Bifurcation control of pathological heart rhythms

Cardiac arrhythmias have been closely linked to a variety of dynamic bifurcations such as Hopf bifurcation and period doubling bifurcation. This paper describes the utility of bifurcation control for suppressing pathological rhythms (such as cardiac alternans) in nonlinear models of cardiac electro-physiologic activities. Bifurcation control methods that deal with Hopf bifurcation and border-collision bifurcation are employed. Washout filter aided feedback controllers are designed to control the location and stability of the bifurcations, as well as the amplitude of the bifurcated solutions. Important features of the dynamic control laws include equilibrium preservation even in the presence of model uncertainty, and automatic targeting of the orbits to be controlled. An independent experiment of suppressing cardiac alternans in a piece of dissected rabbit heart demonstrates the viability and utility of the proposed bifurcation control approach. Controlling nonlinear cardiac dynamics may have important clinical implications because arrhythmias in the heart such as fibrillation and ectopic foci are life threatening. The controller designs described here can lead to the development of future smart clinical pacemakers.