Arterial Reactivity in Lower Extremities Is Progressively Reduced as Cardiovascular Risk Factors IncreaseComparison With Upper Extremities Using Magnetic Resonance Imaging
Harry A. Silber, MD, PhD*,*,
Joao A.C. Lima, MD, FACC*, ,
David A. Bluemke, MD, PhD,
Brad C. Astor, PhD ,
Sandeep N. Gupta, PhD ,
Thomas K. Foo, PhD and
Pamela Ouyang, MD, FACC*
* Department of Medicine, Division of Cardiology, and the
Department of Radiology, Johns Hopkins University School of Medicine, Baltimore, Maryland
Johns Hopkins University School of Public Health, Baltimore, Maryland
General Electric Healthcare Technologies, Milwaukee, Wisconsin
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Figure 1 Analysis of Velocity-Encoded Images
Velocity-encoded image of brachial and femoral artery cross sections in a typical young, healthy subject during systole. To the right of each image is a plot of the velocity datapoints (open circles) versus their distance from the optimal center of the cross section. Each plot also shows the parabola segment that is best fit to the datapoints near the arterial wall. The distance from the center at which the best-fit parabola equals zero is the radius of the cross section. The slope of the best-fit parabola at the radius of the cross section is shear rate. Flow is the sum of the velocity points in the cross section.
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Figure 2 Velocity Profiles at Baseline and During Hyperemia
Velocity profiles of the brachial and femoral arteries during systole at baseline (left) and at peak hyperemia (right) for the same younger subject as in Figure 1. Also shown are the parabola segments that are best fit to the datapoints near the arterial wall. Shear rate, the slope of the parabola segment near the arterial wall, is increased significantly during hyperemia.
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Figure 3 Change in Shear Rate From Baseline to Hyperemia
(A) Brachial change in systolic shear rate from baseline to peak hyperemia in the 3 groups: reduction with increasing risk factors was not statistically significant. (B) Femoral change in systolic shear rate from baseline to peak hyperemia is progressively decreased as cardiovascular risk factors increase. Horizontal bars represent mean ± SD.
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