Figure 3.

The effects of CQ and AZM on action potential (AP) properties of canine ventricular epicardium. (A) The AP and Ca²⁺ transient of non-treated, CQ 5 μM, AZM 20 μM, and combined groups. The dashed vertical lines indicate the end of the AP with 1 Hz pacing to provide a clearer depiction of the effects of increasing pacing rate and isoproterenol (ISO) on action potential duration (APD). The early afterdepolarization (EAD) is indicated with an arrow. (B) APD and resting membrane potential (RMP) for different pacing rates in the four groups with and without simulated beta-adrenergic stimulation. The occurrence of alternans at 4 Hz pacing is marked with an arrow. AP, action potential; APD, action potential duration; Ctl, control; ISO, isoproterenol; RMP, resting membrane potential.