
* Cardiovascular Institute, Mount Sinai School of Medicine, New York, New York
Imaging Science Laboratory, Mount Sinai School of Medicine, New York, New York
Cardiovascular Biology Research Laboratory, Mount Sinai School of Medicine, New York, New York
Damen Dredging Equipment, Research Department, Nijkerk, the Netherlands
|| Thoraxcenter, Erasmus Medical Center, Rotterdam, the Netherlands
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Figure 1 (A) Location of the predefined quadrants i, ii, iii, and iv relative to the right, left, anterior, and posterior side of the patient. (B) Axial distribution of the four predefined segments (orange), each 2 cm in length, summarizing the wall thickness data beginning 1 cm from the reference cross section, located at the exit of the aortic arch. Segment I is located 1 to 3 cm from reference cross section; segment II is located 3 to 5 cm from reference cross section; segment III is located 5 to 7 cm from reference cross section; and segment IV is located 7 to 9 cm from reference cross section. The location of phase-contrast velocity measurements, in yellow, is positioned in the center of the defined segments. Magnetic resonance imaging slice thickness for the velocity and wall velocity measurements was 5 mm.
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Figure 2 Shear rate determination from velocity profile. (A) The velocity profile measured at segment I at one moment during the cardiac cycle after smoothing is applied. (B) Visualization of determination of velocity gradient (dv/dr). (C) Shear rate at each pixel in the lumen. (D) Determination of shear rate at the vessel wall, with the maximum shear rate in regions of approximately 22.5° at the outer 10% of the radius. (E) Shear rate at 16 locations along the circumference; these are summarized into four quadrants per cross section.
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Figure 3 Plaque distribution depending on axial and circumferential location (A to D) location of segments I to IV on magnetic resonance imaging overview of aorta. (E to H) Average wall thickness at baseline for quadrants i to iv for segments I to IV. (I to L) Magnetic resonance imaging cross sections of aorta of individual patient at segments I to IV. (M to P) Quadrants with an average relative wall thickness exceeding the average of the segment are shown in orange.
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Figure 4 Relationship between change in wall thickness (wall thicknessfollow-up – wall thicknessbaseline) attributable to 24 months of treatment with simvastatin and wall thickness at baseline. Closed circles = 1 to 3 cm, segment I; open squares = 3 to 5 cm, segment II; closed triangles = 5 to 7 cm, segment III; closed squares = 7 to 9 cm, segment IV.
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Figure 5 Shear stress distribution depending on axial and circumferential location with average shear stress for segment in center of circle (standard deviation). Color coding refers to average shear stress over cardiac cycle per quadrant.
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Figure 6 (A) Relationship between baseline wall thickness and shear stress (wall thicknessbaseline = –1.6 x SS + 3.3 [mm], r2 = 0.29, p < 0.05). (B) Relationship between normalized wall thickness and shear stress (normalized wall thickness = –0.63 x SS + 1.23, r2 = 0.59, p < 0.05).
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