A 66-year-old woman with known left bundle branch block presents with 2 hours of chest pain. Which ECG finding among the following satisfies the modified Sgarbossa criteria and supports a diagnosis of acute myocardial infarction?
- A ST depression of 0.5 mm in lead V2
- B ST elevation of 1 mm concordant with the QRS in lead II ✓
- C ST elevation of 1 mm discordant with the QRS in lead V3
- D New Q waves in leads I and aVL
Correct answer: B. ST elevation of 1 mm concordant with the QRS in lead II
Explanation
The modified Sgarbossa criteria are: ST elevation of at least 1 mm concordant with the QRS complex, concordant ST depression of at least 1 mm in leads V1-V3, and discordant ST elevation with an ST/S ratio of 0.25 or more. Concordant changes carry the highest specificity because they reflect true injury current rather than secondary repolarization abnormality. B discordant elevation of only 1 mm fails the ratio requirement, and Q waves cannot be assessed reliably in LBBB.
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.