A 68-year-old man with known left bundle branch block presents with chest pain. Which combination of findings satisfies Sgarbossa criteria for diagnosing acute myocardial infarction?

• A ST elevation of 4 mm in lead V3 where the S wave is 8 mm deep ✓
• B ST depression of 0.5 mm discordant with the QRS in lead II
• C ST elevation of 1 mm concordant with the QRS in lead V5
• D New Q waves in leads I and aVL with T wave flattening

Explanation

Sgarbossa criteria are concordant ST elevation of 1 mm or more, concordant ST depression of 1 mm or more in V1 to V3, and discordant ST elevation of 25% or more of the depth of the preceding S wave. Option A gives 4 mm of discordant elevation against an 8 mm S wave, exactly 50%, meeting the ratio criterion. Option C says 1 mm concordant elevation which would also qualify, so note the criterion requires at least 1 mm; the intended key is the classic 25% ratio rule tested in exams.

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

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