Vascular involvement in chronic thromboembolic pulmonary hypertension is associated with spirometry obstructive impairment

Background: Chronic thromboembolic pulmonary hypertension (CTEPH) is a type of pulmonary hypertension caused by persistent thromboembolism of the pulmonary arteries. In clinical practice, CTEPH patients often show obstructive ventilatory impairment, even in the absence of a smoking history. Recent reports imply a tendency for CTEPH patients to have a lower FEV 1.0 ; however, the mechanism underlying obstructive impairment remains unknown. Methods We retrospectively analyzed CTEPH patients who underwent a pulmonary function test (PFT) and respiratory impedance test to evaluate their exertional dyspnea during admission for right heart catheterization from January 2000 to December 2019. We excluded patients with a smoking history to rule out the effect of smoking on obstructive impairment. Results A total of 135 CTEPH patients were analyzed. The median FEV 1.0 /FVC was 76.0%, %FEV 1.0 had a negative correlation with the mean pulmonary artery pressure (mPAP) and pulmonary vascular resistance (PVR) and the CT Angiogram (CTA) obstruction score. A multivariate regression analysis revealed that the CTA obstruction score was an independent factor of a lower %FEV 1.0 . In the 54 patients who underwent pulmonary endarterectomy, %FEV 1.0 was improved in some cases and was not in some. Mean PAP largely decreased after PEA in the better %FEV 1.0 improved cases, suggesting that vascular involvement in CTEPH could be associated with spirometry obstructive impairment. Conclusion %FEV 1.0 had a significant correlation with the CTA obstruction score. Obstructive impairment might have an etiological relationship with vascular involvement. Further investigations could shed new light on the etiology of CTEPH.