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)
- 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.
Cyanosis of the fingers