Supplementary Material for: Functional Characterization of Patients with Chronic Thromboembolic Disease

<b><i>Background:</i></b> Patients with chronic thromboembolic pulmonary disease (CTED) have persistent pulmonary vascular obstruction and exercise intolerance without pulmonary hypertension at rest and may benefit from pulmonary endarterectomy. However, up to now, CTED has been poorly characterized. <b><i>Objectives:</i></b> This study aimed to analyze the exercise capacity and limiting factors in CTED. <b><i>Methods:</i></b> We compared right heart catheterization and cardiopulmonary exercise test results of patients with CTED [mean pulmonary artery pressure (mPAP) at rest &lt;25 mm Hg, n = 10], chronic thromboembolic pulmonary hypertension (CTEPH, n = 31) and a control group (n = 41) presenting with dyspnea but normal pulmonary vascular imaging and excluded pulmonary hypertension. <b><i>Results:</i></b> Subjects with CTED show a reduced oxygen uptake [median 76/interquartile range (IQR) 22% pred.] and work rate (median 76/IQR 21 W). The work rate was significantly lower compared to control subjects (p = 0.04) but not significantly different from CTEPH patients (p = 0.66). Oxygen pulse and breathing reserve were normal. CTED subjects showed decreased end-tidal CO₂ at anaerobic threshold (28.4/4.3 mm Hg), an elevated VE/VCO₂ slope (42.5/23.5), breathing equivalents (EQO₂ 32.0/8.7, EQCO₂ 39.5/8.8), alveolar-capillary oxygen gradient (34.7/15.5 mm Hg) and capillary end-tidal carbon dioxide gradient (8.8/5.7 mm Hg) compared to control subjects (p &lt; 0.001). The degree of limitation was similar to that in CTEPH. <b><i>Conclusions:</i></b> Despite an mPAP of &lt;25 mm Hg, subjects with CTED show objective functional impairment and similar limitations to patients with CTEPH. Functional limitation is characterized by gas exchange disturbance and ineffective ventilation.