Simulation of the electrogram from ion currents

Publisher Website
Google Scholar
Abstract
Summary. The electrogram can be constructed as the difference between two action potentials starting with a slight time difference. In the present study, the action potentials were simulated from ion currents showing time‐ and voltage‐dependent activation and inactivation. Simple mathematics like straight lines and single exponential functions were used. The aim was not to give a precise description of the action potential but to obtain a model with electronic interaction between action potentials. Four currents were incorporated. The upstroke of the action potential was due to the inflow of sodium ions. The plateau was maintained by a calcium current and repolarization followed from a slowly activated and outwardly directed potassium current. There was also a time‐independent background current of potassium showing inward rectification. Basically the same equations were used for calculation of the four current voltage relations. Also, currents during a depolarizing voltage step could be reproduced by the model. Two action potentials were coupled to each other by means of a resistor to simulate the behaviour of gap junctions. A flat T‐wave in the electrogram occurred when the action potentials had the same characteristics because of the electrotonic interaction. When the first action potential was longer than the second in a pair positive T‐waves were seen. A negative T‐wave occurred when the second action potential of the pair was made longer. The model forms a base for further simulations of ECG.