🧭 Site	🩸 Likely Vessel Occluded	📉 Typical ECG Changes	💡 Clinical Pearls
Anterior	LAD	ST elevation V1–V6	Large territory infarct → high risk of LV failure & shock
Anteroseptal	LAD	ST elevation I, aVL, V1–V4	Septal involvement → risk of VSD
Anterolateral	Circumflex / LAD diagonal	ST elevation V3–V6, I, aVL	Often subtler, may mimic high lateral MI
Inferior	RCA or Circumflex	ST elevation II, III, aVF	Frequently associated with AV block or bradycardia
Posterior	RCA or Circumflex	ST depression V1–V3, tall R waves V1–2	“Mirror” changes → always check posterior leads
Lateral	Circumflex / diagonal branch of LAD	ST elevation I, aVL, V5–V6	Often accompanies inferior MI

📋 Criteria for Diagnosing STEMI

ST elevation in ≥2 contiguous leads >1 mm (except V2–V3 thresholds below).
V2–V3: ≥2 mm in men >40 yrs, ≥2.5 mm in men <40 yrs, ≥1.5 mm in women.
New or presumed new LBBB.
Isolated posterior MI (diagnose by reciprocal ST depression in V1–V3).
Reciprocal changes support diagnosis.

⚠️ Differentials of ST Elevation

STEMI
Early repolarisation ⭐ (benign, young athletes, no reciprocal change)
Myopericarditis ❤️‍🔥 (saddle-shaped STE in all except aVR)
Prinzmetal’s angina 🌙 (vasospasm, transient)
LV aneurysm (post-MI, persistent STE)
Brugada syndrome ⚡ (V1–V3 STE, risk of sudden death)
Takotsubo cardiomyopathy 🐙
During PCI or angioplasty

🔎 Early Repolarisation (Mimics Anterior STEMI)

Incidence: 5–13% (common in young athletes).
J-point elevation ≥1 mm in ≥2 contiguous leads (often inferior or lateral).
Concave morphology, no reciprocal changes, large T waves.
Benign – but must exclude ACS if uncertain.

🩺 STEMI Evolution

1️⃣ Hyperacute T waves
2️⃣ ST elevation ± reciprocal depression
3️⃣ T wave inversion
4️⃣ Loss of R wave height
5️⃣ Q waves (transmural infarct, “electrical window”)

NSTEMI / Ischaemia

Widespread ST depression
T wave flattening/inversion
Deep anterior T inversions → LAD stenosis
Deep inferior T inversions → RCA stenosis

📐 Modified Sgarbossa Criteria (LBBB)

≥1 mm concordant STE in ≥1 lead
≥1 mm concordant ST depression V1–V3
≥1 mm STE with discordance ≥25% of preceding S-wave depth

🧭 Correlating ECG with Culprit Vessel

Artery	ECG leads affected	Notes
LAD (proximal)	V1–V6, I, aVL	Large anterior wall infarct
LAD (distal)	V3–V4	Smaller anterior infarct
Circumflex	ST depression V1–V3, tall R in V1–2	Posterior MI (“mirror changes”)
RCA	II, III, aVF	Inferior MI ± AV block
Proximal RCA	II, III, aVF + V5–V6	Inferolateral MI
Distal RCA / OM branch	V5–V6	Lateral MI

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ECG - Acute Coronary Syndrome

🫀 ECG, MI & Coronary Arteries