Diagnostic ultrasound ( PDFDrive )

CHAPTER 27 Peripheral Vessels 975
A
B
C
FIG. 27.15 Supericial Femoral Artery Bypass Graft. (A) Color
and spectral Doppler show normal biphasic low in the proximal
bypass graft, with a peak systolic velocity of 83.5 cm/sec. (B) Grayscale
imaging in the midcalf shows a focal area of narrowing or
thrombosis (arrow). (C) Spectral Doppler at the stenosis with aliasing
and a peak velocity of 253 cm/sec, consistent with at least 50%
stenosis. See also Video 27.6.
colleagues suggest that PSV above 300 cm/sec and PSV ratio
above 3.5 should direct the patient to intervention of a vein grat
stenosis. In patients who meet these criteria, the intervention
should be immediate if low velocity within the grat falls below
45 cm/sec. 45 Decreased low relative to a prior study is also a
worrisome inding on spectral Doppler. In surveillance of vein
grats by Doppler with intervention on stenotic lesions, there is
increased survival of the surveillance group. In patients with
greater than 70% stenosis, 100% of grats failed without revision,
but only 10% failed with ultrasound detection and a subsequent
revision pathway. 49
Patients with venous bypass grat may form pseudoaneurysms
or true aneurysms, but these are rare. When present, they occur
most frequently in the anastomotic regions. In a study of saphenous
vein grats, only 10 of 260 (4%) developed true arterial
aneurysm, 50 with higher incidence in patients with preexisting
aneurysm and in males. he average time to diagnosis was 7
years ater grat placement. 51
Upper Extremity Arteries
Normal Anatomy
Each upper extremity arterial system is supplied from either
the brachiocephalic artery (right) or the subclavian artery (let)
in patients without normal anatomic variations. he artery is
anterior to the vein when insonated from the supraclavicular
fossa. he subclavian artery courses laterally and becomes the
axillary artery once it is beyond the lateral margin of the irst
rib. he axillary artery courses medially over the proximal humeral
head to the inferior margin of the pectoralis muscle, where it
becomes the brachial artery. he brachial artery typically courses
along the medial upper arm to the antecubital fossa and divides
into the radial, ulnar, and smaller interosseous arteries.
Occasionally, there is high brachial artery bifurcation above
the antecubital fossa 52 (Fig. 27.16). Regardless of the level of
origin, the radial and ulnar branches extend to the wrist. On
gray-scale imaging, normal upper extremity arteries have smooth