KCND3 and hydrops fetalis: Both forms of Kv4.3 are expressed in human and rat heart (Ohya et al., 1997; Kong et al., 1998) but their expression levels are altered differentially in human heart failure (HF), Kv4.3L expression rising ~33% while that of Kv4.3S falls ~75% (Radicke et al., 2006).