Figure 1

Relationship between action potential alternans and S1S2 restitution. (a) Illustrates the applied protocol for S1S2 restitution. The basic cycle length for restitution was 1000 and 500 ms. The diastolic intervals increased from − 50 to 1000 ms (relative to APD₉₀) and the slope of APD₉₀ restitution was calculated at both 500 and 1000 ms BCLs. After the restitution protocols, alternans were measured from a cycle length of 250 ms to 160 ms. The magnitude of alternans was measured at APD₉₀, APD₅₀, and APD₂₅. (b) Demonstrates correlation tests between S1S2 restitution slope and alternans. The left 6 panels show S1S2 restitutions at BCL of 500 ms, in the right 6 panels the BCL was 1000 ms. The first row demonstrates alternans at APD₉₀ level, middle row at APD₅₀, bottom row at APD₂₅. Our results indicate that alternans developed even if the restitution slope was smaller than 1, furthermore, data show mainly weak and in some cases moderate correlations between variables.