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      Calc Function

    • Calcs that help predict probability of a diseaseDiagnosis
    • Subcategory of 'Diagnosis' designed to be very sensitiveRule Out
    • Disease is diagnosed: prognosticate to guide treatmentPrognosis
    • Numerical inputs and outputsFormula
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    Patent Pending

    Subtle Anterior STEMI Calculator (4-Variable)

    Differentiates normal variant ST elevation (benign early repolarization) from anterior STEMI, more sensitive than 3-variable version.


    Note: this calculator replaces the older 3-variable version and is recommended by MDCalc and Dr. Stephen Smith. Before using this calculator, make sure the EKG shows ≥1 mm ST elevation (STE) in ≥1 of the precordial leads V2-V4. If it shows any one of the following, then it is NOT normal variant, and is very likely to be LAD occlusion; such cases were excluded from the study as "obvious" MI:

    • >5 mm STE.
    • Non-concave STE.
    • Inferior reciprocal changes.
    • Anterior ST depression.
    • Terminal QRS distortion in V2 or V3:
    • Q waves in any of V2 to V4.
    • Any T wave inversion from V2 to V6.
    When to Use
    Why Use

    Use in chest pain patients presenting with an EKG that is non-diagnostic but suspicious for anterior MI.

    • The authors specifically excluded patients with obvious MI. Using the calculator in cases that were excluded in the study may lead to a wrong result.

    Tips for EKG interpretation:

    • Measure STE at 60 ms in lead V3:

    • ST elevation at 60 ms after the J-point in lead V3, relative to the PR segment
      • Measure STE 60 ms (1½ small box after J point).
      • The baseline is the PR segment.
      • In this example, STE 60 = 4 mm.
    • Measure amplitude of R wave in V4:

    • In this example, RV4 = 9 mm.
    • Read the QTc: QTc is simply read from the computerized interpretation (uses Bazett's formula).
    • Both benign early repolarization and STEMI cause ST elevation. The challenge is to differentiate the two entities.
    • Some patients present with subtle EKG changes nondiagnostic for STEMI but still have 100% coronary artery occlusion and benefit from acute percutaneous transluminal coronary angioplasty (PTCA).
    • Using the equation in such cases can lead to timely cath lab activation, or more intensive evaluation.


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    Next Steps
    Creator Insights


    • Cath lab activation is appropriate in Smith-positive patients, in the proper clinical context. At the very least, it should prompt very frequent serial EKGs and echocardiography.
    • The formula is best used to identify patients with LAD occlusion initially thought to have normal variant early repolarization. 
    • If results indicate negative for STEMI, proceed with caution if STEMI was otherwise suspected.
    Content Contributors
    • Dominic Larose, MD
    About the Creator
    Dr. Stephen W. Smith
    Are you Dr. Stephen W. Smith?
    Content Contributors
    • Dominic Larose, MD