3.4 Optical mapping studies in ex vivo heart preparations
We next investigated the effects of HCQ alone and in combination with AZM using optical fluorescence mapping in sinus-paced Langendorff-perfused hearts using the recording and ECG monitoring configurations illustrated in Figure 6A(i). Voltage mapping measurements of action potential initiation and conduction (Fig. 6A(ii)) demonstrated bradycardic effects (A(iii)), visible conduction heterogeneities and slowed conduction (A(ii)) at 10 µM HCQ, effects were augmented by combination with 10 µM AZM (Fig. 6A (iv)). Similarly, optical potentiometric mapping revealed that 10 µM HCQ prolonged action potential duration at 90% repolarisation (APD­90) (B(i and ii)) with 10 µM HCQ, effects further prolonged by its combination with AZM (Fig.5B(iii)).
Ca2+ dye, Rhod-2 AM (CaD), mapping of ventricular calcium transient (CaT) characteristics demonstrated increased magnitudes of and dispersions in CaD durations at 90% recovery (CaD90) (Figure 6C(i)). The latter were attributed to changes late in the CaT records (C(ii)). The quantified CaD90 magnitudes (B(iii)) and dispersions (B(iv)) both increased with 10 but not 1.0 µM HCQ. The combination of 10 µM HCQ with either 1 or 10 µM AZM exerted significantly greater effects than 10 µM HCQ alone.