Cycle length oscillation in a single cell model.

V_m, Ca_i, CL, APD, and Ca_i transient amplitude before and during CLO for u = 6 (A) and 10 (B) s⁻¹. L and S indicate long and short APDs and large and small Ca_i transient amplitudes, respectively. In B, CLO applied in-phase (after 50 beats, black traces) and out-of-phase (after 51 beats, red traces) are shown. Phase reversal is indicated by a red arrow.