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Transient coronary occlusion during elective PTCA: QRS changes are consistent with the timing of regional ventricular
1Investigaciones Médicas Florida, Buenos Aires, Argentina.
Background:
Electrocardiographic assessment of acute myocardial ischemia has traditionally emphasized ST-segment changes, whereas QRS alterations have received comparatively less attention. Whether the timing of ischemia-induced QRS changes is related to the normal timing of regional ventricular activation remains unknown.
Objective:
To determine whether the timing of QRS changes during acute coronary occlusion follows the timing of regional ventricular activation according to the occluded coronary artery.
Methods:
Electrocardiograms from 45 patients were recorded during controlled balloon occlusion of the left anterior descending (LAD), right coronary (RCA), and left circumflex (LCx) arteries. High-resolution, time-aligned analysis (1-ms) was performed using standard and derived leads, including regional loops and precordial bipolar and averaged signals. The timing and distribution of ischemia-induced QRS changes were compared between baseline and coronary occlusion.
Results:
The onset of ischemia-induced QRS changes differed according to the occluded coronary artery. In LAD occlusions, QRS vector changes occurred significantly earlier (40.7 ms), whereas RCA occlusions showed later changes (53.6 ms, p = 0.003 for LAD vs RCA comparison). Overall, the timing of QRS vector changes was consistent with the expected activation sequence of the myocardial territory supplied by the occluded artery.
Conclusions:
During acute coronary occlusion, ischemia-induced QRS changes were consistent with the expected activation timing of the myocardial territory supplied by the occluded artery. These exploratory findings support a physiological framework for interpreting QRS changes during ischemia and suggest that the standard ECG contains underrecognized temporal information. Whether these temporal features can help identify the occluded coronary territory remains a hypothesis that requires prospective diagnostic-performance studies.
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