Figure 7.

Representative sample (0.1% of 20,000 CRUs) of detected calcium sparks in the local subspace from 20 CRUs. Superimposed action potential from pacing at 0.5 Hz depicting relationship between AP and Ca²⁺ sparks (N_sparks). (A) Ca²⁺ spark behavior in a normally functioning human AP. Minimal Ca²⁺ leak was observed in the late phase of the AP during extrusion of Ca²⁺ ions in cell repolarization. (B) Ca²⁺ spark behavior in heart failure with superimposed AP in the occurrence of early afterdepolarization (EAD). An increase in diastolic spark rate is evident in the late phase of the action potential, which causes APD prolongation and potential presence of EADs. The different colors in the plots indicate the Ca²⁺ spark from different CRUs.