Ionic mechanism of electrical alternans

Although alternans of action potential duration (APD) is a robust feature of the rapidly paced canine ventricle, cur-rently available ionic models of cardiac myocytes do not recreate this phenomenon. To address this problem, we de-veloped a new ionic model using formulations of currents based on previous models and recent experimental data. Compared with existing models, the inward rectifier K current (IK1) was decreased at depolarized potentials, the maximum conductance and rectification of the rapid compo-nent of the delayed rectifier K current (IKr) were increased, and IKr activation kinetics were slowed. The slow component of the delayed rectifier K current (IKs) was increased in magnitude and activation shifted to less positive voltages, and the L-type Ca2 current (ICa) was modified to produce a smaller, more rapidly inactivating current. Finally, a simpli