Controlling alternans in cardiac cells

Electrical alternans, the alternation in action potential morphology, has been suggested as an important cause of potentially dangerous cardiac rhythm disorders. Previous studies have developed alternans control strategies based on the dynamics of the relationship between action potential duration and the previous diastolic interval. We demonstrate that alternans in a single cardiac cell can also be controlled by directly modifying the underlying ion channel dynamics. Surprisingly, we find that, for a detailed canine ventricular cell model, the best time to apply the control stimulus is not during the repolarization phase of the action potential, but rather during the early plateau phase, when the charge requirements are two orders of magnitude smaller. Computer simulations show that a single control stimulus applied during the early plateau can completely eliminate small-amplitude alternans, while a small number of stimuli can rapidly extinguish large-amplitude alternans. We have also developed an effective control algorithm that uses only the membrane potential as control input and requires no prior detailed knowledge of the cell dynamics. The study suggests that control strategies based on ion channel dynamics can provide new directions for the development of algorithms intended to control dangerous cardiac rhythm disorders.