Spatial proximity or vector orientation? Re-evaluating ECG interpretation in anterior myocardial infarction using cardiac magnetic resonance.
BACKGROUND: The electrocardiogram (ECG) is widely used to infer infarct location and extent in anterior myocardial infarction (MI), based on either anatomical lead proximity or vectorial orientation of ST-segment deviation. However, the validity of these approaches against direct imaging of myocardial injury remains uncertain. METHODS: In this prospective study, 105 patients with anterior MI underwent cardiac magnetic resonance (CMR) imaging 3-7 days after presentation. Admission ECGs were analyzed using (1) conventional ECG localization categories, and (2) simplified frontal and horizontal ST-axis orientation. CMR-defined injury distribution was assessed using late gadolinium enhancement and myocardial edema imaging. RESULTS: Conventional ECG localization categories demonstrated no significant association with CMR-defined infarct distribution (P = 0.24), with poor agreement (κ = 0.122) and substantial overlap across categories. Simplified ST-axis orientation showed modest and inconsistent associations with infarct location and did not meaningfully explain infarct size. In contrast, global ST-segment burden was associated with CMR-defined infarct size (ΣSTE: standardized β = 0.307, P = 0.002; lead count: standardized β = 0.267, P = 0.007). CONCLUSIONS: In this selected cohort of reperfused LAD-related anterior STEMI patients undergoing early CMR, conventional ECG localization categories and simplified ST-axis orientation showed poor or inconsistent correspondence with CMR-defined infarct distribution, whereas global ST-segment burden showed a modest association with infarct size. These findings suggest that, in this cohort, the ECG may be better suited to reflect the extent of myocardial injury rather than its precise anatomical location.