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Coronary heart disease causes irreversible consequences in the heart muscle. Prolonged disruption of the metabolism of heart cells leads to circulatory failure and can be complicated by myocardial infarction.

This is a complication that is characterized by the death of cardiomyocytes and is the most common cause of cardiac arrest.

The symptoms that characterize myocardial infarction differ and depend on the form of the disease. Hypertensive crisis, excessive fatigue, severe physical activity or stress are factors that contribute to the manifestation of the disease.

Prehospital diagnostic measures

Preclinical diagnosis consists of interviewing the patient and identifying symptoms. Features of the development of a heart attack include:

• atypically prolonged pain syndrome;
• lack of effect from taking nitrates;
• no dependence of pain on body position;
• greater intensity of symptoms compared to attacks that occurred earlier and did not end in a heart attack.

Instrumental diagnostics

The main ones in making a diagnosis are instrumental research methods, such as EGC and EchoCG.

Electrocardiography

ECG - the most common way to detect myocardial infarction, even if it is asymptomatic. The acute stage and the recovery process are characterized by a negative T wave. With a large-focal infarction, a pathological QRS complex or Q wave is detected. Healed myocardial infarction is manifested in a decrease in the amplitude of the R wave and preservation of the Q wave.

The photo pictures below show options for what changes on the ECG look like during myocardial infarction with interpretation and description, signs by stage (from acute to post-infarction) and localization.

Click on the image above to see it in full.

EchoCG

Echocardiography reveals thinning of the ventricular wall and decreased contractility. The accuracy of the study depends on the quality of the resulting image.

The study does not make it possible to distinguish a fresh lesion from a healed scar, but is mandatory to exclude concomitant pathologies and complications.

Laboratory methods

There are changes in biochemical blood parameters, therefore, this analysis is performed when diagnosing myocardial infarction.

• The number of neutrophils increases in the first two days, reaching a peak on the third day. After which it returns to normal levels.
• ESR is increasing.
• The activity of liver transfer enzymes AsAt and AlAt increases.

Such changes are explained by the inflammatory process in myocardial tissue and scar formation. Changes in the level of enzymes and proteins are also detected in the blood, which is important for making a diagnosis.

• Increase in quantity myoglobin- within 4-6 hours after the onset of pain.
• Creatine phosphokinase(CPK) increases by 50% 8-10 hours after the onset of the disease. After two days it returns to normal.
• Lactate dehydrogenase(LDH) - enzyme activity increases on the second day of the disease. The values ​​return to normal after 1 - 2 weeks.
• Troponin- a contractile protein, the amount of which increases with unstable angina. Its isoforms are highly specific for myocardial infarction.

Additional Research

In some cases, the above studies may not be enough. To definitively establish a diagnosis or clarify the nuances of the course of the disease, the following procedures may be required:

• Chest X-ray. Myocardial infarction may be accompanied by pulmonary congestion. This is noticeable on an x-ray. Confirmation of a complication requires adjustment of the treatment regimen.
• Coronary angiography. Coronary artery angiography helps detect thrombotic occlusion. Determines the degree of decrease in ventricular contractility. This study is carried out before surgical interventions - angioplasty or coronary artery bypass surgery, which help restore blood flow.

If the patient experiences symptoms similar to those of a myocardial infarction, he should be immediately taken to the hospital for further examination and treatment. The sooner treatment for the disease is started, the greater the likelihood of a favorable outcome.

To prevent a heart attack, you should And, avoid stress, excessive exertion, physical and emotional fatigue.

28.04.2017

Myocardial infarction is one of the serious diseases. The prognosis directly depends on how correctly the diagnosis was made and adequate therapy was prescribed.

The earlier specialists diagnose the disease, the more effective the treatment will be. Electrocardiography (ECG) is more accurate than all studies; it can 100% confirm the diagnosis or exclude it.

Cardiac cardiogram

Human organs pass a weak current. This is precisely what allows us to make an accurate diagnosis using a device that records electrical impulses. The electrocardiograph consists of:

• a device that enhances weak current;
• voltage measuring device;
• recording device on an automatic basis.

Based on the cardiogram data, which is displayed on the screen or printed on paper, the specialist makes a diagnosis.

There are special tissues in the human heart, otherwise called the conduction system, they transmit signals to the muscles indicating relaxation or contraction of the organ.

The electric current in the heart cells flows in periods, these are:

• depolarization. The negative cellular charge of the heart muscles is replaced by a positive one;
• repolarization. The negative intracellular charge is restored.

A damaged cell has lower electrical conductivity than a healthy one. This is exactly what the electrocardiograph records.

Passing a cardiogram allows you to record the effect of currents that arise in the work of the heart.

When there is no current, the galvanometer records a flat line (isoline), and if the myocardial cells are excited in different phases, the galvanometer records a characteristic tooth directed up or down.

An electrocardiographic test records three standard leads, three reinforced leads and six chest leads. If there are indications, then leads are also added to check the posterior parts of the heart.

The electrocardiograph records each lead with a separate line, which further helps to diagnose cardiac lesions.

As a result, a complex cardiogram has 12 graphic lines, and each of them is studied.

On the electrocardiogram, five teeth stand out - P, Q, R, S, T, there are cases when U is also added. Each has its own width, height and depth, and each is directed in its own direction.

There are intervals between the teeth, they are also measured and studied. Interval deviations are also recorded.

Each tooth is responsible for the functions and capabilities of certain muscular parts of the heart. Experts take into account the relationship between them (it all depends on the height, depth and direction).

All these indicators help to distinguish normal myocardial function from impaired functioning caused by various pathologies.

The main feature of the electrocardiogram is to identify and record symptoms of pathology that are important for diagnosis and further treatment.

Determination of a heart attack on an ECG

Due to the fact that areas of the heart muscles begin to die, electrical capabilities begin to decrease locally compared to the remaining undamaged tissues.

Precisely, this indicates where exactly the myocardial infarction is localized. The slightest changes in the ECG indicate the affected areas of the myocardium, which occur in ischemic heart diseases:

• cell death - as a rule, this occurs in the center of the organ, the Q, R, S complex changes. Basically, a painful Q wave is formed;
• damaged zone - localized around dead cells, on the ECG it is noticeable that the S, T segment is displaced;
• zone with reduced blood circulation - located on the line with unaffected myocardium. The amplitude and polarity of the T wave changes.

Changes in the electrocardiogram determine the depth of necrosis of cardiac muscle cells:

• transmural myocardial infarction - the R wave disappears in the graphic image, and instead of the Q,R,S complex, Q.S is obtained;
• subepicardial myocardial infarction - indicates segmental depression of S, T. and the T wave itself changes, while the Q, R, S complex does not change;
• intramural myocardial infarction is accompanied by changes in Q, R, S and the height of the S, T segment, which is accompanied by fusion with a positive T wave.

Signs of myocardial infarction on the ECG have three stages of development:

• the first stage can last from a couple of hours to 68 (three days). When conducting an electrocardiogram, specialists notice that the ST segment rises (a dome-shaped rise is obtained) and merges with the positive wave. The segment begins with a low descending tooth. In this case, a Q wave appears on the image and is considered pathological.
• second stage, subacute. It can last about a month, sometimes two. The cardiogram shows a reduced S, T segment and it approaches the isoline. A negative T wave is formed and the pathological Q increases.
• the third stage is cicatricial. It can last for a very long time. The myocardium has the appearance of post-infarction cardiosclerosis and can be recorded on the electrocardiogram throughout the life of a patient who has suffered a heart attack. The cicatricial stage is depicted on the ECG as a reduced S, T segment. It decreases to the level of the isoline and forms a negative characteristic T wave, which has a triangular appearance. The Q wave remains unchanged. After some time, it does not disappear, but simply smoothes out, and is constantly determined by doctors.

In most patients, cardiac dynamics on the electrocardiogram do not coincide with the morphological changes in the muscles of the heart.

For example, when conducting an ECG, doctors determined the scar stage of the development of a heart attack, but the scar tissue had not yet begun to form.

Or vice versa, the second stage (subacute) is determined on the electrocardiogram for several months, while the scar is already fully formed.

Therefore, when making a diagnosis, doctors take into account not only the interpretation of the cardiogram and the stage of the infarction, but also the clinical manifestations of the pathology and the results of laboratory tests.

How to determine where a heart attack is located on an ECG

In almost all cases, with reduced blood supply, the infarction is localized in the left ventricle of the muscular layer of the heart; on the right, it is diagnosed in rare cases. The anterior, lateral and posterior parts are affected.

When performing an ECG, signs of myocardial infarction are determined in the leads:

• Coronary heart disease in the anterior part indicates abnormalities in the chest leads - V1, V2, V3, 1 and 2 - this is a normal indicator, and in an increased case, AVL.
• Ischemia on the lateral walls is rarely diagnosed separately; it is more often localized on the anterior and posterior walls of the left ventricle, disturbances are noticeable in leads V3, V4, V5 in addition to 1 and 2 normal values, and in severe cases, AVL.
• Ischemia on the posterior wall has two types: diaphragmatic (pathological disorders are determined by the increased lead AVF, the second and third leads are also affected; basal - the R wave in the left sternal lead increases.

Coronary heart disease in the area of ​​the right ventricle and atrium is diagnosed in rare cases, mainly covered by signs of cardiac lesions in the left part.

Can a cardiogram determine the extent of a heart attack?

The prevalence of cardiac lesions is indicated by changes in leads. Based on these data, two types of myocardial infarction are distinguished:

1. Fine-focal indicates negative T values, while the segmental interval S, T is displaced, and pathological incisors R, Q are not observed.
2. Common is caused by all altered leads.

Determination of the depth of necrosis of the muscle layer

A heart attack varies in the depth of necrosis of the heart walls:

• subepicardial - the area under the outer cardiac layer is affected;
• subendocardial - necrosis occurs near the inner layer;
• transmural - the entire thickness of the myocardium is affected.

A cardiogram performed during a heart attack always determines the depth of necrosis.

Difficulties with electrocardiography

Modern medicine and new ECG machines are able to easily carry out calculations (this happens automatically). Using Holter monitoring, you can record the work of the heart throughout the day.

Modern wards have cardiac monitoring and an audible alarm, which allows doctors to notice altered heartbeats.

The final diagnosis is made by a specialist based on the results of an electrocardiogram and clinical manifestations.

Electrocardiography (ECG) plays an important role in making the diagnosis of myocardial infarction. The technique is simple and informative. Modern portable devices allow you to take ECGs at home, in a factory health center. And in medical institutions, multi-channel technology has appeared that conducts research in a matter of minutes and helps in decoding.

An ECG during myocardial infarction serves as indisputable authoritative evidence for the doctor. Infarction-like changes are possible and do occur in acute pancreatitis and cholecystitis, but in such cases it is better to make a mistake and start treatment.

The nature of the ECG, which reflects the potential difference between healthy and diseased tissue, changes depending on the course of the pathological process in the tissue. Therefore, the results of repeated studies are important.

To decipher an ECG it is necessary to take into account many parameters

What information is included in the ECG technique?

100 years ago, a method was developed to record electrical changes in the heart muscle. Electrocardiography is a method that allows you to record the action currents arising in the beating heart. In their absence, the galvanometer needle writes a straight line (isoline), and at different phases of excitation of myocardial cells, characteristic teeth appear with the direction up or down. The processes occurring in the heart tissue are called depolarization and repolarization.

It will tell you more about the mechanisms of contraction, changes in depolarization and repolarization.

The ECG is recorded in three standard leads, three enhanced leads and six chest leads. If necessary, special leads are added to study the posterior parts of the heart. Each lead is fixed with its own line and is used in diagnosing heart damage. The complex ECG contains 12 graphic images, each of which must be studied.

In total, there are 5 waves on the ECG (P, Q, R, S, T), an additional U rarely appears. They are normally directed in their own direction, have width, height and depth. There are intervals between the teeth, which are also measured. In addition, the deviation of the interval from the isoline (up or down) is recorded.

Each of the teeth reflects the functionality of a specific part of the heart muscle. The relationship between individual teeth in height and depth and direction is taken into account. The information obtained allows us to establish the differences between normal myocardial function and altered ECG by various diseases.

Features of the ECG during myocardial infarction make it possible to identify and record signs of the disease that are important for diagnosis and subsequent therapy.

What indicates the period and duration of the disease

Acute infarction with a typical course goes through 3 periods of development. Each of them has its own manifestations on the ECG.

1 and 2 - indicate an acute period, with 3 a zone of necrosis is formed, then gradual scarring is shown, 9 - complete recovery, 10 - a scar remains

The early period - the first 7 days, is divided into the following stages:

• stage of ischemia (usually the first 2 hours) - a tall T wave appears above the focus;
• stage of damage (from a day to three) - the ST interval rises and the T wave moves down, it is important that these changes are reversible, with the help of treatment it is still possible to stop myocardial damage;
• formation of necrosis - an expanded and deep Q wave appears, R wave is significantly reduced. The focus of necrosis is surrounded by a zone of damage and ischemia. How large they are is indicated by the distribution of changes in different leads. Due to damage, the heart attack may increase. Therefore, treatment is aimed at helping the cells in these areas.

At the same time, various rhythm disturbances occur, so the ECG is expected to identify the first symptoms of arrhythmia.

Subacute - from 10 days to a month, the ECG gradually returns to normal, the ST interval drops to the isoline (the doctors at the functional diagnostics office say “sits down”), and signs of a scar form at the site of necrosis:

• Q decreases and may disappear completely;
• R rises to its previous level;
• only negative T remains.

The scarring period is from a month or more.

Thus, based on the nature of the ECG, the doctor can determine how long ago the disease appeared. Some authors distinguish separately the formation of cardiosclerosis at the site of a heart attack.

How is the location of a heart attack determined?

In most cases of ischemia, the infarction is located in the myocardium of the left ventricle; right-sided localization is much less common. Lesions on the anterior, lateral and posterior surfaces are distinguished. They are reflected in different ECG leads:

• with an anterior infarction, all characteristic signs appear in chest leads V1, V2, V3, 1 and 2 standard, in enhanced AVL;
• lateral wall infarction in isolation is rare, more often spreads from the anterior or posterior wall of the left ventricle, characterized by changes in leads V3, V4, V5, in combination with 1 and 2 standard and enhanced AVL;
• posterior infarction is divided into: lower (diaphragmatic) - pathological changes are found in the enhanced lead AVF, the second and third standard; upper (basal) - manifested by an increase in the R wave in leads to the left of the sternum, V1, V2, V3, the Q wave is rare.

Infarctions of the right ventricle and atria are very rare; they are usually “covered” by symptoms of damage to the left side of the heart.

A 4-channel device is used, it calculates the rhythm frequency itself

Is it possible to find out how extensive the area of ​​damage to the heart is?

The prevalence of a heart attack is judged by identifying changes in the leads:

• small focal infarction is manifested only by a negative “coronary” T and a shift in the ST interval, no R and Q pathology is observed;
• widespread infarction causes changes in all leads.

Diagnosis of the depth of myocardial necrosis

Depending on the depth of penetration of necrosis, the following are distinguished:

• subepicardial localization - the affected area is located under the outer layer of the heart;
• subendocardial - necrosis is localized near the inner layer;
• transmural infarction - affects the entire thickness of the myocardium.

When interpreting the ECG, the doctor must indicate the expected depth of the lesion.

Difficulties of ECG diagnostics

The arrangement of teeth and intervals is influenced by various factors:

• the patient's obesity changes the electrical position of the heart;
• cicatricial changes after a previous heart attack do not allow identifying new ones;
• conduction disturbance in the form of a complete block along the left bundle branch makes it impossible to diagnose ischemia;
• A “frozen” ECG against the background of a developing cardiac aneurysm does not show new dynamics.

Modern technical capabilities of new ECG devices make it possible to simplify the doctor’s calculations (they are done automatically). Holter monitoring provides continuous recording throughout the day. Cardiac monitoring in the room with an audible alarm allows you to quickly respond to changes in heart rate.

The diagnosis is made by a doctor, taking into account clinical symptoms. ECG is an auxiliary method that can become the main one in decisive situations.

It appears on the ECG depending on the stage of development. This procedure is always carried out to determine the location and size of the necrosis focus. This is a reliable study, the decoding of which helps to notice any pathological changes in the heart.

What is ECG

An electrocardiogram is a diagnostic technique that detects disruptions in the functioning of the heart. The procedure is performed using an electrocardiograph. The device provides an image in the form of a curve, which indicates the passage of electrical impulses.

This is a safe diagnostic technique and is approved for use during pregnancy and childhood.

Using a cardiogram, the following is determined:

• what is the state of the structure that promotes myocardial contraction;
• heart rate and rhythm;
• work of pathways;
• assess the quality of supply to the heart muscle through the coronary vessels;
• detect the presence of scars;
• heart pathologies.

For more accurate information about the condition of the organ, 24-hour monitoring, stress ECG, and transesophageal ECG can be used. Thanks to these procedures, the development of pathological processes can be detected in a timely manner.

Currently, myocardial infarction is a fairly common disease. If its initial manifestations are confused with angina pectoris, this can lead to sad consequences and often death. To avoid such a development of events, it is necessary to call a doctor as soon as possible. An ECG during myocardial infarction can sometimes save life and return the patient’s life to its usual rhythm.

ECG performance

A cardiogram for a heart attack is the “gold standard” for diagnosis. The greatest information content occurs in the first hours after the development of the pathological focus. It is at this time during the recording that the signs of myocardial infarction on the ECG are especially acute as a result of the cessation of blood saturation of the cardiac tissues.

The film on which the result of examination of an already developed pathology is recorded reflects the initial disturbance of blood flow, unless, of course, it was formed during the procedure. This is manifested by an altered ST segment in relation to the lines of various leads, which is related to the need for a typical manifestation:

• impaired support through cardiac tissue, which is formed after complete cell death or necrosis;
• changed electrolyte composition. After a heart attack, there is extensive release of potassium.

Both processes require a certain amount of time. Based on this, a heart attack usually appears on the ECG 2–3 hours after the onset of the infarction. The changes are associated with the following processes occurring in the affected area, resulting in its division: necrosis of the myocardium (necrosis), tissue damage, which can then turn into necrosis, insufficient blood supply, which with timely treatment can result in complete recovery.

Photo of myocardial infarction

Signs of a heart attack on the ECG over the area of ​​the formed pathological zone are as follows: the absence of an R wave or a significant decrease in its height, the presence of a deep pathological Q wave, elevation of the S-T segment above the isoline, the presence of a negative T wave. On the side opposite to the infarction zone, the presence of an S-T segment is determined, which is located below the isoline level.

It is important to consider that, based on the size of the disturbed blood flow and its location relative to the membrane of the heart muscle, diagnostics can register only some of these disorders.

As a result, the signs detected on the ECG make it possible to:

• determine the presence of a heart attack;
• locate the area of ​​the heart where the heart attack occurred;
• determine how long ago the infarction occurred;
• decide on further treatment tactics;
• predict the possibility of further complications and the risk of death.

What does a heart attack of different time periods look like on an ECG?

Changes in the ECG appear in accordance with how long ago the pathology developed. This information is extremely important for further treatment. The most striking display occurs in infarcts that have a large volume of affected tissue. During the study, the following stages are determined:

• acute type of disease has a time period from several hours to 3 days. On the ECG it looks like a high location of the S-T segment relative to the isoline located above the affected area. Due to this, during diagnostics it is impossible to see the T wave;
• subacute stage lasts from the first day to 3 weeks. The cardiogram shows a slow decrease in the S-T segment to the isoline. If the isoline is reached by the segment, then this stage is over. Also during the procedure, negative T is determined;
• scarring stage, in which a scar is formed. This stage lasts from several weeks to 3 months. During this period, the T wave gradually returns to the isoline. It can be positive. The increased height of the R wave is determined on the tape. If the Q wave is present, its pathological size decreases.

How are heart attacks of different sizes determined?

During a cardiogram, it is possible to identify pathological foci depending on the affected area. If it is located close to the outer wall of the cardiac tissue, an anterior type of infarction develops, which can cover the entire wall of the blood vessel. This will disrupt the blood flow of a large vessel. A small lesion affects the end of arterial branches. There are the following types of pathological lesions.

Large-focal

There are two options. Transmural type, in which the affected area covers the entire thickness of the myocardial wall. In this case, the ECG shows the absence of the R wave, the expansion of the deep Q wave. As a result of the sawing of the S-T segment high above the isoline, the T wave merges with the infarction zone. In the subacute period, a negative T wave is determined.

Large-focal lesions of the subepicardial type are characterized by the location of the affected area near the outer membrane. In this case, a reduced R wave and an increase and expansion of the Q wave are recorded. The S-T complex is located above the area of ​​the infarction, below the lines of other leads. Negative T is determined in the presence of a subacute type.

Finely focal

Subendocardial infarction is defined by damage to the area near the inner lining of the heart. In this case, the ECG will show a smoothing of the T wave. Intramural is characterized by a lesion in the muscle layer. In this case, no pathologies of the Q and R waves are detected.

Variation depending on the location of the pathology

To detect the presence of changes, 12 electrodes must be installed. If there is even the slightest suggestion of a heart attack, then using fewer electrodes is prohibited. Based on the location of the pathological focus, the cardiogram is recorded in different ways.

There are different localizations of the pathological focus:

• anterior infarction is characterized by the departure from the right arm of a deep Q wave, from the right leg - the S-T segment, turning into a negative T wave. Sensors emanating from the chest area record the absence of an R wave, from the right hand - a displacement of the S-T segment;
• lateral infarction is represented by changes emanating from the left arm, right leg in the form of an expanded Q wave, an increase in the S-T segment;
• Q infarction is characterized by changes emanating from the chest electrodes in the form of a significant elevation of the S-T segment, positive T;
• the posterior one shows an altered state emanating from the right leg in the form of a wide Q wave, a positive T wave, which is marked by deformation;
• infarction of the interventricular septum is represented by changes from the left arm, thoracic region. In this case, the lower S-T segment shifts, a positive T wave is determined, and Q deepens;
• Right ventricular infarction on the ECG is quite difficult to determine as a result of the common source of blood flow. Its detection requires the application of additional electrodes.

Is it always possible to determine pathology?

Despite the high effectiveness of the method, there are some difficulties that make it difficult to decipher in determining a heart attack using an electrocardiogram. These include excess weight of the subject, which affects the conductivity of the current, detection of new scars is difficult if there are scar changes on the heart, if the conductivity of the block is disrupted, old aneurysms of the heart muscle make it difficult to diagnose new dynamics.

However, provided that modern devices are used, it is possible to carry out automatic calculations of infarction lesions. If you carry out daily monitoring, you can track the patient’s condition throughout the day. ECG is the first method of detecting a heart attack. With its help, pathological foci can be detected in a timely manner, which increases the chance of recovery.