Figure 5. Effects of Ranolazine on Maximum Rate of Phase-Zero Action Potential Depolarization (dV/Dt_max) of Phase Zero Action Potential, Conduction Velocity, and Ca_i²⁺ Transient Decline Rate Constant (τ).

(A) Ranolazine causing rate-dependent significant decrease in dV/Dt_max at faster pacing cycle length (PCL) (<130 ms). (B, left) Isochronal activation maps with a color code (right) during pacing from the base at a PCL of 200 ms under different conditions. (C) H₂O₂ prolongs τ, whereas ranolazine (10 μM) has no effect on τ either before or after H₂O₂, as shown by the adjoining superimposed Ca_i²⁺ transients.