Electrophysiological changes of ventricular tissue under ischemic conditions: a simulation study

Ischemic injury to cardiac tissue incorporates a broad spectrum of pathologies and can result in a highly complicated series of electrophysiological changes. From investigations that dissect the process of ischemic damage into its constituent components, three principal components that pertain to electrophysiological changes have been identified: 1. an increase in extracellular potassium concentration ([K]/sub 0/), 2. acidosis, and 3. hypoxia. To simulate ischemia the authors incorporated the effects of these principal ischemic conditions on the transmembrane currents and passive properties of the Luo-Rudy cell model. The authors studied the effects of simulated ischemia on the single cell and propagating action potential. As the simulated ischemic conditions are made more severe, resting membrane potentials depolarize, conduction velocity undergoes a non-monotonic increase then decrease towards block and (dV/dt)/sub max/ plateaus initially and then declines towards block. Action potential shortening, as occurs in myocardial ischemia, could be reproduced quantitatively by increased conductance of I/sub K(ATP)/.<
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