Diagnostic ultrasound ( PDFDrive )

944 PART III Small Parts, Carotid Artery, and Peripheral Vessel Sonography
A
B
C
FIG. 26.37 Post–Carotid Endarterectomy (CEA)
Appearances. (A) Normal post-CEA changes with
a vein patch (arrows). (B) Abnormal wedge of
residual/recurrent plaque/thrombus in newly symptomatic
post-CEA patient. (C) Post-CEA sutures
(arrow) with a residual intimal lap in lumen.
and distal to the stent. he rate of post-CAS restenosis has been
reported as between 1.9% and 16%. 198-203 Velocity criteria for
grading stenoses in a stent may not be the same as for those in
the native carotid artery. 204,205 Some investigators have shown
that velocities along the stent are routinely higher than those in
a nonstented vessel. Velocity elevations in the range of 125 to
140 cm/sec are fairly common in widely patent stents. In addition,
sonographers normally see an increase in velocity in the distal
ICA beyond the deployed stent. At present, slight increases in
velocity in a stent that appears widely patent on power or color
Doppler are unlikely to indicate signiicant narrowing or warrant
further assessment or intervention.
Fleming et al. 198 and Chahwan et al. 206 showed that normal
Doppler ultrasound reliably identiies arteriographically normal
carotid arteries ater CAS. hey also reported that post-CAS
carotid velocities did not always correlate with the prestent
low-limiting stenosis assessments and that the velocities are
disproportionately elevated in mild and moderately restenotic
vessels. he disproportionate velocity elevations along the stent
may be caused by several factors, including changes in vessel
wall compliance and shunting of blood low away from the ECA.
Also, the technique used in many stent trials, which require
strict adherence to the 60-degree angle theta technique for Doppler
interrogation, may result in systematic velocity increases. As
such, it was realized that new tables must be established and
validated for the follow-up of patients ater CAS. Multiple proposals
for grading post-CAS parameters have been suggested 207-211
(Table 26.4).
NONATHEROSCLEROTIC CAROTID
DISEASE
Nonatherosclerotic carotid disease is much less common than
plaque disease. Fibromuscular dysplasia, a noninlammatory
process with hypertrophy of muscular and ibrous arterial walls
separated by abnormal zones of fragmentation, involves the middle
and distal ICA more frequently than other carotid segments. A
characteristic “string of beads” appearance has been described
on angiography. Only a few reports describe sonographic features
of ibromuscular dysplasia. 212-214 Many patients with ibromuscular
dysplasia demonstrate nonspeciic or no obvious abnormalities
on ultrasound; however, some patients may demonstrate redundancy
of the mid to distal ICA causing an S-shaped curve. 215
Fibromuscular dysplasia may be asymptomatic or can result in