Diagnostic ultrasound ( PDFDrive )

992 PART III Small Parts, Carotid Artery, and Peripheral Vessel Sonography
A
B
FIG. 27.41 Normal Brachiocephalic Veins. Gray-scale (A), and color and spectral Doppler (B) of left and right brachiocephalic veins (arrows)
and cranial superior vena cava (SVC; *).
subclavian vein. In many cases the subclavian vein can be
compressed.
Accurate spectral waveform evaluation is critical to this
examination. Documentation of normal low in the medial
subclavian vein conirms patency of the brachiocephalic vein
and superior vena cava, which cannot be examined directly. Each
spectral image obtained in the longitudinal plane of the vessel
with angle of insonation maintained at less than 60 degrees is
evaluated for spontaneous, phasic, and pulsatile low. Demonstration
of transmitted cardiac pulsatility and respiratory phasicity
is necessary in the spectral analysis of the caudal IJV and medial
subclavian vein. A normal spectral tracing should return to
baseline. Absence of pulsatility may be caused by a more central
venous stenosis or obstruction (Fig. 27.42). 97
Spectral tracings from the medial subclavian vein should be
compared with tracings from the lateral subclavian vein. A change
between these two tracings suggests midsubclavian vein stenosis.
Response to a brisk inspiratory snif or Valsalva maneuver may
assist evaluation of venous patency. During a snif, the normal
IJV or subclavian vein normally decreases in diameter or collapses
completely. he Valsalva maneuver will increase the vein diameter,
demonstrating response to the increased thoracic pressure and
documenting communication with the central vasculature.
Patients with signiicant stenosis or obstruction of the central
brachiocephalic vein of the superior vena cava will lose this
response. 97
he upper extremity venous imaging protocol includes the
following images for each deep venous segment:
1. Transverse gray-scale image at rest and with compression, or
a cine clip of the compression maneuver of the proximal and
distal IJV, subclavian, axillary, and brachial veins. he basilic
and cephalic veins are evaluated in the upper arm to the
elbow.
2. Longitudinal color Doppler with spectral waveform analysis
is performed of the IJV, both proximal and distal portions,
as well as the subclavian vein, both medially and laterally,
and the axillary vein. If only a unilateral examination
is requested, the contralateral subclavian vein is also
evaluated.
3. Evaluation of focal symptomatic areas if present, including
the forearm.
Upper Extremity Acute Deep Venous Thrombosis
Current literature shows the sensitivity and speciicity of venous
Doppler ultrasound for upper extremity DVT to range from
78% to 100% and 82% to 100%, respectively. 96,98-102 he classic
ultrasound inding in acute upper extremity DVT is an enlarged,
tubular structure illed with thrombus showing variable echogenicity
and absence of color Doppler low (Fig. 27.43, Video
27.21). Nonocclusive thrombus may show low outlining the
thrombus, with a variable appearance depending on whether
the nonocclusive thrombus is acute or chronic. Nonocclusive
thrombus usually does not result in enlargement of the vein
(Fig. 27.44). When the obstruction is incomplete, nonphasic
low is demonstrated when the luminal narrowing is signiicant
enough to afect the transmitted cardiac pulsatility and respiratory
phasicity from the thorax. Attention to detail is important in
the normally paired brachial veins to avoid overlooking thrombus
in one of the veins (Fig. 27.45, Video 27.22).
Evaluation of central thrombus relies on spectral analysis.
he presence of a nonpulsatile waveform (similar to portal venous
low) that does not cross the baseline strongly suggests central
venous thrombosis, stenosis, or extrinsic compression from an
adjacent mass. 96 A suspicious waveform should always be
compared with the contralateral side to assess a unilateral versus
bilateral process. Patel and colleagues 103 found that absent or
reduced cardiac pulsatility was a more sensitive parameter in
patients who had unilateral venous thrombosis, even though
respiratory phasicity oten was asymmetric. In cases of bilateral
subclavian vein or superior vena cava occlusion, a high level of
suspicion must be maintained to detect central thrombus or
stenosis. Of importance, because of high-volume low, there may