QRS prolongation on the signal‐averaged electrocardiogram versus st‐segment changes on the 12‐lead electrocardiogram: Which is the most sensitive electrocardiographic marker of myocardial ischemia?

summary Background: ST-segment changes and QRS prolongation are electrocardiographic (ECG) markers of myocardial ischemia Hypothesis: This study was undertaken to investigate the appearance of QRS duration changes with or without concomitant ST-segment changes during atypical anginal episode. Methods: For this purpose, 126 patients underwent 12lead surface ECG and signal-averaged electrocardiogram (SAECG) during typical anginal pain as well as at the time the patient was asymptomatic. In both periods, QRS duration and ST-segment changes were evaluated. All patients underwent cardiac catheterization. Results: Of the 126 patients, 108 (86%) had coronary artery disease (CAD), whereas the remaining 18 (14%) patients had normal coronary arteriograms. During typical anginal pain, 75 of the 108 (70%) patients with CAD and 2 of the 18 (1 1%) patients with normal coronary arteriograms developed QRS prolongation, whereas 60 of the 108 (56%) patients with CAD and 2 of the 18 (1 1 %) patients with normal coronary vessels developed ST-segment changes. Thus, the sensitivities of QRS prolongation measured by SAECG and of STsegment changes on the surface ECG for the detection of