Fig. 6.

The time course of the progressive APD₈₀ shortening during ischemia. The data are from 4 groups: 300ms (black), 200ms (red), 300ms_Iso (blue), and 200ms_Iso (green). In each experiment, the APD₈₀ values for the RV and the LV were obtained by averaging over all pixels in the respective mapped regions. Note that APD₈₀ measurements were not performed fort the time points before 3 min of ischemia, due to the presence of motion artifact in the optical signals in isoproterenol-treated groups, despite the use of the electromechanical uncoupler BDM. Starting from 3 min of ischemia, the motion artifact was minimal in all groups due to ischemic suppression of contractility. For all time points after 3 min of ischemia, the APD₈₀ data are shown only if at least 3 hearts in a given experimental group remained in regular paced rhythm and maintained excitability in at least 80% of mapped regions in both the RV and the LV. A and B: time course of APD₈₀ decline during ischemia in the RV and the LV, respectively. The comparison between groups in each chamber was performed for the time interval between 3 and 8 min of ischemia. C–F: RV and the LV curves of APD₈₀ decline in individual experimental groups (as indicated) are superimposed to highlight the inter-chamber differences. (The curves are the same as shown in A and B, just grouped differently). In each group, the inter-chamber difference in APD₈₀ was analyzed for all time points satisfying the criteria stated above. Note that a prominent right-to-left APD₈₀ gradient developed in all groups except 200ms_Iso. *P < 0.05. See article for more detail.