A, Confocal line scan fluo-4 fluorescence in nonischemic zone (NIZ)- and ischemic zone (IZ)-isolated myocytes. Calcium spark frequency and amplitude are increased in the IZ (N=3, n=6 IZ, and n=6 NIZ). B, Caffeine-induced Ca2+-transient amplitude (ΔF) in IZ and NIZ myocytes (N=3, n=9 IZ, and n=11 NIZ). ΔF=Fmax-Fmin. F0 indicates resting diastolic calcium fluorescence in the absence of pacing; Fmax, maximal fluorescence during the Ca2+ transient; Fmin, resting fluorescence during pacing; and ns, nonsignificant. *P<0.05.