Simulation of re-entry in a piece of myocardial tissue: strong sensitivity to spatial and temporal conditions.
A simple model for the simulation of re-entrant excitation was created. The model consists of a matrix of 15x15 compartments, where each compartment has its own action potential that depends dynamically on four ion currents (INa, ICa, Ik and Ib) having time and voltage-dependent activation and inactivation kinetics. The compartments were combined with resistors to simulate electrotonic interaction. At short excitation intervals the action potential was shortened in duration, and at even shorter coupling intervals decremental propagation occurred. Re-entry around an obstacle could be elicited in response to a properly timed extra stimulus. A time dependent unidirectional block was made by making some of the action potentials longer in duration. An obstacle was not a necessary substrate for re-entry, but the timing of the extra stimulus was critical. In the presence of an obstacle, the induction of re-entry was critically dependent on the shape of the obstacle. The most important result of the simulations is that the system is highly sensitive to the initial spatial and temporal conditions. These sensitivities are generic features of dynamic systems that are described by non-linear differential equations and are typical for chaotic systems. The system studied shows features associated with deterministic chaos.
Wohlfart
B
B
Department of Clinical Physiology, University of Lund, Sweden.
Ohlén
G
G
Karlsson
L
L
D000200:Action Potentials / Q000502:physiology; D000818:Animals; D001145:Arrhythmias, Cardiac / Q000378:metabolism / Q000503:physiopathology*; D002642:Chick Embryo; D006321:Heart / Q000502:physiology*; D007473:Ion Channels / Q000378:metabolism; D008962:Models, Theoretical
D007473:Ion Channels