The Value Of Electrocardiogram In Predicting The Infarction Related Artery In Inferior Wall Acute Myocardial Infarction

Objective:To determine whether 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:Fifty-four patients were included in this study.All these patients met the following criteria:①ypical chest pain of>30 minutes duration,②ST-segment elevation of≥0.1mv in≥2 inferior leads(Ⅱ,ⅢaVF),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 percuta-neous transluminal coronary angioplasty,②electrocardiographic evidence of intraventricular conduction disturbance or complete atrioventricular block or left ventricular hypertrophy,③concomitant valvular or myocardial disease.In 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 at 0.08 second after the J point. 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 was deleted by coronary angiography which features suggested 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 or with severe 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 Students t test.The chi-square test was used to compare differences between discrete variables. Ap value<0.01 was considered statistically significant. The Sensitivity(Se), Specificity(Sp), Positive predicitive value(PPV), Negative predicitive value(NPV) were analysed.Results:Patients were classified into the two groups according to the IRA:group RCA(n=41)and group LCX(n=13).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: Patients with inferior wall myocardial infarction, the ECG were significantly more likely to have the following changes:(1) ST-segment depression in leadⅠand lead aVL>0.1mv, RCA group 38 cases(92.68%), LCX group 3 cases(23.08%), P<0.01;(2) deeper ST-segment depression in lead aVL than in lead I, RCA group 34 cases(82.93%), LCX group 2 cases(15.38%), P<0.01;(3)higher ST-segment elevation in lead III than in leadⅡ(STⅢ↑T>STⅡ↑), RCA group 36 cases(87.80%), LCX group 1 case(7.69%), P<0.01;(4)STaVL depression>0.1mv and SavL/RavL>1/3,RCA group 36 cases(87.80%), LCX group 1 case(7.69%), P<0.01;(5)STV4R elevation≥0.1mv, RCA group 16 cases(39.02%), LCX group 0 case, P<0.01;(6)STaV↓>ST↓+STⅢ↑>STⅡ↑,RCA group 32 cases(78.05%), LCX group 0 case, P<0.01;(7)STaVL↓>STⅠ↓+SaVL/RaVL>1/3, RCA group 34 cases(82.93%), LCX group 1 case(7.69%), P<0.01;(8)STaVL↓>STⅠ↓+SaVL/ RaVL>1/3+STV4R↑>0.1mv, RCA group 15 cases(36.59%), LCX group 0 case, P<0.01.Patients having the LCX as the IRA were significant having the following criteria:(1)STⅠ,STavL depression< 0.1mv,RCA group 2 cases (4.88%), LCX group 8 cases(61.54%), P<0.01; (2) higher ST-segment elevation in leadⅡthan in leadⅢ(STⅡ↑>STⅢ↑)5 RCA group 5 cases (12.20%), LCX group 12 cases(92.31%), P<0.01 (3)SavL/RaVL<1/3, RCA group 0 case, LCX group 10 cases(76.92%), P<0.01.All the predictive criteria were evaluated by X2 test.Patients having the RCA as the IRA in AIMI:(1)ST-segment depression in leadⅠand lead aVL, Se92.68%, Sp 76.92%,PPV92.68%,NPV76.92%;(2)deeper ST-segment depression in lead aVL than in leadⅠ, Se82.93%,Sp84.62%,PPV94.44%, NPV61.11%; (3) higher ST-segment elevation in lead III than in leadⅢ(STⅢ↑T>STⅡ↑), Se87.80％,Sp92.31％,PPV97.30％,NPV70.59％；(4)STaVL depression≥0.1mv and SaVL／RaVL>1／3, Se87.80％, Sp92.31％, PPV97.30％, NPV70.59％；(5)STV4R elevation≥0.1 mv,Se39.02％,Sp100％,PPV 100％,NPV34.21％；(6)STaVL↓>STⅠ↓+STⅢ↑>STⅡ↑,Se78.05％,Sp100％,PPV100％,NPV59.09％；(7)STaVL↓>STⅠ↓+SaVL／RaVL>1／3, Se82.93％, Sp92.31％, PPV97.14％, NPV63.16％；(8)STaVL↓>STⅠ↓+SaVL／RaVL>1／3+STV4R↑≥0.1mv,Se36.59％, Sp100％,PPV100％,NPV33.33％.Patients having the LCX as the IRA in AIMI:(1)ST I,STaVL depression<0.1mv,Se72.73％,Sp95.12％,PPV80％, NPV92.86％；(2)higher ST-segment elevation in lead II than in leadⅢ(STⅡ↑>STⅢ↑),Se92.31％,Sp87.80％,PPV70.59％,NPV97.30％；(3)SaVL／RaVL<1／3,Se76.92％,Sp100％,PPV100％,NPV93.18％.Conclusion:STⅠ↓and STaVL↓,STaVL↓>STⅠ↓,STⅢ↑>STⅡ↑,STaVL↓≥0.1mv and SaVL／RaVL>1／3.STV4R↑≥0.1 mv.STaVL↓>STⅠ↓+STⅢ↑>STⅡ↑. STaVL↓>STⅠ↓+SaVL／RaVL>1／3. STaVL↓>STⅠ↓+SaVL／RaVL>1／3+STV4R↑≥0.1mv means RCA as the cause of AIMI；STⅠ↓<0.1mv and STaVL↓<0.1mv. STⅢ↑