EXERCISE-INDUCED U-WAVE INVERSION INDICATING THE SITE OF MYOCARDIAL-ISCHEMIA IN PATIENTS WITH CORONARY-ARTERY DISEASE

Eighty-seven unipolar electrocardiograms were simultaneously recorded before and after symptom-limited treadmill exercise in 103 patients having coronary artery narrowing (≥ 70%) and without previous myocardial infarction. Body surface distributions of exercise-induced U-wave inversion were studied in each case. Exercise-induced ST-segment depression, number of leads of ST depression (nST), maximal voltage of ST depression (maxST) were also studied. These data were compared with the location of ischemia determined by T1-201 exercise myocardial perfusion imaging (anterior, inferior, and anterior + inferior). Exercise-induced U-wave inversion was observed in 38 patients (37% of the total subjects); in patients with anterior ischemia, 21/37 i.e. 57%; in patients without significant response in the exercise myocardial scintigraphy, 0/17 i.e. 0%. Patients with exercise-induced U wave inversion had a greater number of diseased coronary arteries (2.3 ± 0.9 vs. 1.7 ± 0.8; p < 0.001), greater nST (20.2 ± 7.3 vs. 13.3 ± 7.6 leads, p < 0.001), greater maxST (0.26 ± 0.15 vs. 0.14 ± 0.07 mV, p < 0.001), smaller pressure rate product at peak exercise (1.88 ± 0.50 vs. 2.18 ± 0.67 104 mm Hg/min, p < 0.01), and shorter exercise duration (4.2 ± 2.8 vs. 6.6 ± 3.2 min, p < 0.001) than patients without exercise-induced U-wave inversion. According to the location of maximal U-wave inversion, patients were divided into 3 groups; (1) upper type U-inversion group, the point of maximal U inversion occurring at or above the 5th intercostal level; (2) lower-type U-inversion group, the point of maximal U inversion occurring below the 5th intercostal level, and (3) no U inversion group. Upper-type U-inversion tended to be associated with anterior ischemia, lower-type U inversion with inferior ischemia. Assuming that the upper-type U inversion indicated the anterior ischemia and lower-type U inversion indicated the inferior ischemia, the sensitivity and specificity were 52 and 100% for anterior ischemia, and 22 and 100% for inferior ischemia, respectively. The point of maximal ST depression had the same tendency but showed large overlapping. Exercise-induced U inversion was considered to be a sign of severe myocardial ischemia, and its body surface distribution reflected the ischemic sites.