Ionic characteristics in cardiac alternans suppression using T ± ϵ feedback control

Using the Luo-Rudy I model, the recently proposed $T\pm \epsilon$ feedback control for suppressing cardiac alternans is investigated. It is shown that cardiac alternans, induced by fast pacing (of period T ), can be dramatically reduced by small changes of fixed magnitude ( ϵ ) under feedback control when ϵ exceeds a critical threshold. Detail information on various ionic currents and cytosolic calcium concentration $\big([\text{Ca}]_{\text{i}}\big)$ are examined when the cardiac cell is under control. In particular, the alternans in ionic currents and [Ca] i are also reduced under the control. Furthermore, when ϵ exceeds the threshold value, the average [Ca] i level is significantly higher when the alternans is under control, suggesting a possible physiological improvement of cardiac contractions.