U waves in ventricular hypertrophy: possible demonstration of mechano-electrical feedback.

The relation between ventricular function and electrocardiographic evidence of hypertrophy (by voltage criteria, "strain", and U wave inversion) was examined by means of M mode echocardiography and apex cardiography in 73 patients with diseases associated with left ventricular hypertrophy and 10 normal volunteers. In patients with disease, left ventricular cavity dimension and fractional shortening were unrelated to electrocardiographic findings, but left ventricular posterior wall thickness was greater in those with strain or U wave inversion. Without U wave inversion, hypertrophy and strain were weakly related to diastolic abnormalities, but the addition of U wave inversion was strongly associated with a reduced rate of early diastolic posterior wall thinning, prolonged isovolumic relaxation time, delayed mitral valve opening after minimum cavity dimension, and a pronounced increase in transverse dimension during the isovolumic period suggesting incoordinate relaxation. It is concluded that, whereas a negative U wave frequently occurs in association with the pattern of left ventricular hypertrophy or strain, it alone is strongly related to abnormalities of isovolumic relaxation. The close relation between incoordinate relaxation and U wave inversion, events which occur virtually simultaneously during the isovolumic period, suggests a mechanical influence on U wave genesis.