The left subclavian vein runs under the left clavicle and atop the left first rib, notes AnatomyExpert. At the joint between the first rib and sternum, the subclavian veins join the internal jugular veins to form the brachiocephalic veins. The subclavian veins are extensions of the corresponding left and right axillary veins, which themselves originate from the teres major muscle located near the bottom of the scapula.
One dangerous disorder of the subclavian veins is axillo-subclavian vein thrombosis, also known as Pagett-Schroetter Syndrome or PSS, according to Cleveland Clinic. PSS develops from the repeated compression of a subclavian vein by the surrounding bones and muscles, eventually leading to the formation of a blood clot.
Symptoms of PSS include pain, swelling and blue skin on the affected arm, explains Cleveland Clinic. PSS can also cause the neck and face on the affected side to swell and turn blue. This disorder can lead to pulmonary hypertension, stroke and even heart failure. People at risk of PSS include people who regularly raise their arms, such as baseball players or weightlifters. People with implanted pacemakers or central venous catheters are also at risk.
Treatment involves the breaking up or removal of the clot, followed by the use of blood thinners, states Cleveland Clinic. A doctor may also recommend physical therapy. However, some cases of PSS may require the surgical removal of bone and muscle from the affected area.