HERG Channel Dysfunction in LQT2. LQT2 is one form of the congenital long QT syndrome, It results from mutations in the human ether‐a‐go‐go‐related gene (HERG), and more than 80 mutations, usually causing single amino acid substitutions in the HERG protein, are known, HFRG encodes the ion channel pore‐forming subunit protein for the rapidly activating delayed rectifier K⁺ channel (I_Kr) in the heart. This review summarizes current findings about mutations causing LQT2, the mechanisms by which mutations may cause the clinical phenotype of a reduction in I_Kr and a prolonged QT interval, and how this may be involved in the generation of ventricular arrhythmias.