The main findings of this study are: (i) Serum sST2 concentration is increased in CTEPH patients, with significantly higher baseline sST2 concentration in patients with complications in postprocedural period; (ii) serum sST2 levels significantly increased early after the BPA procedure, regardless of complications in the postprocedural period; (iii) on the contrary, no similar increase in NT-proBNP concentration was observed in the group with no complications, which may suggest a predominant non-cardiac source of sST2 in CTEPH patients. This evidence concerns the gene NPPB and chronic thromboembolic pulmonary hypertension.