Diagnostic ultrasound ( PDFDrive )

978 PART III Small Parts, Carotid Artery, and Peripheral Vessel Sonography
A
B
C
FIG. 27.18 Subclavian Artery Stenosis Due to Atherosclerotic
Disease. (A) Focal hypoechoic approximately 50% stenosis (arrow)
in the proximal subclavian artery, outlined by color Doppler. (B) Peak
systolic velocity (PSV) elevation at 208 cm/sec at stenosis. (C) PSV
2 cm upstream (proximal) to stenosis is 89.1 cm/sec for a PSV ratio
of greater than 2 : 1.
low to the hand. he ulnar artery supplies the supericial palmar
arch, which is oten incomplete. he radial artery supplies the
deep palmar arch, which is more commonly complete, in communication
with the ulnar artery. If the supericial palmar arch
in the hand is patent, thus allowing low to the entire hand
through the ulnar artery, then the radial artery is harvested.
hus evaluation of palmar arch patency is necessary before harvest.
Doppler evaluation of patency is more accurate than the modiied
Allen test on physical examination, because only about 5 of 43
(12%) patients with an abnormal modiied Allen test result will
have abnormal Doppler indings. 60
A small linear array 12- to 15-MHz “hockey stick” transducer
initially is used to determine antegrade low of the ulnar artery
and radial artery at the wrist. With duplex Doppler, arterial low
to the hand in the supericial palmar arch at the thenar eminence
near the crease of the base of the thumb is characterized irst
with normal distal radial artery inlow. Subsequently, the radial
artery is transiently occluded by direct compression of the radial
artery at the wrist, and the resultant spectral Doppler waveform
is evaluated. Care should be taken during examination not to
hyperextend the hand with regard to the wrist, because a falsenegative
examination inding may incorrectly suggest lack of
patency of the arch. In patients with a patent supericial palmar
arch, there should be reversed low of the radial artery in the
hand, measured at the thenar eminence or in the region of the
snuf box between the irst metacarpal and second carpal bone. 61,62
If there is no low or absent reversed low, then the radial artery
of that upper extremity is not suitable for harvest owing to an
incomplete arch (Fig. 27.22). Increased low in the ulnar artery
may also occur during radial artery compression if the arch is
patent. 63
PERIPHERAL VEINS
Evaluation of the upper and lower extremity venous system
is primarily performed with sonography. Useful applications