Background Pulmonary hypertension (PH) is a significant complication of mitral regurgitation (MR), leading to worse outcomes [1]. PH is not prominent at rest during an early stage of MR, but could be induced during stress. Elevated levels of natriuretic peptides are related to subclinical myocardial injury [2,3] including elevated systolic pulmonary artery pressure (SPAP) and it has a prognostic impact in patients with primary MR [4,5]. Aim The aim of this study was to evaluate correlation between NT-proBNP and SPAP at rest and during stress in asymptomatic patients with primary MR and preserved left ventricular ejection fraction. Methods Resting and stress (veloergometry as per protocol 25+25 W every 3 minutes) 2D transthoracic echocardiography was performed for 60 asymptomatic patients (age 61.45±11.99 years) with moderate–severe MR and preserved left ventricular ejection fraction (>60%) at rest. According to the presence of exercise induced pulmonary hypertension ((EIPH) SPAP >60 mmHg during stress) patients were divided into PH (n=20, 33.33%) and non-PH (n=40, 66.67%) groups. Statistical analysis was performed using the SPSS 27.0 software. The value of p<0.05 was considered as statistically significant. Results Age, gender ratio, clinical characteristics, LV volume and diameter indexes, RV size and conventional functional parameters were similar in both groups. NT-proBNP concentration was significantly higher in PH group than in patients without EIPH (261.50 [138–543] pg/ml vs. 92 [58.95–149.50] pg/ml, p=0.002). Also, NT-proBNP concentration has significant moderate correlation with SPAP at rest (r=0.599, p<0.001) and during peak stress (r=0.652, p<0.001). NT-proBNP >122 pg/ml could predict the presence of EIPH with 91.7% sensitivity and 66.7% specificity in patients with primary moderate–severe MR with preserved left ventricular ejection fraction (Picture 2). Conclusions In patients with primary moderate-severe MR and preserved left ventricular ejection fraction, higher levels of NT-proBNP correlated with higher SPAP at rest and during stress and was related to EIPH. NT-proBNP >122 pg/ml is a sensitive predictive value of EIPH in cases of primary MR and preserved left ventricular ejection fraction. Funding Acknowledgement Type of funding sources: None.