Keywords: 6-minute walking distance; 6MWD; Biomarkers; CHF; CMR; Cardiac magnetic resonance; IL-33; N-terminal fragment of pro-B-type natriuretic peptide; NT-proBNP; PAH; PVR; Pulmonary arterial hypertension; RHC; RV; RVEDVi; RVEF; RVESVi; Right ventricular function; ST2; cardiac magnetic resonance imaging; chronic left-sided heart failure; interleukin 33; pulmonary arterial hypertension; pulmonary vascular resistance; right heart catheterization; right ventricle; right ventricular ejection fraction; right ventricular end-diastolic volume index; right ventricular end-systolic volume index; sST2; soluble ST2.