The unmet medical need of pulmonary hypertension in idiopathic pulmonary fibrosis

Pulmonary hypertension (PH) is defined as a mean pulmonary artery pressure (PAP) greater or equal to 25 mmHg, and is a frequent complication in patients with idiopathic pulmonary fibrosis (IPF) [1], especially at an advanced stage of the disease, or when emphysema is associated, as in the syndrome of combined pulmonary fibrosis and emphysema [2]. At diagnosis, 8% to 15% of patients with IPF may already have precapillary PH [3], a proportion which rises up to 30% to 50% of patients at the time of evaluation for lung transplantation [4–7]. The frequency of PH further increases with comorbidities such as obstructive sleep apnoea, thromboembolism or cardiac diastolic dysfunction [8]. PH, when present, is associated with dramatic worsening of shortness of breath, greater oxygen requirements, more severe limitation to exercise capacity and increased mortality [4, 8–10]. PH in IPF (group 3 of the World Health Organization pulmonary hypertension classification [11]) is usually of mild or moderate haemodynamic severity, although 2–10% of patients have a mean PAP greater than 35–40 mmHg [3–5].