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

Abstract

Using the Luo-Rudy I model, the recently proposed 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 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.

Effect of Extracellular Calcium Concentration on Controlling Cardiac Alternans

“…Since the results for APD alternans suppression are similar to that of peak-[Ca]i alternans suppression, we will only present the results for controlling peak-[Ca]i alternans. high possibility that the alternans cannot be suppressed if  is lower than its critical value [11][12][13] …”

“…The numerical integration of the differential equations was performed using the MATLAB subroutine ode15s [21,22], which is a variable-step and variable-order solver, with error tolerance of 10 -6 . In the T+T-control method [11][12][13][14] that was employed in our study to suppress the alternans, the basic cycle length at the n-th beat (Tn) depends on two successive peak-[Ca]i as follows…”

“…Besides the earlier proposed methods for alternans suppression: the proportional feedback control [6,7] and adaptive scheme [8][9][10], a new control scheme, the T+T-feedback control [11][12][13][14] was proposed recently. The basic pacing period T in this method is designed to change between two values, T +  and T - (where  is a predetermined control parameter and is much less than T), repeatedly until the alternans is suppressed.…”

“…It may lead to life-threatening cardiac arrhythmias [3,4], such as ventricular tachycardia and ventricular fibrillation, or sudden cardiac death [4,5] if it is left without any further medical treatment or intervention. Therefore, searching for an effective alternans control method is crucial.Besides the earlier proposed methods for alternans suppression: the proportional feedback control [6,7] and adaptive scheme [8][9][10], a new control scheme, the T+T-feedback control [11][12][13][14] was proposed recently. The basic pacing period T in this method is designed to change between two values, T +  and T - (where  is a predetermined control parameter and is much less than T), repeatedly until the alternans is suppressed.…”

“…The basic pacing period T in this method is designed to change between two values, T +  and T - (where  is a predetermined control parameter and is much less than T), repeatedly until the alternans is suppressed. Experiments [11,13] and theoretical [11][12][13][14] studies have been carried out and the results showed that the T+T-control method can suppress alternans effectively. However, when the pacing rate continues to increase, the amplitude of the alternans also increases and becomes more difficult to be controlled.…”