Session S83.4

The Role of Extracellular Potassium Concentration and Stimulus Period on the Functional Inhomogeneity of Cardiac Tissue: A Simulation Study

I Chouvarda*, N Maglaveras

Aristotle University of Thessaloniki
Thessaloniki, Greece

The relation between extracellular potassium concentration increase and action potential duration decrease is well established. In this work, potassium concentration changes in relation with various activation patterns in an inhomogeneous tissue were in focus and effort was paid to investigate spatial patterns and draw quantitative conclusions about their effects. A series of simulations were performed with different combinations of short stimulus periods and increased extracellular potassium concentrations. The effect of these perturbations on the cellular and overall tissue activation and wave propagation characteristics was investigated.The 2D monodomain model of cardiac muscle and the Luo-Rudy I model for ionic kinetics were employed in a rectangular grid of cells. Regions of scar tissue were defined, introducing heterogeneity and causing a zigzag wavefront pathway. Experiments were repeated with varying periodic stimulus Ts and extracellular potassium concentration Kout, and for each grid point in focus, morphological features related to the action potential and to the ionic currents (Ionmin) were calculated. Average (AV) and standard deviation (ST) in the area of interest were calculated per feature, and differences related to were assessed. Wavefront rotation areas were defined according to each grid-point's polar coordinate with respect to the rotation center, and spatial variation induced by the parameters were detected. Kout increase was found to affect activation characteristics more significantly than Ts decrease. Maximum Kout and minimum Ts give the biggest differences. The AVs of all features decrease with increased Kout. ST increases for APD while it decreases for AP max and slope. The latter features along with the Ionmin show AVs with higher Ts, especially for high Kout. Regarding the differences per rotation area, changes gradually increase in the rotation area, and do not get restored when wave becomes planar in the vicinity of the barrier. For a high Kout, Ts affects the variability of each feature, especially in the last part of the rotation area and after. Concluding, factors of increased heterogeneity were explored in order to investigate vulnerable states. The analysis shows that in a rotating wavefront, the differences from the initial planar wavefront are intensified at the ending part of the rotation and not restored when wave is restored to planar.

(Abstract Control Number: 131)