Peripheral right arm injection showed normal passage of activity through the axillosubclavian system through the SVC to the right heart. A study from a third patient show normal flow through a catheter in the right subclavian vein, but multiple collaterals after injection of both arms simultaneously. Discussion Thrombosis of the axillosubclavian venous system may be primary or secondary. Primary thrombosis has been referred to as idiopathic, spontaneous, or effort induced. There are multiple causes for secondary thrombosis, all of which may be attributed to factors underlying Virchow's triad of venous stasis, vessel injury, and hypercoaguability.
Iatrogenic trauma is an increasingly frequent cause due to subclavian venous catheterization.
In the past 2 decades there has been both increased use of central venous catheters as well as more widespread use of anticoagulation therapy. Persistent focal activity at the tip of the catheter on a radionuclide flow study is consistent with, but not specific for, fibrin sheath formation. Clinically it may present as resistance to injection or inability to withdraw blood. The diagnosis of subclavian thrombosis has been historically made by standard contrast venography. However, it is invasive and expensive.