Fig. 6.

Effects of sympathetic nervous stimulation on optical wave similarity (OWS) and APD alternans (ΔAPD₈₀) measures. A) Example OWS (i) and APD₈₀ alternans (ii) maps from 130 to 70 ms PCL in a guinea pig heart without (control, black) and with SNS (red). The transition to ventricular fibrillation (VF) is marked by the dashed line in both conditions. Blue areas in APD alternans maps denote areas not analysed due to 80% repolarisation not being reached. B) Grouped data of mean OWS values as a function of PCL in control hearts with/without SNS, before (solid line) and during (dashed line) VF. C) Grouped data of mean ΔAPD₈₀ as a function of PCL in control hearts before and during SNS, before onset of VF. D) Example single pixel optical traces recorded during 170 ms PCL stimulation and during VF induced via pacing. E) Anatomical locations of left ventricle (LV) Apex (blue), base (purple) and right ventricle (RV, green) on fluorescence image of voltage dye loaded guinea pig whole heart used for regional studies of OWS. F) Grouped data of regional OWS values as a function of PCL in control hearts with (i) and without (ii) SNS. n = 6 hearts, *P < 0.05, **P < 0.01 control vs SNS, #P < 0.05 LV Apex vs RV (green) or LV Base (purple).