Obstructive Ventilatory Defects in Pulmonary Arterial Hypertension and Chronic Thromboembolic Pulmonary Hypertension

Background/Objectives: Patients with pulmonary arterial hypertension (PAH) may display obstructive ventilatory defects outside of defined obstructive lung disease. However, its pathogenesis and prognostic relevance remain unknown. Similar data have emerged for patients with chronic thromboembolic pulmonary hypertension (CTEPH), but there is no description in a real-world European cohort. Methods: We performed a single-center, retrospective, cross-sectional study of patients with PAH (n = 46) and CTEPH (n = 45) at an academic PH center. Data were collected on pulmonary function tests, DLCO, right heart catheterization results, pre-existing diagnoses of asthma and chronic obstructive pulmonary disease (COPD), current medications, and adverse outcomes. Results: Patients with PAH and CTEPH showed a reduced FVC (81% for both groups), FEV1 (74 and 75%) and DLCO (54 and 53%). A previous diagnosis of COPD was documented in 11% of patients, and asthma in 11% of patients with PAH and 4.5% of patients with CTEPH respectively. Even after excluding patients with asthma or COPD, ventilatory obstruction was still present in at least 22% of patients and 16% were being treated with long-acting bronchodilators or inhaled corticosteroids. Of these patients, those who had adverse outcomes (active listing for lung transplantation, lung transplantation or death) had a significantly lower FVC (68 vs. 83%, p = 0.026), FEV1 (61 vs. 79%, p = 0.01) and MEF50 (38 vs. 59%, p = 0.021). All patients with adverse outcomes had a mean expiratory flow at 50% vital capacity (MEF50) < 60%, as opposed to 57% of those without an adverse event, however MEF50 did not predict adverse outcomes after adjusting for FVC. Conclusions: Ventilatory obstruction is common in patients with PAH and CTEPH even when excluding patients with asthma/COPD or a history of smoking. Symptomatic treatment with bronchodilators is common even without these comorbidities. Patients with adverse outcomes had lower FEV1, FVC and MEF50, but the functional relevance of the latter remains to be explored.