It is becoming increasingly clear that, while FQs are generally known to block the inward delayed rectifier current IKr through the potassium channel, QT prolongation and TdP risk cannot be considered a class effect, as the individual FQ affinities for the hERG-IKr receptor (both in absolute terms and relative to plasma levels) vary widely. Here, KCNA3 is linked to torsades de pointes.