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Negative u wave during percutaneous transluminal coronary angioplasty

To clarify the clinical significance of the negative U wave during acute myocardial ischemia, the appearance of the U wave and ST‐segment elevation on electrocardiography during percutaneous transluminal coronary angioplasty (PTCA) of the left anterior descending artery (LAD group: 11 patients) or right coronary artery (RCA group: 18 patients) was studied. During PTCA, U‐wave inversion (newly developed negative U wave, and increased negativity of the pre‐existing negative U wave) was observed in 37 (90%) of 41 patients in the LAD group and in 16 (89%) of 18 patients in the RCA group. The incidence of ST‐segment elevation was similar to that of U‐wave inversion; however, U‐wave inversion appeared before detectable ST‐segment elevation in 20 patients (49%) in the LAD group and in 4 patients (22%) in the RCA group. Moreover, U‐wave inversion was observed frequently in a wider range of leads than ST‐segment elevation. These results suggest that the U wave is a more sensitive indicator of myocardial ischemia than ST‐segment elevation in some patients, and that a negative U wave may be produced by a different mechanism than that which produces ST‐segment deviation, although both are related to myocardial ischemia.