FIELD : medicine.SUBSTANCE : group of inventions relates to medicine, specifically to the diagnosis of the cardiovascular system. Method comprises acquiring a current beat from a continuously measured ECG signal of a patient using a data acquisition unit. Calculating a correlation coefficient between a previous mean value beat and the current beat in the ECG signal using a first computing unit. Determining the weights to be assigned to the previous mean value beat and the current beat based on the correlation coefficient using a determining unit. Calculating a current mean value beat using a second computing unit based on the previous mean value beat, the current beat, and the weights thereof, assigned to the previous mean value beat based on a correlation coefficient. Different coefficients in dynamic mode are assigned to both the previous meal value beat and the current beat according to the correlation between the shape of the current beat and the previous mean value beat. Method is carried out using the device.EFFECT : group of inventions enables to reduce ECG artifacts caused by patient movement, so that the SNR of the ECG signal can be significantly increased.12 cl, 6 dwg