| Background and ObjectWith the aging population, stress in work and life and the effects of risk factors such as hypertension, diabetes, abnormal blood lipid, smoking, obesity and less physical activities, the incidence of acute myocardial infarction(AMI) is increasing year to year. So many cardiovascular internists have paid significant attention to AMI. Correct diagnosis and treatment in a timely manner are important to rescue and improve the prognosis of patients.As a noninvasive, simple, immediate and widely used clinical assistant examination, electrocardiogram(ECG) plays an important role in diagnosis and treatment. It is far from enough to recognize the ECG of AMI simply for a cardiovascular internist. With different illness conditions caused by coronary artery occlusion and different clinical prognosis, ECG can show difference even in the same part of myocardial infarction. On average, the right coronary artery (RCA) supplies 70% of blood flow to the inferior wall myocardium,20% of blood flow comes from both RCA and left circumflex artery (LCX),10% of blood flow comes from LCX independently, and rarely the left anterior descending artery (LAD) is long wrapped around the apex to supply blood to inferior wall. The acute inferior wall ST-segment elevation myocardial infarction(AI-STEMI) usually indicates occlusion of RCA, less often LCX and rarely LAD may be the cause. The different coronary artery occlusion or the different segments of the same coronary artery occlusion can present the similar or various ECG characteristic. It is difficult to predict the infarct-related artery(IRA) in AI-STEMI by the changes of ECG, and further research of its potential clinical values is needed.The study is designed to discuss the ECG criteria for predicting infarct-related artery in acute inferior wall ST-segment elevation myocardial infarction and intend to work out a new sequential ECG algorithm.MethodThis clinical research was carried on retrospectively in a single center.367 continue cases diagnosed with AI-STEMI were collected from the First Affiliated Hospital of Sun Yat-sen University between September 2010 and September 2014 and 186 patients including 153 men and 33 women were studied eventually. The average age was 61.6±12.3 years old. All patients underwent coronary angiography were divided into 4 groups:RCA occlusion group(134 cases), LCX occlusion group(27 cases), LAD occlusion group(17 cases) and normal group(8 cases). The ST-segment deviation on ECG and the clinical features were recorded and analyzed.Electrocardiographic evaluation:The presenting ECGs were recorded at a paper speed of 25mm/s and a voltage of 10 mm/mv. The ST-segment deviation was measured at 0.08 seconds after the J point. The TP-segment was used as the isoelectric line unless tachycardia caused fusion of the T and P waves, in which case the PR-segment was used. ECGs were analyzed by specialist who were blinded to the angiographic results.Angiographic evaluation:According to the result of coronary angiography (CAG), the dominance, occluded location, number of lesion vessels, degree of stenosis, vascular malformation,collateral circulation and myocardial bridge were recorded by an experienced angiographer. Coronary artery stenosis of more than 70% were considered significant lesion. The IRA was regarded as the total or subtotal occlusion or thrombus shadow can be seen.Statistical methods:Using SPSS 13.0 software(SPSS Inc, USA) for statistics analysis. The measurement data which satisfies normal distributions was presented as mean±tandard deviation(x±s), meanwhile t-test was applied to the comparison between 2 groups and ANOVA(analysis of variance) was applied to the comparison among multiple groups. The measurement data was represented by frequency and Chi-squared test was used for comparisons between groups. When frequency was less than 5, Fisher’s exact test probability was token. All test of significance were 2-tailed, and P<0.05 were considered statistically significant. Diagnostic test fourfold table and calculation of sensitivity, specificity, positive predictive value, negative predictive value and Youden index were carried out for the data which was significative for the difference examination.Applied R statis software to build the decision tree.Results1.186 patients were enrolled. According to the results of CAG, it was devided into 4 groups:RCA occlusion group(134 cases), LCX occlusion group(27 cases), LAD occlusion group(17 cases) and normal group(8 cases). The normal coronary artery was indicated to no stenosis can be seen and it might be caused by thrombus autolysis, transient platelet aggregation or the persistent coronary artery spasm.2. Male, older, smoking, hypertension and diabetes are the risk factors of cardiovascular disease. The incidence of male is significantly higher than female (82.3% vs 17.7%). The old patients occupied the most and with the aging the number of coronary artery lesions are increasing gradually. The diabetes patients tend to have two or triple-vessel lesions. In our study, the value of Body Mass Index(BMI) and low density lipoproten-cholesterol(LDL-C) have no significant greater than the normal level, it may be related to the thinner body type and light diet in guangdong procince.3.The RCA occlusion is the most common in AI-STEMI. There is no statistical si gnificance about the difference of Killip classification among RCA, LCX and LAD oc clusion groups(P>0.05). The distribution of Coronary artery dominance is right dominant based(88.7%), next is left dominant(8.6%), the last is balanced dominan t (2.7%). Most of LCX occlusion group are right dominant(66.7%) and LCX occlusio n is the most common among left dominant patients.4. ECG criteria for RCA occlusion:(1)STⅢ↑>STⅡ↑; (2)STaVL↓ or STaVL↓> STⅠ↓; (3)STaVR(?)or↓< 1.0mm; (4)STV1↑and STV2↓(proximal to RCA); (5)STⅢ↑> STV6↑and(or)STV6(?),↓; (6)STV4R↑≥1.0mm or STV3R-V5R↑≥0.5mm(proximal to RCA); (7)STV3↓/STⅢ↑< 0.5(proximal to RCA); (8)0.5≤STV3↓/STⅢ↑≤1.2(distal to RCA). Among these ECG criteria, the criterion of STaVL↓ has the highest sensitivity(99.3%) and negative predictive value(93.3%); the criterion of STV3↓/STⅢ↑≤1.2 has the highest specificity(90.9%) and positive predictive value(93.8%); the highest Youden’s index of criterion for RCA occlusion is STV3R-V5R↑≥0.5mm(161.4%).5. ECG criteria for LCX occlusion:(1) STⅢ↑/STⅡ↑≤1; (2) STⅠ,aVL↑or(?) (3) STaVR↓≥1.0mm; (4) STV5↑or STV6↑; (5) STⅢ↑≤STV6↑; (7) STV7-V9↑; (8) STV3R-V5R(?) or↓; (9) STV3↓/STⅢ↑>1.2. All of these ECG criteria have lower sensitivity. The criterion of STV3↓/STⅢ↑> 1.2 has the highest specificity(92.7%). The highest Youden’s index of criterion for LCX occlusion is STV3R-V5R(?)or↓(158.4%).6. ECG criteria for RCA occlusion in patients with right coronary dominant:the highest sensitivity is the criterion of STaVL↓, next is criterion of STmT>STV6↑.And both of the above ECG criteria have higher specificity than the value of before grouping(55.6% vs 31.8%,50% vs 40.9%). The highest Youden’s index is the criterion of STV3R-V5R↑≥0.5mm, and it’s higher than before grouping(168.4% vs 161.4%). Besides the criterion of STⅢ↑≤STⅡ↑,others critera for LCX occlusion have the sensitivity and Youden’s index which goes from high to low:right coronary dominant, before grouping, left coronary dominant.7.The more number of coronary artery lesions, the higher Killip classification (r=0.291). The sensitivity and Youden’s index of partly criteria for RCA occlusion in patients with single-vessel disease is higher than before grouping. But there is no significance about the number of vessel disease have effect on the criteria for LCX occlusion.8.Decision tree about ECG criteria for predicting IRA, which included 3 steps. In the first step of the new algorithm, calculate the deviation in lead V3R～V5R respectively, the ST-segment elevation are equal or greater than 0.5mm (STV3R-V5R↑≥0.5mm) indicated RCA as the IRA(96.4%), but in all other cases, a second step is needed. Compare ST-segment elevation in lead Ⅱ with lead Ⅲ. The RCA is predicted as the IRA if the ST-segment elevation in lead Ⅲ greater than in lead Ⅱ (STⅢ↑>STⅡ↑,77.3%). Otherwise, a third step is introduced:LCX is predicted as IRA if the ST-segment is depressed equal or greater than 1.0mm in lead aVR (STaVR↓> 1.0mm,100%); if not, it likely to be RCA occlusion(64.3%).Conclusion1.ECG have an important value for predicting the infarction related-artery in acute inferior wall ST-segment elevation myocardial infarction.2.The most valuable ECG criterion for RCA occlusion is STV3R-V5R↑≥0.5mm, the next is STⅢ↑>STⅡ↑. The most valuable ECG criterion for LCX occlusion is STV3R-V5R↑(?)or↓, the next is STⅢ↑≤STⅡ↑.So, electrocardiographic assessment of right ventricular precordial leads(V3R～V5R) should be routinely performed in all comers with acute inferior wall ST-segment elevation myocardial infarction.3. All the effective ECG criteria for predicting IRA are applied to the patients with right coronary dominant, and the left coronary dominant can weaken the value of criteria for predicting IRA in acute inferior wall ST-segment elevation myocardial infarction to some extent.4. Mutil-vessel disease can weaken the value of criteria for RCA occlusion in acute inferior wall ST-segment elevation myocardial infarction, but there is no significance about the number of vessel disease have effect on the criteria for LCX occlusion. |
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