## Distinguishing Anterior vs Inferior STEMI on ECG ### Anatomical Basis The left anterior descending (LAD) artery supplies the anterior wall (leads V1–V4, I, aVL), while the right coronary artery (RCA) or left circumflex (LCx) supplies the inferior wall (leads II, III, aVF). ### Key ECG Discriminators | Feature | Anterior STEMI | Inferior STEMI | |---------|---|---| | **ST elevation** | V1–V4, I, aVL | II, III, aVF | | **Reciprocal ST depression** | II, III, aVF | I, aVL | | **Coronary occlusion** | LAD | RCA or LCx | | **Complications** | Cardiogenic shock, LV dysfunction | Bradycardia, RV infarction (if inferior RV) | **Key Point:** ST elevation in V1–V4 with reciprocal ST depression in the inferior leads (II, III, aVF) is the hallmark of acute anterior STEMI and is the single best discriminator from inferior STEMI. ### Why Other Features Are Non-Specific **High-Yield:** Pathological Q waves and T wave inversions occur in *both* anterior and inferior infarction during the acute and evolving phases—they are markers of infarction location but not discriminators between the two. **Clinical Pearl:** Reciprocal changes (ST depression in the "opposite" leads) are more specific than the primary ST elevation itself and help confirm the diagnosis and localize the culprit vessel. 
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