U Wave of High-Speed and Magnified Electrocardiogram in Left Ventricular Overloading

Abstract

The U waves of high-speed and magnified electrocardiograms (magnified ECGs) were recorded in 50 normal subjects and 130 patients with left ventricular pressure and volume overloading (LVO). The LVO group was divided into four subgroups. These U waves were examined quantitatively and were correlated with échocardiographie findings. The negative U wave in the LVO group was more clearly observed in the magnified ECG than in the ECG at normal magnification. The corrected T-aU (from the end of the T wave to the apex of the U wave) interval of the LVO group was significantly longer than that of the normal group. The amplitude of the U wave in the LVO group was greater in lead V(2)) and smaller or more negative in leads II and V(6) than in the normal group, suggesting that the negative U wave was related to both hypertrophy and dilatation of the left ventricle. These findings were not observed in mitral regurgitation (MR), although in the MR group the left ventricle was dilated. These findings suggest that the U vector in the LVO group except the MR subgroup is displaced anteriorly and rightward, and that mechanical stretch of the ventricular muscles induced by pressure and volume overloading of the left ventricle may contribute to genesis of the abnormal U wave.