The basics of ecg for beginners. ECG for dummies: norms and interpretation

One of the advantages of an electrocardiogram as a way to assess the work of the heart is the ability to quickly obtain a result. Data on cardiac activity obtained during the study is immediately recorded on a paper tape, which is slowly fed into the ECG apparatus system. On more modern equipment, the values ​​​​can be displayed on a computer monitor, and then printed through a printer. One way or another, leaving the treatment room, we have the result of an electrocardiogram in our hands, which we want to read as soon as possible - decoding the ECG will allow us to conclude that there is or is no cause for concern.

ABC of electrocardiograms

The diagram of the work of the heart is a complex curved continuous line, similar to a sinusoid, with numerous marks and symbols in alphabetic and numerical terms. At first glance, it seems that only a professor can correctly decipher and give an ECG conclusion. medical institute, a doctor of sciences, or at least a cardiologist with many years of experience. This is not entirely true. ECG analysis really requires a high level of attention, concentration, accuracy, knowledge of algebraic foundations and algorithms. However, if you understand and learn, the decoding process becomes quite interesting.

Not only cardiologists should be able to read the ECG scheme and give a conclusion on it. Of course, for doctors of this specialization, the depicted ruler with a curved line will tell much more about the work of the heart. Nevertheless, doctors also have to learn how to conduct a study and read a cardiogram. general practice especially for paramedics. Early examination and interpretation of the ECG even before the provision of care in the hospital allows you to provide timely effective help, for example, with a heart attack and save the life of the patient.

Curiosity, concern for the state of one's health, and even distrust in the attending physician often push one to desire to learn how to read an ECG diagram on one's own. However, the first call to medical directory, as a rule, discourages the desire to delve into the question - an abundance of terms and incomprehensible abbreviations seem like a dense forest. Indeed, the information given in the medical literature is difficult for the perception of the “uninitiated”. However, this is not a reason to abandon the idea of ​​\u200b\u200b"look behind the scenes" of cardiology. And first of all, you need to understand what exactly the cardiogram line reflects.

What is reflected in the ECG picture

From the point of view of physics, the work of the heart is an automatic transition from the phase of depolarization to the phase of repolarization of the heart muscle. In other words, there is a constant change in the states of contraction and relaxation of muscle tissue, in which, respectively, the excitation of myocardial cells is replaced by their recovery.

The design of the ECG apparatus allows you to record the electrical impulses that occur in these phases and register them graphically. This is what explains the unevenness of the curve in the figure of the cardiogram.

To learn how to interpret ECG patterns, you need to know what elements they consist of, namely:

• tooth - a convex or concave part of the curve relative to the horizontal axis;
• segment - a straight line segment between two adjacent teeth;
• interval - a combination of a tooth and a segment.

Recording of cardiac data is carried out over several cycles, since medical significance has not only a characteristic of each of the elements of the electrocardiogram, but also their comparability within several cycles.

Analysis of individual elements of the cardiogram

Formulating the conclusion on the ECG, the teeth are evaluated by amplitude on the vertical axis, and by their duration on the horizontal. Each of the teeth within one cycle is assigned its own letter of the Latin alphabet - it characterizes the passage of an impulse through a certain part of the heart, namely:

• the P wave describes the response of the atria to the propagation of an electrical impulse in them;

AT healthy condition the tooth has a positive value, a rounded top, directed upwards, its height is up to 2.5 mm, the duration does not exceed 0.1 s. A pathological deviation is considered to be a pointed shape of the P-wave, characteristic of right atrial hypertrophy, or a bifurcated apex with left atrial hypertrophy.

• the Q wave characterizes the propagation of the impulse in the interventricular septum;

Normally, it is weakly expressed, has a negative value. Its duration is only 0.03 s. In children, this element of the cardiogram may have a deep position, which is not a cause for alarm.

• the R wave describes the passage of an electrical signal through the ventricular myocardium.

In terms of its amplitude, this is the largest of the teeth, although the duration normally does not exceed the Q value.

• the S wave determines the completion of excitation in the ventricles of the heart. Like the Q-element, it has a negative character and a small depth - only 2 mm.
• the T wave is an indicator of potential recovery in the muscle tissue of the heart.

Normally, this element with a positive value rises above the horizontal axis by no more than a third of the amplitude of the R-wave. The shape of its top is smoothed, the duration is from 0.16 s. up to 2.4 s. A high T-element indicates autonomic disorders of cardiac activity, for example, with hyperkalemia. However, the concave shape of this tooth poses a much greater threat. Negative pointed isosceles shape is a classic sign of myocardial infarction.

• The U wave is rarely recorded on the ECG ruler. Its norm is a height of up to 2 mm.

Often this element can be noted when describing the cardiogram of athletes after physical activity. Otherwise, it may be a sign of bradycardia.

The conclusion on the work of the heart includes an assessment of the segments of the ECG line. Each of them is measured from the end of one tooth to the beginning of the next. Highest value have P-Q and S-T segments. Their analysis includes an assessment of their length and rise above the isoelectric line - the horizontal axis. Normally, this rise should not exceed 1 mm. The duration is directly dependent on the pulse, therefore, may be evidence of violations heart rate.

The work of the heart muscle in time intervals

To learn how to correctly analyze intervals, the greatest attention should be paid to their duration, since each of them characterizes the speed of propagation of an electrical signal in a particular part of the heart and the response of muscle tissue to an impulse. For example, the norm for the QT interval is 0.45 s. Elongation at this site can be caused by ischemia or atherosclerosis.

Thus, the duration of the interval characterizes the work of the heart muscle over time. It is not difficult to learn how to determine the heart rhythm - pulse according to the ECG scheme. Its characteristic will be the distance between the two highest positive teeth - the R-R interval. In a healthy adult at rest, this figure is 70-80 beats per minute. In this case, the distance between the teeth should not differ from the average by more than 10%. Such a rhythm is correct, regular, and in conclusion, the sinus nature of the cardiogram is indicated. Other types of rhythm indicate the presence pathological changes in the work of the heart. In these cases, the maximum and minimum performance heart rate, and specialists begin to search for the source of excitation - the pacemaker.

ECG pattern interpretation plan

All of these readings seem rather difficult to remember. To facilitate the task, a special plan has been developed, using which you can learn to read the results of the conclusion. According to the same plan, the interpretation of the ECG is also carried out by specialists. Its main points are:

• Assessment of heart rate and conduction;
• Determination of the indicator "electrical axis of the heart";
• Analysis of atrial work by P-wave and P-Q interval;
• Characteristics of the indicators of the complex of QRS-T elements;
• Cardiographic conclusion.

The ECG analysis plan should also include checking the correctness of the registration of the cardiogram, which is the supply of a control signal at the beginning of the study - a standard voltage of one millivolt, which is displayed on the diagram as a deviation of 10 mm. Without this procedure, the cardiograph record is considered indicative.

It is impossible to learn how to correctly interpret the results of an ECG without knowing physiological features person that can influence the design of the study. These include age, gender, body type, height, presence of chronic diseases. Without taking into account the individual data of the patient, deviations in the conclusion of the cardiogram can be mistakenly regarded as signs of cardiac pathology. For example, the indicator "electric axis" allows you to roughly determine the location of the body in chest describe its size and shape. However, in thin people, this axis has a vertical position, and in overweight, obese people, it is horizontal, but in both cases the location of the organ is considered normal. In addition, a deep interpretation of the cardiograph pattern requires knowledge of numerous medical terms, which characterize the signs of pathologies, namely: atrial fibrillation, extrasystole, atrial flutter and many others.

In general, two conclusions arise:

• Description of the cardiogram is a whole art!
• Learning to read a healthy ECG chart is much easier than memorizing everything. possible deviations which is an additional incentive to take care of your health!

ECG is considered one of the most common and informative diagnostic methods. With its help, a variety of cardiac pathologies are detected, as well as control the effectiveness of treatment. But what does it show ECG of the heart And how often can you do it? We will talk about its features below.

What is an EKG

Electrocardiography is a method of examining the electrophysiological work of the heart muscle. When diagnosing, a special device is used that registers the slightest change his activities, and after issuing them in a graphic image. Conductivity, contraction rate, hypertrophic changes, scarring and other changes in myocardial function - all this can be detected using an ECG.

In the process of diagnostics, special electrodes record the contraction of the heart, namely the bioelectric potentials that arise in this case. Electrical excitation covers different sections of the heart muscle at different times, therefore, a potential difference is recorded between the unexcited and excited sections. It is these data that are captured by the electrodes placed on the body.

In a simple and accessible form, the video below will tell about the indicators and features of the ECG:

To whom is it assigned

An ECG is used to diagnose a number of cardiac abnormalities. So, the indications for the appointment of the procedure are:

1. Scheduled examination. It is necessary for different categories of people, including adolescents, pregnant women, athletes, before surgery or in the presence of any diseases (lung and gastrointestinal diseases, thyroid gland, diabetes).
2. To diagnose secondary or primary diseases as a preventive measure or to detect possible complications.
3. Monitoring during the period of treatment or after its completion if any diseases are detected.

An electrocardiogram is performed if there are indications for the use of this diagnostic method. It is also required when passing a medical examination of drivers, a draft board, when referring to a sanatorium for treatment. Women in position are examined at least 2 times: at the time of registration and before childbirth.

Why do it

Diagnostics helps to determine the early stages of cardiac dysfunction, as well as the prerequisites for the development of serious pathologies. An electrocardiogram is able to detect the slightest changes that occur with the heart: thickening of its walls, a change in the normal size inside its cavities, and its location, size, and more. This greatly affects the accuracy of the prognosis and the selection of suitable treatment, not to mention the importance of timely prevention.

Doctors note that those who have celebrated the fortieth anniversary require an annual scheduled examination, and even in the absence of objective symptoms and prerequisites for cardiac problems. This is due to the increasing risk of complications in the work of the main “motor” of the body with age. In other cases, it is enough to visit a doctor for this procedure 1 time in 1-2 years.

Types of diagnostics

There are several methods and types of electrocardiographic examination of the heart (ECG):

• At rest. The standard method used in most cases. If the diagnosis at this stage did not give accurate data, resort to other types of ECG.
• With load. This type of examination involves the use of physical (veloergometry, treadmill test) or medication load. This also includes the introduction of a sensor through the esophagus for electrical stimulation of the heart. This technique allows you to identify those diseases that are not detected at rest.
• . A small device is installed in the chest area, which during the day is engaged in fixing cardiac activity. The work of the heart is recorded when performing household activities, which is one of the advantages of the study.
• Transesophageal ECG performed with low information content of electrocardiography through the chest wall.

Indications for holding

It is worth contacting the clinic for an examination if:

• complaints of pain in thoracic region, including the spine;
• over 40 years of age;
• episodes of varying degrees and intensity of pain in the heart, especially those that occur during temperature changes;
• shortness of breath
• diseases respiratory system chronic course;
• , and a number of other cardiac pathologies;
• fainting, episodes of increased heart rate, dizziness, malfunctions of the heart muscle.

The specialist will tell about the indications for the ECG procedure in the video below:

Contraindications for holding

There are no special contraindications that could cause a refusal to conduct an ECG. Difficulty in carrying out the procedure is observed only in some categories of citizens (high degree of hairiness, obesity, chest injuries). Data are distorted in persons with a pacemaker installed.

There are a number of contraindications for stress ECG (an electrocardiogram is performed under stress):

1. exacerbation of the course of existing diseases,
2. acute myocardial infarction,
3. acute infections,
4. (heavy).

If it is necessary to conduct a transesophageal ECG, then contraindications, respectively, are pathologies of the esophagus.

Procedure safety

The cardiogram is completely safe, even for pregnant women. She never gives any complications, including those related to the development of the child.

How to prepare for an ECG of the heart

Special preparation before the study is not necessary.

• You can take food and water without limiting yourself in front of him.
• But it is worth giving up energy drinks, including coffee.
• Cigarettes and alcohol are also best left aside before the examination, so as not to distort the data.

How is the session

To conduct an electrocardiogram, it is not necessary to be in a hospital, just visit the clinic. In case of emergency hospitalization, an initial examination can be carried out immediately on the spot, which will allow the ambulance team to effectively help the victim.

1. In the diagnostic room, the patient should take a supine position on the couch.
2. To ensure good conductivity, skin areas on the chest, ankles and hands are wiped with a damp sponge.
3. After that, a pair of electrodes in the form of clothespins are put on the arms and legs, and 6 “suckers” are superimposed on the left chest area in the projection of the heart.
4. After this preparation, the device is turned on and the electrical activity of the heart muscle begins to be recorded on a special thermal film in the form of a graphic curve. Sometimes the result goes through the device directly to the doctor's computer.

Throughout the entire period of the study, which usually lasts no longer than 10 minutes, the patient does not feel discomfort, everything passes in a calm state and without discomfort. After that, it remains only to wait for the decryption of the received data. This procedure is also done by a doctor, and then transfers the results to the office of the attending doctor or immediately to the hands of the visitor. If pathologies requiring immediate treatment are detected, he can be sent to a hospital, but if there are none, then the patient is sent home.

Read on to learn how to decipher an ECG of the heart.

Results and their interpretation

After receiving the results of the study, it is necessary to decipher the indicators of the electrocardiography of the heart (ECG) in children and adults. The result of the cardiogram includes several main components:

• ST, QRST, TP segments- this is the name of the distance located between the nearest teeth.
• teeth- these are sharp corners, including those directed downwards. These include the designations R, QS, T, P.
• Interval. It includes the entire segment and tooth. This is PQ, that is, the interval, the period of passage of the impulse from the ventricles to the atria.

The cardiologist analyzes these components, they also help determine the time of contraction and excitation of the myocardium. On the ECG, you can determine the approximate location of the organ in the chest, which is possible due to the presence of an electrical axis.

The main indicators of the norm ECG diagnostics, their decoding in adults are expressed in the table. It is worth noting that in some cases they change slightly. Often, such deviations do not indicate the presence of pathology and are also considered the norm.

Now let's talk about the price of electrocardiography (ECG) of the heart.

Average cost of the procedure

The cost of an ECG of the heart varies, as it depends on the city of the procedure and medical center. The average price mark is at the level of 500 rubles.

The following video will talk in more detail about the ECG norms:

An electrocardiographic study is quite simple and effective method diagnostics, used by cardiologists around the world to study the activity of the heart muscle. The results of the procedure in the form of graphs and digital symbols, as a rule, are transferred to specialists for further data analysis. However, in the case of, for example, the absence of the right doctor, the patient has a desire to independently decipher the indicators of his heart.

Preliminary interpretation of the ECG requires knowledge of special basic data, which, due to their specificity, are not subject to everyone. In order to make correct calculations of the ECG of the heart for a person who is not related to medicine, it is necessary to familiarize yourself with the basic principles of processing, which are combined for convenience into the appropriate blocks.

Familiarization with the basic elements of a cardiogram

You should know that the interpretation of the ECG is carried out thanks to elementary, logical rules that can be understood even by an ordinary layman. For a more pleasant and calm perception of them, it is recommended to start familiarizing yourself first with the simplest principles of decoding, gradually moving to a more complex level of knowledge.

Ribbon layout

The paper, which reflects data on the functioning of the heart muscle, is a wide ribbon of a soft pink hue with a clear “square” marking. The larger quadrilaterals are formed from 25 small cells, and each of them, in turn, equates to 1 mm. If a large cell is filled with only 16 dots, for convenience, you can draw parallel lines along them and follow similar instructions.

The horizontals of the cells indicate the duration of the heartbeat (sec), and the verticals indicate the voltage of individual ECG segments (mV). 1 mm is 1 second of time (in width) and 1 mV of voltage (in height)! This axiom must be kept in mind throughout the entire period of data analysis, later its importance will become obvious to everyone.

The paper used allows you to correctly analyze the time intervals

teeth and segments

Before moving on to the names of specific departments of the gear graph, it is worth familiarizing yourself with the activity of the heart itself. The muscular organ consists of 4 compartments: the 2 upper ones are called the atria, the 2 lower ones are called the ventricles. Between the ventricle and the atrium in each half of the heart there is a valve - a leaflet responsible for accompanying blood flow in one direction: from top to bottom.

This activity is achieved due to electrical impulses that move through the heart according to the "biological timetable". They are sent to specific segments of the hollow organ using a system of bundles and nodes, which are miniature muscle fibers.

The birth of the impulse occurs in the upper part of the right ventricle - the sinus node. Further, the signal passes into the left ventricle and excitation of the upper parts of the heart is observed, which is recorded by the P wave on the ECG: it looks like a gentle inverted cup.

After the electric charge reaches the atrioventricular node (or AV node), which is located almost at the junction of all 4 pockets of the heart muscle, a small “point” appears on the cardiogram, pointing down - this is the Q wave. Just below the AV node there is the following item the purpose of the impulse is the bundle of His, which is fixed by the highest tooth R among others, which can be represented as a peak or mountain.

Having overcome half of the way, an important signal rushes to the lower part of the heart, through the so-called legs of the bundle of His, outwardly resembling the long tentacles of an octopus that hug the ventricles. The conduction of the impulse along the branched processes of the bundle is reflected in the S wave - a shallow groove at the right foot of R. When the impulse spreads to the ventricles along the legs of the bundle of His, they contract. The last bumpy T wave marks the recovery (rest) of the heart before the next cycle.

Not only cardiologists, but also other specialists can decipher diagnostic indicators.

In front of the 5 main teeth on the ECG, you can see a rectangular protrusion, you should not be afraid of it, since it is a calibration or control signal. Between the teeth there are horizontally directed sections - segments, for example, S-T (from S to T) or P-Q (from P to Q). To independently make an indicative diagnosis, you will need to remember such a concept as the QRS complex - the combination of the Q, R and S teeth, which registers the work of the ventricles.

The teeth that rise above the isometric line are called positive, and those that are located below them are called negative. Therefore, all 5 teeth alternate one after the other: P (positive), Q (negative), R (positive), S (negative) and T (positive).

Leads

Often you can hear the question from people: why are all the ECG graphs different from each other? The answer is relatively simple. Each of the curved lines on the tape reflects the heart readings obtained from 10-12 colored electrodes, which are installed on the limbs and in the chest area. They read data on the heart impulse, located at different distances from the muscle pump, because the graphics on the thermal tape are often different from each other.

Only an experienced specialist can competently write an ECG conclusion, while the patient has the opportunity to consider general information about your health.

Normal indicators of the cardiogram

Now that it has become clear how to decipher the cardiogram of the heart, one should proceed to the direct diagnosis of normal readings. But before getting acquainted with them, it is necessary to evaluate the ECG recording speed (50 mm / s or 25 mm / s), which, as a rule, is automatically printed on paper tape. Then, starting from the result, you can view the norms for the duration of the teeth and segments that are listed in the table (calculations can be carried out using a ruler or checkered markings on the tape):

Among the most significant provisions of the interpretation of the ECG, the following can be mentioned:

• The S-T and P-Q segments should "merge" with the isometric line without going beyond it.
• The depth of the Q wave cannot exceed ¼ of the height of the most slender tooth - R.
• The exact measurements of the S wave have not been confirmed, but it is known that it sometimes reaches a depth of 18–20 mm.
• The T wave should not be higher than R: its maximum value is ½ of the height of R.

Heart rate control is also important. It is necessary to pick up a ruler and measure the length of the segments enclosed between the vertices of R: the results obtained must coincide with each other. To calculate the heart rate (or heart rate), it is worth counting the total number of small cells between the 3 vertices of R and dividing the digital value by 2. Next, you need to apply one of the 2 formulas:

• 60/X*0.02 (at 50mm/s write speed).
• 60/X*0.04 (at 25mm/s write speed).

If the figure is in the range from 59-60 to 90 beats / min, then the heart rate is normal. An increase in this index implies tachycardia, and a clear decrease implies bradycardia. If for a well-formed person a heart rate of more than 95–100 beats per minute is a rather dubious sign, then for children under 5–6 years old this is one of the varieties of the norm.

Each of the teeth and intervals indicates a certain period of time for the work of the heart muscle.

What pathologies can be identified when deciphering the data?

Although the ECG is one of the extremely simple studies in terms of structure, there are still no analogues of such a diagnosis of cardiac abnormalities. The most "popular" diseases recognized by ECG can be found by examining both the description of their characteristic indicators and detailed graphic examples.

This ailment often recorded in adults during the implementation of the ECG, in children it is extremely rare. Among the most common "catalysts" of the disease are the use of drugs and alcohol, chronic stress, hyperthyroidism, etc. PT is distinguished, first of all, by a frequent heartbeat, the indicators of which range from 138-140 to 240-250 beats / min.

Due to the manifestation of such attacks (or paroxysm), both ventricles of the heart do not have the opportunity to fill with blood in time, which weakens the overall blood flow and slows down the delivery of the next portion of oxygen to all parts of the body, including the brain. Tachycardia is characterized by the presence of a modified QRS complex, a mild T wave, and, most importantly, the absence of a distance between T and P. In other words, the groups of teeth on the electrocardiogram are "glued" to each other.

The disease is one of the "invisible killers" and requires immediate contact with a number of specialists, since if it is extremely neglected, it can lead to the death of a person.

Bradycardia

If the previous anomaly implied the absence segment T-P, then bradycardia is its antagonist. This disease gives out a significant elongation T-P, indicating weak conduction of the impulse or its incorrect accompaniment through the heart muscle. In patients with bradycardia, an extremely low heart rate index is observed - less than 40-60 bpm. If in people who prefer regular physical activity, a mild manifestation of the disease is the norm, then in the vast majority of other cases, we can talk about the emergence of an extremely serious disease.

If obvious signs of bradycardia are found, a comprehensive examination should be carried out in the near future.

Ischemia

Ischemia is called a harbinger of myocardial infarction, for this reason early detection anomalies contributes to the relief of fatal ailments and, as a result, a favorable outcome. It was previously mentioned that the S-T interval should “comfortably lie” on the isoline, however, its omission in the 1st and AVL leads (up to 2.5 mm) signals precisely about IHD. Sometimes ischemic disease only the T wave gives out the heart. Normally, it should not exceed ½ of the R height, however, in this case it can either “grow” to the older element or fall below the midline. The remaining teeth are not subject to significant changes.

Flutter and atrial fibrillation

Atrial fibrillation is an abnormal condition of the heart, expressed in a disorderly, chaotic manifestation of electrical impulses in the upper pockets of the heart. It is sometimes not possible to make a qualitative surface analysis in such a case. But knowing what you should pay attention to first of all, you can safely decipher ECG indicators. QRS complexes are not of fundamental importance, since they are often stable, but the gaps between them are key indicators: when they flicker, they look like a series of notches on a hand saw.

Pathologies are clearly distinguishable on the cardiogram

Not so chaotic, large-sized waves between the QRS already indicate atrial flutter, which, unlike flicker, is characterized by a slightly more pronounced heartbeat (up to 400 beats / min). Contractions and excitations of the atria are subject to control to a small extent.

Thickening of the atrial myocardium

Suspicious thickening and stretching of the muscle layer of the myocardium is accompanied by a significant problem with the internal blood flow. At the same time, the atria perform their main function with constant interruptions: the thickened left chamber “pushes” blood into the ventricle with greater force. When trying to read an ECG graph at home, you should focus on the P wave, which reflects the state of the upper heart.

If it is a kind of dome with two bulges, most likely the patient is suffering from the disease in question. Since thickening of the myocardium in the absence of qualified medical intervention for a long time provokes a stroke or heart attack, it is necessary to make an appointment with a cardiologist as soon as possible, providing a detailed description of uncomfortable symptoms, if any.

Extrasystole

It is possible to decipher the ECG with the "first signs" of extrasystole if there is knowledge about the special indicators of a special manifestation of arrhythmia. By carefully examining such a graph, the patient can detect unusual abnormal jumps that vaguely resemble QRS complexes - extrasystoles. They occur in any area of ​​the ECG, they are often followed by a compensatory pause, allowing the heart muscle to “rest” before starting a new cycle of excitations and contractions.

Extrasystole in medical practice is often diagnosed in healthy people. In the vast majority of cases, it does not affect the usual course of life and is not associated with serious illnesses. However, when establishing an arrhythmia, you should play it safe by contacting specialists.

With atrioventricular heart block, an expansion of the gap between the P waves of the same name is observed, in addition, they can occur at the time of analyzing the ECG conclusion much more often than QRS complexes. The registration of such a pattern indicates a low conductivity of the impulse from the upper chambers of the heart to the ventricles.

If the disease progresses, the electrocardiogram changes: now the QRS “drops out” from the general row of P waves in some intervals

Blockade of the legs of the bundle of His

The failure of such an element of the conduction system as the bundle of His should in no case be ignored, since it is located in close proximity to the Myocardium. The pathological focus in advanced cases tends to "transfer" to one of the most important parts of the heart. Decipher the ECG yourself if there is an extremely unpleasant disease it is quite possible, you just have to carefully examine the highest prong on the thermal tape. If it forms not a “slender” letter L, but a deformed M, this means that the bundle of His has been attacked.

The defeat of its left leg, which passes the impulse into the left ventricle, entails the complete disappearance of the S wave. And the place of contact of the two vertices of the split R will be located above the isoline. The cardiographic image of the weakening of the right bundle crus is similar to the previous one, only the junction point of the already marked peaks of the R wave is under the midline. T is negative in both cases.

myocardial infarction

The myocardium is a fragment of the densest and thickest layer of the heart muscle, which in last years subjected to various ailments. The most dangerous among them is necrosis or myocardial infarction. When deciphering electrocardiography, it is quite distinguishable from other types of diseases. If the P wave, which registers the good condition of the 2 atria, is not deformed, then the remaining segments of the ECG have undergone significant changes. So, a pointed Q wave can “pierce” the isoline plane, and T can be transformed into a negative tooth.

The most telling sign of a heart attack is abnormal elevation R-T. There is a mnemonic rule that allows you to remember its exact appearance. If, when examining this area, one can imagine the left, ascending side of R in the form of a rack tilted to the right, on which a flag flies, then we are really talking about myocardial necrosis.

The disease is diagnosed both in the acute phase and after the attack subsides.

ventricular fibrillation

Otherwise, an extremely serious illness is called atrial fibrillation. A distinctive feature of this pathological phenomenon is considered to be the destructive activity of the conductive bundles and nodes, indicating an uncontrolled contraction of all 4 chambers of the muscle pump. Reading the results of an ECG and recognizing ventricular fibrillation is not at all difficult: on a checkered tape, it appears as a series of chaotic waves and hollows, the parameters of which cannot be correlated with classical indicators. In none of the segments can you see at least one familiar complex.

If a patient with atrial fibrillation is not given premature medical care he will soon die.

WPW syndrome

When, in the complex of classical pathways for conducting an electrical impulse, an abnormal Kent bundle is unexpectedly formed, located in the “comfortable cradle” of the left or right atrium, we can confidently speak of such a pathology as WPW syndrome. As soon as the impulses begin to move along the unnatural cardiac highway, the rhythm of the muscle goes astray. The “correct” conductive fibers cannot fully supply the atria with blood, because the impulses preferred more short cut to complete the functional cycle.

The ECG in SVC syndrome is distinguished by the appearance of a microwave at the left foot of the R wave, a slight widening of the QRS complex, and, of course, a significant reduction in the P-Q interval. Since the decoding of the cardiogram of a heart that has undergone WPW is not always effective, HM comes to the aid of medical personnel - the Holter method for diagnosing an ailment. It involves the round-the-clock wearing on the body of a compact device with attached to skin sensors.

Long-term monitoring provides a better result with a reliable diagnosis. In order to “catch” the anomaly localized in the heart in a timely manner, it is recommended to visit the ECG room at least once a year. If regular medical monitoring of the treatment of cardiovascular disease is necessary, more frequent measurements of cardiac activity may be required.

Formation of the conclusion on the electrocardiogram (ECG) is carried out by a doctor of functional diagnostics or a cardiologist. This is a difficult diagnostic process that requires special training and practice. A doctor describing an ECG should know the basics of cardiac electrophysiology, variants of a normal cardiogram, and be able to identify functional and morphological changes in the heart. He must be able to analyze the violation of the functions of automatism, conduction, excitability of the heart, evaluate the effect of medications and other external factors on the formation of ECG waves and intervals.

The description of the electrocardiogram includes several successive steps. First, the gender and age of the patient are evaluated, since different age groups may have their own ECG features, and the cardiogram is different for men and women. Then the duration and amplitude of the waves and intervals of the cardiogram are determined. After that, the rhythm is assessed, especially the position of the heart in the chest, conduction disturbances, signs focal changes myocardium and hypertrophy of the heart. Then the final conclusion is formed. If possible, the ECG is compared with previously recorded films of the same patient (analysis in dynamics).

Analysis of the P wave involves measuring its amplitude, duration, determining polarity and shape. Determine the duration of the P-Q interval.

Analysis of the ventricular QRS complex is an assessment of the ratio of the teeth in all leads, measuring the amplitude and duration of these teeth.

To analyze the ST segment, it is necessary to determine its displacement up or down relative to the isoelectric line and evaluate the shape of this displacement.

When evaluating the T wave, you need to pay attention to its polarity, shape, amplitude.
Then measured Q-T interval and compared with the proper value, determined by a special table.

Normal ECG

Normally, the rhythm of the heart is regular, correct, its source is the sinus node. Sinus rhythm at rest has a rate of 60 to 100 beats per minute. The heart rate is determined by measuring the distance between adjacent R waves on the ECG (R-R interval).

The direction of the so-called electrical axis of the heart is determined, showing the position of the resulting electromotive force vector (angle alpha). It is indicated in degrees. The normal axis corresponds to an alpha value between 40 and 70 degrees.

The presence of turns of the heart around its axis is determined.

Heart rhythm disorder

A heart rhythm disorder, or arrhythmia, is diagnosed if the following ECG abnormalities are detected:

• an increase in the heart rate of more than 100 per minute or a decrease of less than 60 per minute;
• wrong rhythm;
• non-sinus rhythm;
• violation of the conduction of an electrical signal through the conduction system of the heart.

Arrhythmias are divided into the following main groups.

On the basis of a violation of the formation of an impulse:

1. violations of automatism of the sinus node (sinus tachycardia, bradycardia, arrhythmia);
2. ectopic (non-sinus) rhythms caused by the predominance of automatism of non-sinus centers (slip-out, accelerated ectopic rhythms, pacemaker migration);
3. ectopic rhythms due to the re-entry mechanism (paroxysmal tachycardia, atrial and ventricular fibrillation and flutter).

On the basis of conduction disorders:

1. blockade (sinoatrial, intraatrial, atrioventricular, intraventricular blockade, in particular);
2. ventricular asystole;
3. ventricular preexcitation syndromes, in particular.

The electrocardiographic features of these disorders are varied and complex.

Hypertrophy of the heart

Myocardial hypertrophy is an adaptive reaction of the body in response to an increase in load, manifested in an increase in the mass of the heart and the thickness of its walls.

Changes in hypertrophy of any parts of the heart are due to increased electrical activity of the corresponding chamber, slowing down the propagation of an electrical signal in its wall, as well as ischemic and dystrophic changes heart muscle.

Using the ECG, you can determine the signs of hypertrophy and, as well as their combinations.

Myocardial blood supply disorders

With the help of an ECG, it is possible in some cases to assess the blood supply to the heart muscle. This method has become especially important in the diagnosis of myocardial infarction: acute violation blood flow in coronary vessels, accompanied by necrosis (necrosis) of a section of the heart muscle, followed by the formation of cicatricial changes in this zone.

ECG during the course of myocardial infarction has a natural dynamics, which allows you to monitor the development of the process, determine its prevalence and identify complications. With the help of an ECG, the localization of myocardial infarction is also determined.

Other ECG changes

Analyzing changes in the ventricular complex, the ST segment and the T wave, it is possible to diagnose many other pathological conditions, for example, pericarditis, myocarditis, electrolyte disturbances and other processes.

Video course "ECG for everyone", lesson 1 - "Conducting system of the heart, electrodes"

Video course "ECG for everyone", lesson 2 - "Teeth, segments, intervals"

Video course “ECG is within the power of everyone”, lesson 3 - “ECG analysis algorithm”

Electrocardiography is a method of graphic recording of the potential difference in the electric field of the heart that occurs during its activity. Registration is carried out using an apparatus - an electrocardiograph. It consists of an amplifier capable of capturing very low voltage currents; a galvanometer that measures the magnitude of the voltage; power systems; recording device; electrodes and wires connecting the patient to the device. The recorded waveform is called an electrocardiogram (ECG). Registration of the potential difference of the electric field of the heart from two points on the surface of the body is called abduction. As a rule, an ECG is recorded in twelve leads: three - bipolar (three standard leads) and nine - unipolar (three unipolar enhanced leads from the limbs and 6 unipolar chest leads). With bipolar leads, two electrodes are connected to the electrocardiograph, with unipolar leads, one electrode (indifferent) is combined, and the second (different, active) is placed at a selected point on the body. If the active electrode is placed on a limb, the lead is said to be unipolar, reinforced from the limb; if this electrode is placed on the chest - unipolar chest lead.

To register an ECG in standard leads (I, II and III), cloth napkins moistened with saline are placed on the limbs, on which metal plates of electrodes are placed. One electrode with a red wire and one relief ring is placed on the right, the second - with a yellow wire and two relief rings - on the left forearm and the third - with a green wire and three relief rings - on the left shin. To register the leads, two electrodes are connected in turn to the electrocardiograph. To record lead I, the electrodes of the right and left hands are connected, lead II - electrodes right hand and left leg, III leads - electrodes of the left arm and left leg. Switching leads is done by turning the knob. In addition to the standard ones, unipolar reinforced leads are removed from the limbs. If the active electrode is located on the right hand, the lead is designated as aVR or uP, if on the left hand - aVL or uL, and if on the left leg - aVF or yN.

Rice. 1. The location of the electrodes during registration of the anterior chest leads (indicated by the numbers corresponding to their serial numbers). Vertical stripes crossing the numbers correspond to the anatomical lines: 1 - right sternal; 2 - left sternal; 3 - left parasternal; 4-left midclavicular; 5-left anterior axillary; 6 - left middle axillary.

When registering unipolar chest leads, the active electrode is placed on the chest. ECG is recorded in the following six positions of the electrode: 1) at the right edge of the sternum in the IV intercostal space; 2) at the left edge of the sternum in the IV intercostal space; 3) along the left parasternal line between the IV and V intercostal spaces; 4) along the midclavicular line in the V intercostal space; 5) along the anterior axillary line in the 5th intercostal space and 6) along the midaxillary line in the 5th intercostal space (Fig. 1). Single pole chest leads denoted by the Latin letter V or Russian - GO. Less often, bipolar chest leads are recorded, in which one electrode was located on the chest, and the other on the right arm or left leg. If the second electrode was located on the right hand, the chest leads were designated in Latin letters CR or in Russian - ГП; when the second electrode was placed on the left leg, the chest leads were designated in Latin letters CF or in Russian - GN.

The ECG of healthy people differs in variability. It depends on age, physique, etc. However, normally, certain teeth and intervals can always be distinguished on it, reflecting the sequence of excitation of the heart muscle (Fig. 2). According to the available time stamp (on photographic paper, the distance between two vertical stripes is 0.05 seconds, on graph paper at a speed of 50 mm / s, 1 mm is 0.02 seconds, at a speed of 25 mm / s - 0.04 seconds. ) you can calculate the duration of the teeth and intervals (segments) of the ECG. The height of the teeth is compared with the standard mark (when a pulse of 1 mV is applied to the device, the recorded line should deviate from the initial position by 1 cm). Myocardial excitation begins with the atria, and an atrial P wave appears on the ECG. Normally, it is small: 1-2 mm high and 0.08-0.1 sec long. The distance from the beginning of the P wave to the Q wave ( P-Q interval) corresponds to the propagation time of excitation from the atria to the ventricles and is equal to 0.12-0.2 sec. During excitation of the ventricles, the QRS complex is recorded, and the magnitude of its teeth in different leads is expressed differently: the duration of the QRS complex is 0.06-0.1 sec. The distance from the S wave to the beginning of the T wave - S-T segment, normally located at the same level with the P-Q interval and its displacement should not exceed 1 mm. With the extinction of excitation in the ventricles, a T wave is recorded. The interval from the beginning of the Q wave to the end of the T wave reflects the process of excitation of the ventricles (electrical systole). Its duration depends on the heart rate: with an increase in the rhythm, it shortens, with a slowdown, it lengthens (on average, it is 0.24-0.55 seconds). The heart rate is easy to calculate from the ECG, knowing how long one cardiac cycle lasts (the distance between two R waves) and how many such cycles are contained in a minute. The T-R interval corresponds to the diastole of the heart, the device at this time records a straight (so-called isoelectric) line. Sometimes, after the T wave, a U wave is recorded, the origin of which is not entirely clear.

Rice. 2. Electrocardiogram of a healthy person.

In pathology, the size of the teeth, their duration and direction, as well as the duration and location of ECG intervals (segments), can vary significantly, which gives reason to use electrocardiography in the diagnosis of many heart diseases. With the help of electrocardiography, various cardiac arrhythmias are diagnosed (see), inflammatory and degenerative lesions of the myocardium are reflected on the ECG. Electrocardiography plays a particularly important role in the diagnosis of coronary insufficiency and myocardial infarction.

According to the ECG, you can determine not only the presence of a heart attack, but also find out which wall of the heart is affected. In recent years, to study the potential difference in the electric field of the heart, the method of teleelectrocardiography (radioelectrocardiography), based on the principle of wireless transmission of the electric field of the heart using a radio transmitter, has been used. This method allows you to register an ECG during physical activity, in motion (for athletes, pilots, astronauts).

Electrocardiography (Greek kardia - heart, grapho - write, write down) - a method of recording electrical phenomena that occur in the heart during its contraction.

The history of electrophysiology, and consequently, electrocardiography, begins with the experience of L. Galvani, who discovered in 1791 electrical phenomena in the muscles of animals. Matteucci (S. Matteucci, 1843) established the presence of electrical phenomena in the excised heart. Dubois-Reymond (E. Dubois-Reymond, 1848) proved that the excited part of both nerves and muscles is electronegative with respect to the resting part. Kelliker and Muller (A. Kolliker, H. Muller, 1855), applying a frog neuromuscular preparation to the contracting heart, consisting of sciatic nerve, connected to the gastrocnemius muscle, received a double contraction during the contraction of the heart: one at the beginning of systole and the other (non-constant) at the beginning of diastole. Thus, the electromotive force (EMF) of a naked heart was recorded for the first time. Waller (A. D. Waller, 1887) was the first to register the EMF of the heart from the surface of the human body using a capillary electrometer. Waller believed that the human body is a conductor surrounding the source of EMF - the heart; different points of the human body have potentials of different magnitudes (Fig. 1). However, the recording of the EMF of the heart obtained by a capillary electrometer did not accurately reproduce its fluctuations.

Rice. 1. Scheme of the distribution of isopotential lines on the surface of the human body, due to the electromotive force of the heart. The numbers indicate the magnitude of the potentials.

An accurate recording of the EMF of the heart from the surface of the human body - an electrocardiogram (ECG) - was made by Einthoven (W. Einthoven, 1903) using a string galvanometer built on the principle of devices for receiving transatlantic telegrams.

According to modern ideas cells of excitable tissues, in particular myocardial cells, are covered with a semi-permeable membrane (membrane), permeable to potassium ions and impermeable to anions. Positively charged potassium ions, which are in excess in cells compared to their environment, are retained on the outer surface of the membrane by negatively charged anions located on its inner surface, which is impermeable to them.

Thus, a double electric layer appears on the shell of a living cell - the shell is polarized, and its outer surface is positively charged in relation to the inner content, which is negatively charged.

This transverse potential difference is the resting potential. If microelectrodes are applied to the outer and inner sides of the polarized membrane, then a current appears in the outer circuit. Recording the resulting potential difference gives a monophasic curve. When excitation occurs, the membrane of the excited area loses its semi-impermeability, depolarizes, and its surface becomes electronegative. Registration by two microelectrodes of the potentials of the outer and inner shells of the depolarized membrane also gives a monophasic curve.

Due to the potential difference between the surface of the excited depolarized area and the surface of the polarized, at rest, an action current arises - an action potential. When excitation covers the entire muscle fiber, its surface becomes electronegative. Termination of excitation causes a wave of repolarization, and the resting potential of the muscle fiber is restored (Fig. 2).

Rice. 2. Schematic representation of the polarization, depolarization and repolarization of the cell.

If the cell is at rest (1), then electrostatic equilibrium is observed on both sides of the cell membrane, consisting in the fact that the surface of the cell is electropositive (+) with respect to its inner side (-).

The excitation wave (2) instantly breaks this balance, and the surface of the cell becomes electronegative with respect to its inner side; this phenomenon is called depolarization or, more correctly, inversion polarization. After the excitation has passed through the entire muscle fiber, it becomes completely depolarized (3); its entire surface has the same negative potential. This new equilibrium does not last long, because the wave of excitation is followed by a wave of repolarization (4), which restores the polarization of the resting state (5).

The process of excitation in a normal human heart - depolarization - proceeds as follows. Arising in the sinus node located in the right atrium, the excitation wave propagates at a speed of 800-1000 mm per 1 sec. beam-like along the muscle bundles, first of the right and then the left atrium. The duration of excitation coverage of both atria is 0.08-0.11 sec.

First 0.02 - 0.03 sec. only the right atrium is excited, then 0.04 - 0.06 sec - both atria and the last 0.02 - 0.03 sec - only the left atrium.

Upon reaching the atrioventricular node, the spread of excitation slows down. Then, with a large and gradually increasing speed (from 1400 to 4000 mm in 1 sec.), It is directed along the bundle of His, its legs, their branches and ramifications, and reaches the final endings of the conductor system. Having reached the contractile myocardium, excitation with a significantly reduced speed (300-400 mm per 1 sec.) Spreads through both ventricles. Since the peripheral branches of the conduction system are scattered mainly under the endocardium, the inner surface of the heart muscle comes into excitation first of all. The further course of excitation of the ventricles is not associated with the anatomical location of the muscle fibers, but is directed from the inner surface of the heart to the outer. The time of excitation in the muscle bundles located on the surface of the heart (subepicardial) is determined by two factors: the time of excitation of the branches of the conduction system closest to these bundles and the thickness of the muscle layer that separates the subepicardial muscle bundles from the peripheral branches of the conduction system.

First of all, the interventricular septum and the right papillary muscle are excited. In the right ventricle, excitation first covers the surface of its central part, since the muscular wall in this place is thin and its muscle layers are in close contact with the peripheral branches of the right leg of the conduction system. In the left ventricle, the apex is the first to be excited, since the wall separating it from the peripheral branches of the left leg is thin. For various points on the surface of the right and left ventricles of a normal heart, the excitation period begins at a strictly defined time, and most of the fibers on the surface of the thin-walled right ventricle and only a small number of fibers on the surface of the left ventricle come into excitation first of all due to their proximity to the peripheral branches of the conduction system (Fig. .3).

Rice. 3. Schematic representation of the normal excitation of the interventricular septum and the outer walls of the ventricles (according to Sodi-Pallares et al.). Excitation of the ventricles begins on the left side of the septum in its middle part (0.00-0.01 sec.) and then can reach the base of the right papillary muscle (0.02 sec.). After that, the subendocardial muscle layers of the outer wall of the left (0.03 sec.) and right (0.04 sec.) ventricles are excited. The basal parts of the outer walls of the ventricles are excited last (0.05-0.09 sec.).

The process of cessation of excitation of the muscle fibers of the heart - repolarization - cannot be considered fully understood. The process of atrial repolarization coincides for the most part with the process of depolarization of the ventricles and partly with the process of their repolarization.

The process of ventricular repolarization is much slower and in a slightly different sequence than the process of depolarization. This is explained by the fact that the duration of excitation of muscle bundles of the surface layers of the myocardium is less than the duration of excitation of subendocardial fibers and papillary muscles. Recording the process of depolarization and repolarization of the atria and ventricles from the surface of the human body and gives a characteristic curve - ECG, reflecting the electrical systole of the heart.

The recording of the EMF of the heart is currently being done by slightly different methods than those recorded by Einthoven. Einthoven recorded the current generated by connecting two points on the surface of the human body. Modern devices - electrocardiographs - directly record the voltage caused by the electromotive force of the heart.

The voltage caused by the heart, equal to 1-2 mV, is amplified by radio tubes, semiconductors or a cathode ray tube up to 3-6 V, depending on the amplifier and recording device.

The sensitivity of the measuring system is set in such a way that a potential difference of 1 mV gives a deviation of 1 cm. The recording is made on photographic paper or film or directly on paper (ink writing, thermal recording, inkjet recording). The most accurate results are recorded on photographic paper or film and inkjet recording.

To explain the peculiar form of the ECG, various theories of its genesis have been proposed.

A.F. Samoilov considered the ECG as the result of the interaction of two monophasic curves.

Given that when two microelectrodes register the outer and inner surfaces of the membrane in states of rest, excitation and damage, a monophasic curve is obtained, M. T. Udelnov believes that the monophasic curve reflects the main form of myocardial bioelectric activity. The algebraic sum of the two monophasic curves gives the ECG.

Pathological ECG changes due to shifts of monophasic curves. This theory of ECG genesis is called differential.

The outer surface of the cell membrane in the period of excitation can be represented schematically as consisting of two poles: negative and positive.

Directly before the excitation wave, in any place of its propagation, the cell surface is electropositive (polarization state at rest), and immediately after the excitation wave, the cell surface is electronegative (depolarization state; Fig. 4). These electric charges of opposite signs, grouped in pairs on one and the other side of each place covered by the excitation wave, form electric dipoles (a). Repolarization also creates an incalculable number of dipoles, but unlike the above dipoles, the negative pole is in front and the positive pole is behind in relation to the direction of wave propagation (b). If depolarization or repolarization is completed, the surface of all cells has the same potential (negative or positive); dipoles are completely absent (see Fig. 2, 3 and 5).

Rice. 4. Schematic representation of electrical dipoles during depolarization (a) and repolarization (b), arising from both sides of the excitation wave and the repolarization wave as a result of a change in the electrical potential on the surface of myocardial fibers.

Rice. 5. Scheme of an equilateral triangle according to Einthoven, Far and Warth.

A muscle fiber is a small bipolar generator producing a small (elementary) emf - an elementary dipole.

At each moment of the systole of the heart, depolarization and repolarization of a huge number of myocardial fibers located in different parts of the heart occur. The sum of the formed elementary dipoles creates the corresponding value of the EMF of the heart at each moment of systole. Thus, the heart represents, as it were, one total dipole, which changes its magnitude and direction during the cardiac cycle, but does not change the location of its center. The potential at different points on the surface of the human body has a different value depending on the location of the total dipole. The sign of the potential depends on which side of the line perpendicular to the axis of the dipole and drawn through its center, this point is located: on the side of the positive pole, the potential has a + sign, and on the opposite side - a - sign.

Most of the time of excitation of the heart, the surface of the right half of the trunk, right arm, head and neck has a negative potential, and the surface of the left half of the trunk, both legs and left arm has a positive potential (Fig. 1). This is a schematic explanation of the genesis of the ECG according to the dipole theory.

EMF of the heart during the electrical systole changes not only its magnitude, but also its direction; therefore, it is a vector quantity. The vector is depicted as a straight line segment of a certain length, the size of which, with certain data of the recording apparatus, indicates the absolute value of the vector.

The arrow at the end of the vector indicates the direction of the EMF of the heart.

The emf vectors of individual heart fibers that have arisen simultaneously are summarized according to the rule of vector addition.

The total (integral) vector of two vectors located in parallel and directed in the same direction is equal in absolute value to the sum of its constituent vectors and is directed in the same direction.

The total vector of two vectors of the same size, located in parallel and directed in opposite directions, is equal to 0. The total vector of two vectors directed at an angle to each other is equal to the diagonal of the parallelogram built from its constituent vectors. If both vectors form an acute angle, then their total vector is directed towards its component vectors and is greater than any of them. If both vectors form an obtuse angle and, therefore, are directed in opposite directions, then their total vector is directed towards the largest vector and is shorter than it. Vector analysis of the ECG consists in determining the spatial direction and magnitude of the total EMF of the heart at any moment of its excitation by the ECG teeth.