Fig. 1.

A prolonged action potential duration (APD) by increased inward current and weakened outward currents induced by drugs (A) and manifested on an electrocardiogram (ECG) (B). The hERG channel undergoes a transient activation process of channel opening, followed by rapid inactivation and then recovery from inactivation. At this time, the channel opens again, followed by a slow deactivation process to close the channel. The opening of the channel is necessary for drug binding, and when the channel is closed, the drug is trapped due to the blocking effect and is released when the channel reopens (C).