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PERIPHERAL VASCULAR ULTRASOUND
clavicle (Fig. 10.12). There are no clearly defined criteria as to the point at which TOS is indicated, but a doubling of the peak systolic velocity at one location is indicative of a significant hemodynamic effect. Patients with severe vascular symptoms show complete occlusion of the SA during provocation maneuvers, posing less of a diagnostic dilemma.
Figure 10.11 Scanning for TOS. The SA should be examined from the supraclavicular and infraclavicular fossae while the arm is abducted; see text.
CC
S
AB
Figure 10.12 A: A normal color flow image of the SA (S) as it passes underneath the clavicle (C) with the arm at rest. B: Following arm abduction there is marked compression of the SA associated with color aliasing (arrow), indicating TOS. Note the large acoustic shadow below the clavicle.
ANEURYSMS
Aneurysms involving the upper extremities are rare and are most frequently seen in the SA, associated with TOS. False aneurysms or pseudo-aneurysms are most commonly seen in the radial, brachial or axillary artery following arterial puncture for catheter access. Some patients present to the clinic with visible pulsatile swelling in the supraclavicular fossa, which is usually on the right side of the neck. This is invariably due to tortuosity of the distal bra- chiocephalic artery, proximal common carotid artery and proximal SA. Occasionally, pulsatile swellings are seen in the area of the radial or ulnar artery at the wrist, which can be due to a ganglion lying adjacent to the artery and distorting its path. The ganglion can be surgically removed.
ULTRASOUND ASSESSMENT OF HEMODIALYSIS ACCESS GRAFTS AND ARTERIOVENOUS FISTULAS (AVF)
Hemodialysis access grafts and arteriovenous fistu- las (AVF) are surgically constructed for patients who require long-term dialysis. They provide a superficial high-volume, low-resistance pathway