Rules + Equations



Smith-Modified Sgarbossa Rule for Diagnosis of STEMI in the Presence of Left Bundle Branch Block






Equation for Differentiating the ST Elevation (STE) of Subtle LAD Occlusion from Early Repol



It is critical to use it only when the differential is subtle LAD occlusion vs. early repol. Thus, there must be ST Elevation of at least 1 mm. If there is LVH, it may not apply. If there are features that make LAD occlusion obvious (inferior or anterior ST depression, convexity, terminal QRS distortion, Q-waves), then the equation MAY NOT apply. These kinds of cases were excluded from the study as obvious anterior STEMI.


--QTc is the computer measurement.
--RAV4 = R-wave amplitude, in mm, in lead V4.
--ST elevation (STE) is measured at 60 milliseconds after the J-point, relative to the PR segment, in millimeters.

(1.196 x STE at 60 ms after the J-point in V3 in mm) + (0.059 x computerized QTc) - (0.326 x R-wave Amplitude in V4 in mm).

A value greater than 23.4 is quite sensitive and specific for LAD occlusion.






New 4-variable Formula to Differentiate Normal Variant ST Segment Elevation in V2-V4 (Early Repolarization) from Subtle Left Anterior Descending Coronary Occlusion



It is critical to use it only when the differential is subtle LAD occlusion vs. early repol. Thus, there must be ST Elevation of at least 1 mm. If there is LVH, it may not apply. If there are features that make LAD occlusion obvious (inferior or anterior ST depression, convexity, terminal QRS distortion, Q-waves), then the equation MAY NOT apply. These kinds of cases were excluded from the study as obvious anterior STEMI.


--QTc is the computer measurement.
--RAV4 = R-wave amplitude, in mm, in lead V4.
--ST elevation (STE) is measured at 60 milliseconds after the J-point, relative to the PR segment, in millimeters.

--QRSV2 is the entire QRS amplitude in lead V2 (both R- and S-waves).

(1.062 x STE at 60 ms after the J-point in V3 in mm) + (0.052 x computerized QTc) - (0.151 x QRSV2) - (0.268 x R-wave Amplitude in V4 in mm).

A value greater than 18.2 is quite sensitive and specific for LAD occlusion.


The formula is based on this paper: http://www.sciencedirect.com/science/article/pii/S0022073617301073

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