What does eos mean to the left. Electrical axis and electrical position of the heart

cardiac activity. In many patients, a shift in the electrical axis is detected - a shift either to the right or to the left. How to determine its position, what affects the change in the EOS and why is such a pathology dangerous?

Electrocardiography as a method for determining EOS

Electrocardiography is used to record the electrical activity of the heart in cardiology. The result of this study is displayed in the form of a graphic record and is called an electrocardiogram.

The procedure for taking an electrocardiogram is painless and takes about ten minutes. First, electrodes are applied to the patient, having previously lubricated the surface of the skin with a conductive gel or by placing gauze pads moistened with saline.

The electrodes are applied in the following sequence:

on the right wrist - red
on the left wrist - yellow
on the left ankle - green
on the right ankle - black

Then six chest electrodes are applied in a certain sequence, from the middle of the chest to the left armpit. The electrodes are fixed with a special tape or mounted on suction cups.

The doctor turns on the electrocardiograph, which records the voltage between two electrodes. The electrocardiogram is displayed on thermal paper and reflects the following parameters of the work and condition of the heart:

myocardial contraction rate
regularity of heartbeats
physical
heart muscle damage
electrolyte disturbance
violation of cardiac conduction, etc.

One of the main electrocardiological indicators is the direction of the electrical line of the heart. This parameter allows you to detect changes in cardiac activity or dysfunction of other organs (lungs, etc.).

Electrical axis of the heart: definition and factors of influence

To determine the electrical line of the heart, the conduction system of the heart is important. This system consists of cardiac conductive muscle fibers that transmit electrical excitation from one part of the heart to another.

Shift of the electrical axis to the left

The electric axis is strongly deviated to the left if its value is in the range from 0⁰ to -90⁰. This deviation can be caused by the following:

disturbances in the impulse conduction along the left branch of the His fibers (that is, in the left ventricle)
cardiosclerosis (a disease in which connective tissue replaces the muscle tissue of the heart)
persistent hypertension
heart defects
cardiomyopathy (changes in the heart muscle)
in the myocardium (myocarditis)
non-inflammatory myocardial damage (myocardial dystrophy)
intracardiac calcification and others

Shift of the electrical axis to the right

The EOS value in the range from +90⁰ to +180⁰ indicates a strong deviation of the electrical axis of the heart to the right. The reasons for this change in the position of the axis of the heart can be:

violation of impulse transmission along the right branch of the His fibers (responsible for the transmission of excitation in the right ventricle)
narrowing of the pulmonary artery (stenosis), which prevents the movement of blood from the right ventricle, so inside it
ischemic disease in combination with persistent arterial hypertension (ischemic disease is based on a lack of myocardial nutrition)
myocardial infarction (death of myocardial cells of the right ventricle)
diseases of the bronchi and lungs, forming a "cor pulmonale". In this case, the left ventricle does not function fully, there is congestion of the right ventricle
pulmonary embolism, i.e. blockage of the vessel by a thrombus, as a result, a violation of gas exchange in the lungs develops, narrowing of the vessels of the small blood circle and congestion of the right ventricle
mitral valve stenosis (most often occurs after rheumatism) - fusion of the valve leaflets, preventing the movement of blood from the left atrium, which leads to pulmonary hypertension and increased stress on the right ventricle

The main consequence of all causes is an increased load on the right ventricle. As a result, the walls of the right ventricle occur and the electrical vector of the heart deviates to the right.

The danger of changing the position of the EOS

The study of the direction of the electrical line of the heart is additional, therefore, making a diagnosis only on the basis of the location of the EOS is incorrect. If a patient has an EOS shift beyond the normal range, a comprehensive examination is carried out and the cause is identified, only then treatment is prescribed.

The heart, like any other human organ, is controlled by packets of impulses coming from the brain through the nervous system. Obviously, any violation of the control system leads to serious consequences for the body.

The electrical axis of the heart (EOS) is the total vector of all impulses observed in the conducting system of this organ in one cycle of contraction. Most often it coincides with the anatomical axis.

The norm for the electric axis is the position in which the vector is located diagonally, that is, directed down and to the left. However, in some cases this parameter may deviate from the norm. According to the position of the axis, a cardiologist can learn a lot about the work of the heart muscle and possible problems.

Depending on the physique of a person, there are three main values of this indicator, each of which, under certain conditions, is considered normal.

In most patients with a normal physique, the angle between the horizontal coordinate and the vector of electrodynamic activity is from 30° to 70°.
For asthenics and thin people, the normal value of the angle reaches 90 °.
In short, dense people, on the contrary, the value of the angle of inclination is less - from 0 ° to 30 °.

Thus, the position of the EOS is affected by the constitution of the body, and for each patient the norm of this indicator is relatively individual.

The possible position of the EOS is shown in this photo:

Reasons for change

By itself, the deviation of the vector of electrical activity of the heart muscle is not a diagnosis, but may indicate, among other things, serious disorders. Its position is influenced by many parameters:

organ anatomy, leading to hypertrophy or;
malfunctions in the conductive system of the organ, in particular, which is responsible for conducting nerve impulses to the ventricles;
cardiomyopathy due to various reasons;
chronic heart failure;
persistent hypertension for a long time;
chronic respiratory diseases, such as obstructive pulmonary disease or bronchial asthma, can lead to a deviation of the electrical axis to the right.

In addition to the above reasons, temporary EOS deviations can cause phenomena that are not directly related to the heart: pregnancy, ascites (accumulation of fluid in the abdominal cavity), intra-abdominal tumors.

How to determine on the electrocardiogram

The EOS angle is considered one of the main parameters that is studied at. For a cardiologist, this parameter is an important diagnostic indicator, the abnormal value of which clearly indicates various disorders and pathologies.

By studying the patient's ECG, the diagnostician can determine the position of the EOS, considering teeth of the QRS complex, which show the work of the ventricles on the graph.

An increased amplitude of the R wave in I or III chest leads of the graph indicates that the electrical axis of the heart is deviated to the left or right, respectively.

In the normal position of the EOS, the greatest amplitude of the R wave will be observed in the II chest lead.

Diagnosis and additional procedures

As mentioned earlier, EOS deviation to the right on the ECG is not considered a pathology in itself, but serves as a diagnostic sign of disorders in its functioning. In the vast majority of cases this symptom suggests that the right ventricle and/or right atrium are abnormally enlarged, and finding out the causes of such hypertrophy allows you to make a correct diagnosis.

For more accurate diagnosis, the following procedures can be used:

ultrasound is a method with the highest information content showing changes in the anatomy of an organ;
chest x-ray may reveal myocardial hypertrophy;
apply if, in addition to EOS deviation, there are also rhythm disturbances;
ECG under stress helps in the detection of myocardial ischemia;
Coronary angiography (CAG) diagnoses lesions of the coronary arteries, which can also lead to the tilt of the EOS.

What diseases are caused

A pronounced deviation of the electrical axis to the right can signal the following diseases or pathologies:

Cardiac ischemia. , characterizing the blockage of the coronary arteries that feed the heart muscle with blood. With uncontrolled development leads to myocardial infarction.
congenital or acquired. This is the name given to the narrowing of this large vessel, which prevents the normal exit of blood from the right ventricle. It leads to increased systolic blood pressure and, as a result, to myocardial hypertrophy.
Atrial fibrillation. Random electrical activity of the atria, which, as a result, can cause a cerebral stroke.
Chronic cor pulmonale. Occurs when there is a malfunction of the lungs or pathologies of the chest, which lead to the inability of the left ventricle to fully work. Under such conditions, the load on the right ventricle increases significantly, which leads to its hypertrophy.
Atrial septal defect. It is expressed in the presence of holes in the septum between the atria, through which blood can be discharged from the left side to the right. As a result, heart failure and pulmonary hypertension develop.
mitral valve stenosis- between the left atrium and the left ventricle, which leads to difficulty in diastolic blood flow. Refers to acquired vices.
Pulmonary embolism. It is caused by blood clots, which, after occurring in large vessels, move through the circulatory system and.
primary pulmonary hypertension- blood in the pulmonary artery, which is caused by various reasons.

In addition to the above, the EOS tilt to the right may be a consequence of poisoning with tricyclic antidepressants. The somatotropic effect of such drugs is achieved by the influence of the substances contained in them on the conductive system of the heart, and thus they can harm it.

What to do

If the electrocardiogram showed an inclination of the electrical axis of the heart to the right, it should without delay, conduct a more extensive diagnostic examination by a doctor. Depending on the problem identified during a deeper diagnosis, the doctor will prescribe the appropriate treatment.

The heart is one of the most important parts of the human body, and therefore its condition should be the subject of increased attention. Unfortunately, it is often remembered only when it starts to hurt.

To prevent such situations, you need to follow at least general recommendations for the prevention of cardiac disorders: eat right, do not neglect a healthy lifestyle, and at least once a year undergo an examination by a cardiologist.

If in the results of the electrocardiogram there is a record of the deviation of the electrical axis of the heart, a deeper diagnosis should be immediately carried out to determine the causes of this phenomenon.

From this article you will learn what EOS is, what it should be like in the norm. When the EOS is deviated slightly to the left - what does this mean, what diseases can this indicate. What treatment may be required.

The electrical axis of the heart is a diagnostic criterion that displays the electrical activity of the organ.

The electrical activity of the heart is recorded using an ECG. Sensors are applied to various areas of the chest, and in order to find out the direction of the electrical axis, it is possible to represent it (the chest) in the form of a three-dimensional coordinate system.

The direction of the electrical axis is calculated by the cardiologist during the decoding of the ECG. To do this, he sums the values of the Q, R and S waves in lead 1, then finds the sum of the values of the Q, R and S waves in lead 3. Then he takes the two received numbers and calculates the alpha - the angle according to a special table. It is called the Died table. This angle is the criterion by which it is determined whether the location of the electrical axis of the heart is normal.

EOS offsets

The presence of a significant deviation of the EOS to the left or right is a sign of a violation of the heart. Diseases that provoke EOS deviation almost always require treatment. After getting rid of the underlying disease, the EOS takes on a more natural position, but sometimes it is impossible to completely cure the disease.

To resolve this problem, contact a cardiologist.

The location of the electrical axis is normal

In healthy people, the electrical axis of the heart coincides with the anatomical axis of this organ. The heart is located semi-vertically - its lower end is directed down and to the left. And the electric axis, like the anatomical one, is in a semi-vertical position and tends down and to the left.

The norm of the alpha angle is from 0 to +90 degrees.

The norm of the angle alpha EOS

The location of the anatomical and electrical axes to a certain extent depends on the physique. In asthenics (thin people with tall stature and long limbs), the heart (and, accordingly, its axes) is located more vertically, and in hypersthenics (short people with a stocky build) - more horizontally.

The norm of the alpha angle, depending on the physique:

A significant shift of the electrical axis to the left or right side is a sign of pathologies of the conduction system of the heart or other diseases.

A negative angle alpha indicates a deviation to the left: from -90 to 0 degrees. About its deviation to the right - values \u200b\u200bfrom +90 to +180 degrees.

However, it is not necessary to know these numbers at all, since in case of violations in the ECG decoding, you can find the phrase “EOS is rejected to the left (or right)”.

Reasons for shifting to the left

Deviation of the electrical axis of the heart to the left is a typical symptom of problems with the left side of this organ. It could be:

hypertrophy (enlargement, growth) of the left ventricle (LVH);
blockade of the anterior branch of the left leg of the bundle of His - a violation of the conduction of the impulse in the anterior part of the left ventricle.

Causes of these pathologies:

Symptoms

By itself, the displacement of the EOS has no characteristic symptoms.

The diseases that accompany it can also be asymptomatic. That is why it is important to undergo an ECG for preventive purposes - if the disease is not accompanied by unpleasant symptoms, you can learn about it and start treatment only after deciphering the cardiogram.

However, sometimes these diseases still make themselves felt.

Symptoms of diseases that are accompanied by a displacement of the electrical axis:

But we repeat once again - the symptoms do not always appear, they usually develop in the later stages of the disease.

Additional diagnostics

To find out the reasons for the deviation of the EOS, the ECG is analyzed in detail. They may also assign:

EchoCG (ultrasound of the heart) - to identify possible organ defects.
Stress EchoCG - ultrasound of the heart with a load - for the diagnosis of ischemia.
Angiography of the coronary vessels - their examination to detect blood clots and atherosclerotic plaques.
Holter monitoring - ECG recording using a portable device throughout the day.

After a detailed examination, appropriate therapy is prescribed.

Treatment

By itself, the deviation of the electrical axis of the heart to the left does not require specific treatment, since it is only a symptom of another disease.

All measures are aimed at eliminating the underlying disease, which is manifested by a shift in the EOS.

Treatment for LVH depends on what caused myocardial overgrowth

Treatment of the blockade of the anterior branch of the left leg of the bundle of His - the installation of a pacemaker. If arose as a result of a heart attack - surgical restoration of blood circulation in the coronary vessels.

The electrical axis of the heart returns to normal only if the size of the left ventricle is returned to normal or the impulse conduction through the left ventricle is restored.

The electrical axis of the heart (EOS) is the first words that every person who has a transcript of a cardiogram on his hands sees. When a specialist writes next to them that the EOS is in a normal position, the subject has nothing to worry about his health. But what if the axis takes a different position or has deviations?

It is no secret that the heart is constantly working and generating electrical impulses. The place of their formation is the sinus node, from which they normally go this way:

As a result, the movement is an electric vector with a strictly defined movement. The electrical axis of the heart represents the projection of the impulse on the anterior plane, which is in a vertical position.

Axis placement is calculated by dividing into degrees the circle drawn around the triangle. The direction of the vector gives the specialist a rough idea of the location of the heart in the chest.

The position of the EOS depends on:

The speed and correctness of the movement of the impulse through the cardiac systems.
Quality of myocardial contractions.
Conditions and pathologies of organs that affect the functionality of the heart.
Heart condition.

For a person who does not suffer from serious diseases, the axis is characteristic:

The normal position of the EOS is located along Died at the coordinates 0 - + 90º. For most people, the vector passes the limit of +30 - +70º and goes to the left and down.

At an intermediate position, the vector passes within +15 - +60 degrees.

According to the ECG, the specialist sees that the positive teeth are longer in the second, aVF and aVL leads.

Babies have a strong deviation of the axis to the right side, which during the first year of life goes into a vertical plane. This situation has a physiological explanation: the right side of the heart "overtakes" the left in weight and the production of electrical impulses. The transition of the axis to normal is associated with the development of the left ventricle.

Children's EOS norms:

Up to a year - the passage of the axis between +90 - +170 degrees.
From one to three years - vertical EOS.
6-16 - stabilization of indicators to the norms of adults.

Signs of the ECG in the analysis of the EOS are determined by the right and levograms.

A rightogram is a finding of a vector between indicators 70-900. On electrocardiography, it is demonstrated by long R waves in the QRS group. The vector of the third lead is larger than the wave of the second. For the first lead, the RS group is considered normal, where the depth of S exceeds the height of R.

The levogram on the ECG is the alpha angle, which passes between 0-500. Electrocardiography helps to determine that the usual lead of the first group of the QRS is characterized by an R-type expression, but already in the third lead it has an S-type shape.

When the axis is tilted to the left, this means that the subject has left ventricular hypertrophy.

Causes of illness include:

Hypertension. Especially in cases of frequent increase in blood pressure.
Ischemic diseases.
Chronic heart failure.
Cardiomyopathy. This disease is the growth of the heart muscle in the mass and the expansion of its cavities.
pathology of the aortic valve. They are congenital or acquired. They provoke blood flow disorders and LV reboot.

Important! Very often, hypertrophy is exacerbated in people who spend a lot of time on diverse sports activities.

With a strong deviation of the axis to the right, a person may have PR hypertrophy, which is caused by:

High pressure in the arteries of the lungs, which causes bronchitis, asthma and emphysema.
Pathological diseases of the tricuspid valve.
Ischemia.
Heart failure.
Blocking of the posterior branch of the His node.

The vertical arrangement is characterized by a range of +70 - +90º. It is characteristic of tall, thin people with a narrow sternum. According to anatomical indicators, with such a physique, the heart seems to “hang”.

On the electrocardiogram, the highest positive vectors are observed in aVF, negative - in aVL.

When horizontal, the vector runs between +15 - -30º. Most often observed in people with a hypersthenic physique: short stature, wide chest, overweight. From an anatomical point of view, in this case, the heart is located on the diaphragm.

On the cardiogram in aVL, the highest positive teeth appear, and in aVF - negative.

The deviation of the electric axis to the left is the location of the vector in the limit 0 - -90º. A distance of up to -30º in some cases is normal, but the slightest excess of the indicator can be regarded as a symptom of a serious illness. For some people, such indicators provoke a deep exhalation.

Important! In women, a change in the coordinates of the location of the heart in the chest can be triggered by pregnancy.

The reasons for which the axis deviates to the left:

LV hypertrophy.
Violation or blocking of the bundle of His.
Myocardial infarction.
Myocardial dystrophy.
Heart defects.
Violation of abbreviations SM.
Myocarditis.
Cardiosclerosis.
Calcium accumulation in the body, blocking normal contraction.

These ailments and pathologies can provoke an increase in the mass and size of the LV. Because of this, the tooth on this side is longer, resulting in a deviation of the electrical axis to the left.

The axis deviation to the right is fixed when it passes between +90 - +180º. This shift can be provoked by:

Damage to the pancreas by infarction.
The simultaneous occurrence of coronary artery disease and hypertension - they exhaust the heart with a vengeance and provoke insufficiency.
Pulmonary diseases of a chronic nature.
Incorrect passage of electrical impulses along the right branch of the His bundle.
Pulmonary emphysema.
Strong load on the pancreas caused by obstruction of the pulmonary artery.
Dextrocardia.
Mitral heart disease, which provokes pulmonary hypertension and stimulates the work of the pancreas.
Thrombotic blockage of blood flow in the lungs, which causes a deficiency of the organ in the blood and overloads the entire right side of the heart.

Due to these pathologies, on electrocardiography, the specialist establishes that the EOS is deviated to the right.

If you have found a pathological deviation of the axis, the specialist is obliged to resort to new studies. Each ailment that provokes a shift in the EOS is accompanied by several symptoms that require careful analysis. Most often resort to ultrasound diagnostics of the heart.

Determining the electrical axis of the heart is just a technique that allows you to understand the location of the heart and diagnose it for the presence of pathologies and ailments. A conclusion on it can only be carried out by a qualified specialist, since a deviation does not always mean the presence of heart problems.

EOS deviation to the right is recorded if it is in the range from +90 to +180 degrees.

Let's take a closer look at why this happens and what are the normal numbers.

When deciphering an electrocardiogram, one of the parameters is EOS - the electrical axis of the heart. This indicator indirectly reflects the position of this organ in the chest.

The atria and ventricles of the heart are controlled by impulses that propagate through the conduction system. When taking a cardiogram, electrical signals passing inside the heart muscle are recorded.

For ease of measurement, the heart is schematically represented as a three-dimensional coordinate axis.

In the total addition, the impulses form a directed electric vector. It is projected onto the frontal vertical plane. This is EOS. Usually the electrical axis coincides with the anatomical one.

What should be its normal position?

The anatomical structure of the heart is such that its left ventricle weighs more than the right one. Therefore, the electrical excitation in the left side of the organ is stronger.

Graphically, this is expressed in the fact that the axis is directed diagonally to the left and down. If you look at the projection of the vector, then the left side of the heart is in the area from +30 to +70 degrees. This is the normal value for an adult.

The position of the axis depends, among other things, on the individual characteristics of physiology.

The direction of the EOS is influenced by the following factors:

impulse speed.
The ability of the heart muscle to contract.
Features of the structure of the spine, chest, internal organs that interact with the heart.

Given these factors, the normal value of the axis ranges from 0 to +90 degrees.

In a healthy person, EOS can be in one of the following positions:

Normal - the angle of deviation from the coordinate axis is from +30 to +70 degrees.
Intermediate - from +15 to +60.
Vertical - between +70 and +90. This is typical for thin people with a narrow chest.
Horizontal - from 0 to + 30 degrees. It occurs in people with a wide chest with low stature.

In newborns, EOS deviation to the right is often observed. By one or two years, it moves into an upright position. After the children reach the age of three, the axis usually assumes a normal position.

This is due to the growth of the heart, in particular, with an increase in the mass of the left ventricle.

Why would she move to the right?

A sharp deviation of the electric vector from its axis is sometimes caused by processes occurring inside the body (pregnancy, development of tumors, etc.).

However, most often this means the presence of disorders in the work of the heart muscle.

Axis shift can occur for the following pathological reasons:

Ischemic disease. Blockage of the arteries that supply blood to the myocardium develops.
Violation of blood flow in the branches of the pulmonary artery. It occurs as a result of vasoconstriction, due to which pressure rises in the right side of the heart.
Myocardial infarction. Against the background of ischemic disease, tissue necrosis develops due to insufficient blood supply.
The opening between the left atrium and the ventricle narrows (stenosis), which leads to significant tension in the right side of the organ and its subsequent hypertrophy.
Blockage of the pulmonary artery (thrombosis).
Arrhythmia is a violation of the heartbeat, accompanied by chaotic excitation of the atria.
The occurrence of pulmonary pathology of the chronic type, in which the ventricle is also observed. In medicine, this disease is called "cor pulmonale".
Abnormal development of the myocardium, in which there is a displacement of the organ to the right side. At the same time, the electric axis also deviates.

And also a shift of the axis to the right is observed due to long-term use of tricyclic antidepressants, resulting in severe intoxication of the body. This negatively affects the work of the heart.

When in newborns the EOS is deviated to the right side, this is considered the norm.

However, if the shift is associated with (violation of the passage of the electrical impulse through the bundles of heart cells), then an additional examination of the baby is carried out.

Cardiac pathologies are congenital or acquired during life, which develop as a result of previous serious illnesses or due to increased physical exertion.

For example, professional athletes are often diagnosed with an increase in the mass and volume of the left ventricle (hypertrophy).

Signs of bias on the ECG

The angle of the electrical axis and its direction are the main characteristics when deciphering the ECG.

The interpretation of the cardiogram is given by a cardiologist. To do this, he uses special schemes and tables designed to determine the displacement of the EOS.

The diagnostician examines the QRS teeth on the electrocardiogram. This is a set of notation showing and displaying the polarization of the ventricles.

QRS waves characterize their contraction or relaxation. R - tooth directed upwards (positive), Q, S - negative, or directed downwards. Q is before R and S is after it. By these signs, the cardiologist judges how the axis is shifting.

Deviation of the electrical axis of the heart to the right occurs if R is greater in the third lead than in the first. If the highest amplitude of R is in the second lead, the EOS corresponds to the normal position.

Additional diagnostic methods

If the patient has a tendency to shift the EOS to the right on the ECG, an additional examination is carried out in order to make an accurate diagnosis.

Basically, this indicator indicates an increase in the mass of the right side of the heart.

The following diagnostic methods are used:

Chest X-ray. The pictures show an increase in the heart muscle, if any.
. The method allows you to get a complete visual picture of the state of the myocardium.
. Used in the presence of tachycardia in a patient.
An electronic cardiogram with an additional load (for example,) - to determine coronary disease.
Angiography - reveals abnormalities in the work of the coronary vessels.

Should I be concerned and what should I do?

By itself, the displacement of the electrical axis of the heart is not a disease, it only indicates the possible presence of pathologies. Cardiologists believe that one of the main reasons for the deviation of the cardiac axis to the right is hypertrophy of the heart muscle.

If a shift to the right side is detected, additional examinations should be immediately carried out. Based on their results, the doctor will prescribe treatment if any disorder is identified.

Usually, a sharp deviation of the EOS on the electrocardiogram does not signal a threat to life. Only a strong change in the vector angle (up to +900) can alert the doctor. With this indicator, cardiac arrest may occur. The patient is immediately transferred to the intensive care unit.

In order to avoid serious consequences, in the presence of EOS displacement, it is recommended to be examined by a cardiologist every year.

What exactly does an ECG machine record?

Electrocardiograph fixes total electrical activity of the heart, or more precisely - the difference in electrical potentials (voltage) between 2 points.

Where in the heart there is a potential difference? Everything is simple. At rest, myocardial cells are negatively charged on the inside and positively charged on the outside, while a straight line (= isoline) is fixed on the ECG tape. When an electrical impulse (excitation) arises and propagates in the conduction system of the heart, the cell membranes pass from a state of rest to an excited state, changing the polarity to the opposite (the process is called depolarization). At the same time, the membrane becomes positive from the inside, and negative from the outside due to the opening of a number of ion channels and the mutual movement of K + and Na + ions (potassium and sodium) from the cell and into the cell. After depolarization, after a certain time, the cells go into a state of rest, restoring their original polarity (minus from the inside, plus from the outside), this process is called repolarization.

An electrical impulse sequentially propagates through the heart, causing depolarization of myocardial cells. During depolarization, part of the cell is positively charged from the inside, and part is negatively charged. Arises potential difference. When the entire cell is depolarized or repolarized, there is no potential difference. stages depolarization corresponds to contraction cells (myocardium), and stages repolarization - relaxation. The ECG records the total potential difference from all myocardial cells, or, as it is called, electromotive force of the heart(EMF of the heart). The EMF of the heart is a tricky but important thing, so let's get back to it a little lower.

Schematic arrangement of the EMF vector of the heart(in the center)
at one point in time.

Leads on the ECG

As stated above, the electrocardiograph records the voltage (electrical potential difference) between 2 points, that is, in some abduction. In other words, the ECG machine records on paper (screen) the magnitude of the projection of the electromotive force of the heart (EMF of the heart) on any lead.

A standard ECG is recorded in 12 leads:

3 standard(I, II, III),
3 reinforced from limbs (aVR, aVL, aVF),
and 6 chest(V1, V2, V3, V4, V5, V6).

1) Standard leads(proposed by Einthoven in 1913).
I - between the left hand and the right hand,
II - between the left leg and right hand,
III - between the left leg and left hand.

Protozoa(single-channel, i.e. recording no more than 1 lead at any time) the cardiograph has 5 electrodes: red(applies to right hand) yellow(left hand), green(left leg), black(right leg) and thoracic (suction cup). If you start with the right hand and move in a circle, you can say that you have a traffic light. The black electrode means “ground” and is only needed for safety purposes for grounding so that a person does not get electric shock in case of a possible breakdown of the electrocardiograph.

Multichannel portable electrocardiograph.
All electrodes and suction cups differ in color and place of application.

2) Strengthened limb leads(proposed by Goldberger in 1942).
The same electrodes are used as for recording standard leads, but each of the electrodes in turn connects 2 limbs at once, and a combined Goldberger electrode is obtained. In practice, these leads are recorded by simply switching the handle on a single-channel cardiograph (i.e., the electrodes do not need to be rearranged).

aVR- enhanced lead from the right hand (short for augmented voltage right - enhanced potential on the right).
aVL- enhanced abduction from the left hand (left - left)
aVF- enhanced abduction from the left leg (foot - leg)

3) chest leads(proposed by Wilson in 1934) are recorded between the chest electrode and the combined electrode from all 3 limbs.
The points of location of the chest electrode are located sequentially along the anterior-lateral surface of the chest from the midline of the body to the left hand.

I do not specify in too much detail, because for non-specialists it is not necessary. The principle itself is important (see fig.).
V1 - in the IV intercostal space along the right edge of the sternum.
V2
V3
V4 - at the level of the apex of the heart.
V5
V6 - on the left mid-axillary line at the level of the apex of the heart.

Location of 6 chest electrodes when recording an ECG.

The 12 leads indicated are standard. If necessary, "write" and additional leads:

by Nebu(between points on the surface of the chest),
V7 - V9(continuation of chest leads to the left half of the back),
V3R-V6R(mirror image of chest leads V3 - V6 on the right half of the chest).

Lead value

For reference: quantities are scalar and vector. Scalars haveonly magnitude (numerical value), for example: mass, temperature, volume. Vector quantities, or vectors, haveboth magnitude and direction ; for example: speed, force, electric field strength, etc. Vectors are indicated by an arrow above the Latin letter.

Why invented so many leads? EMF of the heart is vector heart emf in 3d world(length, width, height) taking into account time. On a flat ECG film, we can only see 2-dimensional values, so the cardiograph records the projection of the EMF of the heart on one of the planes in time.

Body planes used in anatomy.

Each lead records its own projection of the EMF of the heart. First 6 leads(3 standard and 3 reinforced from the limbs) reflect the EMF of the heart in the so-called frontal plane(see Fig.) and allow you to calculate the electrical axis of the heart with an accuracy of 30° (180° / 6 leads = 30°). The missing 6 leads to form a circle (360°) are obtained by continuing the existing lead axes through the center to the second half of the circle.

Mutual arrangement of standard and reinforced leads in the frontal plane.
But there is an error in the picture:
aVL and lead III are NOT in line.
Below are the correct drawings.

6 chest leads reflect the emf of the heart in the horizontal (transverse) plane(it divides the human body into upper and lower halves). This allows you to clarify the localization of the pathological focus (for example, myocardial infarction): the interventricular septum, the apex of the heart, the lateral sections of the left ventricle, etc.

When parsing an ECG, projections of the EMF vector of the heart are used, so this ECG analysis is called vector.

Note. The material below may seem very complex. This is fine. When studying the second part of the cycle, you will return to it, and it will become much clearer.

Electrical axis of the heart (EOS)

If draw a circle and draw lines through its center corresponding to the directions of three standard and three reinforced leads from the limbs, then we get 6-axis coordinate system. When recording an ECG in these 6 leads, 6 projections of the total EMF of the heart are recorded, which can be used to assess the location of the pathological focus and the electrical axis of the heart.

Formation of a 6-axis coordinate system.
Missing leads are replaced by extensions of existing ones.

Electrical axis of the heart- this is the projection of the total electrical vector of the ECG QRS complex (it reflects the excitation of the ventricles of the heart) onto the frontal plane. Quantitatively, the electrical axis of the heart is expressed angle α between the axis itself and the positive (right) half of the axis I of the standard lead, located horizontally.

It is clearly seen that the same EMF of the heart in projections
on different assignments gives various forms of curves.

Definition rules the positions of the EOS in the frontal plane are as follows: the electrical axis of the heart matches with that of the first 6 leads, in which highest positive teeth, and perpendicular to the lead in which the size of the positive teeth is equal to the size of the negative teeth. Two examples of determining the electrical axis of the heart are given at the end of the article.

Options for the position of the electrical axis of the heart:

normal: 30° > α< 69°,
vertical: 70° > α< 90°,
horizontal: 0° > α < 29°,
sharp right axis deviation: 91° > α< ±180°,
sharp left axis deviation: 0° > α < −90°.

Options for the location of the electrical axis of the heart
in the frontal plane.

Fine electrical axis of the heart roughly corresponds to anatomical axis(for thin people it is directed more vertically from the average values, and for obese people it is more horizontally). For example, when hypertrophy(growth) of the right ventricle, the axis of the heart deviates to the right. At conduction disorders the electrical axis of the heart can deviate sharply to the left or right, which in itself is a diagnostic sign. For example, with complete blockade of the anterior branch of the left branch of the bundle of His, there is a sharp deviation of the electrical axis of the heart to the left (α ≤ −30°), the posterior branch to the right (α ≥ +120°).

Complete blockade of the anterior branch of the left leg of the bundle of His.
EOS sharply deviated to the left(α ≅− 30°), because the highest positive waves are seen in aVL, and the equality of the waves is noted in lead II, which is perpendicular to aVL.

Complete blockade of the posterior branch of the left leg of the bundle of His.
EOS sharply deviated to the right(α ≅ +120°), because the highest positive waves are seen in lead III, and the equality of the waves is noted in lead aVR, which is perpendicular to III.

Electrocardiogram reflects only electrical processes in the myocardium: depolarization (excitation) and repolarization (recovery) of myocardial cells.

Ratio ECG intervals With phases of the cardiac cycle(ventricular systole and diastole).

Normally, depolarization leads to contraction of the muscle cell, and repolarization leads to relaxation. To simplify further, I will sometimes use “contraction-relaxation” instead of “depolarization-repolarization”, although this is not entirely accurate: there is a concept “ electromechanical dissociation“, in which depolarization and repolarization of the myocardium do not lead to its visible contraction and relaxation. I wrote a little more about this phenomenon before.

Elements of a normal ECG

Before moving on to deciphering the ECG, you need to figure out what elements it consists of.

Waves and intervals on the ECG.
It is curious that abroad the P-Q interval is usually called P-R.

Every ECG is made up of teeth, segments and intervals.

TEETH are convexities and concavities on the electrocardiogram.
The following teeth are distinguished on the ECG:

P(atrial contraction)
Q, R, S(all 3 teeth characterize the contraction of the ventricles),
T(ventricular relaxation)
U(non-permanent tooth, rarely recorded).

SEGMENTS
A segment on an ECG is called straight line segment(isolines) between two adjacent teeth. The P-Q and S-T segments are of the greatest importance. For example, the P-Q segment is formed due to a delay in conduction of excitation in the atrioventricular (AV-) node.

INTERVALS
The interval consists of tooth (complex of teeth) and segment. Thus, interval = tooth + segment. The most important are the P-Q and Q-T intervals.

Teeth, segments and intervals on the ECG.
Pay attention to large and small cells (about them below).

Waves of the QRS complex

Since the ventricular myocardium is more massive than the atrial myocardium and has not only walls, but also a massive interventricular septum, the spread of excitation in it is characterized by the appearance of a complex complex QRS on the ECG. How to pick out the teeth?

First of all, evaluate amplitude (dimensions) of individual teeth QRS complex. If the amplitude exceeds 5 mm, the prong denote capital (big) letter Q, R or S; if the amplitude is less than 5 mm, then lowercase (small): q, r or s.

The tooth R (r) is called any positive(upward) wave that is part of the QRS complex. If there are several teeth, subsequent teeth indicate strokes: R, R’, R”, etc. The negative (downward) wave of the QRS complex located before the R wave, denoted as Q (q), and after - as S(s). If there are no positive waves at all in the QRS complex, then the ventricular complex is designated as QS.

Variants of the QRS complex.

Normal tooth. Q reflects depolarization of the interventricular septum R- the bulk of the myocardium of the ventricles, tooth S- basal (i.e., near the atria) sections of the interventricular septum. The R wave V1, V2 reflects the excitation of the interventricular septum, and R V4, V5, V6 - the excitation of the muscles of the left and right ventricles. necrosis of areas of the myocardium (for example, with myocardial infarction) causes widening and deepening of the Q wave, so this wave is always paid close attention.

ECG analysis

General ECG decoding scheme

Checking the correctness of ECG registration.
Heart rate and conduction analysis:

assessment of the regularity of heart contractions,
counting the heart rate (HR),
determination of the source of excitation,
conductivity rating.

Determination of the electrical axis of the heart.

Analysis of atrial P wave and P-Q interval.

Analysis of the ventricular QRST complex:

analysis of the QRS complex,
analysis of the RS-T segment,
T wave analysis,
analysis of the interval Q - T.

Electrocardiographic conclusion.

Normal electrocardiogram.

1) Checking the correctness of the ECG registration

At the beginning of each ECG tape there should be calibration signal- so-called control millivolt. To do this, at the beginning of the recording, a standard voltage of 1 millivolt is applied, which should display on the tape a deviation of 10 mm. Without a calibration signal, the ECG recording is considered incorrect. Normally, in at least one of the standard or augmented limb leads, the amplitude should exceed 5 mm, and in the chest leads - 8 mm. If the amplitude is lower, it is called reduced EKG voltage which occurs in some pathological conditions.

Reference millivolt on the ECG (at the beginning of the recording).

2) Heart rate and conduction analysis:

assessment of heart rate regularity

Rhythm regularity is assessed by R-R intervals. If the teeth are at an equal distance from each other, the rhythm is called regular, or correct. The variation in the duration of individual R-R intervals is allowed no more than ±10% from their average duration. If the rhythm is sinus, it is usually correct.

heart rate count(HR)

Large squares are printed on the ECG film, each of which includes 25 small squares (5 vertical x 5 horizontal). For a quick calculation of heart rate with the correct rhythm, the number of large squares between two adjacent R-R teeth is counted.

At 50 mm/s belt speed: HR = 600 / (number of large squares).
At 25 mm/s belt speed: HR = 300 / (number of large squares).

On the overlying ECG, the R-R interval is approximately 4.8 large cells, which at a speed of 25 mm/s gives300 / 4.8 = 62.5 bpm

At a speed of 25 mm/s each little cell is equal to 0.04s, and at a speed of 50 mm/s - 0.02 s. This is used to determine the duration of the teeth and intervals.

With an incorrect rhythm, they usually consider maximum and minimum heart rate according to the duration of the smallest and largest R-R interval, respectively.

determination of the source of excitation

In other words, they are looking for where pacemaker which causes atrial and ventricular contractions. Sometimes this is one of the most difficult stages, because various disturbances of excitability and conduction can be very intricately combined, which can lead to misdiagnosis and incorrect treatment. To correctly determine the source of excitation on the ECG, you need to know well conduction system of the heart.

Sinus rhythm(this is a normal rhythm, and all other rhythms are pathological).
The source of excitation is in sinoatrial node. ECG signs:

in standard lead II, the P waves are always positive and are in front of each QRS complex,
P waves in the same lead have a constant identical shape.

P wave in sinus rhythm.

ATRIAL Rhythm. If the source of excitation is in the lower sections of the atria, then the excitation wave propagates to the atria from the bottom up (retrograde), therefore:

in leads II and III, P waves are negative,
There are P waves before each QRS complex.

P wave in atrial rhythm.

Rhythms from the AV junction. If the pacemaker is in the atrioventricular ( atrioventricular node) node, then the ventricles are excited as usual (from top to bottom), and the atria - retrograde (i.e., from bottom to top). At the same time on the ECG:

P waves may be absent because they are superimposed on normal QRS complexes,
P waves may be negative, located after the QRS complex.

Rhythm from the AV junction, P wave overlapping the QRS complex.

Rhythm from the AV junction, the P wave is after the QRS complex.

The heart rate in the rhythm from the AV connection is less than sinus rhythm and is approximately 40-60 beats per minute.

Ventricular, or IDIOVENTRICULAR, rhythm(from lat. ventriculus [ventriculus] - ventricle). In this case, the source of rhythm is the conduction system of the ventricles. Excitation spreads through the ventricles in the wrong way and therefore more slowly. Features of idioventricular rhythm:

the QRS complexes are dilated and deformed (look “scary”). Normally, the duration of the QRS complex is 0.06-0.10 s, therefore, with this rhythm, the QRS exceeds 0.12 s.
there is no pattern between QRS complexes and P waves because the AV junction does not release impulses from the ventricles, and the atria can fire from the sinus node as normal.
Heart rate less than 40 beats per minute.

Idioventricular rhythm. The P wave is not associated with the QRS complex.

conductivity assessment.
To correctly account for conductivity, the write speed is taken into account.

To assess conductivity, measure:

duration P wave(reflects the speed of the impulse through the atria), normally up to 0.1s.
duration interval P - Q(reflects the speed of the impulse from the atria to the myocardium of the ventricles); interval P - Q = (wave P) + (segment P - Q). Fine 0.12-0.2s.
duration QRS complex(reflects the spread of excitation through the ventricles). Fine 0.06-0.1s.
internal deflection interval in leads V1 and V6. This is the time between the onset of the QRS complex and the R wave. Normally in V1 up to 0.03 s and in V6 to 0.05 s. It is mainly used to recognize bundle branch blocks and to determine the source of excitation in the ventricles in the case of ventricular extrasystole(extraordinary contraction of the heart).

Measurement of the interval of internal deviation.

3) Determination of the electrical axis of the heart.
In the first part of the cycle about the ECG, it was explained what electrical axis of the heart and how it is defined in the frontal plane.

4) Atrial P wave analysis.
Normal in leads I, II, aVF, V2 - V6 P wave always positive. In leads III, aVL, V1, the P wave can be positive or biphasic (part of the wave is positive, part is negative). In lead aVR, the P wave is always negative.

Normally, the duration of the P wave does not exceed 0.1s, and its amplitude is 1.5 - 2.5 mm.

Pathological deviations of the P wave:

Pointed high P waves of normal duration in leads II, III, aVF are characteristic of right atrial hypertrophy, for example, with "cor pulmonale".
A split with 2 peaks, an extended P wave in leads I, aVL, V5, V6 is typical for left atrial hypertrophy such as mitral valve disease.

P wave formation (P-pulmonale) with right atrial hypertrophy.

P wave formation (P-mitrale) with left atrial hypertrophy.

P-Q interval: fine 0.12-0.20s.
An increase in this interval occurs with impaired conduction of impulses through the atrioventricular node ( atrioventricular block, AV block).

AV block there are 3 degrees:

I degree - the P-Q interval is increased, but each P wave has its own QRS complex ( no loss of complexes).
II degree - QRS complexes partially fall out, i.e. Not all P waves have their own QRS complex.
III degree - complete blockade of in the AV node. The atria and ventricles contract in their own rhythm, independently of each other. Those. an idioventricular rhythm occurs.

5) Analysis of the ventricular QRST complex:

analysis of the QRS complex.

The maximum duration of the ventricular complex is 0.07-0.09 s(up to 0.10 s). The duration increases with any blockade of the legs of the bundle of His.

Normally, the Q wave can be recorded in all standard and augmented limb leads, as well as in V4-V6. Q wave amplitude normally does not exceed 1/4 R wave height, and the duration is 0.03 s. Lead aVR normally has a deep and wide Q wave and even a QS complex.

The R wave, like Q, can be recorded in all standard and enhanced limb leads. From V1 to V4, the amplitude increases (while the r wave of V1 may be absent), and then decreases in V5 and V6.

The S wave can be of very different amplitudes, but usually no more than 20 mm. The S wave decreases from V1 to V4, and may even be absent in V5-V6. In lead V3 (or between V2 - V4) is usually recorded “ transition zone” (equality of the R and S waves).

analysis of the RS-T segment

The ST segment (RS-T) is the segment from the end of the QRS complex to the beginning of the T wave. The ST segment is especially carefully analyzed in CAD, as it reflects a lack of oxygen (ischemia) in the myocardium.

Normally, the S-T segment is located in the limb leads on the isoline ( ± 0.5mm). In leads V1-V3, the S-T segment can be shifted upward (no more than 2 mm), and in V4-V6 - downward (no more than 0.5 mm).

The transition point of the QRS complex to the S-T segment is called the point j(from the word junction - connection). The degree of deviation of point j from the isoline is used, for example, to diagnose myocardial ischemia.

T wave analysis.

The T wave reflects the process of repolarization of the ventricular myocardium. In most leads where a high R is recorded, the T wave is also positive. Normally, the T wave is always positive in I, II, aVF, V2-V6, with T I> T III, and T V6> T V1. In aVR, the T wave is always negative.

analysis of the interval Q - T.

The Q-T interval is called electrical ventricular systole, because at this time all departments of the ventricles of the heart are excited. Sometimes after the T wave, a small U wave, which is formed due to a short-term increased excitability of the myocardium of the ventricles after their repolarization.

6) Electrocardiographic conclusion.
Should include:

Rhythm source (sinus or not).
Rhythm regularity (correct or not). Usually sinus rhythm is correct, although respiratory arrhythmia is possible.
The position of the electrical axis of the heart.
The presence of 4 syndromes:

rhythm disorder
conduction disorder
hypertrophy and/or congestion of the ventricles and atria
myocardial damage (ischemia, dystrophy, necrosis, scars)

Conclusion Examples(not quite complete, but real):

Sinus rhythm with heart rate 65. Normal position of the electrical axis of the heart. Pathology is not revealed.

Sinus tachycardia with a heart rate of 100. Single supragastric extrasystole.

The rhythm is sinus with a heart rate of 70 beats / min. Incomplete blockade of the right leg of the bundle of His. Moderate metabolic changes in the myocardium.

Examples of ECG for specific diseases of the cardiovascular system - next time.

ECG interference

In connection with frequent questions in the comments about the type of ECG, I will tell you about interference that can be on the electrocardiogram:

Three types of ECG interference(explanation below).

Interference on the ECG in the lexicon of health workers is called tip-off:
a) inductive currents: network pickup in the form of regular oscillations with a frequency of 50 Hz, corresponding to the frequency of the alternating electric current in the outlet.
b) " swimming» (drift) isolines due to poor contact of the electrode with the skin;
c) interference due to muscle trembling(Irregular frequent fluctuations are visible).