myocardial infarction (MI) - a pathology of system of the heart and blood vessels, which is often confused patients with angina pectoris. However, unlike the latter state, MI at untimely provision of skilled care leads to severe consequences: the patient's disability, or even death.
ECG in myocardial infarction - a technique that allows you to detect signs of life-threatening conditions at an early stage.
Just as myocardial itself, ECG changes for this nosologies can be classified depending on the stage of ischemia, the size of the lesion and its localization.
Depending on the stage
ECG in myocardial reveals changes strictly temporary nature. Electrocardiographic curve differs depending on the stage of the disease and the degree of manifestation of ischemia and necrosis.
myocardial steps include the following steps.
The first hours are accompanied by varying degrees of damage to the heart muscle due to ischemia - acute phase. It is characterized by:
- curve monophasic type, arising due to ST segment merging c high tooth T, - is the main indication of ECG;
- the presence or absence of a tooth Q, induced necrotic changes in myocardial tissue;
- disappearance of wave R (observed in those cases where there is a deep Q on cardiogram).
In the acute stage, the duration of which varies from 2 to 10 days, observed:
- forming a negative T or its absence;
- ST segment elevation large relative to the contour, which is located above the region of circulatory disorders;
- Q becomes deeper until the appearance of QT-complex.
In subacute stage of myocardial infarction (30-60 hours) the following ECG parameters:
- tooth contour T below, its amplitude increases due to the expansion zone bled. Normalized tooth in the second half subacute stage;
- ST segment decrease until closure subacute stage;
- for the first three stages of the important features characteristic electrocardiographic curve ST rise in leads that correspond to the area of damage and, conversely, a decrease in opposing portions cardiac ischemic changes muscles.
For scar step (duration is 7-90 days) is characterized by:
- the achievement of T wave contours or positive its location;
- if there is an acute stage of pathological Q, it is stored in the scar;
- R becomes higher.
Depending on the size of the hearth
Electrocardiogram may also vary depending on how extensive area of cardiac muscle fibers breach affected blood flow in vessels.
Ischemia in the large vascular trunks damage is extensive in nature, while the mini-heart attacks are accompanied by circulatory disturbance terminal arterial branches.
Determine infarct on the ECG may be on the basis of which depend on its size:
- Macrofocal transmural (in this type of pathology affected the entire thickness of the cardiac wall):
- missing tooth R;
- Q and advanced deep;
- ST fusion with the tooth T of ischemia area
- T is lower than the isolines in the subacute phase.
- Macrofocal subepicardial (localization in myocardial zone close to the epicardium):
- the presence of reduced tooth R;
- deep and wide tooth Q, which proceeds in high ST;
- tooth T is negative in the subacute phase.
- Melkoochagovyj intramural infarction (characterized by localization in the inner layers of the cardiac muscle).
- unaffected tine R and Q;
- changes in the ST segment are absent;
- for 14 days persists T, located below the contour.
- Melkoochagovyj subendokardialny:
- R and Q pathology is not detected;
- ST to 0,02 mV or more is below isoline;
- T waves flattened.
At different positions of a heart attack
Localization of the ischemia - another factor that affects the ECG signs of myocardial infarction.
Explanation of myocardial infarction on ECG leads is performed at 12, each of which corresponds to the corresponding portion of the heart muscle.
Standard lead:
- I - shows information about the changes that are localized in the front and side of the left ventricle;
- III - to evaluate the state of the back of the diaphragmatic surface of the heart;
- II retraction is used to validate data obtained in the evaluation of I or III diversion.
Reinforced abduction:
- aVL (reinforced by the left hand) - to evaluate changes in the side wall of the left ventricle;
- aVF (reinforced by the right leg) - rear surface of the diaphragm;
- aVR (reinforced by the right hand) - considered uninformative, but may be used to assess infarct changes in the interventricular septum and the lower-side sections of the left ventricle.
Chest leads:
- V1, V2 - changes in the interventricular septum;
- V3 - front wall;
- V4 - apical localization of myocardial;
- V5, V6 - the side portion of the left ventricle.
Front or peredneperegorodochny
With such a location of the lesion on the cardiogram changes evaluated as follows:
- in I, II and standard derivations aVL observed tooth Q and a single tooth T segment ST;
- in III standard and aVF leads - in the transition ST located below the T-prong;
- in 1,2,3 thoracic, and when switching to breastfeeding 4 - absence R and above line arrangement ST 0.2-0.3 cm or more;
- exhaust aVR and 4,5,6 thoracic show the following changes: T wave flattened, ST is shifted down.
Side
ECG in myocardial localization accompanied with side extension and a recess Q-wave, and an increase in ST segment with a compound of the T-wave. These signs are observed in the III standard, 5.6 breast, and aVF leads.
Forward or rear combo
Evaluation of the combined Q-infarct produced in leads: I, III, aVL, aVF, 3, 4, 5, nursing infants. The ECG heart attack is as follows:
- Q is widened and deepened;
- S-T segment rises much above the line;
- positive T is connected to S-T.
Rear or phrenic
Infarction on ECG at diaphragmatic localization has the features:
- II, III, and aVF exhaust: a Q, T positive, coupled with high ST;
- Allocating I: ST fallen below the line;
- in some cases all the precordial T wave changes are visible in the form of negative and decrease deformation ST.
interventricular septum
Defeat ventricular septal myocardial depression manifests on the ECG Q, T, and ST elevation in leads, transmit information about the state the front portion of the baffle (I, aVL, 1,2 breast). When ischemia in the rear portion of the partition (1 and 2 chest leads) are seen enlarged tooth R, atrioventricular block of various degrees, and a slight displacement below isolines ST segment.
front subendocardial
This type of heart attack is characterized by changes in the ECG:
- in I, aVL and 1-4 precordial leads - T wave is positive, its height is greater than R;
- II, III standard - gradual decline ST, the location of the negative T-wave, low R;
- 5 and 6 breast - the separation of T to negative and positive part.
rear subendocardial
When the rear localization features subendocardial infarction on ECG in the II, III, aVF, and 5, 6 precordial leads: R tooth decreases T becomes positive, and later ST begins to descend.
Right ventricular infarction
Because at the right and left ventricles common source of blood supply (coronary artery disease), myocardial at the right half and there are changes in the front section of the left ventricle.
Diagnosis using electrodes rarely allows us to identify right ventricular myocardial effectively even with the use of additional electrodes. With this type of violation of the ECG heart circulation figures preferable ultrasonography.
Despite the informative value of the method, the ECG is not the only test for which data should be based in the diagnosis of heart attack. Along with the changes in the curve recorded cardiographic clinical symptoms and indicators of cardiac enzymes: CPK-MB, CK, LDH and others. Only the presence of 2 or more signs gives rise to an accuracy of a diagnosis.
