Diagnostic ultrasound ( PDFDrive )

976 PART III Small Parts, Carotid Artery, and Peripheral Vessel Sonography
FIG. 27.16 High Brachial Artery Bifurcation. High brachial artery
bifurcation, with two arteries (A) (radial and ulnar) and their paired
accompanying veins (V), above the antecubital fossa.
walls with anechoic lumens and lack of atherosclerotic plaques
or stenosis, similar to lower extremity arteries. Laminar low is
present without turbulence or aliasing on color Doppler. A similar
high-resistance triphasic waveform with sharp upstroke and
transient low reversal is typically present in the upper extremity
arteries on spectral Doppler.
Ultrasound Examination and Imaging Protocol
Higher frequency imaging is usually possible owing to decreased
size of the arm with respect to the leg. he subclavian artery,
axillary artery, and brachial artery are evaluated to the level of
the elbow. Both upper extremities should usually be insonated
so that the symptomatic side can be compared with the asymptomatic.
he ipsilateral innominate artery should be evaluated
to determine an abnormal inlow etiology of the problem when
the subclavian artery waveform is abnormal. In the forearm,
imaging of the radial and ulnar arteries is the key to most
diagnoses.
he ACR-AIUM-SRU practice parameter for the performance
of peripheral arterial ultrasound suggests that upper extremity
ultrasound should examine the subclavian artery, axillary artery,
and brachial artery. 2 Other arteries are examined as deemed
clinically appropriate. It states that these may include “innominate,
radial, and ulnar arteries, and the palmar arch.” he guideline
further suggests that angle-corrected longitudinal Doppler and/
or gray-scale imaging should be documented in each normal
and at any abnormal segment. Angle-corrected spectral Doppler
is recommended proximal to, at, and beyond any suspected
stenosis. 2
Arterial Occlusion, Aneurysm, and
Pseudoaneurysm
Upper arm arterial occlusion is usually the result of trauma,
oten iatrogenic. he rate of radial artery occlusion ater artery
access for coronary angiography may be as high as 30.5%, although
lower rates are also reported in the literature. 53 For surgical bypass
harvest planning, documentation of patency of the palmar arch
is an additional component. For detection and characterization
of arterial aneurysm, the maximal outer diameters of the aneurysm
should be measured in transverse (short axis) with gray-scale
technique. Doppler can diferentiate the patent component from
mural thrombus. In pseudoaneurysm characterization, the size
and Doppler components are also measured, but the pseudoaneurysm
neck is also evaluated with spectral Doppler as detailed
earlier in the section on lower extremity arteries (Fig. 27.17,
Video 27.7 and Video 27.8). If there is concern for AVF, both
the arterial inlow portion and venous outlow should be characterized
by duplex Doppler within several centimeters of the
pseudoaneurysm, because the characteristic arterialization of
the downstream venous waveform may be dampened farther
away from the istula. Turbulent low through the istula may
afect surrounding tissues causing a tissue reverberation artifact,
which may be the irst clue that an AVF is present.
Arterial Stenosis
Atherosclerotic disease can cause upper extremity stenosis but
is a less common problem in the arm than encountered in the
lower extremities. Gray-scale indings are similar to the lower
extremities and include intimal plaques and/or visible irregularity
of the vessel lumen. Color Doppler may show aliasing with
turbulent low similar to those indings seen in lower extremity
arterial stenosis. On spectral Doppler, velocity criteria are not
well deined for the upper extremity arteries. However, for a
stenosis in most nonbranching arteries, a greater than 2 : 1 PSV
ratio of the stenosis relative to the upstream artery within 2 to
4 cm is consistent with at least 50% diameter stenosis. Depending
on the timing and whether collaterals have formed, this degree
of stenosis may or may not be symptomatic or clinically signiicant
(Fig. 27.18).
Subclavian Stenosis
Subclavian stenosis most commonly occurs proximal to the
origin of the let vertebral artery. In a subset of patients, low to
the arm is provided by illing through the vertebral artery via
retrograde low. If this reversed low is signiicant, there can be
a steal phenomenon (“subclavian steal”) from the brain, leading
to dizziness with certain arm movements as additional low is
diverted to the arm. In these patients, the vertebral artery
waveform should be insonated (Fig. 27.19, Video 27.9). Transient
early systolic deceleration with resultant transient cessation of
antegrade low or transient reversal of low (Fig. 27.20) correlated
with subclavian artery mean diameter stenosis of 72% and 78%,
respectively. 54 Similar stenosis can occur in the right subclavian
artery, but less frequently. If these abnormal vertebral artery
waveforms are seen, an attempt should be made to directly
visualize a stenosis by gray-scale and duplex Doppler in the
subclavian artery itself.
Thoracic Outlet Syndrome
In distal upper extremity ischemic symptoms, embolic or
traumatic injury (commonly iatrogenic) to the artery should
also be considered. If embolic phenomena are seen, evaluation
for thoracic outlet syndrome should be considered. In patients
with symptoms elicited by speciic positioning of the arm, thoracic
outlet syndrome is a form of arterial stenosis that should be
considered. It occurs by external compression of the artery by
adjacent muscles during abduction of the arm, and this narrowing