Spatial distribution of exercise-induced ST-segment depression and U-wave inversion in identifying the ischemic site in patients with coronary artery disease

The negative U wave: a pathogenetic enigma but a useful, often overlooked bedside diagnostic and prognostic clue in ischemic heart disease

The pathogenesis of U-wave inversion and its clinical value are still not clear, although the U wave was described by Einthoven together with the other electrocardiographic (ECG) waves. Not considered a useful diagnostic clue, it is not usually mentioned in ECG reports. In recent years, stimulated by the long QT syndromes and by the discovery of U-wave changes in some pathologic, mostly cardiac states, this neglected wave has attracted new interest. This review focuses on the negativity of the U wave in ischemic heart disease. The discovery of M cells and their electrophysiology has established the cellular basis for repolarization and has contributed to our knowledge of U-wave genesis. Hemodynamic changes during diastole in acute ischemia also furnish interesting elements for the interpretation of U-wave changes, and some experimental and clinical studies, besides designating stretch as a cause of U-wave changes, have also proved their value for more accurate bedside diagnosis and prognosis. They may indicate the extent of myocardial ischemia, the presence of collateral circulation, and the possible territory and vessel involved. When U-wave changes are the first and only sign of ischemia, they may contribute to a decision regarding the hospital admission of a patient without typical ischemic symptoms. Furthermore, U-wave changes during exercise tests increase their sensitivity.

Exercise-induced U-wave changes in patients with coronary artery disease--correlation with tomographic thallium-201 myocardial imaging

We studied the relation between exercise-induced U-wave changes and the site of a reversible defect in tomographic 201Tl myocardial imaging. Coronary artery disease and control groups consisted of 116 and 42 patients, respectively. In the anteroapical-ischemia group (n = 37), the sensitivity of U-wave inversion in the anterior precordial leads for ischemia was 62% (23/37) and that of prominent U-waves without an increase in the height of the T-wave in the inferior limb leads was 57% (21/37). In this group, 18 patients (49%) met both criteria (18 [78%] of 23 patients with the former; 18 [86%] of 21 patients with the latter). In the posterior-ischemia group (n = 59), the sensitivity of prominent U-waves with a decrease in the height of the T-wave in the anterior precordial leads for ischemia was 63% (37/59) and that of U-wave inversion in the inferior limb leads was 20% (12/59). In this group, 12 patients (20%) met both criteria (12 [32%] of 37 patients with the former; all 12 patients with the latter). The specificity of U-wave criteria was 100%. In the anteroapical and posterior ischemia group (n = 20), the sensitivity of U-wave criteria for anteroapical and posterior ischemia was 85% (17/20) and 40% (8/20), respectively. In conclusion, U-wave criteria are not only specific but also sensitive for myocardial ischemia determined by 201Tl imaging.