In 1913, Cohn1 and Oppenheimer and Williams2 described cases of heart-block in which the form of the ventricular complex showed frequent change.
In Cohn's case the heart-block was transient. On Aug. 22, 1910, the patient showed partial heart-block with a 3-2 rhythm as shown by polygraphic tracings. On Feb. 10, 1911, this patient was studied again and showed a partial heart-block with a 2-1 rhythm. On February 11 and 13 there was a complete auriculoventricular dissociation. At this time electrocardiographic tracings were made and it was found that successive ventricular complexes changed their outline so that no two were precisely alike. Two general types, however, could be distinguished, the one resembling the type of beat arising from stimuli originating in the wall of the right ventricle and the other those arising in the wall of the right ventricle and the other those arising