A 58-year-old man presents with chest pain. ECG shows horizontal ST depression in V1 to V3 with dominant R waves in V2 and prominent upright T waves in the same leads. To confirm the diagnosis, additional ECG leads should be recorded over which surface?
- A Right precordium, leads V3R and V4R
- B High right parasternal area, lead V1 two intercostal spaces above
- C Posterior thorax, leads V7 to V9 ✓
- D Left mid-axillary line at the fifth intercostal space only
Correct answer: C. Posterior thorax, leads V7 to V9
Explanation
Isolated posterior STEMI produces anterior ST depression with tall R waves and upright T waves in V1-V3, an ECG mirror image of posterior ST elevation. The diagnosis is confirmed by recording posterior leads V7-V9, where ST elevation of 0.5 mm or more establishes the diagnosis. Right-sided leads V3R-V4R detect right ventricular involvement, which is a separate entity associated with inferior STEMI, not isolated posterior infarction.
Reference: Ganong's Review of Medical Physiology, 27th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.