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Venous TOS Diagnosis
DIAGNOSIS CHARACTERISTICS
The diagnostic process for both forms of VTOS is very similar with the main difference being whether or not the testing reveals a blood clot. When a blood clot is found on imaging, and it is verified that the compression of the axillary-subclavian vein is at the costoclavicular space, the diagnosis will be thrombotic VTOS (Paget-Schroetter Syndrome). If a blood clot is not present but imaging shows positional compression of the axillary-subclavian vein at the costoclavicular space resulting in symptoms of venous congestion, then the diagnosis will be non-thrombotic VTOS (McCleery Syndrome). It is very important to confirm the location of the compression and the clot as only 60% of upper extremity (arm) blood clots are TOS related.
Who Diagnoses & Treats VTOS?
Any doctor who is familiar with VTOS can give a preliminary diagnosis. These most commonly are emergency room physicians. Once a diagnosis of VTOS is suspected, referral should be made to a TOS specialist to make a definitive diagnosis and treat accordingly. TOS specialists are usually vascular surgeons and occasionally cardiothoracic surgeons. However, most vascular surgeons and cardiothoracic surgeons DO NOT specialize in TOS. In fact, most of them have very little experience with TOS. Therefore, it needs to be a vascular surgeon or cardiothoracic surgeon who specifically specializes in TOS. For help finding a TOS surgeon, click here.
VASCULAR TESTING
Venous Duplex or Doppler Ultrasound this is the least invasive, least expensive, and most readily available test out there to check for blood clots and blood flow abnormalities. Duplex ultrasound involves using high frequency sound waves to look at the speed of blood flow, and structure of the veins. It involves an instrument called a transducer being placed on the skin in the area of the vein being imaged, and it is moved around on top of the skin to get different views in different areas. It can also be performed with the arm in different positions. However, by itself, compression of the vein with the arm elevated in the absence of symptoms of venous congestion is not diagnostic of either form of VTOS. With thrombotic VTOS, because it is often associated with a sudden onset of very dramatic symptoms, patients often present to their local ER where an ultrasound can be done to check for clots. However, due to the location of the blood clot with VTOS, which can be directly behind the collarbone, it can be difficult to detect and can depend on the level of skill and experience of the ultrasound technician. This is particularly true in the very early stages of the clot when it has not extended further along in the vein. For these reasons, ultrasound can have a fairly high false negative rate with respect to thrombotic VTOS. Some studies have quantified this as high as 30%. Therefore, if the ultrasound does not detect a clot but the clinical suspicion for a clot is still very high due to the patient’s presentation and symptoms, more advanced and definitive imaging should be done as described below. Consequently, a negative ultrasound cannot be used to rule out thrombotic VTOS in the setting of high clinical suspicion. However, an ultrasound which is positive for an axillary-subclavian vein clot is extremely reliable.
CT Angiogram/MR Angiogram of the Chest (CTA or MRA) this is a CT scan or MRI of the chest which can show the vessels particularly the axillary-subclavian vein and axillary-subclavian artery. This is also sometimes referred to as a CT Venogram or MR Venogram. These tests involve injecting contrast material into a vein and taking x-ray images to determine how the blood moves through the vein, the exact location of the vein compression, and to see what physical condition the vein is in as far as damage or blockage. Either test can be performed both with the arm up and with the arm down. Again, by itself, compression of the vein with the arm elevated in the absence of symptoms of venous congestion is not diagnostic of either form of VTOS. For a diagnosis of either form of VTOS, the compression of the vein needs to be shown to occur at the costoclavicular space where the first rib and collarbone intersect. The three most likely scenarios in which to use this test are:
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If a patient has a positive ultrasound showing a clot, these tests can be used to get a closer look at the vein to see exactly where the clot is and the condition of the vein and any collateral veins which have formed. However, in that situation, it is usually recommended to go ahead and perform a direct catheter venogram (described below) as it is the gold standard for vein imaging and allows for thrombolysis to be performed at the same time to break up the clot.
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If a patient has a negative ultrasound which did not show a clot but they have history and symptoms which are highly suspicious for a clot, these tests can be done to get a better look at the vein to see if there is a clot, what the physical condition of the vein is, and what the collateral vein situation looks like. Again, if the suspicion of a clot is high enough, it is usually recommended to perform a direct catheter venogram (described below) as it is the gold standard for vein imaging and allows for thrombolysis to be performed at the same time to break up the clot. There are also rare situations where a clot will not be seen on CTA or MRA and if clinical suspicion remains high, a direct catheter venogram should then be performed.
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If a patient has a negative ultrasound and has intermittent and mostly positional venous congestion symptoms, these are good tests for diagnosing non-thrombotic VTOS. In this instance, it is extremely important to get images with the arm up to determine that the vein is being compressed within the costoclavicular space with the arm in the elevated position. These tests can show where the compression is occurring and how severe the compression is. These tests can also show whether the vein is sustaining damage, which can assist with making treatment decisions pertaining to surgery and perhaps help determine if there is a high risk for clot formation. Because the suspicion of a clot is low in these circumstances, CTA or MRA is a good choice since it is minimally invasive and more readily available than a direct catheter venogram.
Catheter-Directed Venogram This is considered the gold standard for imaging and diagnosing thrombotic VTOS. Not only can it identify clots and assess the condition of the vein and collateral veins, but it can also be used as a first line of treatment via thrombolysis to break up the clot and can be used as an anatomical road map for surgical treatment in the future. This procedure is usually performed by a vascular surgeon or an interventional radiologist. Often, the patient is given mild sedation. It involves inserting a needle or sheath into a vein on the affected arm. A catheter will be inserted into the vein, contrast dye will be injected into the vein, and x-ray images will be taken to assess blood flow and the condition of the vein. Depending on the findings on the images, during the same procedure, this same catheter can be used to reach and try to break through the clot and/or to administer medication to the area of the clot to help dissolve it.
PHYSICAL EXAM
Physical exam is important in a patient with suspected VTOS as it can provide clues as to whether a clot is likely, whether other types of TOS are involved, and it can help determine the best next step in the diagnostic process. Below is a list of what is typically assessed during a targeted VTOS physical exam:
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Magnitude of arm swelling often with comparison to the opposite arm including arm circumference measurements
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Location of the swelling within the arm i.e. fingers, hand, lower or upper arm
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Exam of upper arm veins for signs of clot that has extended from the axillary-subclavian vein
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Presence of very visible collateral veins across the chest, front of the shoulder, and/or upper arm
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Discoloration of the arm and hand
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Whether symptoms are mainly triggered when the arm is raised or when it is at rest
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Temperature of the arm and hand
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Signs of pulmonary embolism (blood clot that traveled to the lungs)
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Identification of any signs of ATOS or NTOS
BLOOD CLOTTING DISORDER TESTING
Some people have specific genetic markers that make their blood more likely to clot which can make them more likely to form blood clots. This is a type of blood clotting disorder. Technically, VTOS is a mechanical issue wherein the clot forms due to physical compression of the vein. Which is a different mechanism for clotting than having a blood clotting disorder. However, it has been shown that a fair number of VTOS patients do have a blood clotting disorder. Therefore, a referral to a hematologist and having lab work done to test for blood clotting disorders is a good idea as having one of these disorders can impact future treatment plans for VTOS.
PUBLISHED DIAGNOSTIC CRITERIA
In 2016, the top TOS specialists in the United States collaborated to come up with standardized diagnostic criteria for all 3 types of TOS. It was published in an article in the Journal of the Society for Vascular Surgery. Below are the published standardized criteria for the diagnosis of VTOS.
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Illig KA, Donahue D, Duncan A, Freischlag J, Gelabert H, Johansen K, Jordan S, Sanders R, Thompson R. Reporting standards of the Society for Vascular Surgery for thoracic outlet syndrome. J Vasc Surg. 2016 Sep;64(3):e23-35.
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