(344e) Annihilation of Cardiac Alternans by Mechanical Perturbation

Alternans is a physiological condition of the heart muscle in which a periodically stimulated cardiac tissue undergoes alternation in electrical and mechanical properties. It has been known that alternans are precursor to the development of life threatening ventricular fibrillation or sudden cardiac death.

The electrical wave propagation in the cardiac tissue is coupled mechanically through the mechanism of mechano-electric feedback to the cardiac tissue contractility (Kiseleva I et al, 2000). The presence of the electrical alternans induces through the mechanism of the mechano-electrical feedback an alternation in the heart muscle contractile activity. That is why the possibility of alternans annihilation can be looked as a successful strategy to prevent onset of ventricular fibrillation.

It has been demonstrated that the alternanas can be annihilated in the finite size tissue with appropriately applied pacing algorithm. However, experimental and theoretical studies showed that there is a finite controllability to annihilate alternans by the boundary applied pacing protocol (Dubljevic S et al, 2008). This limitation of finite controllability to annihilate alternans can be overcomed by applying mechanical perturbation within the cardiac tissue. The aim of our work is to demonstrate the annihilation of cardiac alternans using mechanical perturbation. Electrical propagation is accompanied by mechanical contraction of cardiac tissue. The cardiac mechanics (deformation) has an influence over the electrical activity and excitation via stretch activated channels. We shall develop a computational framework that employs electromechanical and mechanoelectric feedback to couple a two variable Aliev - Panfilov (1996) model with the non-linear stress equilibrium equations. The concept of Cauchy - Green deformation tensor from (Nash M P et al,2004) will be used to relate the cardiac mechanics with the equations of electrical activity (Hodgkin Huxley equation). The coupled model includes an additional variable to represent the active stress which defines the mechanical properties of the tissue. A finite element method in two dimension is employed to integrate the excitation equations and to solve the equations governing tissue mechanics.

Refrences:

Dubljevic S, Lin S, Christofides P D. Studies on feedback control of cardiac alternans. Computers and Chemical Engineering: 2008,32-9, 2086-2098.

Kiseleva I,Kamkin A, Wagner KD, Theres H, Ladhoff A, Scholz H, Gu?nther J, Lab MJ., Echebarria B. Mechano-electric feedback after left ventricular infarction in rats. Cardiovascular research 2000: 45,370 - 378.

Nash M P, Panfilov A V. Electromechanical model of excitable tissue to study reentrant cardiac arrhythmias.Progress in Biophysics and Molecular Biology. 2004; 501-522.