KCNH2 and torsades de pointes: The high sensitivity of the hERG assay can be utilized to define a safety margin threshold to minimize the likelihood of hERG block mediated TdP risk, such as the study by Redfern et al. (Redfern et al., 2003)) to define a threshold of 30 by finding an upper bound of IC50/Cmaxfree among drugs of considerable TdP liability.