Consistent with our recent findings that Kv4.3 expression can selectively inhibit membrane associated CaMKII activation by binding to the Calmodulin-binding site [7], here, we found that Kv4.3 expression reversed ICa remodeling in HF LV by reducing ICa density and acceleration of ICa inactivation, while the transmural gradient was preserved. The gene discussed is KCND3; the disease is hydrops fetalis.