Fig. 5

Thoracic venous outlet obstruction of the left subclavian vein with the left arm raised for CTPA, which subsequently resolves upon positioning the arm down at the side. Axial CECT following the rapid bolus of intravenous contrast in the left upper extremity with the left arm raise (a) shows narrowing of the left subclavian vein at the thoracic inlet and contrast filling multiple small collateral veins in the left shoulder region. The narrowing of the left subclavian vein prevented adequate opacification of the pulmonary artery. Repeat injection with the left arm down by the patient’s side (b) shows excellent opacification of the left subclavian vein and no filling of venous collaterals, permitting a diagnostic scan for evaluation of pulmonary embolus