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?

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 a typical anginal episode. Methods: For this purpose, 126 patients underwent 12‐lead 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 (11%) patients with normal coronary arteriograms developed QRS prolongation, whereas 60 of the 108 (56%) patients with CAD and 2 of the 18 (11%) patients with normal coronary vessels developed ST‐segment changes. Thus, the sensitivities of QRS prolongation measured by SAECG and of ST‐segment changes on the surface ECG for the detection of myocardial ischemia were found to be 70 and 56%, respectively, (p