By Jessica Patterson MD, Kelly Goodsell MD, Meghan Kelly Herbst MD, FACEP & Marsia Vermeulen DO, FACEP
1. What pathology is visualized in the ultrasound clip?
2. What technique is used to perform this POCUS study?
3. What are the potential pitfalls of this study?
A 62 year-old male with a past medical history of hypertension presented to the emergency department (ED) complaining of gradual onset left arm swelling and pain over the past three days. He denied trauma, injury, inciting event, fever, chills, or other constitutional symptoms. He further denied any history of malignancy, coagulopathy, or central venous catheter placement.
On exam, he was non-toxic appearing and in no distress. His left arm was notably erythematous and swollen from the mid-bicep area to his fingers but was not significantly warm to touch. Radial and ulnar pulses were palpable and normal perfusion was appreciated. He displayed full range of motion at the shoulder; he could range the elbow although full flexion and extension were limited by the local pain and swelling. Distal medial, radial, ulnar nerve functions were intact.
POCUS was performed using a high-frequency vascular probe to visualize the deep veins of the upper extremity (see clip 1). The patient was positioned supine with the head of the bed elevated to 30 degrees, with his arm externally rotated and abducted 60-90 degrees. The probe was placed just proximal to the antecubital fossa to visualize the brachial vein in the short axis plane. Gentle compression was applied with the probe until the vein fully collapsed and the walls “kissed” one another. This was repeated moving the probe proximally at approximately 1-2 centimeter (cm) intervals. The entirety of the brachial and axillary veins were sequentially visualized and compressed without difficulty. The subclavian vein was then visualized via an infraclavicular approach, noting a large thrombosis in the distal region. Finally, the internal jugular vein was visualized and compressed with no signs of thrombosis. The patient was started on anticoagulation therapy and admitted for further workup of his subclavian deep vein thrombosis (DVT).
Upper extremity DVTs (UEDVTs) account for about 5-8% of all DVT cases.1 Veins are classically considered to be “deep” if they have an associated artery with the same name. In the upper extremity, DVTs most commonly occur in the axillary and subclavian veins but can also involve the brachial vein.2 Primary UEDVTs can occur from anatomical variants, but most occur secondary to other factors. The most important risk factor is a foreign body in the vasculature such as a venous catheter or pacemaker, and the second most significant risk factor is malignancy.3 DVT should be considered with any presentation of atraumatic unilateral upper extremity swelling, as demonstrated in the case above.
There is currently no well-validated protocol for POCUS in the diagnosis of UEDVT (like the 2-point compression study that has been more extensively studied for the lower extremities).1 However, the evaluation for an upper extremity DVT is not technically difficult and an emergency physician experienced with lower extremity DVT POCUS studies should feel comfortable with the upper extremity deep veins. We recommend that you perform a compression ultrasound study moving the probe in 1-2 cm intervals, using the technique described above.
Like the lower extremity, most of the upper extremity veins can be easily compressed with gentle pressure. However, where the subclavian vein traverses below the clavicle it is no longer compressible and thus patency can no longer be demonstrated by applying direct pressure. The brachiocephalic vein is also noncompressible and not always easily visualized on ultrasound. Sometimes, an echogenic clot in these veins can be easily visualized, as in this case. Another method to evaluate for patency of the subclavian vein once it can no longer be directly compressed is to utilize Doppler flow to determine if there is respirophasic variation in the venous blood flow. Visualize the subclavian vein in the longitudinal view and obtain a pulsed-wave Doppler tracing. Normally, variation is seen in venous flow as intrathoracic pressure changes with inspiration and expiration. With normal venous flow, the tracing will be biphasic with repeated troughs (inspiration) and peaks (expiration). If these variations are absent, it suggests a proximal obstruction (see Image 1 for an example) in the subclavian or brachiocephalic veins.1,4,5
For EP sonographers familiar with Doppler flow studies, this can be a useful adjunct to include in the POCUS when evaluating for UEDVT. However, the presence of biphasic flow does not rule out UEDVT. In one study of images obtained by vascular technicians, the absence of biphasic flow was only 75% sensitive for UEDVT in studies where the thrombosis could not be directly visualized.6
The sensitivity and specificity of POCUS for UEDVT has not yet been extensively studied. A positive finding in an upper extremity POCUS study should be considered specific and therapy can be started accordingly. However, a negative POCUS does not definitively rule out a clot (especially in the subclavian or brachiocephalic veins) and further studies such as a CT or MR venography should still be obtained after a negative POCUS to definitively rule out UEDVT.
Noncompressible echogenic material in the subclavian vein consistent with thrombosis.
Point-by-point sequential compression every 1-2 cm starting in the brachial vein and moving proximally to the axillary, subclavian, and internal jugular veins.
Not all of the subclavian vein is compressible and therefore other modalities such as Doppler flow can be utilized to evaluate patency. A negative study is not definitive and further imaging modalities should be pursued.