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Rationale: More than half of patients with chronic heart failure have a preserved left ventricular ejection fraction. It has been found that sudden cardiac death is more frequent in this patient category. A reliable and easily available marker is needed that would predict the death outcome with a high probability. The use of the late ventricular potentials for this purpose could be reasonable.Aim: To assess the prevalence of the late ventricular potential and their association with the structural and functional parameters of the myocardium in patients with early stages of chronic heart failure with preserved ejection fraction.Materials and methods: We examined 77 patients with chronic heart failure (grade I to IIА, functional class I to III) with preserved ejection fraction (> 50%), aged 47 to 77 years (mean ± SD, 59.7 ± 7.8 years). Echocardiography (SonoScape 8000 and Vivid 3) at М-, В- and Doppler modes was performed in all patients. Ventricular ectopic activity and late ventricular potentials were registered during 24- hour ECG monitoring (Cardiotekhnika, INKART, St. Petersburg).Results: Late ventricular potentials were found in 13% (10 of 77) of patients. The following correlations were found in patients with concentric hypertrophy (n = 53): between the duration of the filtered QRS (TotORSF) and the left ventricular end diastolic diameter (r = 0.27, p = 0.049), TotORSF and the interventricular septum thickness (r = 0.28, p = 0.04), TotORSF and the left ventricular myocardial mass (r = 0.35, p = 0.01), mean square magnitude of fluctuations within the last 40 ms of ORS (RMS40) and the left ventricular end diastolic diameter (r = -0.42, p < 0.01), RMS40 and the left ventricular end-systolic diameter (r = -0.37, p < 0.01). In the patients with eccentric hypertrophy (n = 14), the following correlations were found: between RMS40 and the left ventricular myocardial mass index (r = -0.77, p < 0.01), between duration of the low amplitude signal (< 40 μV) at the end of QRS (LAS40) and the left ventricular myocardial mass index (r = 0.76, p < 0.01), as well as between LAS40 and RMS40 with the end diastolic diameter of the left ventricle adjusted to the body surface area (r = 0.76, p < 0.01 and r = -0.83, p < 0.01, respectively). The patients with a pseudo normal type of diastolic dysfunction (n = 27) showed an association between their NT-proBNP levels and TotORSF (r = 0.56, p < 0.01).Conclusion: The prevalence of late ventricular potentials among patients with early stage chronic heart failure and preserved left ventricular ejection fraction is not high. The parameters of electrophysiological myocardial instability in patients with concentric hypertrophy are mostly influenced by the size of heart chambers, whereas in those with the eccentric one, by the myocardial mass and volume parameters. The risk of sudden cardiac death is higher in patients with a pseudo normal type of diastolic dysfunction.