| Objective: To determine whether standard 12-lead electrocardiogram obtained on admission could identify left-circumflex (LCX) or right coronary artery(RCA) occlusion as the cause of an acute inferior myocardial infarction(AIMI) Methods: Forty-eight patients were included in this study All these patients met the following criteria: ①typical chest pain of ＞30 minutes duration, ② ST-segment elevation of ＞0 1mv in ≥2 inferior leads(Ⅱ,Ⅲ,aVF), ③ ＞2-fold increase in serum creatine kinase levels Patients with the following specific conditions were excluded from the study: ①a history of previous myocardial infarction,coronary artery bypass surgery or percutaneous transluminal coronary angioplasty,②electrocardiographic evidence of intraventricular conduction disturbance or complete atrioventricular block or left ventricular hypertrophy, ③concomitant valvular or myocardial disease ALL these patients, electrocardiogram were studied, the isoelectric line was defined as the level of the preceding P-R segment, ST-segment deviation was measured 0 06 second after the Jpoint Coronary angiography was performed emergently after the onset of symptoms or 7 to 10 days after the onset of symptoms The infarction-related artery (IRA) was determined by the following criteria: coronary artery disease resulting in total or subtotal occlusion of 1 artery supplying the inferior wall as seen on left ventriculography, or arteriographic features suggestive of acute thrombus or a ruptured plaque in 1 artery, or was assumed to be the highest stenosis if these features were absent Patients with no significant coronary stenosis,with similar stenosis in both RCA and LCX or with significant stenosis in the anterior descending artery were excluded from the study For continuous variables, the statistical significance of differences between groups was analyzed by unpaired Student-s t test The chi-square test was used to compare differences between discrete variables A p value ＜0 05 was considered statistically significant Results:Patients, characteristics:Patients were classified into the two groups according to the IRA: group RCA (n=38) and group LCX (n=10) There were no significant differences between the 2 groups in age, gender, time interval from symptom onset to electrocardiographic or clinically relevant concomitant stenosis of the left anterior descending artery Electrocardiographic findings:There were no significant differences between the two groups in the degree of ST-segment deviation and T-wave amplitude in the lead Ⅱ,aVF and V1-4 Patients having the RCA as the IRA were significantly more likely to have the following criteria: (1) higher ST-segment elevation in lead Ⅲ than in leadⅡ, P<0 01; (2) higher T-wave amplitude in lead Ⅲ than in leadⅡ, P<0 01; (3) ST-segment depression in lead I , p<0 05; (4) deeper ST-segment depression in lead aVL than in lead I, P<0 05 Patients having the LCX as the IRA were significant having the following criteria:(1) lower or equal elevation in lead Ⅲ than in leadⅡ, P<0 01; (2) lower or equal T-wave amplitude in lead Ⅲ than in leadⅡ, P<0 01; (3) an isoelectric or elevated ST-segment in lead I with any ST-segment elevation in 1 or more leads(aVL, V5, V6), P<0 01 Moreover, we have an interesting finding The greater the value of the arithmetic sum of ST-segment between the inferior leads and the precordial leads V2, V3, the closer the diagnosis of RCA occlusion And inversely, as the value of this sum decrease, the closer we are to diagnosing LCX occlusion All the predictive criteria were evaluated by stepwise logistic regression analysis By logistic regression analysis, the only independent prognostic criteria for IRA in AIMI was the STⅢ/STⅡ( P < 0 05 ) Conclusion:Our results suggest that the compartion of ST-segment deviation in lead Ⅱ,Ⅲ was the the independent prognostic criteria for IRA in AIMI This criteria is easily obtained from the standard 12-lead electrocardiogram...
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