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Lesson 19 of 21 · Ischemia

ACS Localization

Contiguous leads look at the same wall of the heart, and each wall is fed by a predictable artery. Localize the STE, find the reciprocal changes, and you'll know the culprit.

01Leads → wall → artery

  • V1–V2: septal (LAD)
  • V3–V4: anterior (LAD)
  • I, aVL, V5–V6: lateral (LCx / diagonal)
  • II, III, aVF: inferior (RCA ≈ 85%, LCx)
  • V7–V9 (or ST↓ V1–V3): posterior (RCA / LCx)
  • V4R: right ventricle (proximal RCA)
Coronary territories
AnteriorLateralPosteriorInferiorSeptalLVshort axisAnteriorV3–V4LADLateralI, aVL, V5–V6LCx / diagonalPosteriorV7–V9 (ST↓ V1–V3)RCA / LCxInferiorII, III, aVFRCA (85%) / LCxSeptalV1–V2LAD (septal)Right ventricle: V4R (proximal RCA)

02Inferior MI checklist

  • STE III > II and reciprocal depression in I/aVL → RCA
  • Get V4R: RV infarct → avoid nitrates, give fluids
  • Watch for bradycardia and AV block (AV nodal artery)
III
Inferior STEMI: STE in II, III, aVF.

Key takeaways

  • Inferior = II, III, aVF = RCA
  • Anterior = V1–V4 = LAD
  • Lateral = I, aVL, V5–V6 = LCx