In the human heart, a dysfunctional Kir2.1 channel prolongs phase 3 of the potential, which is characterized by a prolonged QT interval, pathologic U waves, and a special type of polymorphic ventricular tachycardia (VT) called bidirectional ventricular tachycardia (BiVT) in the electrocardiogram.[5] It is not only the heart that expresses Kir2.1, but also the brain. This evidence concerns the gene KCNJ2 and polymorphic ventricular tachycardia.