Clinical significance of exercise-induced negative U-waves in patients with anterior myocardial infarction.

To elucidate the clinical significance of the exercise-induced negative U-wave (NU) in patients with anterior myocardial infarction, we compared the angiographic and scintigraphic findings in 15 patients with and 20 patients without NU, and obtained the following results: 1) On coronary angiography, all patients in the NU (+) group showed over 90% stenosis or total occlusion of the left anterior descending coronary artery (LAD). In the latter cases moderate to abundant collaterals were visualized on the anterior wall. In contrast, such a tendency was not observed in the NU (-) group. 2) Segments composed of viable myocardium (estimated by preservation of contraction at rest and T1-201 redistribution after exercise) numbered 30 of 45 segments (67%) in the NU (+) group, and 13 of 60 segments (22%) in the NU (-) group. Segments composed of lost myocardium (estimated by loss of contraction at rest and persistent defect in T1-201 uptake) numbered 7 of 45 segments (16%) in the NU (+) group, and 38 of 60 segments (63%) in the NU (-) group. 3) Exercise-induced NU was frequently observed on R-wave preserved leads with ST depression, but was also observed over abnormal Q waves, ST elevation and in isolation in some instances. 4) In 3 patients, preexisting exercise-induced NU was no longer observed and a transient stress-induced T1-201 defect disappeared after successful LAD revascularization. In conclusion, exercise-induced NU on precordial leads in patients with anterior myocardial infarction may be a sign suggesting the presence of jeopardized, but still salvageable, myocardium in the infarcted area.