Evidence of increased expression of the NCX in HF is inconsistent (Sipido et al., 2002), although several studies do report enhanced amounts of transporter protein (Hasenfuss et al., 1999; Hobai & O'Rourke, 2000; O'Rourke et al., 1999; Studer et al., 1994). This evidence concerns the gene TLX2 and hydrops fetalis.