Venous TOS is quite uncommon. However, the presentation of venous TOS is quite dramatic, and complications can be serious. Symptoms of venous TOS occur when a blood clot forms in the large vein draining the arm. Doctors treat this blood clot urgently. Following treatment of the blood clot, doctors undertake further diagnosis and definitive treatment of the underlying cause. At the present time, there remain some unsettled questions about the definitive treatment of venous TOS.

Symptoms of venous TOS result from a blood clot

Blood clot in the primary vein draining the arm causes the symptoms of venous TOS. Since the venous blood clot prevents drainage of blood from the arm, the arm may swell. Patients often note ‘heaviness’ of the affected arm. In addition, a blue or purple arm color may also develop. This change in color is caused by 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 blood clot limits or blocks blood flow through the lungs. In that case, patients will have shortness of breath and chest pain, both of which may be severe. Pulmonary embolism may be life-threatening.

Blood clot formation in the subclavian vein completes the process that creates symptoms of venous TOS in the arm and hand. The blood clot blocks venous return from the arm, either partially or completely.

Signs and symptoms include:

• Swelling (edema)
• Cyanosis
• Pain
• Heaviness
• Collateral veins

What causes the symptoms of venous TOS?

Arterial blood enters the arm, but cannot normally drain from the arm. Blood cells remain within the artery and vein, but fluid leaks from small blood vessels into the surrounding tissues. As a result, fluid accumulates within the arm. Edema is the medical term that describes this fluid accumulation. A patient will describe these changes as swelling, heaviness, and pain.

Venous obstruction causes slow flow, oxygen loss, and color changes. Oxygen gives normal arterial blood a bright red color. As oxygen leaves the blood to enter normal tissues, venous blood becomes dark blue or purple. As a result of slow blood flow, bright red arterial blood loses more oxygen than usual in the affected arm. Consequently, the blood changes to a dark blue or purple. Accordingly, the patient or physician sees these changes as cyanosis (see image above).

Because blood cannot drain from the arm through the normal veins towards the heart, many small veins carry more blood. As a result, superficial veins in the shoulder and chest become newly visible. These collateral veins carry blood back to the heart.

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.