Figure 4.

Under β-stimulation, APD is not changed by MI. (A) Effects of MI and/or 1 µM ISO on rabbit isolated heart rate (i) and, in unpaced hearts, optically recorded atrial APs in non-MI (ii) and MI (iii), and on mean APD_50–90 (iv–vi). (B) Corresponding data (i–v) obtained from paced (5 Hz) hearts. n = 13 non-MI, 12 MI. (C) Atrial isolated cardiomyocyte APs (i), at 1 Hz-stimulation, in non-MI (a) and MI (b). Effects of MI and/or ISO on RMP (ii) and, in cells with RMP clamped (−80 mV), APD_50–90 (iii–v). n = 33 cells, 14 non-MI hearts, 22 cells, 11 MI.