Clinical Features of Emergency Electrocardiography in Patients With Acute Myocardial Infarction Caused by Left Main Trunk Obstruction

Abstract

tandard 12-lead electrocardiography (ECG) is the simplest examination for diagnosing acute myocardial infarctions (AMI) because generally the infarct area and the segments with ST elevation correspond well with each other; that is, for AMI of the left anterior descending artery (LAD), right coronary artery (RCA) and left circumflex artery (LCX), the specificity of ST segment elevation is more than 90%. [1][2][3][4][5] Recording the ECG in AMI is very useful for making a prompt and precise diagnosis of the culprit artery, but for left main trunk (LMT) infarction, it is sometimes difficult to obtain the characteristic ECG findings because lethal arrhythmias, such as ventricular fibrillation, or atrioventricular block with hemodynamic compromise often occurs. These unstable hemodynamics can lead to cardiac arrest before the patient arrives at the hospital and thus a poor prognosis. Consequently, it is important to diagnose LMT infarction from the ECG on admission and institute coroCirculation Journal Vol.70, May 2006 nary interventions, such as mechanical assistance by an intra-aortic balloon pump, or surgical treatment without any delay.Some research has indicated that ST-segment elevation in lead aVR may indicate LMT infarction, 5-7 but to the best of our knowledge, the ECG features in LMT infarction have not been fully described. Methods Study PopulationThe records of 2,190 patients admitted to Gifu University Hospital and its referral hospitals with AMI from 1988 to 2004 were retrospectively collected from the data bank and 140 were enrolled and divided into 4 equal groups according to the location of the culprit artery: LMT, LAD, RCA (#3 and #4 AV) and LCX (#13 and #14). All patients immediately underwent coronary angiography and the extent of stenosis was evaluated according to American Heart Association classification. Exclusion criteria were (1) prior Q-wave myocardial infarction (MI), (2) prior coronary artery bypass graft operation, and (3) inability to identify the culprit lesion as a result of severe stenosis in 2 or 3 vessels. 2,3 A lesion was considered to be the culprit when it occluded or showed severe narrowing and ulceration with or without thrombus.Standard 12-lead surface ECG (paper speed: 25 mm/s, calibration: 1 mV =10 mm) was recorded as soon as possible after admission and various parameters (heart rate (HR),

ST‐segment Elevation in Lead Augmented Vector Right may also be Caused by Diffuse Left Main Coronary Artery Vasospasm Without Fixed Stenosis

“…9 The average QRS axis in the present of LMCA obstruction also shows left axis deviation and this indicates an injury current toward the right shoulder induced by severe anterior and posterolateral ischemia. 10 So the QRS axis was horizontal (around −10 • ) during acute ischemia and more vertical after the relieving of vasospasm in our case.…”

Transient Ischemic Right Axis Deviation Tendency of the Frontal Plane QRS Axis in a Case of Inferior Myocardial Ischemia

“…[6][7][8] On admission, however, the patient was hemodynamically stable, no asynergy in the anteroseptal myocardium was observed, and there was no flow limitation in the left coronary artery. We therefore could not conclude whether the initial ECG findings could be explained by ischemia in the anteroseptal myocardium.…”

“…The present case highlights the use of ischemic QRS axis deviation tendency to indicate ischemic heart disease, including left main trunk disease. [6][7][8] Further study is needed to determine the diagnostic value of this informative ECG finding, especially in cases who originally have bundle branch block or frontal plane QRS axis deviation. In our experience, however, ischemic QRS axis deviation tendency is useful to evaluate the ischemia in a case with complete right bundle branch block, where ST-segments are hard to evaluate for ischemic changes ( Figure 5).…”

Acute Myocardial Infarction with a Left Main Trunk Lesion and Documented Lambda-like J Waves

“…It has been said that it is sometimes difficult to interpret ECG findings in patients with LMT infarctions due to the presence of bundle branch block and/or lethal arrhythmias such as VF or atrio-ventricular block. Hirano et al (18) classified the ECG features of LMT infarctions into two main groups; right bundle branch block with a remarkable left axis deviation (RBBB+ LADEV type) and ST segment elevation in leads V2-V5, I and aVL without any abnormal axis deviation (LAD type). According to the classification, our ECG was similar to the first group, an RBBB+ LADEV type.…”

“…According to the classification, our ECG was similar to the first group, an RBBB+ LADEV type. Furthermore, although it has been generally accepted that ST segment elevation in leads V1 and aVR and ST segment changes in various leads are specific features of a LMT lesion, they further summarized the specific features of LMT lesions as follows; [1] relative left axis deviation, [2] prolongation of the QTc interval, [3] prolongation of the QRS interval, [4] ST segment elevation in aVR, [5] ST segment elevation in extensive precordial leads and [6] newly emerged abnormal Q waves (18). In our case, in addition to the main culprit lesion at segment 7 in the LAD, a 75% stenotic lesion in the LMT might also have played a critical role in the genesis of the ECG changes, since the specific features as described by Hirano et al almost matched our case.…”