[Projection of epicardial U-wave change to surface precordial electrocardiogram in coronary artery disease]

U-wave changes on the intracoronary electrocardiogram (ECG) during anterior or inferoposterior myocardial ischemia were correlated with the U-wave changes in the precordial leads of the body surface ECG in 28 patients who underwent coronary angioplasty of the left anterior descending (LAD group; 17 patients) or left circumflex (LC group; 11 patients) coronary artery. The intracoronary ECG was recorded simultaneously with the body surface multiple precordial leads at the baseline and during angioplasty. The amplitude of the U-wave on the intracoronary ECG was measured quantitatively, and U-wave changes from baseline to angioplasty were assessed qualitatively on the body surface ECG. Three different patterns of U-wave changes were distinguishable on the intracoronary ECG from baseline to angioplasty: change to positivity; no change; and change to negativity. The incidence of each pattern was similar in the LAD and LC groups (35 vs 36%; 30 vs 18%; 35 vs 46%, respectively). The intracoronary ECG was more sensitive for detecting U-wave changes during angioplasty than body surface precordial ECG (LAD group 71 vs 47%; LC group 82 vs 27%). When compared to the intracoronary ECG, concordant U-wave changes occurred in the surface precordial ECG in 67% (8/12) of the LAD group with accompanying epicardial U-wave changes, and discordant changes in 33% (3/9) of the LC group with epicardial U-wave changes. The present study provides fundamental information for understanding the correlation of U-wave changes between epicardial and surface precordial ECGs during myocardial ischemia in humans. As well as primary U-wave changes in anterior myocardial ischemia, reciprocal U-wave changes may also be prominent in the surface precordial ECGs in some cases of posterior myocardial ischemia.