Figure 5.

Behavior of ΔIBI(x), Λ_S1S2, and Λ_alt in cultured cardiomyocyte strands. (A) ΔIBI(x) in one preparation during the S1S2 protocol, in normal [K⁺]_o (left) and decreased [K⁺]_o (right). Same format as in Fig. 4A. The vertical markers correspond to the positions of operational electrodes. The dotted shaded curves are exponential fits to the data. (B) A_even(x) and A_odd(x) from the same preparation during alternant pacing. Same format as in panel A and Fig. 4 B. (C) (Top) Summary of Λ_S1S2 and Λ_alt values (represented as their reciprocals 1/Λ) as a function of γ/c^∗2 (according to Eqs. 2 and 4) for all preparations (n = 9). Vertical lines connect data points corresponding to the same preparation in the same [K⁺]_o. The oblique solid line corresponds to Λ_S1S2 = c^∗2/γ (Eq. 2) and the dashed line to Λ_S1S2 = c^∗2/2γ (Eq. 4 with α = 0). (Bottom) Corresponding ratios Λ_alt/Λ_S1S2, and values of α according to Eq. 4.