Aim To study echocardiographic parameters of heart chamber strain in patients with left ventricular (LV) preclinical diastolic dysfunction (PDD) for determining predictors of the PDD transition to heart failure with preserved LV ejection fraction (HFpEF).Material and methods The study included 113 patients (including 69 women) with metabolic syndrome and LV PDD (mean age, 65±7 years). The control group consisted of 40 healthy individuals (mean age, 63.0±6.0 years, including 59% women). Metabolic syndrome was diagnosed in consistency with criteria of NCEP-ATP III 2001. PDD was diagnosed based on the absence of heart failure symptoms, normal level of brain natriuretic peptide, and the presence of at least three of the following echocardiographic criteria at rest or after diastolic stress-echocardiography (stress-echoCG): left atrial volume index (LAVI) >34 ml / m2; the ratio of peak early transmitral filling velocity (E) to average lateral and medial mitral annular velocity (e'), Е / е' >14, е' <8.5, and peak tricuspid regurgitation velocity >2.8 m /s. EchoCG that determined LV longitudinal strain (LS), right ventricular (RV) LS, right atrial (RA) LS, and left atrial (LA) LS was performed every year during the 3-year follow-up.Results During the follow-up period, 31 patients developed HFpEF. 19 of them reported symptoms while in the other 12 patients, HFpEF was detected by diastolic stress-echoCG. Patients with HFpEF had significantly lower absolute values of RV LS, LA LS, and RA LS (-27.8±2.9 in the PDD group vs. -23.8±3.2 in the HFpEF group; р<0.03; 38.2±9.1 vs. 28.6±10.2; р<0.03; and 46.2±10.4 vs. 31.6±8.3; р<0.03, respectively). RV LS and RA LS were the strongest independent predictors for PDD transformation into HFpEF (odds ratio, OR, 2.7; 95 % confidence interval, CI, 1.48-2.91; р<0.001 and OR 2.6; 95 % CI: 1.40-2.75; р<0.001, respectively).Conclusion PDD is not a separate clinical nosology but rather an initial stage in the pathogenesis of HFpEF. Approximately ⅓ of PDD patients develop HFpEF. RV LS and RA LS are considered predictors of HFpEF. The duration of PDD is apparently an important factor that provides the development of HFpEF.