The prevalence of cardiovascular diseases in recent decades has become alarming. Myocardial infarction has become the leading cause of death in developed countries, the numbers continue to rise, the disease is rapidly getting younger, especially among men.
What is myocardial infarction?
A heart attack in the language of specialists is necrosis of the heart muscle, which occurs due to insufficient blood supply to the organ.
An acute condition is preceded by ischemic disease, which is caused by damage or blockage of the coronary arteries by atherosclerotic plaques.
Cholesterol deposits contribute to the formation of blood clots, which interfere with the supply of blood to the heart. If one of the parts of the myocardium does not receive oxygen within 20 minutes, tissue necrosis occurs. The number of dead cells depends on the size of the blocked artery. A heart attack develops quickly, accompanied by severe pain behind the sternum, which cannot be removed with medication.
Symptoms
Not so long ago, a heart attack was considered an age-related disease, but now it often happens in men in their thirties. Women are less likely to get sick, because they are protected by the hormone estrogen before menopause, which prevents the formation of plaques. Although women are less susceptible to heart attacks, they are more likely to suffer from the disease.
The main symptoms of a heart attack:
- Severe sudden chest pain. Pressing and squeezing pain sensations, radiating to the back and shoulder. Unlike angina pectoris, signs of a heart attack appear for no apparent reason and stress. Often, an attack begins at rest.
- Taking the pills does not bring relief.
- Loss of consciousness and breathing difficulties are possible.
- Acute heart attack is accompanied by arrhythmia, increased blood pressure and body temperature up to 38 ° C, increased heart rate.
Heart attack in women
Heart attack symptoms in women may be washed away. In about a month, the disease manifests itself as a loss of strength, insomnia, unreasonable anxiety, edema, discomfort in the abdomen, shortness of breath and aching pain.
The attack begins with severe chest pain, but because women can tolerate the discomfort patiently, they often ignore danger signals. The pain spreads to the neck and left arm, jaw and teeth may hurt. Severe nausea with heartburn and vomiting, dizziness, pain in the back of the head, loss of consciousness, cold sweats, and stiffness are common.
Heart attack in men
Preinfarction is rarely manifested by fatigue and anxiety. Usually, the only signal of impending trouble is pain in the region of the heart. Sometimes the attack begins with nausea, the upper back hurts, there is discomfort in the elbows, arms and legs, less often in the jaw. Choking, a burning sensation in the throat, heartburn, hiccups, pallor and a sharp loss of strength often develop.
Men rarely ignore the disease, therefore, they are provided with timely help and death due to myocardial infarction is less common than in women.
The difference in manifestations is explained by physiological characteristics:
- The size of a man's heart is larger than a woman's.
- Different heart rate for men and women.
To the question: "Is it possible to determine a heart attack by the first signs?" - there is only an affirmative answer. The prognosis for recovery depends on the timeliness of medical care. An ambulance should be called immediately when several signs of an attack appear at the same time.
Heart attack symptoms before diagnosis
| Anginal | The most common form of heart attack. Intense pressing and constricting pain does not go away after taking medication (nitroglycerin). Can be felt behind the breastbone, in the left arm, back, jaw. There is a fear of death, sweating, anxiety, weakness. |
| Asthmatic | An increased heartbeat is accompanied by shortness of breath and suffocation. Pain does not always occur, but it often precedes shortness of breath. Usually, this variant of the disease is observed in elderly people and those who have had a heart attack earlier. |
| Gastralgic | Pain in the upper abdomen may spread to the back at the scapula. Persistent hiccups, belching, nausea, vomiting, bloating. |
| Cerebrovascular | Dizziness often ends with fainting and disorientation. Nausea, vomiting. Diagnostics becomes more complicated, it can only be recognized by the cardiogram. |
| Arrhythmic | Palpitation, with a feeling of interruption in the work of the heart. Minor or unexpressed pain, weakness, shortness of breath, fainting. The condition is due to hypotension. |
| Malosymptomatic | Symptoms are ignored because they are mild. A heart attack is often carried on the legs, not paying attention to weakness, shortness of breath, arrhythmia. It is detected when cicatricial changes are detected when taking an ECG. |
Any of the listed symptoms should be a signal for urgent medical attention.
Diagnostics
An ECG if a heart attack is suspected is done without fail and as early as possible. If abnormalities in the work of the heart are detected, decoding of the cardiogram will show characteristic signs of ischemia or acute infarction, and will also help determine the type of damage and take adequate measures.
What does the electrocardiogram show (photo with decoding)?
The figure shows what the ECG section looks like:
- R- excitation of the atria. A positive value indicates sinus rhythm.
- PQ interval- the time of passage of the excitatory impulse through the atrial muscle to the ventricles.
- QRS complex- electrical activity of the ventricles.
- Q- an impulse in the left side of the interventricular septum.
- R- Excitation of the lower heart chambers.
- S- completion of excitation in the lower left chamber.
- ST segment- the period of excitation of both ventricles.
- T- restoration of the electrical potential of the lower chambers.
- QT interval- the period of contraction of the ventricles. For the rhythm frequency characteristic of sex and age, this value is constant.
- TR segment- a period of electrical passivity of the heart, relaxation of the ventricles and atria.
Types of infarction
With a heart attack, tissue necrosis and cicatricial changes can occur in different parts of the myocardium.
Localization at the site of damage differs as follows:
- Transmural infarction
Damages all layers of the myocardium. On the cardiogram, the penetrating lesion is reflected in a characteristic curve and is called Q infarction. A Q wave is formed, indicating the absence of electroactivity in the scar tissue.
The Q wave forms within hours or days after a heart attack and persists for a long time. With timely medical intervention and sufficient oxygen supply to the heart, damage can be prevented.
The absence of Q waves on the cardiogram does not exclude a heart attack.
- Mini infarction
With this type of lesion, point damage is noted. Necrosis does not interfere with the work of the heart muscle and is often carried on the legs.
A change in tissue condition is often detected on an ECG over time. After a mini-infarction, a Q-wave does not form.
- Subepicardial, subendocardial or non-wave heart attack
The lesion is located in the left ventricle on the inner layer. Depression of the ST segment is reflected on the ECG. The cardiogram does not show the Q wave, and the smoothing of the ST segment becomes evidence of violations.
Such conditions can be caused by anginal attacks or triggered by taking medications for arrhythmias.
Subendocardial infarction is said to be when the T segment shows horizontal or oblique depression. With physical exertion, a decrease of more than 1 mm or an oblique ascent of the curve is considered a sign of illness.
- Intramural
The middle section of the muscle is damaged, and the outer and inner membranes are not affected. In the description of the ECG, the doctor will include a T-wave inversion, which will be negative for up to 2 weeks. The ST segment does not become flat.
With the help of an ECG, the doctor determines the localization of the lesion.
After a heart attack, violations can be located on:
- Front septum
- The anterior wall of the left ventricle (in the endocardium, epicardium, or transmurally)
- On the posterior wall (subendocardial or transmural)
- Sideways
- In the lower section
- Combined arrangement possible
The most severe consequences are observed after anterior septal infarction and violation of the anterior wall of the left ventricle. The prognosis for this form of the disease is negative.
An isolated violation of the right ventricle is extremely rare, usually combined with an inferior lesion of the left ventricle. Mostly the posterior wall of the right ventricle suffers, sometimes the anterior lateral one. The ECG is determined with an additional description of the indicators in the right side of the sternum.
Development stages
With any localization, the development of a heart attack takes place in several stages. Whatever layers of the heart is affected by a heart attack, its development can be traced in several stages. After an ECG study, the doctor receives a photo with a transcript. The stages of the disease are approximately as follows:
| I | The most acute period | Up to 6 hours | In an acute focus, necrosis is formed. In the transmural form on the cardiogram, the monophasic ST curve merges with the T wave. Before the formation of necrosis, there is no Q wave on the ECG. The R peak decreases. The Q wave is more pronounced on the second day or after 4-6 days. With ST segment elevation, the prognosis is poor. |
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| II | Acute period | From the first hours to 7 days | The zone of damage in this period is formed completely, the edges may become inflamed. The ST segment is approaching the isoline. The site of necrosis does not conduct an electrical impulse, therefore, a Q wave and a negative T wave are expressed on the ECG. |
| III | Subacute period | 7-28 days | The most affected cells die, the rest are restored. The necrosis zone stabilizes. The ECG shows a Q wave, but ST is heading towards the baseline |
| IV | Scarring | From 29 days | Connective tissue cannot conduct electrical impulses. The Q wave on the ECG remains. Ischemia gradually disappears, the damaged area is not visible. The ST segment runs along the isoline, the T wave is higher. |
Types of infarction by the area of the lesion
Large focal
Transmural infarctions, which are characterized by such ECG indicators:
- Electrode A registers a Q wave
- Electrode B - R wave
The amplitude of the teeth allows you to judge the depth of the lesion.
Small focal
- Subendocardial infarction. The ECG shows a displacement of the S-T segment below the isoelectric line, but the Q wave is not recorded.
- Intramural infarction is characterized by necrosis of the myocardial wall and the preservation of the endocardium and epicardium.
Why is a heart attack dangerous?
Modern medicine knows how to eliminate the danger of acute heart attacks, but even after a treatment course, the disease is dangerous with complications:
- Acute heart failure;
- The likelihood of myocardial rupture;
- Discoordination of contractions of the heart muscle (fibrillation);
- Arrhythmia;
- Left ventricular aneurysm;
- Thrombosis of the heart.
In addition, the use of drugs can cause ulcers and bleeding in the gastrointestinal tract, hemorrhagic strokes, a sustained decrease in blood pressure to the level of hypotension.
ECG: implications for the diagnosis and treatment of heart attacks
The importance of ECG studies lies not only in the diagnosis of heart attacks, but also in the ability to differentiate diseases with similar symptoms.
So, in acute conditions associated with problems in the abdominal cavity, hernia of the diaphragm, blockage of the pulmonary artery, angina pectoris, pericarditis in the acute stage and other diagnoses, the disease manifests itself in pain, the localization of which allows the likelihood of a heart attack.
At the same time, altered cardiogram indices do not in all cases indicate problems in the work of the heart, and the absence of alarming indicators does not guarantee well-being in relation to cardiac activity.
Early diagnosis can reduce mortality from heart attacks, since the ability to isolate the site of necrosis is only in the first six hours after the first symptoms.
Video: ECG diagnosis of myocardial infarction
Myocardial infarction (necrosis of the tissues of the heart muscle) can be of varying severity, both asymptomatic and with pronounced characteristic pain.
In most cases, this disease at any stage is detected during routine examinations on an electrocardiograph.
This device, which has been used in cardiology for accurate diagnostics for over a hundred years, is able to provide information about the stage of the disease, its severity, as well as the location of the damage.
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Description of the method
An electrocardiograph is a device that can record electrical impulses. Human organs emit currents of very low voltage, therefore, for their recognition, the device is equipped with an amplifier, as well as a galvanometer that measures this voltage.
The resulting data is fed to a mechanical recording device. Under the influence of the currents emitted by the human heart, a cardiogram is built, on the basis of which the doctor can make an accurate diagnosis.
The rhythmic work of the heart is provided by a special tissue called the cardiac conduction system. It is a specially innervated regenerated muscle fibers that transmit commands for contraction and relaxation.
Acute transmural myocardial infarction of the lower LV wall complicated by type II AV block
The cells of a healthy heart perceive electrical impulses from the conducting system, the muscles contract, and the electrocardiograph registers these weak currents.
The device picks up impulses that have passed through the muscle tissue of the heart. Healthy fibers have a known electrical conductivity, while this parameter differs significantly in damaged or dead cells.
On the electrocardiogram, areas are marked, information from which has distortions and deviations, and it is they that carry information about the course of a disease such as a heart attack.
The main ECG signs in myocardial infarction
Diagnostics is based on measuring the electrical conductivity of individual parts of the heart. This parameter is influenced not only by the state of muscle fibers, but also by electrolytic metabolism in the body as a whole, which is disturbed in some forms of gastritis or cholecystitis. In this regard, there are often cases when an erroneous diagnosis of the presence of a heart attack is made based on the results of an ECG.
There are four distinct stages of a heart attack:
Acute transmural antero-septal myocardial infarction with possible transition to the apex of the heart
In each of these periods, the physical structure of the cell walls of muscle tissue, as well as their chemical composition, are different, so the electrical potential also differs significantly. ECG interpretation helps to accurately determine the stage of a heart attack and its size.
Most often, the left ventricle is susceptible to infarction, therefore, the form of a section of the cardiogram, which displays the Q, R and S waves, as well as the S - T interval and the T wave itself, has a diagnostic value.
The teeth characterize the following processes:
The electrodes are fixed on different parts of the body, which correspond to the projection of certain areas of the heart muscle. For the diagnosis of myocardial infarction, the indicators obtained from the six electrodes (leads) V1 - V6, installed on the left chest, are important.
The developing myocardial infarction on the ECG is most clearly manifested by the following signs:
- increase, change, absence or inhibition of the R wave over the infarction zone;
- pathological S wave;
- change in the direction of the T wave and deviation of the S - T interval from the isoline.
When a zone of necrosis is formed, the cells of the heart muscle are destroyed and potassium ions, the main electrolyte, are released.
The electrical conductivity in this area changes sharply, which is displayed on the cardiogram from the lead located directly above the necrotic area. The size of the damaged area is indicated by how many leads record the pathology.
Developing large-focal myocardial infarction of the lower wall of the LV
Indicators of age and frequency
Diagnosis of acute infarction occurs in the first 3-7 days, when there is an active formation of a zone of dead cells, a zone of ischemia and damage. During this period, the electrocardiograph records the maximum affected area, some of which will subsequently degenerate into necrosis, and some will fully recover.
At each stage of a heart attack, there is a specific picture of the diagram with leads located directly above the focus of the heart attack:
| In the acute stage, that is, when the disease is 3-7 days old, the characteristic signs are: |
The change in the direction of the teeth indicates that the walls of the ventricle are strongly hypertrophied, therefore the electric current in them does not move upward, but inward, towards the interventricular septum. At this stage, with proper treatment, it is possible to minimize the area of damage and the future area of necrosis, and with a small area, it can be completely restored. |
| The stage of formation of a necrotic area begins on the 7-10th day and has the following characteristic picture: |
At this stage, treatment is aimed at stabilizing the condition and relieving pain, since it is impossible to restore dead areas. Compensatory mechanisms of the heart are activated, which separate the damaged area. The blood washes away the products of death, and the tissues that have undergone necrosis are replaced by connective fibers, that is, a scar is formed. |
| The last stage is characterized by a gradual restoration of the ECG pattern, however, characteristic signs remain above the scar: |
This type of cardiogram appears because the connective tissue of the scar is not able to be excited and restored, respectively, there are no currents characteristic of these processes in these areas. |
Large-focal anterior-septal-apical-lateral myocardial infarction, complicated by complete blockade of the right bundle branch, AU blockade of the 1st degree and sinus arrhythmia
Determination of the site of circulatory disorders
It is possible to localize the zone of damage to the heart muscle by knowing which parts of the organ are visible on each lead. The placement of the electrodes is standard and provides a detailed examination of the whole heart.
Depending on which lead fixes the direct signs described above, you can determine the location of the heart attack:
Not all affected areas are given here, since a heart attack can occur in the right ventricle and in the posterior parts of the heart. When diagnosing, it is very important to collect as much information as possible from all leads, then the localization will be as accurate as possible. For a confident diagnosis, information must be confirmed by data from at least three leads.
The vastness of the focus
The extent of the lesion is determined in the same way as its localization. Conventionally, the lead electrodes "shoot" the heart in twelve directions, crossing in its center.
If you are examining the right side, then you can add six more to these 12 directions. A diagnosis of myocardial infarction requires conclusive evidence from at least three sources.
When determining the size of the lesion, it is necessary to carefully study the data from the leads located in the immediate vicinity of the lesion. Around the dying tissue there is a zone of damage, and around it there is a zone of ischemia.
Each of these areas has a characteristic ECG pattern, so their detection may indicate the size of the affected area. The true size of a heart attack is determined during the healing phase.
Transmural anterior-septal-apical myocardial infarction with transition to the lateral wall of the LV
Depth of necrosis
Various areas can be subject to death. Necrosis does not always occur along the entire thickness of the walls, more often it is deflected to the inner or outer side, sometimes located in the center.
On the ECG, you can confidently note the nature of the location. The S and T waves will change their shape and size depending on which wall the affected area is attached to.
Cardiologists distinguish the following types of necrosis location:
Possible difficulties
Although the ECG in myocardial infarction is considered an effective diagnostic method, certain difficulties arise with its use. For example, it is very difficult to correctly diagnose people with overweight, since the location of the heart muscle in them is changed.
If electrolyte metabolism is disturbed in the body or diseases of the stomach and gallbladder, it is also possible to distort the diagnosis.
Certain heart conditions, such as scarring or aneurysm, make new lesions barely noticeable. The physiological features of the structure of the conducting system also makes it impossible to accurately diagnose heart attacks of the interventricular septum.
Acute macrofocal myocardial infarction of the LV lower wall with transition to the septum and apex of the heart, LV lateral wall, complicated by atrial fibrillation and blockade of the right bundle branch
Pathology type
Depending on the size and location of the lesion, characteristic patterns are noted on the tape of the cardiograph. Diagnostics is carried out on the 11-14th day, that is, at the healing stage.
Large focal
This type of damage is characterized by the following picture:
Subendocardial
If the damage has affected the tissue from the inside, then the diagnostic picture is as follows:
Intramural
With heart attacks located in the thickness of the ventricular wall and not affecting the membrane of the heart muscle, the ECG graph is as follows:
Myocardial infarction on the ECG has a number of characteristic features that help differentiate it from other conduction and excitability disorders of the heart muscle. It is very important to conduct ECG diagnostics in the first few hours after an attack in order to obtain data on the depth of the lesion, the degree of functional heart failure, and the possible localization of the focus. Therefore, the cardiogram is removed, if possible, while still in the ambulance, and if this is not possible, then immediately upon the patient's arrival at the hospital.
ECG signs of myocardial infarction
The electrocardiogram reflects the electrical activity of the heart - by interpreting the data of such a study, one can obtain comprehensive information about the work of the conducting system of the heart, its ability to contract, pathological foci of excitation, as well as the course of various diseases.
The first sign that you should pay attention to is the deformation of the QRST complex, in particular, a significant decrease in the R wave or its complete absence.
The classic ECG pattern consists of several sections that can be seen on any normal tape. Each of them is responsible for a separate process in the heart.
- P wave- visualization of atrial contraction. By its height and shape, one can judge the state of the atria, their well-coordinated work with other parts of the heart.
- PQ interval- shows the propagation of an impulse of excitation from the atria to the ventricles, from the sinus node down to the atrioventricular. The lengthening of this interval indicates a violation of conductivity.
- QRST complex- the ventricular complex, which provides complete information about the state of the most important chambers of the heart, ventricles. The analysis and description of this part of the ECG is the most important part of the diagnosis of a heart attack, the main data is obtained from here.
- ST segment- an important part, which is normally an isoline (a straight horizontal line on the main axis of the ECG that does not have teeth), which can rise and fall in pathologies. This may be evidence of myocardial ischemia, i.e., insufficient blood supply to the heart muscle.
Any changes in the cardiogram and deviations from the norm are associated with pathological processes in the heart tissue. In the case of a heart attack - with necrosis, that is, the death of myocardial cells with their subsequent replacement with connective tissue. The stronger and deeper the damage, the wider the zone of necrosis, the more noticeable the changes in the ECG will be.
The first sign that you should pay attention to is the deformation of the QRST complex, in particular, a significant decrease in the R wave or its complete absence. This indicates a violation of the depolarization of the ventricles (an electrophysical process responsible for the contraction of the heart).
Any changes in the cardiogram and deviations from the norm are associated with pathological processes in the heart tissue. In the case of a heart attack - with the death of myocardial cells, followed by their replacement with connective tissue.
Further, the changes affect the Q wave - it becomes pathologically deep, which indicates a disruption in the work of pacemakers - nodes of special cells in the thickness of the myocardium, which begin to contract the ventricles.
The ST segment also changes - it is normally on the isoline, but with a heart attack it can rise higher or lower. In this case, they speak of elevation or depression of the segment, which is a sign of ischemia of the heart tissues. By this parameter, it is possible to determine the localization of the area of ischemic damage - the segment is raised in those parts of the heart where the necrosis is most pronounced, and lowered in opposite leads.
Also, after a while, especially closer to the stage of scarring, a negative deep T wave is observed. This wave reflects massive necrosis of the heart muscle and allows you to establish the depth of the damage.
Photo ECG with myocardial infarction with decoding allows you to consider the described signs in detail.
The tape can move at a speed of 50 and 25 mm per second, a lower speed with better detail is of greater diagnostic value. When diagnosing a heart attack, not only changes in leads I, II and III are taken into account, but also in enhanced ones. If the device allows you to record chest leads, then V1 and V2 will display information from the right heart - the right ventricle and atrium, as well as the apex, V3 and V4 about the apex of the heart, and V5 and V6 will indicate the pathology of the left sections.
Closer to the stage of scarring, a negative deep T wave is observed. This wave reflects massive necrosis of the heart muscle and allows you to establish the depth of damage.
Stages of myocardial infarction on ECG
A heart attack occurs in several stages, and each period is marked by special changes in the ECG.
- Ischemic stage (stage of injury, the most acute) associated with the development of acute circulatory failure in the tissues of the heart. This stage does not last long, therefore it is rarely registered on the cardiogram tape, but its diagnostic value is quite high. At the same time, the T wave increases, sharpens - they speak of a giant coronary T wave, which is a harbinger of a heart attack. Then ST rises above the isoline, its position is stable here, but further elevation is possible. When this phase lasts longer and becomes acute, a decrease in the T wave can be observed, as the necrosis focus extends to the deeper layers of the heart. Reciprocal, reverse changes are possible.
- Acute stage (necrosis stage) occurs 2-3 hours after the onset of the attack and lasts up to several days. On the ECG, it looks like a deformed, wide QRS complex, forming a monophasic curve, where it is almost impossible to distinguish individual teeth. The deeper the Q wave on the ECG, the deeper the layers were affected by ischemia. At this stage, you can recognize a transmural infarction, which will be discussed later. Rhythm disturbances are characteristic - arrhythmias, extrasystoles.
- Recognize the onset of a subacute stage it is possible to stabilize the ST segment. When it returns to the baseline, the infarction no longer progresses due to ischemia, the recovery process begins. Of greatest importance in this period is the comparison of the existing sizes of the T wave with the original ones. It can be either positive or negative, but will slowly return to the baseline in sync with the healing process. The secondary deepening of the T wave in the subacute stage indicates inflammation around the zone of necrosis and does not last long, with proper drug therapy.
- In the stage of scarring, the R wave rises again to its characteristic indicators, and T is already on the isoline. In general, the electrical activity of the heart is weakened, because some of the cardiomyocytes have died and are replaced by connective tissue, which does not have the ability to conduct and contract. Pathological Q, if present, is normalized. This stage lasts up to several months, sometimes six months.
It is very important to conduct ECG diagnostics in the first few hours after an attack in order to obtain data on the depth of the lesion, the degree of functional heart failure, and the possible localization of the focus.
The main types of heart attack on the ECG
In the clinic, a heart attack is classified according to the size and location of the lesion. This has implications for the management and prevention of delayed complications.
Depending on the size of the damage, a distinction is made between:
- Large focal, or Q-infarction. This means that a circulatory disorder has occurred in a large coronary vessel, and a large volume of tissue is affected. The main feature is deep and widened Q, and the R wave cannot be seen. If the infarction is transmural, that is, affecting all layers of the heart, the ST segment is located high above the isoline, in the subacute period there is a deep T. If the damage is subepicardial, that is, not deep and located next to the outer shell, then R will be recorded, albeit small.
- Small focal, non-Q-infarction. Ischemia has developed in areas fed by the terminal branches of the coronary arteries; this type of disease has a more favorable prognosis. In intramural infarction (damage does not extend beyond the heart muscle), Q and R do not change, but a negative T wave is present. In this case, the ST segment is on the isoline. With subendocardial infarction (focus in the inner membrane), T is normal, and ST is depressed.
Depending on the location, the following types of heart attack are determined:
- Antero-septal Q-infarction- noticeable changes in 1-4 chest leads, where there is no R in the presence of a wide QS, ST elevation. In I and II standard - classic for this type of pathological Q.
- Lateral Q-infarction- identical changes affect 4-6 chest leads.
- Posterior, or diaphragmatic Q-infarction, it is also lower- pathological Q and high T in II and III leads, as well as enhanced from the right leg.
- Ventricular septal infarction- in I standard deep Q, ST elevation and high T. In 1 and 2 chest pathologically high R, A-V blockade is also characteristic.
- Anterior non-Q infarction- in I and 1-4 chest T is higher than the preserved R, and in II and III, the decrease in all waves along with ST depression.
- Posterior non-Q infarction- in standard II, III and infants 5-6 positive T, decrease in R and ST depression.
Video
We offer you a video on the topic of the article for viewing.
I. Mogelvang, M.D. Cardiologist, Intensive Care Unit, Hvidovre Hospital 1988
Coronary artery disease (CHD)
The main cause of coronary artery disease is obstructive damage to the main coronary arteries and their branches.
The prognosis for ischemic heart disease is determined by:
number of significantly stenotic coronary arteries
functional state of the myocardium
The ECG gives the following information about the state of the myocardium:
potentially ischemic myocardium
ischemic myocardium
acute myocardial infarction (MI)
previous myocardial infarction
localization of MI
depth of IM
the size of IM
Information that is relevant for treatment, control and prognosis.
Left ventricle
In IHD, the myocardium of the left ventricle is primarily affected.
The left ventricle can be divided into segments:
Septal segment
Apical segment
Lateral segment
Posterior segment
Lower segment
The first 3 segments make up the anterior wall and the last 3 segments the posterior wall. The lateral segment can thus be involved in anterior wall infarction as well as posterior wall infarction.
SEGMENTS OF THE LEFT VENTRICLE
ECG LEADS
ECG leads can be unipolar (derivatives of one point), in this case they are denoted by the letter "V" (from the initial letter of the word "voltage").
Classic ECG leads are bipolar (derived from two points). They are designated by Roman numerals: I, II, III.
A: reinforced
V: unipolar lead
R: right (right hand)
L: left (left hand)
F: leg (left leg)
V1-V6: unipolar chest leads
ECG leads reveal changes in the frontal and horizontal planes.
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Hand to hand |
Lateral segment, septum |
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Right arm -> left leg |
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Left hand -> left leg |
Lower segment |
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(Reinforced unipolar) right hand |
Attention! Possible misinterpretation |
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(Reinforced unipolar) left hand |
Lateral segment |
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(Reinforced unipolar) left leg |
Lower segment |
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(Unipolar) at the right edge of the sternum |
Septum / Posterior segment * |
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(Unipolar) |
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(Unipolar) |
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(Unipolar) |
Top |
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(Unipolar) |
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(Unipolar) on the left mid axillary line |
Lateral segment |
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* - V1-V3 mirror image of changes in the posterior segment |
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ECG leads in the frontal plane
ECG leads in the horizontal plane
MIRROR IMAGE(with a specific diagnostic value found in leads V1-V3, see below)
Right and Left Ventricular Cross Sections & Left Ventricular Segments:
Relationship Between ECG Leads and Left Ventricular Segments
Depth and dimensions
QUALITATIVE ECG CHANGES
QUANTITATIVE ECG CHANGES
LOCALIZATION OF INFARCTION: FRONT WALL
LOCALIZATION OF INFARCTION: BACK WALL
V1-V3; FREQUENT CHALLENGES
Heart attack and bundle branch block (BNP)
BNP is characterized by a wide QRS complex (0.12 sec).
Right leg block (RBB) and left leg block (LBB) can be distinguished by lead V1.
RBF is characterized by a positive wide QRS complex, and LBB is characterized by a negative QRS complex in lead V1.
Most often, the ECG does not provide information about a heart attack in LBB, in contrast to RBN.
ECG changes in myocardial infarction over time
Myocardial infarction and silent ECG
Myocardial infarction can develop without the appearance of any specific ECG changes in the case of LBB, but also in other cases.
ECG options for myocardial infarction:
subendocardial MI
transmural MI
no specific changes
ECG for suspected coronary artery disease
Specific signs of coronary heart disease:
Ischemia / Heart attack?
In case of a heart attack:
Subendocardial / transmural?
Localization and size?
Differential diagnosis
ECG DIAGNOSTIC KEY FOR CORONARY HEART DISEASE
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PD KopT - suspected KopT |
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States: |
ECG symbols: |
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1. Ischemia of the anterior segment 2. Ischemia of the lower segment 3. Subendocardial inferior MI 4. Subendocardial inferior-posterior MI 5. Subendocardial inferior-postero-lateral MI 6. Subendocardial anterior infarction (common) 7. Acute inferior MI 8. Acute posterior MI 9. Acute frontal MI 10. Transmural inferior MI 11. Transmural posterior MI 12. Transmural anterior MI (common) (septal-apical-lateral) * Mirror picture (mirror) ST G is visible not only in posterior MI, in this case it is called reciprocal changes. For simplicity, this is released in context. The mirror image of ST Г and ST L cannot be distinguished. |
It is extremely important to determine the heart attack in time. However, it is not always possible to do this by visual examination, since the signs of an attack are nonspecific and may indicate many other cardiac pathologies. Therefore, the patient is obliged to undergo additional instrumental studies, primarily ECG. With this method, the diagnosis can be made in a short time. How the procedure is carried out and how the results are deciphered, we will consider in this article.
An ECG is performed using an electrocardiograph. The curved line that the device gives out is the electrocardiogram. It shows the moments of contraction and relaxation of the heart muscle of the myocardium.
The device detects the bioelectric activity of the heart, that is, its pulsation, caused by biochemical, biophysical processes. They are formed in various lobes of the heart and are transmitted throughout the body, redistributing to the skin.
Attached electrodes to different parts of the body pick up impulses. The device notes the difference in potentials, which immediately fixes. By the specifics of the received cardiogram, the cardiologist concludes how the heart works.
It is possible to distinguish five inconsistencies with the main line - isolines - these are the S, P, T, Q, R teeth. All of them have their own parameters: height, width, polarity. Essentially, the designation is endowed with periodicities limited by the teeth: from P to Q, from S to T, as well as from R to R, from T to P, including their combined connection: QRS and QRST. They are a mirror of the work of the myocardium.
During normal heart operation, P is displayed first, followed by Q. For the time window between the time of atrial pulsation increase and the time of the ventricular pulsation increase, it shows the P - Q interval. This pattern is displayed as QRST.
At the highest limit of ventricular oscillation, an R wave appears. At the peak of the ventricular pulsation, an S wave appears. When the heart rhythm reaches its highest pulsation point, there is no difference between the potentials. This is shown by a straight line. If ventricular arrhythmia occurs, a T wave appears. An ECG with myocardial infarction allows one to judge the deviations of the heart.
Preparation and implementation
Performing an ECG procedure requires careful preparation. On the body where the electrodes are supposed to be placed, hair is shaved off. Then the skin is wiped with an alcohol solution.
Electrodes are attached to the chest and arms. Before recording the cardiogram, set the exact time on the recorder. The main task of the cardiologist is to control the parabolas of the ECG complexes. They are displayed on a special oscilloscope screen. In parallel, listening to all heart sounds is carried out.
ECG signs of acute heart attack
With the help of an ECG, thanks to the leads of the electrodes from the limbs and chest, it is possible to establish the form of the pathological process: complicated or uncomplicated. The stage of the disease is also determined. With an acute degree, the Q wave is not visible. But in the chest bases there is an R wave, indicating pathology.
There are such ECG signs of myocardial infarction:
- There is no R wave in the supra-infarction areas.
- A Q wave appears, indicating an anomaly.
- The S and T segment rises higher and higher.
- The S and T segment is shifting more and more.
- A T wave appears, indicating pathology.
MI on cardiogram
The dynamics in acute heart attack looks like this:
- The heart rate increases.
- The S and T segment begins to rise high.
- The S and T segment goes very low.
- The QRS complex is pronounced.
- A Q wave or a Q and S complex is present, indicating pathology.
An electrocardiogram is able to show the main three phases of an infarction state. It:
- transmural infarction;
- subendocardial;
- intramural.
Signs of a transmural infarction are as follows:
- in the left ventricular wall, the development of necrolysis begins;
- an abnormal Q wave is formed;
- a pathological tooth with a small amplitude appears.
Subendocardial infarction is a reason for urgent surgical intervention. It should be completed within the next 48 hours.
Necrotic cells in this form of an attack form a narrow shelf along the edge of the left ventricle. In this case, it can be noted on the cardiogram:
- absence of a Q wave;
- in all leads (V1 - V6, I, aVL), there is a decrease in the ST segment - an arc down
- decrease in the R wave;
- the formation of a "coronary" positive or negative T wave;
- changes are present during the week.
The intramural form of an attack is quite rare, its sign is the presence of a negative T wave on the cardiogram, which persists for two weeks, after which it becomes positive. That is, when diagnosing, it is the dynamics of the myocardial state that is important.
Decoding cardiogram
In the formulation of the diagnosis, the correct decoding of the cardiogram plays an important role, namely, the establishment of the type of attack and the amount of damage to the heart tissue.
Different types of seizure
The cardiogram allows you to determine which heart attack is taking place - small-focal and large-focal. In the first case, small amounts of damage are present. They are concentrated directly in the region of the heart. Complications are as follows:
- aneurysm of the heart and its rupture;
- heart failure;
- ventricular fibrillation;
- asystological thromboembolism.
The onset of small-focal infarction is not often recorded. Most often, large focal occurs. It is characterized by significant and rapid disruption in the coronary arteries due to thrombosis or prolonged spasms. As a result, a large area of dead tissue appears.
Localization of the lesion is the basis for dividing a heart attack into:
- front;
- rear;
- IM of the septum;
- lower;
- MI of the side wall.
Based on the course, the attack is divided into:
Heart attacks are classified even by the depth of the lesion, depending on the depth of tissue death.
How to determine the stage of pathology?
With a heart attack, the dynamics of necrolysis can be traced in this way. In one of the areas, due to the lack of blood supply, tissues begin to die off. On the periphery, they are still preserved.
There are four stages of myocardial infarction:
- the most acute;
- sharp;
- subacute;
- cicatricial.
Their signs on the ECG are as follows:
ECG today is one of the most common and informative methods for detecting acute cardiac disorders. Revealing signs of any of their stages or forms of heart attack requires immediate treatment or proper restorative therapy. This will prevent the risk of complications, as well as a second attack.
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