Figure 6. Intracellular Ca²⁺ and Na⁺ accumulation in five virtual cell variants during increasingly fast pacing.

(A&B) Ca²⁺ accumulation and corresponding activation of the reverse mode of NCX in four cell model variants (normalized to nSR). (C&D) Na⁺ accumulation and corresponding activation of the forward mode of NCX (normalized to nSR).