How myocardial infarction manifests itself on the ECG: an overview

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From the article you will learn about the role of ECG in myocardial infarction. When there are characteristic signs, what they mean. Cardiogram as an assistant in determining the degree of pathological changes in cardiac tissue and the localization of the process.

content of the article:

  • Temporary stage infarction on ECG
  • Types depending on the size of the hearth: ECG signs
  • ECG changes at a different location of myocardial infarcts

  • Atypical Electrocardiography in acute disorders of blood flow in the myocardium - the "gold standard" diagnostic. The informativity of the study increases during the first hours after the development of the infarct, when when recording the electrical activity of the heart, characteristic signs of the cessation of blood flow to the tissues of the heart appear.
    Click on the picture to enlarge

    The film recorded during the development of pathology may reflect only the phenomena of initial disturbance of the blood flow, provided that they did not develop at the time of recording( ST segment change with respect to the isoline in different leads).This is due to the fact that for typical manifestations it is necessary: ​​

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    • violation of the excitation of myocardial tissue( develops after complete necrosis or necrosis of cells);
    • change in electrolyte composition( extensive yield of potassium from the destroyed tissue of the myocardium).

    Both processes take time, therefore, signs of a heart attack appear at registration of electroactivity of the heart in 2-4 hours from the onset of an infarction.

    ECG changes are associated with three processes that occur in the infarction zone, dividing it into areas:

    1. Necrosis or tissue necrosis( there are only Q-infarcts).
    2. Damage to cells( may subsequently go to necrosis).
    3. Lack of blood supply or ischemia( fully restored in the future).

    Symptoms of a developing infarction on the ECG:

    Changes in the area of ​​the formation of the infarction zone Changes in the infarction-free area of ​​the
    The tooth R is absent or significantly reduced in height The segment S-T lies below the isoline
    There is a deep( pathological) tooth Q
    Segment S-T raised above isoline
    Tine T negative

    It should be borne in mind that, depending on the size of the area with a violation of blood flow and its location relative to the cardiac envelopes on the cardiogrammay register only a part of these symptoms.

    These signs allow:

    • To establish the presence of a heart attack.
    • Determine the area of ​​the heart muscle where the pathology originated.
    • Solve the issue of the limitation period of the process.
    • Choose the appropriate treatment strategy.
    • Forecast the risk of complications, including lethal ones.

    Assigns ECG to any medical professional( doctor, paramedic), who suspected a pathological process in the myocardium.

    The research is carried out by The investigation is carried out by The tape is deciphered by
    Emergency medical personnel in the prehospital phase of
    emergency medical personnel Sisters of functional rooms and intensive care units in a hospital Functional diagnostics physician, therapist or cardiologist at hospital care stage

    Interim stages of ECG

    ECGsigns of myocardial infarction are of a strict temporal nature, which is extremely important for the choice of tactics of medical measures. The most vividly displayed heart attacks with a large amount of tissue damage( large).

    Stage name Time interval ECG symptoms
    Acute From the first hours to three days High S-T position relative to the contour over the infarct area

    Tip T thus not visible

    Subacute From the first days to three weeks Slowreduction of the S-T segment to the line, when it reaches the end of the stage

    Negative T

    Scarring From the first week to three months Gradual return of the T wave to the contour may even become positiveIncreasing the height of the tooth

    R

    Reduction in the amount of pathological Q( in its original stock)

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    Types, depending on the hearth size:

    ECG signs of myocardial infarction on ECG has various displays that depend on the affected area. If it is located close to the external surface of the heart muscle or captures the entire wall, then a violation of blood flow originated in a large vessel. With small foci only the terminal branches of the arteries are affected.

    Type Variants ECG signs
    Large or Q-infarction Transmural - zone captures the entire thickness of the heart wall No tooth R

    Deep, enlarged zQ

    recorded Segment S-T high above the line merges with the T-wave over the infarction zone

    SegmentS-T below the contour line - according to data from the opposite side infarction

    Negative T in the subacute period

    Subepicardial - the zone is located next to the outer shell of the The R tooth is significantly reduced in size, but registering

    There is an enlarged and expanded tooth Q

    Smoothly passes into the high segment of the S-T over the infarction area of ​​the

    Segment S-T below the line in the other leads

    The tine T becomes negative in the subacute stage of the

    Small-focal or infarction without Q Intramural -layer No pathology of R and Q teeth

    Segment S-T unchanged

    Negative tooth T recorded, which persists for more than two weeks

    Subendocardial - an area adjacent to the inner shell of the heart Teeth R and Q without pathology

    Segment S-T below the line more than 0.02 mV

    Tine T smoothed or without pathology

    Click on photo to enlarge

    ECG changes in different location of infarction

    Localization of myocardial infarction is determined by data,which are removed by different electrodes from all regions around the heart muscle.

    For accurate diagnosis, all 12 electrodes must be applied:

    • three standard( I, II, III);
    • three reinforced: from the right and left hands, right legs( AVR, AVL, AVF);
    • six thoracic( V1-V6).
    Click on photo to enlarge

    If you suspect a violation of blood flow in the myocardium of an acute nature, it is absolutely unacceptable to use fewer electrodes!

    Depending on the location of the affected area on the ECG, the infarction is displayed in the recordings from each of the sensors in its own way.

    Anterior or anteroposterior Q-infarction

    Leads Type of changes
    Standard 1, 2 and left hand Abnormal deep tooth Q

    Segment S-T above the contour, forms a single curve with a positive tooth T

    Standard 3 and from the right leg The segment S-T below the line passesin the negative tooth T
    Thoracic 1-3( with the transition to the apex and 4 thoracic) No tooth R, instead of it a wide complex QS

    Segment S-T above the isoline more than 2-3 mm

    From the right arm and pectoral 4-6 Flat tooth T

    Slight offset withS-T down

    Click on photo to enlarge

    Lateral Q-infarction

    Leads Nature of changes
    Standard 3, from left hand, right foot and thoracic 5-6 Deep, greatly expanded tooth Q

    Increase segment S-T

    Tine as a single line with segment S-T

    Click on photo to enlarge

    Anteroposterior or combined Q-infarction

    Leads Nature of changes
    Standard 1, 3, from left hand and right foot, thoracic 3-6 Extensionand a deepening of the tooth Q

    Significant elevation of the S-T segment above the

    isolate. Tine T positive and merging with the S-T segment.

    . Click on the photo to enlarge

    . Back or diaphragmatic Q-infarction.

    . leads.
    . Standard 2, 3 and from the right leg. . Deep,wide tooth Q

    Segment S-T above the contour, merges with T

    Tine T positive

    Standard 1 Segment S-T falls below the line
    Chest 1-6( not always) Segment S-T below the contour

    The tooth T is deformed,is closer to the negative

    Click on photo to enlarge

    Q-infarction of interventricular septum Leads Nature of changes Standard 1, left-handed, thoracic 1-2( front part of partition) Digestion Q

    Elevation of segment S-T

    Positive tooth T

    Thoracic 1-2( posterior part of septum) Pathological enlargement of the tooth R

    Segment of the S-T on the contour or slightly biased down

    A-V blockade of any degree

    Click on photo to enlarge

    Anterior subendocardial not Q-infarction

    Leads Type of changes
    Standard 1, left hand, pectoral 1-4 Positive T wave, above R
    Standard 2, 3 Gradual reduction of segment S-T

    T negative

    Decrease in tooth height R

    Breast 5-6 Tine T is half positive and the other part below the isoline
    Click on photo for enlargement

    Rear subendocardial not Q-infarction

    Leads Nature of changes
    Standard 2, 3, from the right leg and thoracic 5-6( latter less often) Decrease of the toothR

    Positive T

    Later - lowering the segment S-T

    Click on the picture to enlarge

    Any right ventricular infarction

    Combined with anterior lesions of the left ventricle due to a common source of blood flow. According to the ECG, myocardial infarction in the right ventricle is extremely complicated in diagnosis, requires additional electrodes and even rarely is diagnosed in this case.

    For its diagnosis, an ultrasonographic examination of cardiac tissue is indicated.

    Atypical infarctions

    This group includes:

    1. Blood flow disturbances in the myocardium against the background of any forms of bundle bundle blockade.
    2. Early recurrent infarctions.
    3. Repeated abnormalities in the area of ​​cicatrical changes in the heart muscle.
    Click on the picture to enlarge

    Such pathologies are extremely difficult to diagnose. The main role is played by the degree of doctor's experience, which deciphers the tape, and the presence of previous "pre-infarction" ECG films to isolate new changes.

    Without following these requirements, all three types of acute pathology may not be diagnosed.