Possible role of a ventricular conduction disturbance in the electrogenesis of the ECG-VCG signs of myocardial infarction

Abstract

The typical QRS patterns of myocardial infarction (MI-QRS) are commonly attributed to myocardial cellular death. However, observation of a transient appearance of MI-QRS during coronary insufficiency, the disappearance of MI-QRS after coronary by-pass surgery and the appearance of MI-QRS after intracranial hemorrhage suggest that a different electrophysiological mechanism may be at work. There is a single convincing explanation for all these observations. It seems possible, at least theoretically, that a localized conduction disturbance can generate or contribute to the generation of the MI-QRS. The results obtained in nine out of 194 cases studied by means of premature right atrial stimulation (PRAS) in our laboratory seem to confirm this hypothesis. In five of them we observed typical MI-QRS in the aberrant beats which were absent in the basal tracings. In the other four cases, MI-QRS which were present in basal tracings disappeared in the aberrant beats. In three of these a reduction in the duration of QRS was also observed, while in the fourth the duration of QRS did not change. In no case could the alterations of QRS (induction or disappearance of MI-QRS) be explained by a classical conduction disturbance, preexcitation or by a premature ventricular beat. While the induction of MI-QRS was clearly due to an aberrant conduction in the supraventricular beats, the disappearance of basal MI-QRS changes in premature supraventricular beats is more difficult to explain. One possible electrophysiological mechanism could be a supernormal phase conduction. If this is the case, the basal MI-QRS could be due to a ventricular conduction disturbance. In conclusion, our results suggest that MI-QRS can be generated, at least in our cases, by a localized conduction disturbance.