Abstract 14455: A New 4-Variable Formula to Differentiate Early Repolarization From Subtle Left Anterior Descending Coronary Occlusion -- Adding QRS Amplitude of V2 Improves the Model
Introduction: Precordial normal variant ST elevation (STE), or “early repolarization” (ER), may be difficult to differentiate from subtle ischemic STE due to LAD occlusion. We previously derived and validated a logistic regression tool that was far superior to STE alone for differentiating the two on the ECG. The tool uses R-wave amplitude in lead V4 (RAV4), ST elevation at 60 milliseconds after the J-point in lead V3 (STE60V3) and the computerized Bazett-corrected QT interval (QTc). The 3-variable formula is: 1.196 x STE60V3 + 0.059 x QTc – 0.326 x RAV4 with a cutpoint of 23.4.
Hypothesis: Adding QRS voltage in V2 (QRSV2) would improve the accuracy of the formula.
Methods: Of 355 consecutive LAD occlusions, non-obvious (subtle) ones were studied and “obvious” ones were excluded: one straight or convex ST segment in V2-V6, any ST depression, Q-waves, “terminal QRS distortion,” or any ST elevation > 5 mm. ER group were emergency department patients with chest pain who ruled out for acute MI by serial troponins, had a cardiologist ECG read of “ER,” and had at least 1 mm of STE in V2 and V3. QRSV2 was blindly measured in all ECGs. A 4-variable formula was derived to more accurately classify MI and ER and optimize area under the curve (AUC).
Results: There were 143 subtle LAD occlusions and 171 ER. A low QRSV2 added diagnostic sensitivity. The derived 4-variable formula is: 0.052*QTc - 0.151*QRSV2 - 0.268*RV4 + 1.062*STE60V3. The 3-variable formula had an AUC of 0.9538 vs. 0.9686 for the 4-variable formula (p = 0.0092). The 3-variable formula, at a specificity of 87.7% (cutpoint 23.4), had a sensitivity of 87.4%, identifying 125 of 143 subtle LAD occlusions; at the same specificity, the sensitivity of the new formula is 92.3%, identifying 132 of 143 LAD occlusion, or an additional 7 cases. The cutpoint with the highest accuracy (92.0%) was at a cutoff value ≥ 18.2, with 91.6% sensitivity, 93.6% specificity, and a positive and negative likelihood ratio of 16.9 and 0.12.
Conclusion: On the ECG, a 4-variable formula which adds QRSV2 differentiates subtle LAD occlusion from ER better than the 3-variable formula. At a value ≥ 18.2, the formula (0.052*QTc - 0.151*QRSV2 - 0.268*RV4 + 1.062*STE60V3) was very accurate, sensitive, and specific, with excellent positive and negative likelihood ratios.
Author Disclosures: S.W. Smith: None. A. Adil: None. F. Kazmi: None. B.E. Driver: None.
- © 2016 by American Heart Association, Inc.