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 ty pical anginal episode. Methods: For this purpose, 126 patients underwent 12-lead surface ECG and s ignal-averaged electrocardiogram (SAECG) during typical anginal pain as wel l as at the time the patient was asymptomatic. In both periods, QRS duratio n and ST-segment changes were evaluated. All patients underwent cardiac cat heterization. Results: Of the 126 patients, 108 (86%) had coronary artery disease (CAD), whereas the remaining 18 (14%) patients had normal coronary arteriograms. D uring typical anginal pain, 75 of the 108 (70%) patients with CAD and 2 of the 18 (11%) patients with normal coronary arteriograms developed QRS prolo ngation, 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 fo und to be 70 and 56%, respectively, (p < 0.01), whereas the specificities w ere both found to be 89% (p = NS). Conclusions: During typical anginal pain, QRS prolongation on the SAECG is more sensitive than are ST-segment changes on the ECG for the detection of myocardial ischemia.