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J Korean Soc Emerg Med > Volume 19(2); 2008 > Article
Journal of The Korean Society of Emergency Medicine 2008;19(2): 171-177.
Electrocardiographic Differential Diagnosis between Anterior wall ST Elevation Myocardial Infarction and Benign Early Repolarization in Patients with Chest Pain
Young Joo Lee, Kyoung Soo Lim, Won Kim, Bum Jin Oh, Jae Ho Lee
1Department of Emergency Medicine, University of Konkuk College of Medicine, Konkuk University Hospital, Korea. brugada@naver.com
2Department of Emergency Medicine, University of Ulsan College of Medicine, Asan Medical Center, Korea.
In patients presenting at emergency department with chest pain, acute myocardial infarction is not the only cause of ST segment elevation on electrocardiography. Among the mulitple causes of noninfarction ST elevation, benign early repolarization (BER) is one of the frequent cause of confusing finding with ST elevation myocardial infarction (STEMI). The differential diagnosis between STEMI and BER is a challenging problem and definitive electrocardiographic differential diagnostic criteria are not known.
One hundred thirty-five consecutive patients with chest pain who visited an emergency medical center from January 2006 to July 2007 were prospectively recruited. Anterior wall STEMI criteria were 1) positive cardiac marker, 2) precordial lead indication of ST elevation, and 3) identification of left anterior descending artery total occlusion by primary coronary angiography in less than 90 minutes of presentation. Criteria for BER were 1) widespread precordial lead indication of ST elevation, 2) J point elevation, 3) concavity of the initial portion of ST segment, 4) notching of the J point, and 5) prominent concordant T waves.
Mean precordial leads ST segment amplitude in BER was lower than in STEMI. Among the six precordial leads, lead V3 was the most accurate lead for diagnosing STEMI (area under the curve was 0.90 [95% CI: 0.83- 0.95]). The optimal cutoff value for lead V3 ST segment elevation was 3.0 mm, and at this cutoff value, sensitivity and specificity were 62.7% and 96.4%, respectively. The new electrocardiographic index for diagnosing STEMI was JT ratio in lead V3. The area under the curve was 0.84 (95% CI: 0.74-0.92), and the optimal cutoff value was 0.25. At this cutoff value, sensitivity and specificity were 72.5% and 92.9%, respectively. With combination of these two criteria, the diagnostic algorithm consisted of two steps. The first step was lead V3 ST segment elevation >3.0 mm, and the second step was lead V3 JT ratio >0.25. At this final step of the diagnostic algorithm, the sensitivity and specificity for diagnosing STEMI were 86.3% and 90.5%, respectively.
This new diagnostic algorithm for differentiating anterior wall STEMI from BER is crucial for identifying emergency reperfusion therapy candidates among patients presenting with chest pain.
Key words: Myocardial infarction, Diagnosis, Electrocardiography
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