By using the rat model of early CKD, we discovered an EPI-predominant lengthening of the APD via a reduction of Ito currents in EPI cardiomyocytes secondary to downregulation of KChIP2 without alteration of Kv4.2, Kv4.3, and Kv1.4 protein expression. The gene discussed is KCNA4; the disease is chronic kidney disease.