A Simulation Study on the Pacing and Driving of the Biological Pacemaker

The research on the biological pacemaker has been very active in recent years. And turning nonautomatic ventricular cells into pacemaking cells is believed to hold the key to making a biological pacemaker. In the study, the inward-rectifier K⁺ current (I _K1) is depressed to induce the automaticity of the ventricular myocyte, and then, the effects of the other membrane ion currents on the automaticity are analyzed. It is discovered that the L-type calcium current (I _CaL) plays a major part in the rapid depolarization of the action potential (AP). A small enough I _CaL would lead to the failure of the automaticity of the ventricular myocyte. Meanwhile, the background sodium current (I _bNa), the background calcium current (I _bCa), and the Na⁺/Ca²⁺ exchanger current (I _NaCa) contribute significantly to the slow depolarization, indicating that these currents are the main supplementary power of the pacing induced by depressing I _K1, while in the 2D simulation, we find that the weak electrical coupling plays a more important role in the driving of a biological pacemaker.