Additional insight into TdP risk for hERG-blocking and QT-prolonging drugs can be determined by also assessing whether drugs block inward currents such as, L-type calcium or late sodium (Duff et al., 1987; January and Riddle, 1989; Chézalviel-Guilbert et al., 1995; Guo et al., 2007). This evidence concerns the gene KCNH2 and torsades de pointes.