Cardiopulmonary exercise testing to evaluate the exercise capacity of patients with inoperable chronic thromboembolic pulmonary hypertension: An endothelin receptor antagonist improves the peak PETCO₂

Aims The 6-min walking distance is often used for assessing the exercise capacity under the treatment with an endothelin receptor antagonist (ERA) in patients with chronic thromboembolic pulmonary hypertension (CTEPH). The cardiopulmonary exercise testing (CPX) was reported to be more useful for the patients with pulmonary arterial hypertension (PAH), however, few reports exist in patients with inoperable CTEPH. The aim of this study was to investigate the effects of an oral dual ERA, bosentan, on exercise capacity using CPX in patients with PAH and inoperable CTEPH. Main methods This study included all patients diagnosed with 17 PAH and 12 CTEPH in the World Health Organization functional classes II–IV who started treatment with bosentan therapy. They underwent CPX, which was performed before bosentan therapy and at 3 to 6 months of the treatment. Key findings In PAH patients, peak VO₂ significantly increased after the bosentan treatment (p = 0.009). On the other hand, in CTEPH patients, there were no significant differences in the peak VO₂. However, the peak PETCO₂ was significantly increased from 23.9 ± 5.2 mm Hg at baseline to 29.3 ± 10.7 mm Hg after the bosentan treatment (p = 0.040). In addition, peak heart rate during exercise tended to decrease after the bosentan therapy (p = 0.089). Significance Bosentan therapy improved peak PETCO₂ but not peak VO₂ in patients with inoperable CTEPH. These findings demonstrated that CPX is useful for assessing the exercise capacity of patients with PAH and inoperable CTEPH under the treatment with an ERA.