Electrocardiographic differentiation of early repolarization from subtle anterior ST-segment elevation myocardial infarction.
Anterior ST-segment elevation myocardial infarction (STEMI) can be difficult to differentiate from early repolarization on the ECG. We hypothesize that, in addition to ST-segment elevation, T-wave amplitude to R-wave amplitude ratio (T-wave amplitude(avg)/R-wave amplitude(avg)), and R-wave amplitude in leads V2 to V4, computerized corrected QT interval (QTc) and upward concavity would help to differentiate the 2. We seek to determine which ECG measurements best distinguish STEMI versus early repolarization.
This was a retrospective study of patients with anterior STEMI (2003 to 2009) and early repolarization (2003 to 2005) at 2 urban hospitals, one of which (Minneapolis Heart Institute) receives 500 STEMI patients per year. We compared the ECGs of nonobvious ("subtle") anterior STEMI with emergency department noncardiac chest pain patients with early repolarization. ST-segment elevation at the J point and 60 ms after the J point, T-wave amplitude, R-wave amplitude, QTc, upward concavity, J-wave notching, and T waves in V1 and V6 were measured. Multivariate logistic regression modeling was used to identify ECG measurements independently predictive of STEMI versus early repolarization in a derivation group and was subsequently validated in a separate group.
Of 355 anterior STEMIs identified, 143 were nonobvious, or subtle, compared with 171 early repolarization ECGs. ST-segment elevation was greater, R-wave amplitude lower, and T-wave amplitude(avg)/R-wave amplitude(avg) higher in leads V2 to V4 with STEMI versus early repolarization. Computerized QTc was also significantly longer with STEMI versus early repolarization. T-wave amplitude did not differ significantly between the groups, such that the T-wave amplitude(avg)/R-wave amplitude(avg) difference was entirely due to the difference in R-wave amplitude. An ECG criterion based on 3 measurements (R-wave amplitude in lead V4, ST-segment elevation 60 ms after J-point in lead V3, and QTc) was derived and validated for differentiating STEMI versus early repolarization, such that if the value of the equation ([1.196 x ST-segment elevation 60 ms after the J point in lead V3 in mm]+[0.059 x QTc in ms]-[0.326 x R-wave amplitude in lead V4 in mm]) is greater than 23.4 predicted STEMI and if less than or equal to 23.4, it predicted early repolarization in both groups, with overall sensitivity, specificity, and accuracy of 86% (95% confidence interval [CI] 79, 91), 91% (95% CI 85, 95), and 88% (95% CI 84, 92), respectively, with positive likelihood ratio 9.2 (95% CI 8.5 to 10) and negative likelihood ratio 0.1 (95% CI 0.08 to 0.3). Upward concavity, upright T wave in V1 or T wave, in V1 greater than T wave in V6, and J-wave notching did not provide important information.
R-wave amplitude is lower, ST-segment elevation greater, and QTc longer for subtle anterior STEMI versus early repolarization. In combination with other clinical data, this derived and validated ECG equation could be an important adjunct in the diagnosis of anterior STEMI.
Smith SW
，Khalil A
，Henry TD
，Rosas M
，Chang RJ
，Heller K
，Scharrer E
，Ghorashi M
，Pearce LA
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Electrocardiographic ST segment elevation: a comparison of AMI and non-AMI ECG syndromes.
Chest pain (CP) patients presenting to the ED may manifest electrocardiographic ST segment elevation (STE). AMI (acute myocardial infarction) is a less frequent cause of such abnormality and one of many patterns responsible for ST segment elevation in ED CP patients. We performed a retrospective comparative review of the electrocardiographic features of various STE syndromes, focusing on differences between AMI and non-AMI syndromes. The electrocardiograms (ECGs) of consecutive ED adult CP patients (with 3 serial troponin I determinations) were interpreted by 3 attending emergency physicians. These ECGs with STE represented the study population used for analysis. Various electrocardiographic features such as STE, ST segment depression (STD), STE morphology, anatomic distribution of STE, and the number of leads with STE were recorded; derived values such as total STE, total ST segment deviation, and average STE per lead were calculated. Interobserver reliability concerning STE morphology was determined. AMI was diagnosed by abnormal serum troponin I values (>0.1 mg/dL) followed by a rise and fall of the serum marker; STE diagnoses of non-AMI causes were determined by medical record review. Five hundred ninety-nine CP patients were entered in the study with 212 (35%) individuals showing STE, 55 (26%) with electrocardiographic AMI and 157 (74%) with non-AMI electrocardiographic syndromes. Anatomic location within the AMI group included 32 inferior and inferior variants, 18 anterior and anterior variants, and 5 lateral; non-AMI anatomic locations included 56 inferior and inferior variants, 98 anterior and anterior variants, and 3 lateral; anterior STE occurred significantly more often in non-AMI syndromes. Total STE was 15.3 mm in AMI patients and 7.4 mm in non-AMI patients (P =.0004). The number of leads with STE was not significantly different between the two groups, 3.4 mm in AMI and 4.1 in non-AMI syndromes. ST segment elevation per lead was not significantly different in the 2 groups, 4.4 mm in AMI versus 1.8 mm in non-AMI syndromes. Total ST segment deviation (sum of STE and STD) was significantly greater in AMI syndromes, 17.8 mm in AMI compared with 10.5 mm in non-AMI syndromes (P =.00009). The presence of STD occurred at statistically similar rates in both groups. The morphology of the STE occurred in significantly different rates between AMI and non-AMI patterns, concave more often in non-AMI patterns (P <.00001) and nonconcave more often in AMI (P <.00001). Non-AMI causes of STE account for the majority of electrocardiographic syndromes encountered in ED chest pain patients. These findings alone are not adequate to determine the electrocardiographic cause of the ST segment elevation in chest pain patients. When determining AMI versus non-AMI with the ECG, these various findings should be used in the consideration of the overall clinical picture (history, examination, and electrocardiogram) in chest pain patients with ST segment elevation.
Brady WJ
，Perron AD
，Ullman EA
，Syverud SA
，Holstege C
，Riviello R
，Ghammaghami C
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《AMERICAN JOURNAL OF EMERGENCY MEDICINE》
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