Effects of Transient Myocardial Ischemia on the Signal-averaged Electrocardiogram

The relation between myocardial ischemia and signal-averaged electrocardiogram (SAECG) was investigated in 59 patients with documented coronary artery disease. Transient myocardial ischemic attacks (TMIAs, ST>1 mm for>3 minute) were observed during 3- channel Holter recordings. TMIAs mean duration and degree of ST changes were 15±7 min and 2.4±0.9 mm. SAECGs were obtained from Holter tapes at baseline and during TMIAs and analyzed at 25 to 250 Hz and 40 to 250 Hz for Iate potential detection, and also analysed at spectrocardiography, a new technique for spectral turbulence analysis. All patients had SAECG with noise level ?1.0 uV at 25 Hz and ?0.8 uV at 40 Hz and with the difference in noise level between baseline SAECGs and SAECGs at TMIA s?0.2 to 0.3 uV. Comparison between SAECGs at baseline and at the peak of TMIAs revealed no significant differences in the incidence of Iate potentials [20 %(12/59)-19 % (11/59)] and spectral turbulences [24 %(14/59)-27 % (16/S9)]. These data suggest that electrophysiologic changes induced by transient myocardial ischemia may not provide the anatomic electrophysiologic substrate for reentrant ventricular tachycardia, as reflected by Iate potentials and spectral turbulence of the SAECG.