For the most part, doctors can make the presumptive diagnosis of venous TOS quite promptly, based on a clinical examination. Your doctor will usually find secondary signs of a large venous blood clot, although they cannot directly see the clot. Subsequently, he or she will order imaging tests to confirm the blood clot. Doctors consider the prompt treatment of this clot as the first step in the definitive treatment of venous TOS.

Clinical Diagnosis of Venous TOS

A single large subclavian vein drains most of the blood flow from the arm. Blood clot in the subclavian vein prevents adequate drainage of blood from the arm. In this setting, arm swelling will occur. As a result, patients often describe ‘heaviness’ of the arm. In addition, a blue or purple color may develop, due to loss of oxygen from the trapped blood. In the event the blood clot breaks off, patients may experience a pulmonary embolism. Pulmonary embolism occurs when the blood flow through the lungs is blocked or decreased. In that case, patients will have shortness of breath and chest pain. Pulmonary embolism may be life-threatening.

To begin with, a doctor will look for some or all of the following signs:

Cyanosis is a blue or purple color of the skin. Arterial blood is full of oxygen and appears bright red. Venous blood is low in oxygen and appears dark red to purple. When blood enters the arm but cannot leave normally, more oxygen leaves the blood. As a result, the blood turns darker than normal, and the skin reflects this color change.

Collateral veins appear because the blood cannot leave the arm through the normal venous channels. Blood clot in the large subclavian vein blocks normal blood flow returning towards the heart. As a result, very small superficial veins have to expand to carry the blood back towards the heart. Your doctor can see these collateral veins in the skin of the shoulder and chest. It is important to note that collateral veins represent secondary or indirect evidence of the subclavian vein blood clot.

The venous angle indicates the ability of blood to exit the arm and flow towards the heart. In a normal person, a doctor will slowly raise the arm from the waist until it points forward. In this position, the superficial veins on the back of the hand should empty. If a blood clot is present in the subclavian vein, the doctor will need to raise the arm higher than usual before these veins empty. The venous angle demonstrates secondary or indirect evidence of limited blood flow in the subclavian vein. It may result from blood clot in the vein, or from extrinsic compression of the vein.

Rarely, your doctor may be able to feel the blood clot within the subclavian vein by pressing deep within the armpit.

After a doctor makes the appropriate initial diagnosis of venous TOS, he or she will order imaging tests. The first imaging tests focus on confirming the presence and extent of venous blood clot. Following prompt treatment of this blood clot, further imaging tests evaluate the subclavian vein in detail. These imaging tests focus on demonstrating extrinsic structures compressing the vein and the resulting intrinsic damage to the vein.

Laboratory Diagnosis of Venous TOS

In most cases, laboratory tests reveal little useful information in patients with venous TOS. However, in a few patients, laboratory tests may demonstrate blood that forms clots more easily than normal. Learn more about the laboratory diagnosis of venous TOS here.

Imaging Diagnosis of Venous TOS

Your doctor can see indirect signs of a blood clot blocking venous outflow from the arm. Imaging tests are often a vital part of the initial demonstration of this blood clot, as well as demonstrating structures that compress the vein and secondary damage to the vein. Learn more about the clinical diagnosis and imaging of venous TOS here.

Treatment of Venous TOS

Primary treatment is performed by urgent treatment of the venous blood clot. Following this, structures that compress the vein are often reduced or removed, and repair of the vein is performed if it is damaged. Learn more about the treatment of venous TOS here.