Furthermore, in patients with CTEPH, IP-10 levels were negatively correlated with cardiac output, a 6 min walking distance, and carbon monoxide diffusing capacity, whereas IL-6 levels were positively correlated with pulmonary vascular resistance, right atrial pressure, and N-terminal pro-brain natriuretic peptide (NT-proBNP) [19]. Here, NPPB is linked to chronic thromboembolic pulmonary hypertension.