Physiological consequences of transient outward K+ current activation during heart failure in the canine left ventricle

► Heart failure (HF) reduced phase 1 repolarization in single and multicellular tissue. ► Ito density was reduced in HF Epi cells compared to normal Epi cells. ► The Ito activator NS5806 increased Ito density toward normal in HF cells. ► NS5806 restored phase 1 repolarization in wedge preparations from failing hearts. ► Restoration of Ito may be a novel approach to the treatment of HF.