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AngioScan Medical Tests 49
© 2014 AngioScan-Electronics LLC
4.2.3.3 Phase shift
The phase shift parameter is computed at the end of an occlusion test and characterizes the vasomotor
response in major arteries.
It has been shown that the pulse waves velocity decreases after an occlusion in arteries distal to the site
of occlusion. This phenomenon is mainly due to the effect of post-occlusion nitric oxide production on
the smooth muscle of large arteries (brachial and radial arteries).
Phase shift is determined by the time delay with which the pulse waves travel in the occluded arm as
compared to that of the reference arm. The phase shift parameter is used to assess endothelial
function.
The phase shift of 10 ms or more is typical for a normal endothelial function. The phase shift is less than
10 ms in patients with impaired endothelial function. In the example below, the phase shift is equal to
10.2 ms, indicating a normal endothelial function.