A 66-year-old man with known left bundle branch block presents with 2 hours of typical chest pain. ECG shows ST elevation of 2 mm in leads II, III, and aVF directed the same way as the main QRS deflection. Which feature of this ECG carries the highest diagnostic weight for acute myocardial infarction?

• A New onset atrial fibrillation with rapid ventricular response
• B Discordant ST elevation exceeding 25 percent of the depth of the preceding S wave
• C Concordant ST depression of 1 mm in lead V1 to V3
• D Concordant ST elevation of at least 1 mm in a lead with a positive QRS complex ✓

Explanation

The Sgarbossa criteria diagnose MI in the presence of LBBB. Concordant ST elevation of 1 mm or more in any lead scores 5 points and is the single highest-weighted criterion because the ST vector normally opposes the QRS in bundle branch block. Discordant elevation of 25 percent of the S wave scores only 2 points, and concordant ST depression in V1 to V3 scores 3 points. D score of 3 or more supports urgent reperfusion.

Reference: Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine, 12th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.