INTRODUCTION

At the present stage of providing medical care to patients with ACS, the importance of the electrocardiographic (ECG) research method can hardly be underestimated. In the literature ECG variants of myocardial infarction (MI) are widely covered. Despite this, the topical diagnosis of MI and the determination of an infarct-associated artery on the basis of interpretation of changes in the terminal part of the ventricular complex on ECG, which are of a nonspecific nature, cause difficulties1-3.

According to a number of authors, ST segment depression is recorded in patients with critical stenosis of the proximal anterior interventricular branch (LAD), and in some patients with complete occlusion of the named artery, which is associated with a high risk of developing widespread MI of the anterior wall of the left ventricle4.

V.N. Orlov describes depression of the ST segment with the arch turned convex towards displacement as a sign of subendocardial damage to the anterior wall of the left ventricle under the electrode or in transmural damage located on the wall opposite to the electrode, as a result of reciprocal changes. The ST segment displacement in case of myocardial injury differs from those in the case of ventricular hypertrophy and complete intraventricular bundle branch blocks, in which the convexity of the ST segment arc is directed in the direction opposite to its displacement5.

ST segment depression with a high pointed T wave in the anterior chest leads within the de Winter electrocardiographic pattern is also associated with LAD occlusion. Critical stenosis or occlusion of the LAD on the ECG may not always be accompanied by an elevation of the ST segment in the leads of the anterior wall. Often, the registration of an inverted T wave or biphasic T wave with an isoelectric position of the ST segment or its minimal elevation (less than 1 mm) can be interpreted as Wellens syndrome by the name of the author who described it.

Taking into account the variety of changes in the ST segment and T wave against the background of coronary artery disease, the interpretation of ECG data with the determination of the localization and depth of myocardial damage causes difficulties. The implementation of hightech

methods for diagnosing coronary heart disease (coronary angiography, magnetic resonance imaging, myocardial scintigraphy) in an urgent situation and nowdays is not possible in all medical hospitals. It is the cumulative assessment of ECG data, taking into account complaints, clinical manifestations, anamnestic findings, the level of biomarkers of myocardial necrosis and such an accessible non-invasive, easily reproducible research method as echocardiography (EchoCG) that makes it possible to increase the accuracy of the diagnostic conclusion, which is important for determining further treatment tactics for a patient with MI. Transthoracic echocardiography allows not only a differential diagnostic search in a patient with nonspecific ST-T changes accompanied by chest pain, but also clarifies the topical localization of myocardial infarction6-10.