A 62-year-old man presents with severe chest pain. ECG shows horizontal ST depression in leads V1 through V3 with upright T waves and prominent broad R waves in V1 and V2. No lead shows ST elevation on the standard 12-lead tracing. Which of the following is the correct interpretation?

• A Anterior NSTEMI requiring only medical management
• B Reciprocal changes of a lateral STEMI involving leads I and aVL
• C Right ventricular infarction, confirmed with lead V4R
• D Posterior STEMI, confirmed by recording leads V7 to V9 ✓

Explanation

ST depression maximal in V1-V3 with dominant R waves represents reciprocal change of ST elevation from the posterior wall, usually due to left circumflex occlusion. It is treated as a STEMI equivalent and requires urgent reperfusion. Posterior extension is confirmed by ST elevation in leads V7-V9 placed on the left back. Lead V4R detects right ventricular involvement, and lateral STEMI produces elevation, not isolated precordial depression, in I and aVL.

Reference: Braunwald's Heart Disease, 12th ed.

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Written and medically reviewed by the StethoPrep medical team.