Regional transmural ischemia produces distinct ECG patterns based on coronary anatomy and the direction of injury vectors (presented at length in The Masterclass in Advanced Electrocardiography). Understanding these relationships improves diagnostic accuracy. Do NOT confuse with subendocardial ischemia which is characterized by ST depression with or without T wave inversion. Subendocardial ischemia does NOT localize (discussed at length in Getting Acquainted With Ischemia and Infarction).
Inferior Transmural Ischemia
Typically reflects RCA or LCx involvement. ECG features:
- ST changes in II, III, aVF
- reciprocal changes in aVL
- vector shifts influenced by dominance
Posterior Transmural Ischemia
Posterior injury produces:
- ST depression in V1–V3
- tall R waves in V1–V2
- upright T waves in the anterior leads
These are not “anterior changes” but posterior injury seen from the front.
Lateral Transmural Ischemia
Involves the LCx or diagonal branches of the LAD. ECG features:
- ST changes in I, aVL, V5–V6
- reciprocal changes inferiorly
Coronary Dominance Matters
Right‑dominant vs left‑dominant circulation alters which regions are affected and how the ECG appears.
Related: Key Mechanism‑Based Concepts in Ischemia and Infarction