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Posterior MI Recognition — EECC MCQ

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ModerateGeneral CardiologyPosterior MI RecognitionEECC

A 65-year-old man presents with chest pain and ST elevation in the inferior leads (II, III, aVF). His 12-lead ECG also shows ST depression in leads V1-V3. What additional diagnosis should be suspected beyond inferior STEMI?

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Correct answer: C — Concomitant posterior MI — reciprocal ST depression in V1-V3 may represent 'mirror-image' ST elevation in the posterior wall; posterior leads (V7-V9) should be recorded and will show ≥0.5 mm ST elevation if posterior MI is present

Inferior STEMI commonly involves the posterior wall (supplied by the PDA from the RCA in 85% or from the LCx in 15% of patients). Standard 12-lead ECG has no leads directly overlying the posterior wall, so posterior MI manifests as 'reciprocal' changes in V1-V3: (1) ST depression (mirror of posterior ST elevation); (2) tall R waves (mirror of posterior Q waves); (3) upright T waves (mirror of posterior T inversions). Posterior leads V7-V9 (placed on the back at the same horizontal level as V6): ≥0.5 mm ST elevation confirms posterior STEMI. The 2023 ESC ACS Guidelines recommend recording posterior leads in all suspected inferior STEMI. This is important because: (1) larger MI territory = worse prognosis; (2) primary PCI strategy may differ (culprit vessel identification); (3) posterior MI may occasionally occur in isolation (LCx occlusion without inferior changes).

Reference: ESC (2023): ACS Guidelines