Fig. 2.

Dynamic obstruction of the left brachiocephalic vein due to extrinsic compression.

A. Transverse CT scan obtained during inspiration after ipsilateral contrast material injection shows a moderate degree of stenosis (curved arrow) in the left brachiocephalic vein due to extrinsic compression between the right brachiocephalic artery and sternum.

B. Digital subtraction venography at expiration reveals complete occlusion of the left brachiocephalic vein (arrow), and prominent collateral veins.

C. Digital subtraction venography at inspiration demonstrates restoration of blood flow through the left brachiocephalic vein, without the involvement of collateral veins. This phenomenon indicates that according to the point reached in the respiration cycle, extrinsic compression of the left brachiocephalic vein between the arch vessels and the sternum exaggerated at inspiration, can cause dynamic obstruction.