KCNH2 also known as HERG is a voltage-activated potassium channel belonging to the eag family. KCNH2 plays a crucial role in cardiac repolarization. KCNH2 is a core determinant of the rapid delayed rectifier current that shapes cardiac action potential repolarization. Channel gating and surface expression integrate with membrane excitability programs and are modulated by signaling pathways that influence phosphorylation, trafficking, and proteostasis in excitable cells. Genetic and functional perturbation of KCNH2 is strongly associated with inherited and acquired long QT syndromes and arrhythmogenic susceptibility, making it a key node for studying electrophysiology, ion channel regulation, and cardiotoxicity mechanisms.