ECG signs of myocardial infarction, transcript, photo

Myocardial infarction is characterized by lesions and necrosis miocardiotita (heart cells) as a result of the disruption or cessation of blood supply to a particular area of the myocardium. Diagnosis of this disease is clinical picture (symptoms), and ECG (electrocardiographic study of the heart, showing the work of the myocardium).

It shows an ECG in myocardial infarction?

The ECG reflects the process of heart muscle contraction (systole) and relaxation (diastole). ECG signs it is possible to determine the location (location), size of damage (necrosis), depth of necrosis, stage of heart attack and even some of the damage. The period of systole the ECG is reflected by the QRS complex, the period of diastole – the period of ST.

During normal operation of the heart the electrodes of the electrocardiograph record the nerve impulses in the period of excitation, which is reflected on the ECG tine R. the development of necrosis and atrophy of an area of the myocardium in this area foci of excitation does not occur, so the electrode will not be able to register them. In this case, instead of the R-wave is reflected pathological (not normal), the q wave.

ECG changes may occur before the development of infarction. The process preceding the occurrence of heart attack called ischemia. This is when the heart muscle receives less oxygen and is in a state of hypoxia (oxygen starvation). This phase can be noted and prevented the development of necrosis.

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ECG signs of myocardial ischemia

In this phase changes are observed only in the tooth T, QRS complexes and the ST segment remained unchanged. T may fall below the contour, and then it is called negative. It can be high if its height above the contour higher than normal, and may be two-phase, if the visual wave is formed. At the stage of ischemia of the myocardium is still able to recover, and if the time to see EKG changes, you can prevent a heart attack by restoring blood flow to the heart muscle.

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ECG signs of myocardial infarction

  • The disappearance of the R-wave in the area where is located the area of necrosis in the myocardium.
  • The emergence of the complex pathological wave Q. As you know, this prong reflects the time of excitation of the muscular septum between the ventricles and the rate is 0.03 seconds. The Q-wave duration in excess of this time is called pathological.
  • Discordance of the ST segment. Normally, this gap reflects the repolarization (recovery between contractions of the myocardium). During a heart attack violated the metabolic processes in the myocardium, which is reflected by ST elevation on the contour in the center of necrosis, and on the opposite side from the pathological focus occurs the omission of the ST below the contour line. This multidirectional offset of the segment and is called discordant. The ST-segment elevation is called the syndrome of «cat’s back».
  • The omission of the element of T that is below the contour. The lower prong of T characterizes the depletion of the processes of repolarization of the myocardium in the zone of necrosis.
  • Признаки ЭКГ инфаркта миокарда, расшифровка, фото

    The ECG interpretation depending on stage of a heart attack

    At the time of the development of necrosis distinguish and stage of the disease – acute, acute, subacute and scar. Depending on these different stages and the signs on the electrocardiogram.

    • The acute stage, which may last from 3 hours to 3 days, on an ECG looks like a monophasic curve. It is raised above the contour of the ST segment and tooth T, with the result that they look as a raised curve. Such a phenomenon can occur in any of the 12 leads and indicates the beginning of myocardial infarction.
    • In the acute stage, which lasts up to 3 weeks, is characterized by the expansion of the zone of necrosis around it formed a wide area of ischemia. On ECG, this is manifested pathological Q wave, ST segment gradually approaching (falls or rises) to the contour, and the tooth T, on the contrary, is lowered, which is evidence of increasing ischemia.
    • The subacute stage of infarction lasts about 3 months, sometimes longer. Is characterized by the extension of ischemia, which is reflected by the formation of large low wide tine T. the Second half of the stage is the recovery of the heart muscles, reducing ischemia, which is manifested by the aspiration of the tooth T to become positive.
    • Cicatricial stage is scarring or scar in the area of necrosis. It never disappears and persists until the last contraction of the cardiac muscle. On ECG, this stage can manifest in reduced q wave. Sometimes you may experience changes in tooth T, it can be smoothed or even negative, but should the height exceed 5 mm, and the length – half the length of the R-wave or Q.
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    How to determine the location of the necrosis in the ECG signs?

    Localization is determined by the ECG signs in certain leads. ECG changes are the same, but depending on the location of the heart attack will change their appearance in leads. Just on the electrocardiogram there are 12 leads (standard, reinforced and breast). One of the most frequent locations of infarction is the left ventricle. In turn, a heart attack can strike back, front, lateral or basal walls of the left ventricle and septum of the ventricles.

    So, when infarction of the anterior wall ECG signs will be marked in the chest leads V1 – V4. With the defeat of the rear wall of the myocardium changes in the standard leads I, III, and aVF emergency. At lateral left ventricular infarction signs will be visible in the standard leads I, aVL emergency and chest leads V5 and V6. Septal myocardial changes in left chest leads V1, V2.