An additional ECG finding worth mentioning in the context of the congenital and acquired long QT syndromes is T Wave Alternans. Shown here is an example of this phenomenon recorded from a patient with the congenital long QT syndrome by Dr Jervell who published this figure in 1971 (Adv. Int. Med. 17:25, 1971). T wave alternans as obvious as this is quite rare. It is most likely the result of alternating changes in the shape and/or duration of the ventricular action potential.