Analysis of non-linear properties of cardiomyocyte cellular membranes

Non-linear properties of cardiomyocyte membranes are poorly understood. We model a cell membrane using the Beeler-Reuter model with the Drouhard-Roberge modification (the BRDR model). Simulations are performed using AC voltage test excitation of 1 or 100kHz frequency and 1 or 10mV RMS. Values of currents flowing through the cell membrane are considered to be the response. The BRDR response is presented at the fundamental frequency and at its second and third harmonics. The response is mainly contributed to by the time-independent potassium current (iK1) during resting membrane potential. The level of currents varies strongly during the period of action potential. However, the linear response from the membrane capacitance is relatively high. The second and third harmonics of the 1kHz/10mV probing voltage carry some information about the action potential. In particular, it may be used to investigate the process of repolarization and its disorders.