An Analog-Digital Hybrid Model of Electrical Excitation in a Cardiac Ventricular Cell

抄録

Contraction of the heart is controlled by electrical excitations of cardiac cell membranes. The electrical excitations of the cells and their propagation within the heart tissue provide a basis of the physiological function of the heart through the cardiac excitation-contraction coupling mechanism. A large number of studies have been carried out using mathematical models of the cardiac excitation in order to understand normal and abnormal dynamics of the heart. However, simulating the dynamics of a tissue or organ model with a large number of cellular models requires an immense amount of computational time. Here, in order to reduce the computational time required for the simulation, we developed an analog-digital hybrid model of the electrical excitation of cardiac cells based on Luo-Rudy phase I (LR1) model for the action potential generation in a mammalian cardiac ventricular cell. The hybrid model includes analog circuits and a dsPIC microcontroller that could reproduce time-dependent and time-independent nonlinear current-voltage characteristics of six-type of ionic currents in LR1 model. The analog circuits were used to implement the ionic currents either of timeindependent or with relatively short time constants, and the dsPIC was used to implement the ionic currents with long time constants, connecting in parallel with a model of the membrane capacitance. The constructed model could realize real-time simulation of the action potential generation that was quantitatively comparable with the cardiac excitation of LR1 model. In particular, we showed that response characteristics of the hybrid model to periodic trains of impulsive current stimulation were also comparable with those of LR1 model.