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NEGATIVE U waves are usually preceded by negative T waves. It also seems that only secondarily inverted T waves are followed by inverted U waves. It was found by us, however, that the U wave was inverted in less than one half of the electrocardiograms that showed presumably secondary inversion of the T wave. The presence of an upright U wave in leads where the T wave was already inverted could be explained by the existence of a time lag between the inversion of the T wave and the inversion of the U wave in the evolution of a "left ventricular strain pattern." An isolectric U wave would probably signify a transitional phase preceding actual U wave inversion. Our previous clinical observations tended to support such a concept. If this assumption was correct and the occurrence of an inverted U wave was a late finding in 'left ventricular strain patterns," then an inverted U wave should be associated with clinical findings of more advanced disease of the left ventricle. METHODS AND MATERIALSBecause the majority of negative U waves are found in electrocardiograms of patients with hypertension, a group of 287 patients with elevated blood pressures who had electrocardiograms in which the U-wave amplitude and polarity could be accurately determined were selected from the files of the Division of Cardiology of the Philadelphia General Hospital. The method of selection was described in the previous communication.' The interpretations of the electrocardiograms were performed without knowledge of the clinical findings. The latter were obtained later from the hospital records.The electrocardiographic diagnosis ( "left ventricular hypertrophy" was based on the presence of left axis deviation with the sum of the deepest S wave in the right precordial leads plus the tallest R wave in the left precordial leads exceeding 35 mm. without T-wave inversion. "Left ventricular strain" was defined as the left ventricular hypertrophy pattern plus T-wave inversion in the left precordial leads.In analysing the clinical findings, the degree of congestive heart failure was determined on the basis of the physical examination performed at the time the electrocardiogram was taken. Renal function was determined by urinalyses and blood urea nitrogen values, (available in all cases), phenolsulfonphthalein tests, Fishberg concentration tests, intravenous pyelography, blood creatinine levels, and urea clearance tests (obtained in many cases). Heart size was determined by teleroentgenogram or orthodiagram. The fundoscopic examinations were performed by a staff ophthalmologist.In evaluating the mortality (table 2), all deaths occurring within 6 months of the time the electrocardiogram was taken were recorded and the cause of death noted. RESULTSThe sex, color, and age distribution of the cases studied are presented in table 3. The distribution by sex and color was about the same for both the negative and positive U-wave groups. The age range and distribution were also similar. It should be noted, however, that the Negro women, who made up the largest ...

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