ECG Patterns of Coronary Artery Occlusion and Clinical Implications

Left Anterior Descending (LAD) Artery Occlusion

Anterior‑wall MI with ST‑segment elevation in V1‑V6 is the hallmark of LAD occlusion, whereas RCA occlusion produces inferior ST elevation and LCx occlusion often lacks ST elevation. [American College of Cardiology] 1
Proximal LAD (“widow‑maker”) occlusion produces ST elevation in V1‑V4, I, aVL (often aVR) and reciprocal depression in II, III, aVF (often V5); the injury vector is left‑ward (greater aVL than aVR elevation, greater III than II depression) and involves the basal left ventricle, anterior/lateral walls, and interventricular septum. [American College of Cardiology] 1
Mid‑LAD occlusion spares the basal septum (no ST elevation in V1) and shows ST elevation in aVL with reciprocal depression in III; the basal interventricular septum is not involved. [American College of Cardiology] 2
Distal LAD (wrap‑around) occlusion yields prominent ST elevation in V3‑V6 (less in V2), no ST elevation in V1, aVR, or aVL, and typically no ST depression in II, III, or aVF; instead, inferior leads may show ST elevation because the infarct “wraps” around the apex, producing an inferiorly directed injury vector. [American College of Cardiology] 3

Typical inferior MI pattern: ST elevation in leads II, III, and aVF. [American College of Cardiology] 1
RCA occlusion with right‑ventricular involvement: ST elevation appears in right‑sided leads V3R and V4R; these changes resolve within ≈ 10 hours in about 50 % of patients, yet the combination carries higher mortality despite a smaller infarct size and an increased risk of ventricular septal rupture. [Praxis Medical Insights] 4
Diagnostic pitfall: When ST elevation is present simultaneously in anterior leads (V2‑V4) and inferior leads (III, aVF), distal LAD wrap‑around occlusion is the most common cause, although proximal RCA with RV extension must also be considered. [Praxis Medical Insights] 4

LCx occlusion is frequently missed because it often presents without classic ST elevation; only ≈ 45 % of cases show ST elevation compared with ≈ 70 % for RCA/LAD. [European Society of Cardiology] 5
Posterior MI sign: Isolated ST depression ≥ 0.05 mV in V1‑V3 indicates a posterior infarction and should be managed as a STEMI. [European Society of Cardiology] 5
Posterior lead strategy: Recording posterior leads V7‑V9 and identifying ST elevation ≥ 0.05 mV (≥ 0.10 mV in men > 40 yr) improves detection of LCx‑related posterior/lateral MI. [European Society of Cardiology] 6
Emergency angiography is recommended for patients with ongoing ischemic symptoms even when diagnostic ST changes are absent. [European Society of Cardiology] 6

Catastrophic ECG pattern: ST elevation in aVR and/or V1 together with widespread ST depression > 0.1 mV in ≥ 8 surface leads. [European Society of Cardiology] 5
Clinical picture: Rapid development of hypotension, cardiogenic shock, or pulmonary edema is common. [Praxis Medical Insights] 7
Prognosis: In‑hospital mortality ≈ 31 % and ≈ 59 % of patients have severe multivessel disease. [Praxis Medical Insights] 7
Management: Immediate activation of the cardiac catheterization laboratory without awaiting troponin results is advised. [Praxis Medical Insights] 7

Deep, symmetric T‑wave inversions (≥ 0.5 mV) in V2‑V4 with QT prolongation signal severe proximal LAD stenosis and a high risk of imminent anterior MI; emergent angiography within 2 hours is recommended regardless of TIMI risk score. [Praxis Medical Insights] 8

New or persistent left bundle‑branch block (LBBB) with ongoing ischemic symptoms. [European Society of Cardiology] 5
Ventricular paced rhythm that precludes reliable ST‑segment interpretation. [European Society of Cardiology] 6
Persistent ischemic symptoms despite the absence of diagnostic ST changes on the standard 12‑lead ECG. [European Society of Cardiology] 5
Hyperacute T waves preceding ST elevation in very early presentations. [European Society of Cardiology] 6

The hallmark electrocardiographic pattern for left main coronary artery (LMCA) disease is ST‑segment elevation in lead aVR together with diffuse ST‑segment depression in eight or more surface leads; the pattern is especially diagnostic when the magnitude of aVR elevation is equal to or exceeds that in V1. 9
The European Society of Cardiology states that when this pattern occurs alongside hemodynamic compromise (e.g., hypotension, cardiogenic shock, pulmonary edema), it strongly suggests multivessel or left‑main obstruction and warrants immediate catheter‑based evaluation. 9
Counting ≥ 8 leads with ST depression improves specificity for identifying LMCA or severe multivessel disease. 9

Activate the cardiac catheterisation laboratory without waiting for cardiac biomarkers (e.g., troponin) when the LMCA pattern is present. 9
Do not postpone further testing or risk stratification; rapid intervention is essential. 9
Obtain the ECG during active symptoms (e.g., chest pain) because the pattern may resolve once ischemia abates. 9

LMCA pattern: ST elevation in aVR greater than in aVL, aVR ≥ V1, and diffuse ST depression in ≥ 8 leads. 10
Proximal LAD pattern: ST elevation in leads V1‑V4, I, and aVL (with aVL > aVR), reciprocal ST depression in inferior leads (II, III, aVF), and typically fewer than 8 leads showing depression. [10][11]
The American College of Cardiology notes that proximal LAD occlusion located above the first septal and diagonal branches produces the V1‑V4, I, aVL elevation pattern, but it differs from LMCA disease by the less extensive ST‑segment depression and the opposite aVR/V1 relationship. [10][11]

LMCA occlusion may present without the classic ST‑elevation pattern; clinicians should remain vigilant for atypical ECG presentations. 9
When circumflex involvement is suspected, add posterior leads V7‑V9 to the recording to improve detection. 9
Persistent ischemic symptoms despite a non‑diagnostic ECG mandate emergency coronary angiography. 9

Although the aVR + diffuse ST‑depression pattern is highly suggestive, it is not 100 % specific for LMCA disease; other causes of circumferential subendocardial ischemia (e.g., severe three‑vessel disease, demand ischemia) can produce similar findings. [No citation – omitted]
Nevertheless, because true LMCA occlusion carries a catastrophic prognosis, the presence of this ECG pattern should trigger emergency catheterisation regardless of alternative differential diagnoses. 9