Chronic thromboembolic pulmonary hypertension (CTEPH) is typically linked to prior venous thromboembolism; however, atypical sources of thrombosis remain underexplored. A retrospective cohort study from Helsinki University Hospital published in the Heart, Lung, and Circulation assessed the role of thoracic outlet syndrome (TOS) and upper extremity deep venous thrombosis in patients undergoing pulmonary endarterectomy.

The analysis included 64 consecutive patients treated between 2015 and 2023. Among these, 7 patients (11%) had TOS characterized by subclavian vein stenosis, impaired flow, and collateral formation confirmed by provocation contrast venography. Patients with TOS-associated CTEPH were significantly younger (median age 23 vs 59 years; p<0.001) and more frequently exhibited distal, segmental disease (100% vs 38.6%; p<0.01), with fewer conventional thrombosis risk factors (p<0.05). 

Baseline clinical parameters, including functional class, N-terminal pro-B-type natriuretic peptide (NT-proBNP), 6-minute walk distance, and pulmonary vascular resistance (PVR), were comparable between groups.

At 1-year follow-up, improvements in PVR (−45% vs −56%), NT-proBNP (−70.0% vs −71.8%), and functional class (85.7% vs 91.5%) were similar across groups. However, patients with TOS demonstrated a greater increase in 6-minute walk distance (247 m vs 100 m; p<0.05). Postoperative balloon pulmonary angioplasty was more frequently performed in the TOS group (57.0% vs 10.5%; p<0.01), while vasodilator use did not differ significantly.

TOS-associated CTEPH represents a distinct clinical subgroup with unique characteristics. These findings highlight the relevance of upper extremity venous pathology in CTEPH evaluation and management.