Suppression of cardiac alternans by alternating-period-feedback stimulations
S. Sridhar, Duy-Manh Le, Yun-Chieh Mi, Sitabhra Sinha, Pik-Yin Lai, and C. K. Chan
Accepted
Alternans response of sequence of alternating long and short action potential durations in cardiac tissue during fast periodic pacing can lead to conduct block, causing fatal cardiac failure. A novel method of pacing with feedback control is proposed to reduce the alternans and therefore the subsequent cardiac failure. The reduction is achieved by feedback control using fixed small perturbations to the original alternans generating pacing period T, by sequences of two alternating periods of T+DT and T-DT, with DT << T. Such a control scheme for alternans suppression is demonstrated experimentally in isolated whole heart experiments. This alternans suppression scheme is further confirmed and investigated in detail by simulations of ion-channel based cardiac models, both for a single cell level and in one-dimensional spatially extended systems. The mechanism of the success of our method can be understood in terms of dynamics in phase space, such that the state of activity of the cell being confined within a narrow volume of phase space for the duration of control; resulting in extremely diminished variation in successive action potential durations. Our method is much more robust to noise than previous alternans reduction techniques based on fixed point stabilization and should thus be more efficient in terms experimental implementation which has implications for clinical treatment for arrhythmia.