Thoracic Outlet Syndrome Unexpectedly Common in Iliac Vein Stenosis

Introduction: We unexpectedly observed many patients undergoing iliac vein stenting for proximal venous outflow obstruction (PVOO) also had symptoms suggestive of Thoracic Outlet Syndrome (TOS). This study aims to elucidate this association. Methods: 99 consecutive patients undergoing iliac vein stenting for PVOO at tertiary hospital from 12/2019 to 06/2021 were retrospectively reviewed. Exclusions: absent follow-up, prior vein stenting, acute DVT. TOS symptoms included upper extremities weakness, paresthesia, edema, pain, shoulder pain, upper back pain, neck pain, or impaired arm abduction. Categorical variables analyzed using Fisher’s exact tests. Continuous variables compared by two-sample Welch t-test. Results:>2 TOS symptoms present in 62 patients. Subclavian venogram also performed in 76 patients with PVOO showing 70.7% had subclavian stenosis or thrombosis. Preoperative TOS symptoms included upper extremity weakness (28.3%), paresthesia (67.7%), upper back pain (50.5%), impaired arm abduction (10.1%), shoulder pain (50.5%), and neck pain (37.4%). Comparing symptomatic TOS to those without, CEAP class (P = 0.137), preoperative VCSS composite scores (P = 0.643), stent laterality (P = 0.342), and number of stents (P = 0.275) were similar. All patients were seen postoperatively, mean postoperative follow-up >176 days (P = 0.632). Among TOS patients, improvement observed postoperatively in upper extremity weakness (33.9%), paresthesia (45.2%), shoulder pain (69.4%), neck pain (58.1%), and upper back pain (75.8%). Conclusion: TOS symptoms were unexpectedly common in patients with chronic PVOO undergoing iliac vein stenting, suggesting an important and previously unrecognized concurrence. While venous hypertension is the primary cause of lower extremity symptoms in PVOO, the cephalad location of these TOS symptoms suggests a pathophysiology unrelated to venous hypertension.