Isolated U wave negativity.

Inversion of U as the only abnormal electrocardiographic finding is here shown to be the first change to occur in certain cases of hypertension, coronary artery sclerosis, and other organic heart disease. It is also found in association with certain metabolic and electrolyte changes. Its recognition will enhance the value of the electrocardiogram in clinical diagnosis. T HE CLINICAL significance of inverted U waves has received scant attention from cardiologists. Although its association with other electrocardiographic abnormalities has been described,'-3 this has not contributed significantly to diagnosis or prognosis. Reports of only a very few cases of isolated U wave negativity have appeared in the literature. Nahum and Hoffl reported two, Papp2 one, and Palmer4 four. In every case the finding was considered abnormal. On the other hand, Katz' has observed that "little clinical weight would be given to an electrocardiogram in which the only deviation from the normal was in the U wave." The author has shown4 that U may temporarily become negative during exercise tests for angina pectoris, suggesting that such inversion should be regarded as one of the criteria of acute coronary insufficiency. Valuable confirmation of this is afforded by the later, but apparently independent, observations of Holzmann.fi The physiology of the U wave is imperfectly understood. Hoff and Nahum7 concluded that it forms part of the ventricular complex and is coincident in time with the supernormal phase. Zuckermann and Cabrera' have suggested that it originates in the interventricular septum and is a result of retardation of re-polarization in that structure by the compression brought to bear on it by both ventricles. Zuckermann and Estandia9 later claimed support for this hypothesis by showing that while 205 extrasystoles originating in the ventricular walls usually appear coincidentally with the U wave, those originating in the septum appear after the U wave, that is, at the end of the septal refractory period. It was felt that while an analysis of clinical records might add little to our knowledge of the causation of the U wave, much might be learned concerning its incidence and clinical significance. Such empirical knowledge is long overdue. METHOD The present communication is based on the findings in approximately 10,000 electrocardiograms personally read by the author in the course of a four-year period during which each tracing was especially observed for negative U waves. Many of the tracings had actually been taken previously and came to notice …