Lack of specificity of new negative U waves for anterior myocardial ischemia as evidenced by intracoronary electrogram during balloon angioplasty.

Negative U waves on the surface electrocardiogram are reported to be a specific marker of myocardial disease. In the setting of ischemia, they correlate with stenosis of the left main and left anterior descending coronary arteries. To determine whether U wave changes are unique for anterior ischemia, the development of new U waves on the intracoronary electrogram was correlated with the location and magnitude of ischemia during coronary balloon angioplasty. Recordings were obtained during dilation of 43 vessels in 37 patients. New negative U waves developed during dilation of 12 vessels (7 of the left anterior descending, 4 of the left circumflex and 1 of the right coronary artery). New positive U waves developed during dilation of 18 vessels (12 of the left anterior descending, 3 of the left circumflex and 3 of the right coronary artery). The magnitude of ST segment change was 10.9 +/- 6.7 mm in the presence of a new U wave but only 3.4 +/- 2.8 mm in the absence of a new U wave (p less than 0.001). It is concluded that 1) negative U waves on the intracoronary electrogram are not specific for anterior ischemia; 2) new positive U waves on the intracoronary electrogram are as sensitive as new negative U waves for acute ischemia; 3) the development of a new positive or negative U wave is associated with the magnitude of myocardial ischemia; and 4) the recording of U waves may be related to the proximity of the recording leads to the location of ischemia.