Effects of KATP channel openers diazoxide and pinacidil in coronary-perfused atria and ventricles from failing and non-failing human hearts

► We investigated ATP-regulated potassium channels in diseased and normal human heart. ► Pinacidil decreased APD in atria and ventricles in all physiological states. ► Diazoxide decreased APD in both chambers and all states, except normal human atria. ► Heart failure and/or previous infarct potentiated diazoxide-induced APD shortening. ► Activation of human KATP channels enhances arrhythmogenicity.