Figure 3.

Dynamic slow–rapid–slow pacing (0.5–2.5–0.5 Hz) [Ca²⁺]_myo concentrations between normal, HF with K⁺ block (i.e., It_o, I_K1, I_Kr, and I_Ks), and HF without K⁺ block. To ensure steady state conditions, 45 s simulations were performed. (A) Erratic Ca²⁺ transient peaks were observed during 0.5 Hz pacing in failing hearts. HF with reduced K⁺ currents (red) slightly elevated the [Ca²⁺]_myo amplitude during high pacing (2.5 Hz) as compared to normal (black) and HF without K⁺ reductions (yellow). (B) Predicted force using the same color schemes. HF with reduced K⁺ currents (red) exhibit higher predicted force using peak systolic [Ca²⁺]_myo concentrations in rapid pacing.