Transient U wave inversion during variant angina

We studied the prevalence and clinical significance of transient U wave inversion in 43 patients with variant angina. Twenty-four patients (group A) had ST segment elevation in the anterolateral and 19 patients (group B) had this finding in the inferoposterior leads of the ECG during spontaneous angina. In none of these patients was U wave inversion present on the resting 12-lead ECG in the absence of anginal attack. During anginal attacks, U wave inversion developed in association with ST segment elevation in 16 patients (66.7%) of group A but in no patient of group B. To exclude the possibility that a transient rise of systolic blood pressure during angina caused U wave inversion, treadmill exercise testing was done in the 16 patients after the discontinuation of antianginal drugs. In 12 of the 16 patients, exercise testing did not produce angina or U wave inversion despite a marked elevation of systolic blood pressure. These results indicate that transient U wave inversion frequently develops with anterolateral ischemia but not with inferoposterior ischemia during attacks of variant angina. It is likely that transient U wave inversion was caused by myocardial ischemia but not by a rise of blood pressure during angina.