Effects of Ionic Conductances on Spiral-Wave Dynamics in a Ventricular Tissue Model

Irregular electrical activities in cardiac tissue, manifested as spiral waves, often lead to fibrillation—a major cause of heart failure. Such irregularities may arise due to the abnormal action potentials of cardiac cells during various disease conditions. In this study, we show, using a ventricular model, the impact of conductances of ionic currents on the action potentials of a single cardiac cell and the formation of spiral waves in cardiac tissue. When conductances, \(\varvec{G}_{\varvec{ca}}\) ${\mathit{G}}_{\mathit{ca}}$ and \(\varvec{G}_{\varvec{k}}\) ${\mathit{G}}_{\mathit{k}}$ , are altered from their model values, we observe four distinct types of action potential (AP) states: normal-type AP, early afterdepolarization (EAD)-type AP, repolarization oscillation (RO)-type AP, and repolarization failure (RF)-type AP. Our systematic numerical studies on cardiac tissue reveal four different spiral states, namely, (a) a periodic spiral (PS) state, (b) a quasi-periodic spiral (QPS) state, (c) an absorbed spiral (AS) state, and (d) a no-spiral (NS) state. The superimposed phase diagrams of AP and spiral states on the \(\varvec{G}_{\varvec{ca}}-\varvec{G}_{\varvec{k}}\) ${\mathit{G}}_{\mathit{ca}}-{\mathit{G}}_{\mathit{k}}$ parameter space highlight the role of AP states in spiral wave dynamics.