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Lack of correlation between transient myocardial ischemia and late potentials on the signal-averaged
Insights
Transient myocardial ischemia, induced by dipyridamole, did not alter signal-averaged electrocardiogram late potentials in coronary artery disease patients. This suggests ischemia-related electrophysiologic changes are not linked to the substrate for chronic ventricular arrhythmias.
Area of Science:
- Cardiology
- Electrophysiology
- Medical Diagnostics
Background:
- Late potentials on signal-averaged electrocardiograms (SAECG) are linked to ventricular arrhythmias.
- The relationship between transient myocardial ischemia and these electrophysiologic markers is not fully understood.
Purpose of the Study:
- To investigate the association between transient myocardial ischemia and late potentials.
- To determine if ischemia-induced electrophysiologic changes correlate with the substrate for chronic ventricular tachyarrhythmias.
Main Methods:
- 100 coronary artery disease patients underwent serial SAECG recordings.
- Dipyridamole infusion was used to induce transient myocardial ischemia.
- SAECG parameters, including QRS duration and root mean square voltage of the last 40 ms of QRS (RMS40), were analyzed before, during, and after the test.
Main Results:
- Transient myocardial ischemia occurred in 47 patients during dipyridamole infusion.
- No significant changes in QRS duration or RMS40 were observed in either ischemic or non-ischemic groups.
- Only 2 patients showed a decrease in RMS40 to abnormal values during ischemia.
Conclusions:
- Electrophysiologic abnormalities induced by transient myocardial ischemia do not appear to be related to the substrate for chronic reentrant ventricular tachyarrhythmias.
- Signal-averaged electrocardiogram late potentials may not be a reliable indicator of ischemia-induced electrophysiologic substrate changes.
Abstract:
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.