Obstructive ventilatory defects in PAH and CTEPH

Introduction Pulmonary arterial hypertension (PAH) is a rare and deadly disease of the pulmonary vasculature. Diagnosis is frequently delayed, and misdiagnosis is common. The prevalence of obstructive ventilatory defect as defined by a FEV-1/FVC < 70% on spirometry, is elevated at 22% in patients with idiopathic (or primary) pulmonary arterial hypertension (IPAH) (Meyer et al 2002). Some degree of obstruction has also been described in patients with PH associated with congenital cardiac defects or connective tissue disease (Jing et al. 2009). Small airway obstruction in IPAH responds partially to bronchodilator treatment (Spiekerkötter et al. 2002). Since previous studies did not provide a thorough workup for asthma and COPD, it is not conclusively shown whether airway obstruction in PH represents comorbidity, or constitutes a genuine feature of PH.

Therefor the aim of this study is to assess the prevalence of obstructive ventilatory defects in a current cohort of PAH and CTEPH and provide a thorough characterization of airway physiology and comorbidities.

Methods We reviewed the spirometries of all patients who attended our pulmonary hypertension clinic from 01. 02. 2018 – 19. 09. 2018 and recorded the prevalence of an FEV-1/FVC < 70% in the following subgroups regardless of treatment status, smoking history or comorbidities:

1: IPH and hereditary PH (Nizza 1.1 and 1.2)

2: PH associated with connective tissue disease (CTD-PH, Nizza 1.4.1)

3: Chronic thrombembolic pulmonary hypertension (CTEPH, Nizza 4.1)

Results The prevalence of FEV-1/FVC < 70% was 11/45 (24.4%) in IPH and hereditary PH, 2/8 (25%) in CTD-PH and 11/36 (30,6%) in CTEPH patients.

Discussion and Conclusion Airway obstruction is common in IPAH, but also other forms like CTD-PAH and CTEPH. Further characterization of airway obstruction by MEF-50, MEF-25 and plethymographic measures is under way.

The etiology and relevance of this obstruction remains unclear. We will address this by analysis of comorbidities, smoking history, concurrent medication, sensitization profile, presence of atopy, FeNO, reversibility of obstruction with bronchodilator treatment and spiroergometry.