Staged ECG changes in myocardial infarction

The main method for diagnosing myocardial infarction is the analysis of electrocardiographic criteria for coronary circulation disorders. ECG - an indispensable study in case of a heart attack, confirming the diagnosis of the disease. It can not be replaced by any other, like the ECG in blockades.

Myocardial infarction or necrosis is characterized by non-recurrent changes in muscle fibers. Necrotic tissue does not participate in the excitement. Therefore, on the ECG over the necrosis site, a violation of the ventricular myocardial depolarization is detected, which is manifested by a change in the QRS complex. This change consists in a decrease in the R wave and deepening of the Q wave. Myocardial infarction is characterized by the dynamics of changes in the electrocardiogram. It shows the presence of three zones of a heart attack - the central site of necrosis, the zone of damage surrounding the necrosis, and the ischemic zone around the area of injury.

The area of necrotically altered tissue in case of myocardial infarction can cover the entire thickness of the muscular wall of the heart. Such a heart attack is called transmural. If necrosis is located under the endocardium - subendocardial, under the epicardium - subepicardial, in the thickness of the heart muscle - intramural.

On the ECG, regardless of the clinical form of the infarct, a regular pattern is observed, which is determined by the location, depth, spread of the heart muscle damage and the stage of the process. ECG signs of myocardial infarction vary depending on the stage of the disease.

A typical course of myocardial infarction is divided into four stages: acute, acute, subacute and stage scarring.

ECG with myocardial infarction in the most acute stage

The disease begins with the acute stage of myocardial infarction. This is the time from the onset of severe myocardial ischemia to the formation of signs of necrosis. On the ECG, this stage is characterized by the appearance of an arched ST segment that merges with the R wave on one side and the T wave on the other. Thus, the Pardi arc typical for myocardial infarction or the "cat's back" symptom is formed.

ECG with acute myocardial infarction

In the acute stage of the infarction, the site of necrosis is finally formed and myomalation develops (softening of the altered myocardium). The pathological Q wave forms on the ECG. It gradually becomes broad and deep, which indicates the development of the necrosis zone. Simultaneously with the appearance of this tooth, the ST segment begins to decrease, which indicates a reduction in the damage zone. At the same time begins to form a sharp negative tooth T.

ECG with myocardial infarction in subacute stage

During the subacute stage, the initial processes of scar organization are completed. The main ECG sign of this stage is the gradual reduction of the ST segment to the isoline and the final formation of a deep, symmetrically pointed, so-called coronary wave. At this time, Zubets Q acquires its shape, which remains unchanged for many years or remains for life.

ECG with myocardial infarction in cicatricial stage

In the cicatrical stage, the scar is compacted. A characteristic feature of this stage is the location of the ST segment on the isoelectric line. About the transferred infarction the pathological prong Q and stably negative tooth T testify. Over time, the magnitude of the negative T wave can decrease, even a positive tooth T can appear.

With small-focal myocardial infarction, ECG changes are limited to a slight shift of the ST segment from the isoline up or down, depending on the location of the infarction, and the inversion of the T wave.

Myocardial infarction develops mainly in the left ventricle. The localization of the focus of necrosis in the myocardium is indicated by the appearance of electrocardiographic signs characteristic of the infarction in the corresponding leads.