Lack of correlation between transient myocardial ischemia and late potentials on the signal-averaged electrocardiogram
Cardiac Pacing, Artificial
The relation between transient myocardial ischemia and late potentials was investigated in 100 patients with coronary artery disease who underwent serial recordings of the signal-averaged electrocardiogram before, during and after dipyridamole infusion. During this test, 47 patients (group 1) developed transient myocardial ischemia (with ST elevation in 14 cases and ST depression in 33), whereas 53 patients (group 2) did not. Baseline signal-averaged electrocardiogram was abnormal in 20 patients (20%): a QRS duration greater than 115 ms was seen in 6 patients, a late potential (root mean square voltage of last 40 ms of QRS [RMS40] less than 25 microV) in 9, both abnormalities in 5, with no significant differences between groups 1 and 2 (26 vs 15%, respectively). In both groups, comparison of recordings obtained before, during and after dipyridamole test revealed no significant changes in QRS duration and RMS40. Absence of significant differences was also observed when patients with transient ischemic ST elevation or ST depression were examined separately. During the test, 100% of abnormal basal recordings remained abnormal and 98% of normal recordings remained within normal limits. In only 2 patients (from group 1) RMS40, which showed borderline values at baseline, decreased to abnormal values during dipyridamole test. These data suggest that electrophysiologic abnormalities induced by transient myocardial ischemia may not bear any relation with the substrate for chronic reentrant ventricular tachyarrhythmias, as reflected by late potentials on the signal-averaged electrocardiogram.