The significance of U wave polarity in patients with a prior anterior myocardial infarction.

The significance of the polarity of U waves in left precordial leads in patients with a prior anterior myocardial infarction was evaluated in relation to left ventricular function and wall motion by left ventriculography. Ninety-six such patients, with a mean age of 53 years, were divided into three groups according to the polarity of U waves: positive U waves (group P), isoelectric or flat U waves (group F), and negative U waves (group N). The following parameters were analysed: (1) Selvester ECG score; (2) global ejection fraction (EF); (3) regional area change; (4) number of asynergic and akinetic segmental radii; (5) asynergic and akinetic areas. Fifteen patients served as controls. The Selvester ECG scores increased progressively and EF decreased successively with statistically significant differences between groups P, F, and N (P less than 0.01, respectively). The sensitivity of negative U waves for predicting EF of less than 50% was 88.0%, the specificity 81.9%, and the accuracy 84.4%. The incidence of regional area change at the apex of less than 20% was 10.0% in group P, 35.9% in group F, and 74.3% in group N (P less than 0.01). The number of dyssynergic and akinetic radii, and asynergic and akinetic areas increased progressively from group P to F, to N (P less than 0.01). These results demonstrate that the polarity of U waves correlated significantly with left ventricular function and wall motion as well as the size of myocardial infarction. Negative U waves are an important sign of extensive myocardial infarction involving the apex with global ejection fraction of less than 50%. Negative U waves may be associated with lateral ischaemia.