Myocardial infarction is a severe disease that develops as a result of occlusion of the lumen of the vessel that supplies blood to the heart muscle. The outcome of it depends not only on the timeliness of the provision of medical care, but also on the correctness of diagnostic activities. One of the important studies in this case is cardiac electrocardiography (ECG).
Through the ECG method, performed with the device of a cardiograph, specialists receive written on the paper wavy lines that reflect the work of the heart muscle, periods of contraction and relaxation. Conduction of electrocardiography allows to detect the affected area, as well as to reveal the perinfarction zone. By ECG with myocardial infarction, one can judge the localization and size of the necrosis focus, follow the dynamics of the pathological process.
ECG diagnostics of myocardial infarction
ECG readings, already obtained during a pain attack of myocardial infarction, in typical cases can be changed. Assessing the parameters of teeth, segments and intervals on the electrocardiogram responsible for the work of specific parts of the heart, experts diagnose pathological abnormalities. The stages of myocardial infarction on the ECG are characterized by the following symptoms:
- Ischemic (early) stage (duration - 20-30 minutes) - tine T enlarged, pointed, displacement of the ST segment upwards.
- The stage of damage (duration - from several hours to 3 days) is the shift of the ST interval below the isoline, and further the ST offset by the dome to the top, the decrease of the T wave and its fusion with the ST interval.
- Acute stage (duration - 2-3 weeks) - the appearance of a pathological Q wave, which in depth exceeds a fourth of the tooth R, and width is more than 0.03 s; reduction or complete absence of R wave in transmural infarction (QRS or QS complex); the dome-shaped displacement of the ST segment above the isoline, the formation of a negative T.
- Subacute stage of infarction (duration - up to 1.5 months) - reverse development, characterized by the return of the ST segment to the isoline and the positive dynamics of the T wave.
- The cicatricial stage (lasts all subsequent life) is the presence of a pathological Q wave, while the T wave is positive, smoothened or negative.
Reliability of ECG signs in myocardial infarction
In some cases, changes in the ECG with myocardial infarction are not characteristic, are found later or completely absent. With repeated heart attacks, typical abnormalities are very rare, and in some patients even a false improvement in the electrocardiogram is possible. With a small-focal form of the disease, ECG changes only affect the final part of the ventricular complex, often are uncharacteristic or not recorded.
When the right ventricular tissue is damaged, ECG diagnostics can not be applicable. Often, intracardiac hemodynamics is used to assess the condition of such patients. But sometimes with necrosis of the right ventricular muscle in
Significant difficulties in deciphering the ECG after myocardial infarction may appear in case of cardiac rhythm and conduction failures ( paroxysmal tachycardia , blockade of the bundle of the bundle, etc.). Then for diagnostics it is recommended to carry out an electrocardiogram in dynamics, especially after the rhythm is normalized. Also, the results obtained should be compared with the data of laboratory and other studies observed by the clinical picture.