Anosov O.L., Nikitin O.R.

The response of the cardiac cell to stimulation by the pulse sequence with weak uniformly distributed noise periods was investigated using the numerical simulation based on the ionic cardiac cell model. The mean period of the stimulation pulse sequence was choosen in the range of , where (without the bifurcation point ) the cardiac cell demonstrated the normal stable 1:1 response in the noiseless condition. If stimulation period was less than , then the cardiac cell lost the stability of normal state. The uniformly distributed small noise was added to constant period , thus the instantaneous stimulation periods fluctuated weakly around mean value in the range . We have used three noise levels , and , so that the period fluctuations were much smaller than the values of the mean stimulation period . The numerical experiments have shown that the fluctuation characteristics of action potential duration (APD) of the cardiac cell caused by the weak noise in the stimulation periods are essentially different distantly and in the neighbourhood of the point of stability loss for the cardiac cell. At the large the cell responded weakly to the noise in the stimulation periods - dispersion of APD-fluctuations was small, distribution of APD-fluctuations followed to uniform distribution of noise in the pulse sequence periods and the cell responses were uncorrelated. As the pulse sequence period went to the point of stability loss for the cardiac cell ( ), the functions describing dispersion, kurtosis and correlation radius of APD-fluctuations rapidly grew and close to the point of the cell stability loss were saturated. Simultaneously, the distribution of APD-fluctuations transformed from uniform (kurtosis ) to domal form (kurtosis ). To control stability of the cardiac cell, we propose a method that uses the analysis of APD-fluctuations in the cell responses to the stimulation by the pulse sequence with weak noise periods. The beginning of saturation for dispersion, kurtosis and correlation radius of APD-fluctuations can be used to indicate if the cardiac cell is approaching the point of stability loss. The method can be used to design new electronic devises for heart diagnostics.