The prevalence of cardiovascular diseases has become alarming in recent decades. Myocardial infarction has become the leading cause of death in developed countries, the numbers continue to rise, and the disease is rapidly becoming younger, especially among men.
What is myocardial infarction?
In the language of specialists, a heart attack is necrosis of the heart muscle that occurs due to insufficient blood supply to the organ.
The acute condition is preceded by ischemic disease, the cause of which is damage or blockage of the coronary arteries by atherosclerotic plaques.
Cholesterol deposits contribute to the formation of blood clots, which impair the blood supply to the heart. If one of the areas 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 and is accompanied by severe pain in the chest, which cannot be relieved with medications.
Symptoms
Not so long ago, heart attack was considered an age-related disease, but now it often occurs in thirty-year-old men. Women get sick less often because before menopause they are protected by the hormone estrogen, which prevents the formation of plaques. Although women are less susceptible to heart attacks, they suffer more severely from the disease.
Main symptoms of a heart attack:
- Severe sudden pain in the chest. Pressing and squeezing pain, radiating to the back and shoulder. Unlike angina, signs of a heart attack appear without apparent cause or stress. Often the attack begins at rest.
- Taking pills does not bring relief.
- Possible loss of consciousness and difficulty breathing.
- An acute heart attack is accompanied by arrhythmia, increased blood pressure and body temperature up to 38 o C, and increased heart rate.
Heart attack in women
Symptoms of a heart attack in women may be blurred. In about a month, the disease manifests itself as loss of strength, insomnia, unreasonable anxiety, swelling, discomfort in the abdomen, shortness of breath and aching pain.
The attack begins with severe pain in the chest, but since women are able to patiently endure unpleasant sensations, they often ignore danger signals. The pain spreads to the neck and left arm, and the jaw and teeth may hurt. Often there is severe nausea with heartburn and vomiting, dizziness, pain in the back of the head, loss of consciousness, cold sweat and stiffness in the body.
Heart attack in men
The pre-infarction state is rarely manifested by fatigue and anxiety. Usually the only signal of impending trouble is pain in the heart area. Sometimes an attack begins with nausea, the upper back hurts, there is discomfort in the elbows, arms and legs, and less often in the jaw. Choking, burning in the throat, heartburn, hiccups, pallor and sudden loss of strength often develop.
Men rarely ignore the disease, so they receive help in a timely manner 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 that of a woman's.
- Different heart rates in 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 simultaneously.
Symptoms of a heart attack before diagnosis
| Anginal | The most common form of heart attack. Intense pressing and squeezing pain does not go away after taking medications (nitroglycerin). It can be felt behind the sternum, in the left arm, back, jaw. There is a fear of death, sweating, anxiety, and weakness. |
| Asthmatic | Increased heart rate is accompanied by shortness of breath and suffocation. Pain does not always occur, but it often precedes shortness of breath. Typically, this variant of the disease is observed in older people and those who have had a previous heart attack. |
| Gastralgic | Pain in the upper abdomen may spread to the back near the shoulder blade. Persistent hiccups, belching, nausea, vomiting, bloating. |
| Cerebrovascular | Dizziness often ends in fainting and loss of orientation. Nausea, vomiting. Diagnosis becomes more complicated; it can only be recognized by a cardiogram. |
| Arrhythmic | Palpitations with a feeling of interruptions in the heart. Minor or unexpressed pain, weakness, shortness of breath, fainting. The condition is caused by hypotension. |
| Asymptomatic | Symptoms are ignored due to their mild severity. A heart attack is often suffered on the legs, not paying attention to weakness, shortness of breath, and arrhythmia. It is detected when an ECG reveals scar changes. |
Any of the listed symptoms should be a signal to urgently seek medical help.
Diagnostics
If a heart attack is suspected, an ECG must be done as early as possible. If disturbances in the functioning of the heart are detected, deciphering the cardiogram will show characteristic signs of ischemia or acute infarction, and will also allow you to determine the type of damage and take adequate measures.
What does an electrocardiogram show (photo with transcript)?
The figure shows what an ECG section looks like:
- R- atrial excitation. A positive value indicates sinus rhythm.
- PQ interval- time of passage of the exciting impulse through the atrium muscle to the ventricles.
- QRS complex- electrical activity of the ventricles.
- Q- impulse in the left part of the interventricular septum.
- R- stimulation of the lower cardiac chambers.
- S- completion of excitation in the lower left chamber.
- ST segment- period of excitation of both ventricles.
- T– restoration of the electrical potential of the lower chambers.
- QT interval- period of ventricular contraction. For rhythm frequency characteristic of gender and age, this value is constant.
- TR segment- a period of electrical passivity of the heart, relaxation of the ventricles and atria.
Types of heart attack
During a heart attack, tissue necrosis and scar changes can occur in different parts of the myocardium.
Localization at the site of damage varies as follows:
- Transmural infarction
Damages all layers of the myocardium. On the cardiogram, a penetrating lesion is reflected in a characteristic curve and is called a Q infarction. A Q wave is formed, indicating the absence of electrical activity in the scar tissue.
The Q wave forms within a few 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-heart attack
With this type of lesion, point lesions are noted. Necrosis does not interfere with the functioning 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 infarction
The source of damage is located in the left ventricle on the inner layer. ST segment depression is reflected in the ECG. The cardiogram does not show a Q wave, and the smoothing of the ST segment becomes evidence of disturbances.
Such conditions can be caused by anginal attacks or provoked by taking medications for arrhythmia.
Subendocardial infarction is said to occur when the T segment shows horizontal or oblique depression. During physical activity, a decrease of more than 1 mm or a sloping ascent of the curve is considered a sign of disease.
- Intramural
The middle section of the muscle is damaged, but the outer and inner membranes are not affected. In the ECG description, the doctor will include T-wave inversion, which will be negative for up to 2 weeks. The ST segment does not become flat.
Using an ECG, the doctor determines the location of the lesion.
After a heart attack, disorders can be located on:
- Anterior septum
- Anterior wall of the left ventricle (in the endocardium, epicardium or transmural)
- On the posterior wall (subendocardial or transmural)
- Side
- In the lower section
- Combined arrangement possible
The most severe consequences are observed after anteroseptal infarction and disruption of the anterior wall of the left ventricle. The prognosis for this form of the disease is negative.
An isolated disorder of the right ventricle is extremely rare and is usually combined with an inferior lesion of the left ventricle. It is mainly the posterior wall of the right ventricle that is affected, sometimes the anterior lateral wall. The ECG is determined with an additional description of the indicators on the right side of the sternum.
Stages of development
At any location, the development of a heart attack occurs in several stages. Whatever layers of the heart are affected by a heart attack, its development can be tracked in several stages. After the ECG examination, the doctor receives a photo with a transcript. The stages of the disease look something like this:
| I | The most acute period | Up to 6 hours | In an acute focus, necrosis forms. In the transmural form, the monophasic ST curve on the cardiogram merges with the T wave. Before the formation of necrosis, the Q wave is absent on the ECG. The R peak decreases. The Q wave is more pronounced on the second day or after 4-6 days. ST segment elevation has a poor prognosis. |
|---|---|---|---|
| II | Acute period | From the first hours to 7 days | During this period, the damaged area is completely formed; the edges may become inflamed. The ST segment approaches the isoline. The area of necrosis does not conduct an electrical impulse, so the ECG shows a Q wave and a negative T wave. |
| III | Subacute period | 7-28 days | The most damaged cells die, the rest are restored. The necrosis zone is stabilized. The ECG shows a Q wave, but the ST is directed towards the baseline |
| IV | Scarring | From 29 days | Connective tissue cannot conduct electrical impulses. The Q wave on the ECG remains. Ischemia gradually passes, the damaged area is not visible. The ST segment runs along the isoline, the T wave is higher. |
Types of heart attack by area affected
Large-focal
Transmural infarctions, which are characterized by the following ECG indicators:
- Electrode A registers the Q wave
- Electrode B - R wave
The amplitude of the teeth allows us to judge the depth of the lesion.
Finely 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 preservation of the endocardium and epicardium.
Why is a heart attack dangerous?
Modern medicine can eliminate the danger of acute heart attacks, but even after a course of treatment the disease is dangerous due to complications:
- Acute heart failure;
- Possibility of myocardial rupture;
- Uncoordinated 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, and a sustained decrease in blood pressure to the level of hypotension.
ECG: significance for the diagnosis and treatment of heart attacks
The importance of an ECG study lies not only in the diagnosis of heart attacks, but also in the ability to differentiate diseases with similar symptoms.
Thus, in acute conditions associated with problems in the abdominal cavity, diaphragmatic hernia, blockage of the pulmonary artery, angina pectoris, pericarditis in the acute stage and other diagnoses, the disease is manifested by pain, the localization of which allows the possibility of a heart attack.
At the same time, altered cardiogram indicators do not in all cases indicate problems in the functioning 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 it is possible to isolate the area of necrosis only in the first six hours after the first symptoms.
Video: ECG diagnosis of myocardial infarction
Myocardial infarction (necrosis of cardiac muscle tissue) can have varying severity, occurring both asymptomatically and with pronounced characteristic pain.
In most cases, this disease at any stage is detected during routine examinations with an electrocardiograph.
This device, which has been used in cardiology for accurate diagnosis for over a hundred years, can 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 technique
An electrocardiograph is a device that is capable of recording electrical impulses. Human organs emit currents of very low voltage, therefore, to recognize them, the device is equipped with an amplifier, as well as a galvanometer that measures this voltage.
The resulting data is sent to a mechanical recording device. Under the influence of currents emitted by the human heart, a cardiogram is constructed, on the basis of which the doctor can make an accurate diagnosis.
The rhythmic functioning of the heart is ensured by a special tissue called the cardiac conduction system. It is a specially innervated degenerated muscle fiber that transmits commands to contract and relax.
Acute transmural myocardial infarction of the inferior wall of the left ventricle, complicated by type II degree AV block
Cells in a healthy heart receive electrical impulses from the conduction system, the muscles contract, and the electrocardiograph records 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 in damaged or dead cells this parameter is significantly different.
The electrocardiogram shows areas from which information is distorted and abnormal, and it is they that carry information about the course of a disease such as a heart attack.
Main ECG signs of myocardial infarction
Diagnosis is based on measuring the electrical conductivity of individual areas of the heart. This parameter is affected not only by the state of muscle fibers, but also by electrolytic metabolism in the body as a whole, which is disrupted in some forms of gastritis or cholecystitis. In this regard, there are often cases when the ECG results make an erroneous diagnosis of the presence of a heart attack.
There are four distinct stages of a heart attack:
Acute transmural anteroseptal myocardial infarction with possible transition to the apex of the heart
In each of these periods, the physical structure of the cell membranes 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 stages of a heart attack and its size.
Most often, the left ventricle is susceptible to infarction, so the type of section of the cardiogram that displays the Q, R and S waves, as well as the S-T interval and the T wave itself is of diagnostic importance.
The teeth characterize the following processes:
Electrodes are fixed on various 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 six electrodes (leads) V1 – V6 installed on the chest on the left are important.
Developing myocardial infarction on the ECG is most clearly manifested by the following signs:
- increase, change, absence or suppression of the R wave over the infarction area;
- pathological S wave;
- change in the direction of the T wave and deviation of the S – T interval from the isoline.
When a necrosis zone forms, the heart muscle cells are destroyed and potassium ions, the main electrolyte, are released.
The electrical conductivity in this area changes sharply, which is reflected in the cardiogram from the lead that is 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 inferior wall of the LV
Indicators of recency and frequency
Diagnosis of an acute infarction occurs in the first 3-7 days, when the active formation of a zone of dead cells, a zone of ischemia and damage occurs. During this period, the electrocardiograph records the maximum affected area, some of which will later degenerate into necrosis, and some will completely recover.
At each stage of a heart attack, it has its own specific diagram pattern from the leads located directly above the heart attack:
| At the acute stage, that is, when the disease is 3–7 days old, the characteristic signs are: |
A change in the directions of the teeth indicates that the walls of the ventricle are greatly hypertrophied, so 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 if the area is small, it can be completely restored. |
| The stage of formation of the necrotic area occurs on days 7–10 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. The 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, but 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; accordingly, the currents characteristic of these processes are absent in these areas. |
Large-focal anteroseptal-apical-lateral myocardial infarction, complicated by complete block of the right bundle branch, AV block of the first degree and sinus arrhythmia
Determining the location of the circulatory disorder
You can localize the area of damage to the heart muscle by knowing which parts of the organ are visible in each lead. Electrode placement is standard and provides detailed examination of the entire heart.
Depending on which lead records the direct signs described above, the location of the infarction can be determined:
Not all affected areas are shown here, since infarction can occur in both the right ventricle and 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.
Extensiveness of the outbreak
The extent of the source of damage is determined in the same way as its location. Conventionally, the lead electrodes “shoot” the heart in twelve directions, intersecting in its center.
If the right side is examined, then six more directions can be added to these 12 directions. To make a diagnosis of myocardial infarction, convincing data from at least three sources is required.
When determining the size of the focus of damage, it is necessary to carefully study the data from the leads located in the immediate vicinity of the focus of necrosis. 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 the infarction is determined during the healing stage.
Transmural anteroseptal-apical myocardial infarction with transition to the lateral wall of the LV
Depth of necrosis
Various areas may be susceptible to dieback. Necrosis does not always occur throughout the entire thickness of the walls; more often it is deviated towards the inner or outer side, sometimes located in the center.
On the ECG one 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 ECG for myocardial infarction is considered an effective diagnostic method, certain difficulties arise in its use. For example, it is very difficult to correctly diagnose overweight people, since the location of their heart muscle is changed.
If there is a violation of electrolyte metabolism in the body or diseases of the stomach and gallbladder, distortion in the diagnosis is also possible.
Some heart conditions, such as scarring or an aneurysm, make new damage barely noticeable. The physiological features of the structure of the conduction system also make it impossible to accurately diagnose infarctions of the interventricular septum.
Acute large-focal myocardial infarction of the lower wall of the LV with transition to the septum and apex of the heart, the lateral wall of the LV, complicated by atrial fibrillation and right bundle branch block
Type of pathology
Depending on the size and location of the lesion, characteristic patterns are noted on the cardiograph tape. Diagnosis is carried out on days 11–14, that is, at the healing stage.
Large-focal
The following picture is typical for this type of damage:
Subendocardial
If the damage has affected the tissue from the inside, then the diagnostic picture is as follows:
Intramural
For heart attacks located deep in the ventricular wall and not affecting the lining of the heart muscle, the ECG graph is as follows:
Myocardial infarction on the ECG has a number of characteristic signs that help differentiate it from other disorders of conduction and excitability of the heart muscle. It is very important to conduct an ECG diagnosis 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 lesion. Therefore, if possible, the cardiogram is taken 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
An electrocardiogram reflects the electrical activity of the heart - by interpreting the data from such a study, one can obtain comprehensive information about the functioning of the conduction system of the heart, its ability to contract, pathological foci of excitation, as well as the course of various diseases.
The first sign to look for is deformation of the QRST complex, in particular, a significant reduction in the R wave or its complete absence.
The classic ECG picture consists of several areas 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 coordinated work with other parts of the heart.
- PQ interval– shows the spread of the excitation impulse from the atria to the ventricles, from the sinus node down to the atrioventricular node. Prolongation of this interval indicates a conduction disorder.
- QRST complex– ventricular complex, which provides complete information about the state of the most important chambers of the heart, the ventricles. Analysis and description of this part of the ECG is the most important part of diagnosing 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, without teeth), in pathologies it can fall and rise. 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 cardiac tissue. In the case of a heart attack - with necrosis, that is, necrosis of myocardial cells with their subsequent replacement with connective tissue. The stronger and deeper the damage, the wider the area of necrosis, the more noticeable the changes on the ECG will be.
The first sign to look for is deformation of the QRST complex, in particular, a significant reduction in the R wave or its complete absence. This indicates a violation of ventricular depolarization (the electrical process responsible for heart contraction).
Any changes in the cardiogram and deviations from the norm are associated with pathological processes in the cardiac tissue. In the case of a heart attack - with the necrosis of myocardial cells, followed by their replacement with connective tissue.
Further changes affect the Q wave - it becomes pathologically deep, which indicates a disruption in the functioning of pacemakers - nodes made of special cells in the thickness of the myocardium that begin contraction of the ventricles.
The ST segment also changes - normally it is on the isoline, but during a heart attack it can rise higher or fall lower. In this case, they speak of elevation or depression of the segment, which is a sign of ischemia of the heart tissue. Using 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 necrosis is most pronounced, and lowered in the opposite leads.
Also, after some time, especially closer to the scarring stage, a negative deep T wave is observed. This wave reflects massive necrosis of the heart muscle and makes it possible to determine the depth of damage.
An ECG photo for myocardial infarction with interpretation allows you to consider the described signs in detail.
The tape can move at speeds of 50 and 25 mm per second; lower speeds with better detail have greater diagnostic value. When diagnosing a heart attack, not only changes in leads I, II and III are taken into account, but also in the reinforced ones. If the device allows you to record the chest leads, then V1 and V2 will display information from the right parts of the 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 parts.
Closer to the scarring stage, a negative deep T wave is observed. This wave reflects massive necrosis of the heart muscle and allows you to determine 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 on the ECG.
- Ischemic stage (damage stage, acute) associated with the development of acute circulatory failure in the tissues of the heart. This stage does not last long, so it is rarely recorded on a cardiogram tape, but its diagnostic value is quite high. At the same time, the T wave increases and becomes sharper - they speak of a giant coronary T wave, which is a harbinger of a heart attack. Then ST rises above the isoline; its position here is stable, but further elevation is possible. When this phase lasts longer and becomes acute, a decrease in the T wave can be observed, as the focus of necrosis spreads to the deeper layers of the heart. Reciprocal and 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 waves. The deeper the Q wave on the ECG, the deeper layers were affected by ischemia. At this stage, transmural infarction can be recognized, which will be discussed later. Characteristic rhythm disturbances are arrhythmias, extrasystoles.
- Recognize the onset of the subacute stage possible by stabilizing the ST segment. When it returns to the baseline, the infarction no longer progresses due to ischemia, and the recovery process begins. The greatest importance in this period is the comparison of the existing T wave sizes with the original ones. It can be either positive or negative, but will slowly return to the baseline in sync with the healing process. Secondary deepening of the T wave in the subacute stage indicates inflammation around the necrosis zone and does not last long, with proper drug therapy.
- In the scarring stage, the R wave rises again to its characteristic values, 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 been 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 an ECG diagnosis 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 lesion.
Main types of heart attack on ECG
In the clinic, a heart attack is classified depending on the size and location of the lesion. This is important in the treatment and prevention of delayed complications.
Depending on the size of the damage, there are:
- Large-focal, or Q-infarction. This means that the circulatory disorder occurred in a large coronary vessel, and a large volume of tissue is affected. The main sign is a deep and widened Q wave, 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 a deep T is observed. 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 developed in areas supplied by the terminal branches of the coronary arteries; this type of disease has a more favorable prognosis. With an intramural infarction (the 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. In subendocardial infarction (focus near the inner lining), T is normal and ST is depressed.
Depending on the location, the following types of heart attack are determined:
- Anteroseptal Q-infarction– noticeable changes in 1-4 chest leads, where there is no R in the presence of wide QS, ST elevation. In standard I and II – pathological Q, classic for this type.
- Lateral Q-infarction– identical changes affect chest leads 4-6.
- Posterior or diaphragmatic Q-infarction, also known as inferior– pathological Q and high T in leads II and III, as well as intensified from the right leg.
- Interventricular septal infarction– in standard I, deep Q, ST elevation and high T. In thoracic 1 and 2, R is pathologically high, and A-V block is also characteristic.
- Anterior non-Q infarction– in thoracic I and 1-4 T is higher than the preserved R, and in II and III there is a decrease in all waves along with ST depression.
- Posterior non-Q infarction– in standard II, III and chest 5-6 positive T, decreased R and depression ST.
Video
We offer you to watch a video on the topic of the article.
I. Mogelwang, M.D. Cardiologist of the intensive care unit of the Hvidovre Hospital 1988
Coronary heart disease (CHD)
The main cause of IHD is obstructive damage to the main coronary arteries and their branches.
The prognosis for IHD is determined by:
number of significantly stenotic coronary arteries
functional state of the myocardium
The ECG provides the following information about the state of the myocardium:
potentially ischemic myocardium
ischemic myocardium
acute myocardial infarction (MI)
previous myocardial infarction
MI localization
MI depth
MI sizes
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 make up the posterior wall. The lateral segment may 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 which case they are designated by the letter “V” (after the initial letter of the word “voltage”).
Classic ECG leads are bipolar (derivatives of 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 hand -> left foot |
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Left hand -> left foot |
Lower segment |
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(Enhanced unipolar) right hand |
Attention! Possible misinterpretation |
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(Enhanced unipolar) left hand |
Lateral segment |
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(Enhanced 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) along the left middle 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 detected in leads V1-V3, see below)
Cross section of right and left ventricles & Left ventricle segments:
Relationship between ECG leads and left ventricular segments
Depth and dimensions
QUALITATIVE ECG CHANGES
QUANTITATIVE ECG CHANGES
LOCALIZATION OF INFARCTION: ANTERIOR WALL
LOCALIZATION OF INFARCTION: POSTERIOR WALL
V1-V3; COMMON DIFFICULTIES
Infarction and bundle branch block (BBB)
LBP is characterized by a wide QRS complex (0.12 sec).
Right bundle branch block (RBB) and left bundle branch block (LBB) can be distinguished by lead V1.
RBP is characterized by a positive wide QRS complex, and LBP is characterized by a negative QRS complex in lead V1.
Most often, the ECG does not provide information about a heart attack in LBBB, unlike in LPN.
ECG changes in myocardial infarction over time
Myocardial infarction and silent ECG
Myocardial infarction can develop without the appearance of any specific changes on the ECG in the case of LBBB, but also in other cases.
ECG options for myocardial infarction:
subendocardial MI
transmural MI
without specific changes
ECG for suspected coronary heart disease
Specific signs of coronary heart disease:
Ischemia/Infarction?
In case of a heart attack:
Subendocardial/transmural?
Localization and sizes?
Differential diagnosis
ECG DIAGNOSTICS KEY FOR CORONARY HEART DISEASE
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PD KopT - suspicion of KopT |
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States: |
ECG symbols: |
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1. Anterior segment ischemia 2. Ischemia of the lower segment 3. Subendocardial inferior MI 4. Subendocardial infero-posterior MI 5. Subendocardial infero-posterior-lateral MI 6. Subendocardial anterior infarction (common) 7. Acute inferior MI 8. Acute posterior MI 9. Acute anterior MI 10. Transmural inferior MI 11. Transmural posterior MI 12. Transmural anterior MI (widespread) (septal-apical-lateral) * The mirror pattern (zer) of ST G is visible not only with posterior MI, in this case it is called reciprocal changes. For simplicity, this is released in context. The mirror image of ST G and ST L cannot be distinguished. |
It is extremely important to detect a heart attack in a timely manner. However, this is not always possible to do by visual examination, since the signs of an attack are nonspecific and may indicate many other cardiac pathologies. Therefore, the patient must undergo additional instrumental studies, primarily an ECG. Using this method, it is possible to establish a diagnosis in a short time. We will look at how the procedure is carried out and how the results are interpreted in this article.
An ECG is performed using an electrocardiograph. The curved line that the device produces is an electrocardiogram. It shows the moments of contraction and relaxation of the myocardial cardiac muscle.
The device detects the bioelectrical activity of the heart, that is, its pulsation caused by biochemical and biophysical processes. They are formed in various lobes of the heart and are transmitted throughout the body, redistributing to the skin.
Electrodes attached to various parts of the body pick up the impulses. The device notes the difference in potentials, which it immediately records. Based on the specifics of the resulting cardiogram, the cardiologist makes a conclusion about how the heart works.
It is possible to identify five inconsistencies with the main line - isolines - these are the teeth S, P, T, Q, R. They all have their own parameters: height, width, polarity. Essentially, the designation is given to the 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 function, P is shown first, followed by Q. The time window between the time of increase in atrial pulsation and the time of increase in ventricular pulsation is shown by the P - Q interval. This picture is displayed as QRST.
At the highest limit of ventricular oscillation, the R wave appears. At the peak of ventricular pulsation, the S wave appears. When the heart rate reaches the highest point of pulsation, there is no difference between the potentials. This is shown by a straight line. If ventricular arrhythmia occurs, a T wave appears. An ECG during myocardial infarction allows one to judge abnormalities in the functioning of the heart.
Preparation and execution
Carrying out the ECG procedure requires careful preparation. Hair on the body where the electrodes are supposed to be placed 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 a cardiologist is to monitor the parabolas of ECG complexes. They are displayed on a special screen of the oscilloscope. At the same time, all heart sounds are listened to.
Signs of acute heart attack on ECG
Using an ECG, thanks to electrode leads 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. In the acute stage, the Q wave is not visible. But in the thoracic bases there is an R wave, indicating pathology.
The following ECG signs of myocardial infarction are noted:
- There is no R wave in supra-infarct areas.
- A Q wave appears, indicating an anomaly.
- The S and T segment rises higher and higher.
- The S and T segment is increasingly shifting.
- A T wave appears, indicating pathology.
MI on the cardiogram
The dynamics of an acute heart attack look 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 Q and S complex is present, indicating pathology.
An electrocardiogram can show the main three phases of a heart attack. This:
- transmural infarction;
- subendocardial;
- intramural.
Signs of a transmural infarction are:
- necrolysis begins to develop in the left ventricular wall;
- an abnormal Q wave is formed;
- a pathological wave with small amplitude appears.
Subendocardial infarction is a reason for urgent surgical intervention. It must be carried out within the next 48 hours.
Necrotic cells in this form of attack form a narrow shelf along the edge of the left ventricle. In this case, the cardiogram can be noted:
- absence of Q wave;
- in all leads (V1 - V6, I, aVL) there was a decrease in the ST segment - downward arc
- decreased R wave;
- the formation of a “coronary” positive or negative T wave;
- changes are present throughout the week.
The intramural form of the 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 state of the myocardium that is important.
Decoding the cardiogram
In making a diagnosis, the correct interpretation of the cardiogram plays an important role, namely, establishing the type of attack and the extent of damage to the cardiac tissue.
Different types of attack
A cardiogram allows you to determine what kind of heart attack is taking place - small-focal and large-focal. In the first case, there are small amounts of damage. They are concentrated directly in the heart area. Complications are:
- cardiac aneurysm and rupture;
- heart failure;
- ventricular fibrillation;
- asystological thromboembolism.
The onset of small focal infarction is not often recorded. Most often it occurs macrofocally. It is characterized by significant and rapid damage to the coronary arteries due to thrombosis or prolonged spasms. As a result, a large area of dead tissue appears.
The localization of the lesion is the basis for dividing the infarction into:
- front;
- rear;
- septal MI;
- lower;
- Side wall MI.
Based on its course, the attack is divided into:
Heart attacks are also classified according to the depth of the lesion, depending on the depth of tissue death.
How to determine the stage of pathology?
During a heart attack, the dynamics of necrolysis can be traced in this way. In one of the areas, due to lack of blood supply, tissue begins to die. They are still preserved on the periphery.
There are four stages of myocardial infarction:
- acute;
- acute;
- subacute;
- cicatricial.
Their signs on the ECG are:
ECG today is one of the most common and informative methods for identifying acute cardiac disorders. Identification of signs of any of their stages or forms of heart attack requires immediate treatment or proper rehabilitation therapy. This will prevent the risk of complications, as well as a recurrent attack.
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