When to use: ST elevation ≥ 1 mm in any lead from V2 to V4 and a clinical picture consistent with ACS. Do not use if there are obvious signs of anterior MI. Do not use the QTc if HR < 60. Do not use if LVH is present.
A tool to support learning and decision-making. The result does not replace clinical evaluation of the patient.
About: 4-variable formula
Subtle ST elevation in V2–V4 may be a normal variant (the so-called male pattern or early repolarization) or the first sign of left anterior descending artery occlusion. The 4-variable formula combines four ECG measurements to tell these apart.
It updated the 3-variable formula by adding QRS amplitude in V2.
How to use
Confirm the prerequisites: ST elevation ≥ 1 mm in V2, V3 or V4 and a clinical picture consistent with acute coronary syndrome.
Enter the Bazett QTc, the QRS amplitude in V2, the ST elevation 60 ms after the J point in V3 and the R-wave amplitude in V4.
Result < 18.2: favors a normal variant, without ruling out ischemia when the clinical picture is suggestive.
Limitations
Do not use it if there are obvious signs of anterior MI, if the heart rate is below 60 bpm (the QTc is distorted) or if there is left ventricular hypertrophy. Serial ECGs remain essential.
References
Driver BE, Khalil A, Henry T, et al. A new 4-variable formula to differentiate normal variant ST segment elevation in V2–V4 (early repolarization) from subtle left anterior descending coronary occlusion — adding QRS amplitude of V2 improves the model. J Electrocardiol. 2017;50(5):561–9.
Smith SW, Khalil A, Henry TD, et al. Electrocardiographic differentiation of early repolarization from subtle anterior ST-segment elevation myocardial infarction. Ann Emerg Med. 2012;60(1):45–56.
