Effort thrombosis, also known as Paget-Schroetter syndrome, is due to repetitive activity of the upper extremities with compression and thrombosis of the axillary-subclavian veins.

Any anatomical abnormality at the thoracic outlet and repetitive trauma are predisposing factors for its initiation.

This patient has bilateral thoracic outlet syndrome with a thrombus at the left subclavian vein, the costoclavicular space, which is anatomically limited superiorly by the clavicle, anteriorly by the subclavian muscle and posteriorly by the first rib and middle scalene muscle.