Previous studies by Nagaya et al. (12) in Chronic Thromboembolic Pulmonary Hypertension (CTEPH) patients and Wilkins et al. (26) who treated patients with sildenafil and bosentan have shown that circulating BNP concentration correlates with the response to therapy in PH patients. This evidence concerns the gene NPPB and chronic thromboembolic pulmonary hypertension.