Clinical Implication Of ST Segment Depression In AVR&aVL In Patients With Acute Inferior Wall Myocardial Infarction

Objective:The aim of this study was to determine ECG parameters, assess the role of ST segment depression in the leads aVL and aVR to locate the culprit artery accurately as compared to coronary angiography and other parameters like Troponin Ⅰ, CPK MB and ejection fraction in acute inferior myocardial infarction.Background:Inferior wall acute myocardial infarction (AMI) characteristically causes ST-segment elevation in some or all of the inferior leads (Ⅱ, Ⅲ, and aVF). During inferior acute myocardial infarction, ST-segment depression often occurs in leads aVL, which represents mirror image, but for lead aVR its clinical implications remain unclear. As ECG [electrocardiogram] continues to be the most frequently ordered cardiac test; of the electrocardiographic leads, aVR has traditionally received less attention in clinical evaluation of the ECG. The present study discusses instances with pictorial examples in which lead aVR provides valuable clinical information and makes a case for close attention being paid to this forgotten lead. Therefore, the presumption prediction of a culprit artery based on the electrocardiographic recorded at the time of admission is of clinical importance to predict the outcome of patients. Without any doubt, the electrocardiogram (ECG) is the most useful, feasible, cheap and universally available tool for the initial evaluation, early risk stratification, triage, and guidance of therapy in patients with a suspicion of an acute ischemic event. More profound ST-segment changes or T wave inversion involving multiple leads and territories is associated with a greater degree of myocardial ischemia and a worse prognosis. The current guidelines for the ECG diagnosis of acute myocardial infarction require at least≥1mm (≥0.1mV) of ST segment elevation in the limb leads, and at least≥2mm elevation in the precordial leads. These elevations must be present in an anatomically contiguous leads, leads Ⅰ, aVL, V5, V6correspond to the lateral wall; V1-V4correspond to the anterior wall; and Ⅱ, Ⅲ, aVF corresponds to the inferior wall. Beside lead aVR which is usually not the preferred lead to diagnose myocardial infarction in clinical settings, all leads in ECG analysis are considered for recognition of MI and localisation of STEMI.The ST elevation and depression is measured60ms from the J point.Methods:We prospectively analyzed368patients having an acute inferior wall MI, admitted and underwent coronary angiography in the cardiovascular department of the first hospital of Norman Bethune College of medicine under Jilin University from January1st2014to January7th2015. Only159patients (male104and female55) met our inclusion criteria of chest pain for≥30minutes before hospital admission. Elevation of Troponin I (>0.01ng/ml) and creatinine kinase (CK-MB) greater than twice the upper limit.(Normal:0-3.5ng/ml). The ECG shows ST segment≥>0.1mV (lmm) in at least2of3inferior leads (Ⅱ, Ⅲ, aVF). Coronary angiography showing total occlusion or critical stenosis>70%in single vessel either RCA or LCX. Whereas, exclusion criteria includes lack of ST elevation≥0.1mV (1mm) in the inferior leads (II, III, aVF), previous history of acute myocardial infarction, coronary artery bypass surgery or percutaneous coronary intervention prior to current hospitalization, evidence of recent left bundle branch block or left ventricular hypertrophy on ECG, and significant stenosis in both LCX and RCA or triple vessel disease so that a single infarct related artery could not be defined.Results:A total of159patients with a first inferior wall AMI (male104and female55) were included in the study. Patients were divided according to the presence (n-69) and absence (n-90) of ST depression of≥1mm in leads aVR and aVL on admission. Patients with ST depression in leads aVR and aVL were further subdivided into the2groups according to the degree of ST depression in lead aVL and in lead aVR. ST depression in lead aVL greater than in aVR (n-46) and ST depression in lead aVL equal to or less than in aVR (n-23). There were no significant differences between3groups in baseline clinical characteristics and prevalence of risk factors. The mean age for No ST-depression in leads aVL and aVR, ST depression in leads aVL and aVR with ST depression in lead aVL greater than in aVR, and ST depression in leads aVL and aVR with ST depression in lead aVL equal to or less than in aVR are59.78±11.807,58.65±10.429, and59.30±13.461respectively. ST elevation in leads II, III and aVF with ST depression in lead aVR and aVL was more common in more male than in female (72%vs28%). In the ECG of ST elevation in the inferior leads (II, III and aVF), ST elevation in leads III>II was highly associated with ST depression in aVL and aVR with ST depression in lead aVL>aVR than in ST depression in lead aVL and aVR with ST depression in lead aVL<aVR (98%vs22%)(p=<0.0001), whereas ST elevation in lead Ⅱ>Ⅲ was more associated with ST depression in lead aVL and aVR with ST depression in lead aVL≤aVR (78%vs2%)(P=<0.0001). There was no much difference in KILIP Ⅰ and ejection fraction between three groups. Among69patients with ST depression in leads aVL and aVR, the infarct related artery was right coronary artery in49patients (71%) and left circumflex artery in20(29%). In No ST depression in leads aVL and aVR and ST depression in leads aVL and aVR with ST depression in lead aVL> aVR were strongly associated with RCA occlusion;87%and98%respectively. Whereas, ST depression in leads aVL and aVR with ST depression in lead aVL≤aVR was associated with LCX,83%occlusion. TIMI0coronary flow was found in107patients (67%). No differences were found between three groups regarding TIMI0flow score. The right coronary artery (RCA) disease was found significantly higher proportion in ST depression in leads aVL and aVR with ST depression in lead aVL> aVR (n-45;98%) than in ST depression in leads aVL and aVR with ST depression in lead aVL≤aVR (n-4;17%)(p=0.0001), whereas the left circumflex artery (LCX) disease was found very frequently in ST depression in leads aVL and aVR with ST depression in aVL≤aVR (n-19;83%) than in ST depression in leads aVL and aVR with ST depression in lead aVL>aVR (n-1;2%)(p-0.0001).In our study, out of159patients;57%(n-90) had no ST depression in leads aVL and aVR,43%(n-69) patients had ST depression in leads aVL and aVR in relation to ST elevation in the inferior leads (II, III and aVF). Out of69patients,67%(n-46) had ST depression in leads aVL and aVR with ST depression in lead aVL> aVR, whereas33%(n-23) had ST depression in leads aVL and aVR with ST depression in lead aVL<aVR. According to coronary angiography findings the sensitivity, specificity and positive predictive value and negative predictive value in ST depression in leads aVL and aVR with ST depression in lead aVL>aVR to predict right coronary artery (RCA) as a culprit artery are98%,82%,92%and95%respectively. And, the sensitivity, specificity, positive predictive value and negative predictive value in ST depression in leads aVL and aVR with ST depression in lead aVL≤aVR to predict left circumflex artery (LCX) as a culprit artery are83%,98%,95%and92%respectively.The ST segment elevation of≥1mm (>0.1mv) in inferior leads Ⅱ, Ⅲ and aVF is significant to make the diagnosis of acute inferior wall STEMI. The ratio of ST elevation in leads Ⅱ and Ⅲ has a clinical implication to predict the culprit artery. In our study, ST elevation in lead Ⅲ≤Ⅱ was seen in31(19%) patients, and in lead III>II in128(81%) patients. Right coronary artery (RCA) was frequently involved in ECG with ST elevation in lead III>II (n-127;99%)(p-0.0001) and left circumflex artery (LCX) in lead III<II (n-29;94%)(p-0.0001). The sensitivity, specificity, positive predictive value and negative predictive value for ST elevation in lead Ⅲ≤Ⅱ to predict LCX as a culprit artery are94%,99%,97%and98%, respectively, whereas sensitivity, specificity, positive predictive value and negative predictive value for ST elevation in lead Ⅲ>Ⅱ to predict RCA as a culprit artery are99%,94%,98%and97%respectively.ConclusionIn conclusion, ST segment depression in leads aVL and aVR suggests a greater risk area in-patient with acute inferior wall myocardial infarction. The right coronary artery occlusion was most common in ST depression in leads aVL and aVR with ST depression in lead aVL>aVR and the left circumflex artery occlusion in ST depression in leads aVL and aVR with ST depression in lead aVL≤aVR. And, while evaluating risk in an acute inferior wall myocardial infarction, therefore we should also look for ST depression in leads aVL and aVR, as it signify a larger perfusion territory and demands for more aggressive reperfusion therapy.