Abstract BACKGROUND Heart failure with preserved ejection fraction (HFpEF) is characterized by heart failure symptoms despite preserved LV systolic function together with at least one among left ventricle hypertrophy/left atrial enlargement plus diastolic dysfunction (DD) and increased brain natriuretic peptide levels. Rest echocardiography could still be normal despite patients experience HF symptoms. Speckle tracking analysis (STE) analyzes myocardial deformation and is able to identify subtle left ventricular dysfunction. PURPOSE to analyze the added value of stress echocardiography to improve diagnostic accuracy in patients with normal ejection fraction and unexplained dyspnoea by evaluating DD, lung B lines and STE. METHODS Main inclusion criteria were: suspected heart failure, EF > 40%, DD up to moderate at rest (E/e"<14), age < 85 and >18 years, satisfactory acoustic window. Exclusion criteria were: comorbidities limiting the prognosis, valvulopathy more than moderate, coronary artery disease, moderate to severe DD at rest (E/e"≥14; E/A≥2), pregnancy or lactation. Each patient underwent physical stress echo and STE by GE Vivid 7, (AFI). RESULTS After measuring diastolic function parameters variation with stress, HFpEF was diagnosed in 8 patients, who had baseline non-diagnostic echocardiogram (Table 1). In the remaining 20 patients a non-cardiac etiology of dyspnoea was diagnosed (NCD). EF did not significantly change from rest to stress either in HFpEF group (58 ± 6 vs 61 ± 8.7 p:0.62) or in DNC group (59 ± 8 vs 62.2 ± 7.4; p:0.26). GLS values tended to decrease in patients with HFpEF (-18.5 ± 2.2 at baseline vs -15.96 ± 6.67 at peak stress; p:0.33), and it was stable in DNC (-17.69 ± 1.15 at baseline vs - 18.04 ± 2.02 at peak stress; p:0.64). CONCLUSIONS Study of diastolic function during stress echocardiography is a useful diagnostic tool to reveal HFpEF in patients with dyspnea and unremarkable baseline echocardiogram. STE could offer useful adjunctive diagnostic information but further studies are needed to confirm its value. Table 1 HFpEF NCD p HFpEF NCD p GLS -18,5 ± 2,2 -17,6 ± 1,15 0,23 -15,96 ± 6,67 18,04 ± 2,02 0,26 E/A 0,8 ± 0,1 1 ± 0,7 0,55 1,67 ± 0,7 1,26 ± 0,6 0,07 E/e’ 10,1 ± 2,2 9,9 ± 3,7 0,4 16,4 ± 0,9 13,8 ± 5 0,16 PAP 25,6 ± 4,1 22,33 ± 0,55 0,57 49,8 ± 9,65 28,27 ± 4,35 0,001 LA 35,5 ± 8,5 23,44 ± 4,9 0,001 34,45 ± 4,88 27,32 ± 7,33 0,018 EF 58 ± 6 59 ± 8 0,6 61 ± 8,7 62,2 ± 7,4 0,7 Echocardiographic parameters at baseline and at peak stress in patients with HFpEF and with NCD