Diagnostic ultrasound ( PDFDrive )

970 PART III Small Parts, Carotid Artery, and Peripheral Vessel Sonography
A
B
FIG. 27.8 Calciication of the Supericial Femoral Artery (SFA). (A) Severe calciication of the SFA limits ability to see within the artery
lumen with gray-scale imaging. Color Doppler is useful to locate a place where spectral Doppler can be sampled. (B) Spectral Doppler of the artery
has mild spectral broadening but otherwise normal triphasic waveform, without signiicant stenosis in this location. See also Video 27.3.
2 to 4 cm proximal
Time
Velocity
Velocity
At the stenosis
FIG. 27.9 Blood Flow Velocity Alterations Occur With Stenosis of at Least 50%. Proximal to the lesion, the low pattern is normal. At the
stenosis, the peak systolic velocity increases in proportion to the degree of stenosis. Alterations in the diastolic portion of the Doppler waveform
sampled at the lesion depend on the state of the distal arteries and the severity and geometry of the lesion; diastolic low may increase dramatically
or may be almost absent.
Time
Ultrasound can direct intervention in these patients. Patients
with nonacute conditions can beneit from ultrasound to characterize
subacute occlusion or embolic disease versus chronic
ischemic disease to help the surgeon decide among therapies
such as thrombectomy or bypass procedure. 12,13 Mapping with
Doppler before bypass is very useful. Lesions are characterized
by severity using the Trans-Atlantic Inter-Society Consensus
(TASC) guidelines. 14 Isolated and short category A and B lesions
typically are directed to endovascular repair, whereas more
complex or longer lesions, C and D, in general require bypass.
In one study of 622 TASC C or D lesions, Doppler mapping
successfully identiied lesions for intervention with sensitivity
of 97% and speciicity of 99%. 15 Similar high accuracy has been
shown in other studies as well. 16,17
Doppler can also predict which lesions are suitable for
percutaneous transluminal angioplasty with good success. 18,19
However, duplex assessment may underestimate the length of
stenosis. he lesions treated by angioplasty are generally short