KCNH2 and heart failure: For example, the ventricular action potential has a rapid upstroke and long plateau, defined by the balance of inward L-type Ca2+ current (Cacna1c) and repolarizing currents carried by the inward rectifier K channel (Kcnj2), and the rapid (Kcnh2) and slow (Kcnq1/Kcne1) components of the delayed rectifier K current, as well as the long cellular action potential plateau morphology that contributes to the prolonged QT interval of human heart failure.