Discordant alternans in a one dimensional cable of ischemic heart tissue

T-wave alternans in the ECG are related to discordant alternans (DA) in the cardiac action potential. T-wave alternans have been associated with block in the electrical activity of the heart, induction of reentry and to ventricular arrhythmias. The hypothesis of this study is that discordant alternans can be initiated in a simulated one dimensional cable of heart tissue during ischemia. The effect of ischemia was model by raising the external potassium concentration [K+]o in strips of ventricular cardiac tissue modeled with the Lou Rudy 1 model. [K+]o increases from 5.00 up to 12.00 mM. To search for the DA, the stimulation period (T) varied from 250 ms up to 500 ms. DA were generated in the cables, they appeared at short T during ischemia. After analyzing the dynamics of the electrical propagation patterns for each [K+]o and T, five types of patterns were found in the cables. The most common pattern was regular propagation, in second place are the concordant alternans at high degrees of ischemia, in between these two the DA occur, transient states and finally the patterns with irregular propagation. We have shown that DA can occur in cardiac tissue with ischemia just as in healthy tissue. Also, the DA formed in the cables of ischemic heart tissue present one or multiply nodes.