Vertical direction of the electrical axis of the heart. Determination of the position of the electrical axis of the heart

The concept of the electrical axis is used in cardiology to identify heart pathologies. The vertical position of the EOS may indicate dysfunction of the conduction system, which includes the sinus node, Hiss bundle, atrioventricular node and fibers. These elements transmit electrical impulses and ensure the functioning of the heart muscle in the system.

Determining the position of the EOS using the ECG

The simplest diagnostic method gives a quick result, but does not contain accurate information. It only allows you to roughly assess the situation and suspect possible pathologies.

The following indicators are taken into account on the ECG tape:

• The R waves are greatest in lead 2. This indicates a normal level of EOS.
• The teeth are higher in the first lead - in this case, the electrical axis of the heart has a horizontal position.
• If the highest R is in the third lead, then the EOS is considered vertical.

Often such superficial research is not enough. A more accurate method is used to reveal the full picture. Its result is established according to special schemes, and certain calculations are carried out.

To do this, all indicators of positive and negative teeth of the ventricular complex are summed up. Only the first and third leads are taken into account. Their size is measured in millimeters, then the total amount is found. The teeth below the line will have indicators with a “-” sign.

After calculating the sizes of the teeth and their sums in two leads, the results are compared against the table. The necessary intersection point is found - it is an indicator of the alpha angle, by which the position of the EOS is determined.

What does the vertical placement of the axis mean?

Most often, the identified deviations in EOS are a variant of the norm and arise due to the individual characteristics of human anatomy. But there are cases when the displacement is too large - this may indicate diseases, including:

• pulmonary hypertension;
• pulmonary stenosis;
• pathology of the atrial septum;
• cardiac ischemia.

Stenosis is determined on the electrocardiogram due to myocardial hypertrophy. Both congenital and acquired forms are detected. In the first case, the diagnosis can be established in early childhood when performing the first ECG.

Atrial septal defects cause a vertical position of the EOS. This happens when the hole size is sufficiently large.

With ischemia of the disease, the lumen of the coronary arteries narrows, which causes insufficient blood supply to the myocardium. In severe form, there is a risk of pathology developing into a heart attack.

How is the EOS normally placed?

The electrical axis of the heart can have one of three locations:

• horizontal– most common in obese people;
• vertical– the norm for patients with asthenic physique;
• normal– in people with a normal body structure.

All these options do not cause concern if their deviation is not large, is not accompanied by symptoms, and the ECG results do not show pathologies. In this case, there are no health risks and no treatment is needed.

Normally, placement should be within +30...+90 degrees with sinus rhythm.

If a sharp deviation to the right or left is detected, this may indicate the presence of a disease. In such situations, the patient is sent for additional medical examinations.

Why is displacement dangerous?

The vertical position of the EOS itself is not a diagnosis, but rather relates more to individual characteristics. But if the axis is significantly shifted, this is an alarming signal that may indicate diseases:

• chronic heart failure;
• congenital heart abnormalities;
• cardiomyopathy.

If there are diseases, then ECG indicators are not the only sign. Usually there are symptoms specific to them - surges in blood pressure, rhythm disturbances, which manifest themselves as an increase in lower pressure.

Shift of the heart axis to the left

Most often, such a deviation accompanies left ventricular hypertrophy, in which it increases in size. This most often occurs due to an advanced form of hypertension.

Because there is constant resistance to blood flow in the vascular system, the ventricle needs to push blood out with greater force.

To do this, more intense contractions of the heart occur, which leads to overload. The muscle mass of the ventricle increases and hypertrophy occurs.

Ischemia and chronic heart failure also lead to hypertrophy. Pathological changes in its myocardium are the most common cause of incorrect location of the EOS.

The disease can also cause problems with the left ventricular valves. They are provoked by stenosis of the aortic mouth, which is accompanied by difficult ejection of blood, as well as pathologies of the aortic valve, which provoke the return of part of the blood and overload.

All these pathologies are both congenital and acquired. If heart defects appeared over time, they could be caused by rheumatic fever. Left ventricular hypertrophy is often found in people who play sports professionally. In this case, the question of suspension from training may arise, which requires examination by a highly qualified sports doctor.

Deviation of the heart axis to the left is also detected in the presence of heart blocks, that is, disturbances in the conduction of impulses. Left displacement of the EOS is one of the signs of pathology of the His bundle, which is responsible for contractions of the left ventricle.

Axis offset to the right

This orientation often indicates hypertrophy of the right ventricle, the blood from which is sent to the lungs for oxygen enrichment. Pathology can be caused by chronic diseases, such as obstructive disease and bronchial asthma, pulmonary stenosis, and valve pathologies.

Just as in the case of the left ventricle of the heart, hypertrophy of the right can be provoked by ischemia, cardiomyopathy and heart failure.

Another reason for deviation to the right is blockade of the left bundle branch, which leads to heart rhythm disturbances.

Vertical position of the axis in pregnant women and children

During pregnancy, the EOS becomes upright quite rarely. This is due to the physiological characteristics of the body of the woman carrying the baby. The uterus is constantly enlarging, thereby beginning to affect other internal organs. Because of this, the EOS shifts in most cases in the horizontal direction.

If the ECG showed a vertical position of the axis, the patient will require additional examination. The cause may be heart disease.

In children, such placement is usually attributed to age-related characteristics. As the body matures, it acquires the proper structure, and after complete formation, the electrical axis of the heart returns to its normal location. In some cases, it remains vertical due to the individual structural features of the body.

Only a sharp right or left shift can warn of pathologies, most likely congenital. In this case, the child will need to continue examination to identify the true cause of EOS deviation and make a diagnosis, after which treatment will be prescribed. The position of the axis itself is not the basis for determining the exact pathology or its absence.

The definition of “rotation of the electrical axis of the heart around an axis” may well be found in descriptions of electrocardiograms and is not something dangerous. When the electrical axis of the heart deviates to the right, the alpha angle will be determined within 70-90°.

The direction of the electrical axis of the heart shows the total magnitude of bioelectric changes occurring in the heart muscle with each contraction. The heart is a three-dimensional organ, and in order to calculate the direction of the EOS, cardiologists represent the chest as a coordinate system. If you project the electrodes onto a conventional coordinate system, you can also calculate the angle of the electrical axis, which will be located where the electrical processes are strongest.

Horizontal position of the electrical axis of the heart (e.o.s.)

The conduction system of the heart consists of sections of the heart muscle consisting of so-called atypical muscle fibers. These fibers are well innervated and provide synchronous contraction of the organ. Myocardial contraction begins with the appearance of an electrical impulse in the sinus node (which is why the correct rhythm of a healthy heart is called sinus).

The posterior branch of the left bundle branch is located in the middle and lower third of the interventricular septum, the posterolateral and inferior wall of the left ventricle. The myocardial conduction system is a powerful source of electrical impulses, which means that electrical changes that precede cardiac contraction occur in it first of all in the heart. The mass of the cardiac muscle of the left ventricle is normally much greater than the mass of the right ventricle.

This position of the heart axis is found in tall, thin people - asthenics. The horizontal position of the EOS is more common in short, stocky people with a wide chest - hypersthenics, and its value ranges from 0 to + 30 degrees. All five position options (normal, horizontal, semi-horizontal, vertical and semi-vertical) occur in healthy people and are not pathological.

The position of the EOS itself is not a diagnosis. However, there are a number of diseases in which there is a displacement of the heart axis. These defects can be either congenital or acquired. The most common acquired heart defects are a consequence of rheumatic fever. In this case, a consultation with a highly qualified sports doctor is necessary to decide on the possibility of continuing to play sports.

A shift in the electrical axis of the heart to the right may indicate right ventricular hypertrophy (RVH). Blood from the right ventricle enters the lungs, where it is enriched with oxygen. None of the above diagnoses can be made on the basis of EOS displacement alone. The position of the axis serves only as an additional indicator in diagnosing a particular disease.

And yet, the main reason for the displacement of the EOS is myocardial hypertrophy. The situation should be alarming when, with a pre-existing position of the EOS, its sharp deviation on the ECG occurs. In this case, the deviation most likely indicates the occurrence of a blockade. In itself, the displacement of the electrical axis of the heart does not require treatment; it refers to electrocardiological signs and requires, first of all, to determine the cause of its occurrence. Attention! We are not a #171;clinic#187; and are not interested in providing medical services to readers.

Variations in the shape of the QRS complex of a normal ECG may be due to variations in the sequence of intraventricular conduction or the anatomical location of the heart in the chest. When RaVF=SaVF angle a = 0°, i.e. AQRS on the border of horizontal position and deviation to the left. The TIII and PIII waves are low and sometimes negative or isoelectric.

The resulting vector of ventricular excitation is the sum of three momentary excitation vectors: the interventricular septum, the apex and base of the heart. This vector has a certain orientation in space, which we interpret in three planes: frontal, horizontal and sagittal. In each of them, the resulting vector has its own projection. Change the alpha angle within 0 #8212; minus 30° indicates a sharp deviation of the electrical axis of the heart to the left or, in other words, a sharp leftogram.

On the contrary, if in standard lead I we have the S-type of the ventricular complex, and in lead III the R-type of the QRS complex, then the electrical axis of the heart is deviated to the right (rightogram). Simplified, this condition is written as SI-RIII. The resulting vector of ventricular excitation is normally located in the frontal plane so that its direction coincides with the direction of axis II of the standard lead.

In this case, the deviation of the electrical axis is determined by analyzing the R and S waves in standard leads I and III. This, of course, does not mean that with a normal or, for example, vertical position of the electrical axis, significant changes in the ventricular myocardium cannot take place. As in the case of the left ventricle, RVH is caused by coronary heart disease, chronic heart failure and cardiomyopathies. In some cases, it is not possible to find on the electrocardiogram the conditions described for determining the electrical position of the heart.

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Electrical axis of the heart: norm and deviations

Electrical axis of the heart #8212; those words that appear first when deciphering an electrocardiogram. When they write that her position is normal, the patient is satisfied and happy. However, in conclusions they often write about the horizontal, vertical axis, and its deviations. In order not to experience unnecessary anxiety, it is worth having an understanding of EOS: what it is, and what the dangers are if its position is different from the normal one.

General overview of EOS #8212; What is this

It is known that the heart, during its tireless work, generates electrical impulses. They originate in a certain area - in the sinus node, then normally the electrical excitation passes to the atria and ventricles, spreading along the conducting nerve bundle, called the bundle of His, along its branches and fibers. In total, this is expressed as an electric vector, which has a direction. EOS #8212; projection of this vector onto the front vertical plane.

Doctors calculate the position of the EOS by plotting the amplitudes of the ECG waves on the axis of the Einthoven triangle formed by standard ECG leads from the limbs:

• the amplitude of the R wave minus the amplitude of the S wave of the first lead is plotted on the L1 axis;
• a similar magnitude of the amplitude of the teeth of the third lead is deposited on the L3 axis;
• from these points, perpendiculars are set towards each other until they intersect;
• the line from the center of the triangle to the intersection point is the graphic expression of the EOS.

Its position is calculated by dividing the circle describing the Einthoven triangle into degrees. Typically, the direction of the EOS roughly reflects the location of the heart in the chest.

Normal position of EOS #8212; What is this

Determine the position of the EOS

• speed and quality of passage of the electrical signal through the structural divisions of the conduction system of the heart,
• the ability of the myocardium to contract,
• changes in internal organs that can affect the functioning of the heart, and in particular the conduction system.

In a person who does not have serious health problems, the electrical axis can occupy a normal, intermediate, vertical or horizontal position.

It is considered normal when the EOS is located in the range from 0 to +90 degrees, depending on constitutional features. Most often, normal EOS is located between +30 and +70 degrees. Anatomically, it is directed down and to the left.

The intermediate position is between +15 and +60 degrees.

On the ECG, positive waves are higher in the second, aVL, aVF leads.

Vertical position of the EOS

When verticalized, the electrical axis is located between +70 and +90 degrees.

It occurs in people with a narrow chest, tall and thin. Anatomically, the heart literally “hangs” in their chest.

On the ECG, the highest positive waves are recorded in aVF. Deep negative – in aVL.

Horizontal position of the EOS

The horizontal position of the EOS is between +15 and -30 degrees.

It is typical for healthy people with a hypersthenic physique - wide chest, short stature, increased weight. The heart of such people “lies” on the diaphragm.

On the ECG, the highest positive waves are recorded in aVL, and the deepest negative ones in aVF.

Deviation of the electrical axis of the heart to the left #8212; what does it mean

The deviation of the EOS to the left is its location in the range from 0 to -90 degrees. Up to -30 degrees can still be considered a variant of the norm, but a more significant deviation indicates a serious pathology or a significant change in the location of the heart. for example, during pregnancy. Also observed with maximally deep exhalation.

Pathological conditions accompanied by deviation of the EOS to the left:

• hypertrophy of the left ventricle of the heart is a companion and consequence of prolonged arterial hypertension;
• violation, blockade of conduction along the left leg and fibers of the His bundle;
• left ventricular myocardial infarction;
• heart defects and their consequences that change the conduction system of the heart;
• cardiomyopathy, which impairs the contractility of the heart muscle;
• myocarditis - inflammation also impairs the contractility of muscle structures and the conduction of nerve fibers;
• cardiosclerosis;
• myocardial dystrophy;
• calcium deposits in the heart muscle, preventing it from contracting normally and disrupting innervation.

These and similar diseases and conditions lead to an increase in the cavity or mass of the left ventricle. As a result, the excitation vector travels longer on the left side and the axis deviates to the left.

The ECG in the second and third leads is characterized by deep S waves.

Deviation of the electrical axis of the heart to the right #8212; what does it mean

Eos is deviated to the right if it is in the range from +90 to +180 degrees.

Possible reasons for this phenomenon:

• violation of the conduction of electrical excitation along the fibers of the His bundle, its right branch;
• myocardial infarction in the right ventricle;
• overload of the right ventricle due to narrowing of the pulmonary artery;
• chronic pulmonary pathology, the consequence of which is “pulmonary heart”, characterized by intense work of the right ventricle;
• the combination of coronary artery disease with hypertension - depletes the heart muscle, leading to heart failure;
• PE - blocking of blood flow in the branches of the pulmonary artery, of thrombotic origin, as a result the blood supply to the lungs is depleted, their vessels spasm, which leads to a load on the right side of the heart;
• mitral heart disease, valve stenosis, causing congestion in the lungs, which causes pulmonary hypertension and increased work of the right ventricle;
• dextrocardia;
• emphysema – moves the diaphragm down.

On the ECG, a deep S wave is noted in the first lead, while in the second and third it is small or absent.

It should be understood that a change in the position of the heart axis is not a diagnosis, but only signs of conditions and diseases, and only an experienced specialist should understand the reasons.

What is the electrical axis of the heart?

The electrical axis of the heart is a concept that reflects the total vector of the electrodynamic force of the heart, or its electrical activity, and practically coincides with the anatomical axis. Normally, this organ has a cone-shaped shape, with its narrow end directed downwards, forward and to the left, and the electrical axis has a semi-vertical position, that is, it is also directed downwards and to the left, and when projected onto the coordinate system it can be in the range from +0 to +90 0.

An ECG conclusion is considered normal if it indicates any of the following positions of the heart axis: not deviated, semi-vertical, semi-horizontal, vertical or horizontal. The axis is closer to the vertical position in thin, tall people of asthenic physique, and closer to the horizontal position in strong, stocky people of hypersthenic physique.

Electric axis position range is normal

For example, in the conclusion of an ECG, the patient may see the following phrase: “sinus rhythm, EOS is not deviated...”, or “the axis of the heart is in a vertical position,” this means that the heart is working correctly.

In the case of heart disease, the electrical axis of the heart, along with the heart rhythm, is one of the first ECG criteria that the doctor pays attention to, and when interpreting the ECG, the attending physician must determine the direction of the electrical axis.

Deviations from the norm are deviation of the axis to the left and sharply to the left, to the right and sharply to the right, as well as the presence of a non-sinus heart rhythm.

How to determine the position of the electrical axis

Determination of the position of the heart axis is carried out by a functional diagnostics doctor who deciphers the ECG using special tables and diagrams using the angle α (“alpha”).

The second way to determine the position of the electrical axis is to compare the QRS complexes responsible for the excitation and contraction of the ventricles. So, if the R wave has a greater amplitude in the I chest lead than in the III, then there is a levogram, or deviation of the axis to the left. If there is more in III than in I, then it is a legal grammar. Normally, the R wave is higher in lead II.

Reasons for deviations from the norm

Axial deviation to the right or left is not considered an independent disease, but it can indicate diseases that lead to disruption of the heart.

Deviation of the heart axis to the left often develops with left ventricular hypertrophy

Deviation of the heart axis to the left can occur normally in healthy individuals who are professionally involved in sports, but more often develops with left ventricular hypertrophy. This is an increase in the mass of the heart muscle with a violation of its contraction and relaxation, necessary for the normal functioning of the entire heart. Hypertrophy can be caused by the following diseases:

• cardiomyopathy (increase in myocardial mass or expansion of the heart chambers), caused by anemia, hormonal imbalances in the body, coronary heart disease, post-infarction cardiosclerosis. changes in the structure of the myocardium after myocarditis (inflammatory process in cardiac tissue);
• long-term arterial hypertension, especially with constantly high blood pressure numbers;
• acquired heart defects, in particular stenosis (narrowing) or insufficiency (incomplete closure) of the aortic valve, leading to disruption of intracardiac blood flow and, consequently, increased load on the left ventricle;
• congenital heart defects often cause a deviation of the electrical axis to the left in a child;
• conduction disturbance along the left bundle branch - complete or incomplete blockade, leading to impaired contractility of the left ventricle, while the axis is deviated, and the rhythm remains sinus;
• atrial fibrillation, then the ECG is characterized not only by axis deviation, but also by the presence of non-sinus rhythm.

Deviation of the heart axis to the right is a normal variant when conducting an ECG in a newborn child, and in this case there may be a sharp deviation of the axis.

In adults, such a deviation is usually a sign of right ventricular hypertrophy, which develops in the following diseases:

• diseases of the bronchopulmonary system - long-term bronchial asthma, severe obstructive bronchitis, emphysema, leading to increased blood pressure in the pulmonary capillaries and increasing the load on the right ventricle;
• heart defects with damage to the tricuspid (three-leaf) valve and the valve of the pulmonary artery, which arises from the right ventricle.

The greater the degree of ventricular hypertrophy, the more the electrical axis is deflected, respectively, sharply to the left and sharply to the right.

Symptoms

The electrical axis of the heart itself does not cause any symptoms in the patient. Impaired health appears in the patient if myocardial hypertrophy leads to severe hemodynamic disturbances and heart failure.

The disease is characterized by pain in the heart area

Signs of diseases accompanied by deviation of the heart axis to the left or right include headaches, pain in the heart area, swelling of the lower extremities and face, shortness of breath, asthma attacks, etc.

If any unpleasant cardiac symptoms appear, you should consult a doctor for an ECG, and if an abnormal position of the electrical axis is detected on the cardiogram, further examination must be performed to determine the cause of this condition, especially if it is detected in a child.

Diagnostics

To determine the cause of an ECG deviation of the heart axis to the left or right, a cardiologist or therapist may prescribe additional research methods:

1. Ultrasound of the heart is the most informative method that allows you to assess anatomical changes and identify ventricular hypertrophy, as well as determine the degree of impairment of their contractile function. This method is especially important for examining a newborn child for congenital heart pathology.
2. ECG with exercise (walking on a treadmill - treadmill test, bicycle ergometry) can detect myocardial ischemia, which may be the cause of deviations in the electrical axis.
3. Daily ECG monitoring in the event that not only an axis deviation is detected, but also the presence of a rhythm not from the sinus node, that is, rhythm disturbances occur.
4. Chest X-ray - with severe myocardial hypertrophy, an expansion of the cardiac shadow is characteristic.
5. Coronary angiography (CAG) is performed to clarify the nature of lesions of the coronary arteries in coronary artery disease.

Treatment

Direct deviation of the electrical axis does not require treatment, since it is not a disease, but a criterion by which it can be assumed that the patient has one or another cardiac pathology. If, after further examination, some disease is identified, it is necessary to begin treatment as soon as possible.

In conclusion, it should be noted that if the patient sees in the ECG conclusion a phrase that the electrical axis of the heart is not in a normal position, this should alert him and prompt him to consult a doctor to find out the cause of such an ECG sign, even if there are no symptoms does not arise.

Normal location of the EOS and reasons for its displacement

The electrical axis of the heart is a concept that reflects electrical processes in this organ. The direction of the EOS shows all the bioelectric changes in total that occur during the work of the heart muscle. During the recording of an electrocardiogram, each electrode records the bioelectric reaction in a strictly designated part of the myocardium. Then, to calculate the position and angle of the EOS, doctors represent the chest in the form of a coordinate system in order to subsequently project the indicators of the electrodes onto it. Horizontal position of the EOS, vertical and a number of other options are possible.

The importance of the cardiac conduction system for EOS

The conduction system of the heart muscle is atypical muscle fibers that connect various parts of the organ and help it contract synchronously. Its beginning is considered to be the sinus node, located between the mouths of the vena cava, so in healthy people the heart rate is sinus. When an impulse occurs in the sinus node, the myocardium contracts. If the conduction system malfunctions, the electrical axis changes its position, since this is where all the changes occur before the contraction of the heart muscle.

Axis directions and offset

Since the weight of the left ventricle of the heart muscle in completely healthy adults is greater than the right, all electrical processes occur there more strongly. Therefore, the axis of the heart is directed towards it.

Normal position. If we project the location of the heart onto the expected coordinate system, then the direction of the left ventricle from +30 to +70 degrees will be considered normal. But it depends on the characteristics of each person, so the norm for this indicator for different people is considered to be a range from 0 to +90 degrees.

Horizontal position (from 0 to +30 degrees). Displayed on the cardiogram in short people with a wide sternum.

Vertical position. EOS ranges from +70 to +90 degrees. It is observed in tall people with a narrow chest.

There are diseases in which the axis shifts:

Deviation to the left. If the axis deviates to the left, this may indicate enlargement (hypertrophy) of the left ventricle, which indicates its overload. This condition is often caused by arterial hypertension that lasts for a long time, when blood has difficulty passing through the vessels. As a result, the left ventricle works harder. Deviation to the left occurs with various blockades and lesions of the valve apparatus. With progressive heart failure, when the organ cannot fully perform its functions, the electrocardiogram also records a shift of the axis to the left. All these diseases force the left ventricle to work harder, so its walls become thicker, the impulse through the myocardium passes much worse, the axis deviates to the left.

Offset to the right. Deviation of the electrical axis of the heart to the right most often occurs when the right ventricle is enlarged, for example, if a person has heart disease. This may be cardiomyopathy, coronary disease, structural abnormalities of the heart muscle. Right deviation is also caused by problems with the respiratory system such as pulmonary obstruction and bronchial asthma.

EOS norm indicators

So, in healthy people, the direction of the heart axis can be normal, horizontal, vertical, the heart rhythm can be regular sinus. If the rhythm is not sinus, then this indicates some kind of disease. Irregular sinus rhythm is an indicator of the disease if it persists during breath holding. A shift of the cardiac axis to the left or right may indicate problems with the heart and respiratory system. In no case should the diagnosis be made solely on the basis of EOS displacement. A cardiologist can determine the disease and prescribe treatment after a series of additional studies.

Electrical axis of the heart (EOS): essence, norm of position and violations

Electrical axis of the heart (EOS) is a term used in cardiology and functional diagnostics, reflecting the electrical processes occurring in the heart.

The direction of the electrical axis of the heart shows the total magnitude of bioelectric changes occurring in the heart muscle with each contraction. The heart is a three-dimensional organ, and in order to calculate the direction of the EOS, cardiologists represent the chest as a coordinate system.

When taking an ECG, each electrode records bioelectrical excitation occurring in a certain area of ​​the myocardium. If you project the electrodes onto a conventional coordinate system, you can also calculate the angle of the electrical axis, which will be located where the electrical processes are strongest.

Conducting system of the heart and why is it important for determining EOS?

The conduction system of the heart consists of sections of the heart muscle consisting of so-called atypical muscle fibers. These fibers are well innervated and provide synchronous contraction of the organ.

Myocardial contraction begins with the appearance of an electrical impulse in the sinus node (which is why the correct rhythm of a healthy heart is called sinus). From the sinus node, the electrical impulse travels to the atrioventricular node and further along the His bundle. This bundle passes through the interventricular septum, where it divides into the right, heading towards the right ventricle, and the left legs. The left bundle branch is divided into two branches, anterior and posterior. The anterior branch is located in the anterior sections of the interventricular septum, in the anterolateral wall of the left ventricle. The posterior branch of the left bundle branch is located in the middle and lower third of the interventricular septum, the posterolateral and inferior wall of the left ventricle. We can say that the posterior branch is located slightly to the left of the anterior one.

The myocardial conduction system is a powerful source of electrical impulses, which means that electrical changes that precede cardiac contraction occur in it first of all in the heart. If there are disturbances in this system, the electrical axis of the heart can significantly change its position, as will be discussed below.

Variants of the position of the electrical axis of the heart in healthy people

The mass of the cardiac muscle of the left ventricle is normally much greater than the mass of the right ventricle. Thus, the electrical processes occurring in the left ventricle are overall stronger, and EOS will be directed specifically at it. If we project the position of the heart on the coordinate system, the left ventricle will be in the area +30 + 70 degrees. This will be the normal position of the axis. However, depending on the individual anatomical characteristics and physique, the position of the EOS in healthy people ranges from 0 to +90 degrees:

• So, the vertical position will be considered EOS in the range from + 70 to +90 degrees. This position of the heart axis is found in tall, thin people - asthenics.
• The horizontal position of the EOS is more common in short, stocky people with a wide chest - hypersthenics, and its value ranges from 0 to + 30 degrees.

The structural features for each person are very individual; there are practically no pure asthenics or hypersthenics; more often they are intermediate body types, therefore the electrical axis can have an intermediate value (semi-horizontal and semi-vertical).

All five position options (normal, horizontal, semi-horizontal, vertical and semi-vertical) occur in healthy people and are not pathological.

So, in the conclusion of an ECG in an absolutely healthy person it can be said: “EOS is vertical, sinus rhythm, heart rate - 78 per minute,” which is a variant of the norm.

Rotations of the heart around the longitudinal axis help determine the position of the organ in space and, in some cases, are an additional parameter in diagnosing diseases.

The definition of “rotation of the electrical axis of the heart around an axis” may well be found in descriptions of electrocardiograms and is not something dangerous.

When can the position of the EOS indicate heart disease?

The position of the EOS itself is not a diagnosis. However, there are a number of diseases in which there is a displacement of the heart axis. Significant changes in the position of the EOS result from:

1. Cardiac ischemia.
2. Cardiomyopathies of various origins (especially dilated cardiomyopathy).
3. Chronic heart failure.
4. Congenital anomalies of the heart structure.

EOS deviations to the left

Thus, deviation of the electrical axis of the heart to the left may indicate left ventricular hypertrophy (LVH), i.e. an increase in size, which is also not an independent disease, but may indicate an overload of the left ventricle. This condition often occurs with long-term arterial hypertension and is associated with significant vascular resistance to blood flow, as a result of which the left ventricle must contract with greater force, the mass of the ventricular muscles increases, which leads to its hypertrophy. Ischemic disease, chronic heart failure, and cardiomyopathies also cause left ventricular hypertrophy.

hypertrophic changes in the myocardium of the left ventricle are the most common cause of deviation of the EOS to the left

In addition, LVH develops when the valve apparatus of the left ventricle is damaged. This condition is caused by stenosis of the aortic mouth, in which the ejection of blood from the left ventricle is difficult, and aortic valve insufficiency, when part of the blood returns to the left ventricle, overloading it with volume.

These defects can be either congenital or acquired. The most common acquired heart defects are a consequence of rheumatic fever. Left ventricular hypertrophy is found in professional athletes. In this case, a consultation with a highly qualified sports doctor is necessary to decide on the possibility of continuing to play sports.

Also, the EOS can be deviated to the left in cases of intraventricular conduction disorders and various heart blocks. Deviation el. the axis of the heart to the left, together with a number of other ECG signs, is one of the indicators of blockade of the anterior branch of the left bundle branch.

EOS deviations to the right

A shift in the electrical axis of the heart to the right may indicate right ventricular hypertrophy (RVH). Blood from the right ventricle enters the lungs, where it is enriched with oxygen. Chronic respiratory diseases accompanied by pulmonary hypertension, such as bronchial asthma, chronic obstructive pulmonary disease over a long period of time cause hypertrophy. Pulmonary stenosis and tricuspid valve insufficiency lead to right ventricular hypertrophy. As in the case of the left ventricle, RVH is caused by coronary heart disease, chronic heart failure and cardiomyopathies. Deviation of the EOS to the right occurs with complete blockade of the posterior branch of the left bundle branch.

What to do if EOS displacement is found on the cardiogram?

None of the above diagnoses can be made on the basis of EOS displacement alone. The position of the axis serves only as an additional indicator in diagnosing a particular disease. If the deviation of the heart axis is outside the normal range (from 0 to +90 degrees), consultation with a cardiologist and a series of studies are necessary.

And yet, the main reason for the displacement of the EOS is myocardial hypertrophy. The diagnosis of hypertrophy of a particular part of the heart can be made based on ultrasound results. Any disease that leads to a displacement of the heart axis is accompanied by a number of clinical signs and requires additional examination. The situation should be alarming when, with a pre-existing position of the EOS, its sharp deviation on the ECG occurs. In this case, the deviation most likely indicates the occurrence of a blockade.

In itself, the displacement of the electrical axis of the heart does not require treatment; it refers to electrocardiological signs and requires, first of all, to determine the cause of its occurrence. Only a cardiologist can determine the need for treatment.

When the EOS is in a vertical position, the S wave is most pronounced in leads I and aVL. ECG in children aged 7–15 years. Characterized by respiratory arrhythmia, heart rate 65-90 per minute. The position of the EOS is normal or vertical.

Regular sinus rhythm - this phrase means an absolutely normal heart rhythm, which is generated in the sinus node (the main source of cardiac electrical potentials).

Left ventricular hypertrophy (LVH) is a thickening of the wall and/or enlargement of the left ventricle of the heart. All five position options (normal, horizontal, semi-horizontal, vertical and semi-vertical) occur in healthy people and are not pathological.

What does the vertical position of the heart axis on an ECG mean?

The definition of “rotation of the electrical axis of the heart around an axis” may well be found in descriptions of electrocardiograms and is not something dangerous.

The situation should be alarming when, with a pre-existing position of the EOS, its sharp deviation on the ECG occurs. In this case, the deviation most likely indicates the occurrence of a blockade. 6.1. P wave. Analysis of the P wave involves determining its amplitude, width (duration), shape, direction and degree of severity in various leads.

The always negative wave vector P is projected onto the positive parts of most leads (but not all!).

6.4.2. The degree of severity of the Q wave in various leads.

Methods for determining the position of the EOS.

To put it simply, an ECG is a dynamic recording of the electrical charge that makes our heart work (that is, contract). The designations of these graphs (they are also called leads) - I, II, III, aVR, aVL, aVF, V1-V6 - can be seen on the electrocardiogram.

An ECG is a completely painless and safe test; it is performed on adults, children and even pregnant women.

Heart rate is not a disease or a diagnosis, but just an abbreviation for “heart rate,” which refers to the number of contractions of the heart muscle per minute. When the heart rate increases above 91 beats/min, they speak of tachycardia; if the heart rate is 59 beats/min or less, this is a sign of bradycardia.

Electrical axis of the heart (EOS): essence, norm of position and violations

Thin people usually have a vertical position of the EOS, while thick people and obese people have a horizontal position. Respiratory arrhythmia is associated with the act of breathing, is normal and does not require treatment.

Requires mandatory treatment. Atrial flutter - this type of arrhythmia is very similar to atrial fibrillation. Sometimes polytopic extrasystoles occur - that is, the impulses that cause them come from various parts of the heart.

Extrasystoles can be called the most common ECG finding; moreover, not all extrasystoles are a sign of the disease. In this case, treatment is necessary. Atrioventricular block, A-V (A-V) block - a violation of the conduction of impulses from the atria to the ventricles of the heart.

Block of the branches (left, right, left and right) of the His bundle (RBBB, LBBB), complete, incomplete, is a violation of the conduction of an impulse through the conduction system in the thickness of the ventricular myocardium.

The most common causes of hypertrophy are arterial hypertension, heart defects and hypertrophic cardiomyopathy. In some cases, next to the conclusion about the presence of hypertrophy, the doctor indicates “with overload” or “with signs of overload.”

Variants of the position of the electrical axis of the heart in healthy people

Cicatricial changes, scars are signs of a myocardial infarction once suffered. In such a situation, the doctor prescribes treatment aimed at preventing a recurrent heart attack and eliminating the cause of circulatory problems in the heart muscle (atherosclerosis).

Timely detection and treatment of this pathology is necessary. Normal ECG in children aged 1 – 12 months. Typically, heart rate fluctuations depend on the child’s behavior (increased frequency when crying, restlessness). At the same time, over the past 20 years there has been a clear trend towards an increase in the prevalence of this pathology.

When can the position of the EOS indicate heart disease?

The direction of the electrical axis of the heart shows the total magnitude of bioelectric changes occurring in the heart muscle with each contraction. The heart is a three-dimensional organ, and in order to calculate the direction of the EOS, cardiologists represent the chest as a coordinate system.

If you project the electrodes onto a conventional coordinate system, you can also calculate the angle of the electrical axis, which will be located where the electrical processes are strongest. The conduction system of the heart consists of sections of the heart muscle consisting of so-called atypical muscle fibers.

Normal ECG readings

Myocardial contraction begins with the appearance of an electrical impulse in the sinus node (which is why the correct rhythm of a healthy heart is called sinus). The myocardial conduction system is a powerful source of electrical impulses, which means that electrical changes that precede cardiac contraction occur in it first of all in the heart.

Rotations of the heart around the longitudinal axis help determine the position of the organ in space and, in some cases, are an additional parameter in diagnosing diseases. The position of the EOS itself is not a diagnosis.

These defects can be either congenital or acquired. The most common acquired heart defects are a consequence of rheumatic fever.

In this case, a consultation with a highly qualified sports doctor is necessary to decide on the possibility of continuing to play sports.

A shift in the electrical axis of the heart to the right may indicate right ventricular hypertrophy (RVH). Blood from the right ventricle enters the lungs, where it is enriched with oxygen.

As in the case of the left ventricle, RVH is caused by coronary heart disease, chronic heart failure and cardiomyopathies.

/ 22.02.2018

Sinus rhythm horizontal position eos. Normal location of the EOS and reasons for its displacement

Additional Research

The detection of a deviation of the EOS to the left side on the cardiogram is not in itself the basis for the doctor’s final conclusion. In order to determine what specific changes occur in the heart muscle, additional instrumental studies are required.

• Bicycle ergometry(electrocardiogram while walking on a treadmill or on an exercise bike). Test to detect ischemia of the heart muscle.
• Ultrasound. Using ultrasound, the degree of ventricular hypertrophy and disturbances in their contractile function are assessed.
• . The cardiogram is taken within 24 hours. Prescribed in cases of rhythm disturbance, which is accompanied by deviation of the EOS.
• X-ray examination chest. With significant hypertrophy of myocardial tissue, an increase in the cardiac shadow in the image is observed.
• Coronary artery angiography (CAG). Allows you to determine the degree of damage to the coronary arteries with diagnosed ischemic disease.
• Echocardioscopy. Allows targeted determination of the condition of the patient’s ventricles and atria.

Treatment

Deviation of the electrical axis of the heart to the left from the normal position is not in itself a disease. This is a sign determined using instrumental research, which allows us to identify disturbances in the functioning of the heart muscle.

The doctor makes a final diagnosis only after additional research. Treatment tactics are aimed at eliminating the underlying disease.

Ischemia, heart failure and some cardiopathy are treated with medications. Additional maintaining a diet and healthy lifestyle leads to normalization of the patient's condition.

In severe cases, surgery is required, for example, with congenital or acquired heart defects. In case of severe disruption of the conduction system, it may be necessary to transplant a pacemaker, which will send signals directly to the myocardium and cause its contraction.

Most often, deviation is not a threatening symptom. But if the axis changes its position suddenly, reaches values ​​of more than 90 0, this may indicate a blockade of the Hiss bundle branches and threatens cardiac arrest. Such a patient requires urgent hospitalization in the intensive care unit. A sharp and pronounced deviation of the electrical axis of the heart to the left looks like this:

Detection of a displacement of the electrical axis of the heart is not a cause for concern. But If this symptom is detected, you should immediately consult a doctor for further examination. and identifying the cause of this condition. Annual planned electrocardiography allows for timely detection of cardiac dysfunction and immediate initiation of therapy.

In the direction of the axis, the doctor determines the bioelectrical changes that occur in the myocardium during contraction.

To determine the direction of the EOS, there is a coordinate system that is located throughout the chest.

With electrocardiography, the doctor can install the electrodes according to the coordinate system, and it will be clear where the axis angle is located, that is, the places where the electrical impulses are strongest.

This means that stronger electrical processes occur in the left ventricle, and accordingly the electrical axis is directed there.

If we denote this in degrees, then the LV is in the region of 30-700 with a value of +. This is considered the standard, but it should be said that not everyone has this axis arrangement.

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There may be a deviation greater than 0-900 with a value of +, since it is necessary to take into account the individual characteristics of each person’s body.

The doctor may make the following conclusion:

• no deviations;
• semi-vertical position;
• semi-horizontal position.

All these conclusions are the norm.

Projection of the average result vector QRS to the frontal plane is called average electrical axis of the heart (AQRS). Rotations of the heart around the conventional anteroposterior axis are accompanied by a deviation of the electrical axis of the heart in the frontal plane and a significant change in the configuration of the complex QRS in standard and reinforced unipolar limb leads.

As shown in Fig. 4.10, the position of the electrical axis of the heart in the six-axis Bailey system is quantitatively expressed by the angle a, which is formed by the electrical axis of the heart and the positive half of the axis of the standard lead. The positive pole of the axis of this lead corresponds to the origin - 0 negative - ±380 The perpendicular drawn from the electrical center of the heart to the horizontal zero line coincides with the axis of lead aVF, the positive pole of which corresponds to +90°, and the negative pole corresponds to minus 90 e. The positive pole of axis II of the standard lead is located at an angle break +60 V, III standard lead - at an angle of +120%, lead aVL - at an angle -30°, and lead aVR - at an angle -150°, etc.

In a healthy person, the electrical axis of the heart is usually located in the sector from 0° to +90°, only occasionally going beyond these limits. Normally, the electrical axis of the heart approximately corresponds to the orientation of its anatomical axis. For example, the horizontal position of the electrical axis of the heart (angle a from 0° to 29°) is often found in healthy people with a hypersthenic body type, and the vertical position of the electrical axis is often found in people with a vertically located heart.

More significant turns of the electrical axis of the heart around the anteroposterior axis, both to the right (more than +9(G)) and to the left (less than 0°), are usually caused by pathological changes in the heart muscle - hypertrophy of the ventricular myocardium or disturbances of intraventricular conduction (see . below). However, it should be remembered that with moderate pathological changes in the heart, the position of the electrical axis of the heart may not differ in any way from that in healthy people, i.e. it can be horizontal, vertical or even normal.

Let's consider two methods for determining the position of the electrical axis of the heart.

Determination of angle a by graphical method. To accurately determine the position of the electrical axis of the heart using a graphical method, it is enough to calculate the algebraic sum of the amplitudes of the teeth of the complex QRS in any two leads from the limbs, the axes of which are located in the frontal plane. Typically, standard leads I and III are used for this purpose (Fig. 4.11). Positive or negative value of an algebraic sum

teeth QRS on an arbitrarily chosen scale is plotted on the positive or negative part of the axis of the corresponding lead in the six-axis Bailey coordinate system.

For example, on the ECG shown in Fig. 4.11, algebraic sum of the teeth of the complex QRS in standard lead I is + 12 mm (R== 12 mm, Q = 0 mm, S= Oh mm). This value is plotted on the positive part of the lead axis I. The sum of teeth in standard lead III is -12 mm (R= + 3 mm, S=- 15 mm); it is placed on the negative part of this lead.

These quantities (corresponding to the algebraic sum of ampli tud teeth) actually represent projections of the desired electrical axis of the heart on the axis I and III of standard leads. From the ends of these projections, perpendiculars to the axes of the leads are restored. The intersection point of the perpendiculars is connected to the center of the system. This line is the electrical axis of the heart (AQRS). In this case, angle a is -30 e (sharp deviation to the left of the electrical axis of the heart).

Angle a can also be determined after calculating the algebraic sums of the amplitudes of the teeth of the complex QRSb two limb leads according to various tables and diagrams given in manuals on electrocardiography.

Visual determination of angle a. The graphical method described above for determining the position of the electrical axis of the heart, although it is the most accurate, in practice is rarely used in clinical electrocardiography. A simpler and more accessible method is the visual method for determining the position of the electrical axis of the heart, which allows you to quickly assess the angle a with an accuracy of ±10°. The method is based on two well-known principles.

1. The maximum positive or negative value of the algebraic sum of the teeth of the complex QRS observed in that electrocardiographic lead, the axis of which approximately coincides with the location of the electrical field of the heart and is parallel to it.

2. Complex type R.S. where the algebraic sum of the teeth is zero (R = S or I = Q+ S), is recorded in the lead whose axis is perpendicular to the electrical axis of the heart.

As an example, we will try to determine the position of the electrical axis of the heart using the visual method using the ECG shown in Fig. 4.12. Maximum algebraic sum of teeth of the complex QRS and the highest tooth R are observed in standard lead II, and the type complex RS(R*S)- in lead aVL. This indicates that the electrical axis of the heart is located at an angle a of about 60° (coinciding with axis II of the standard lead and perpendicular to the axis of lead aVL). This is also confirmed by the approximate equality of the amplitude of the teeth R in leads I and III, the axes of which in this case are located at some identical (!) angle to the electrical axis of the heart (R ] l > R t ~ R ul). Thus, the ECG shows a normal position of the electrical axis of the heart (angle a = 60°).

Let's consider another option for the normal position of the electrical axis of the heart (angle A= 45°), shown on rice. 4.13.a. In this case, the electrical axis of the heart is located between the axes of leads II and aVR. Maximum tooth R will be registered in the same way as in the previous example, in lead II, and

/?,>/?,> Rul*. In this case, the electrical axis is perpendicular to a hypothetical line, which seems to pass between the axes of standard lead III and lead aVL. Under certain assumptions, it can be considered that the axes of leads III and aVL are almost perpendicular to the electrical axis of the heart. Therefore, it is in these leads that the algebraic sum of the teeth approaches zero, and the complexes themselves QRS take the form R.S. where are the teeth/? w and i? aVL have a minimum amplitude, only slightly exceeding the amplitude of the corresponding teeth Sj n and S sVL .

At vertical position of the electrical axis of the heart (Fig. 4.13, b), when angle a is about +90°, the maximum algebraic sum of the teeth of the complex QRSn maximum positive wave R will be detected in lead aVF, the axis of which coincides with the direction of the electrical axis of the heart. Complex type R.S. Where R-S, is recorded in standard lead I, the axis of which is perpendicular to the direction of the electrical axis of the heart. The negative wave predominates in lead aVL S, and in lead III there is a positive wave R.

With an even more pronounced rotation of the electrical axis of the heart to the right, for example, if angle a is +120°, as shown in Fig. 4.13, in, maximum tooth R is recorded in standard lead III. A com is recorded in lead aVR.

plex QR, Where R= Q. Positive waves predominate in lead II and aVF R, and in leads I and aVL there are deep negative waves S.

On the contrary, when horizontal position of the electrical axis of the heart, (angle a from +30° to 0°) maximum tooth R will be fixed in standard lead I (Fig. 4.14, a), and the type complex RS- in lead aVF. A deepened wave is recorded in lead III S y and in lead aVL there is a high tooth R.R [ > R ll > R lli< S uy

With a significant deviation of the electrical axis of the heart to the left (angle a - -30), as shown in Fig. 4.14, b, maximum positive tooth R shifts to lead aVL, and the complex QRSuxcm RS - to lead II. High prong R is also recorded in lead I, and in leads III and aVF deep negative waves predominate S. R x > R li > R m .

So, for practical determination of the position of the electrical axis of the heart, we will further use the visual method of determining angle a. We suggest you independently complete several tasks to determine the position of the electrical axis of the heart visually (see Fig. 4.16-4.19). In this case, it is advisable to use a pre-prepared diagram of a six-axis coordinate system (see Fig. 2.6), as well as the following algorithm.

Algorithm for determining the position of the electrical axis of the heart in the frontal plane

1. Find one or two leads in which QRS approaches zero ( R S or R* Q+ L). The axis of this lead is almost perpendicular to the desired direction of the electrical axis of the heart.

2 Find one or two leads in which the algebraic sum of the teeth of the complex QRS has the maximum positive value. The axis of this lead approximately coincides with the direction of the electrical axis of the heart.

3. Adjust the two results. Determine angle a.

An example of using this algorithm is shown in Fig. 4.15. When analyzing the ECG in 6 limb leads presented in Fig. 4.15, the normal position is approximately determined

study of the electrical axis of the heart R H = A, > L,. The algebraic sum of the teeth of the complex (DO" is equal to zero in lead III (R= 5). Consequently, the electrical axis is presumably located at an angle a+30° to the horizontal, coinciding with the aVR axis. Algebraic sum of teeth QRS has a maximum value in leads I and II, with A, - Rxv This confirms the assumption made about the value of angle a (+30°), since identical projections on the lead axis (equal teeth R, and /?,) are possible only with this arrangement of the electrical axis of the heart.

Conclusion. Normal position of the electrical axis of the heart. Angle a - +30°.

Now, using the algorithm, independently determine the position of the electrical axis of the heart on the ECG shown in Fig. 4.16-4.19.

Check the correctness of your decision.

Standards of correct answers

Rice. 4.16, a. Analysis of the relationships between the teeth of the complex QRSw The presented ECG suggests that there is a normal position of the electrical axis of the heart (R il > R l > R m). Indeed, the sum of the teeth of the complex QRS equals zero in lead aVL (R ~ S). Consequently, the electrical axis of the heart is presumably located at an angle of +60° to the horizontal and coincides with axis II of the standard lead. Algebraic sum of teeth of the complex QRS has a maximum value in standard lead II. This confirms the assumption made about the value of the angle a+60". Conclusion. The normal position of the electrical axis of the heart is Angle a+60°.

Rice. 4.16, b. The ECG shows a deviation of the electrical axis of the heart to the left: high waves R registered in leads I and aVL, deep waves S- in leads III and aVF, with i ^> R II > i ^ II.

Algebraic sum of the amplitudes of the teeth of the complex QRS is equal to zero in standard lead II. Therefore, the electrical axis of the heart is perpendicular to the axis of lead II, i.e., located at an angle a = -30°. Maximum positive value of the sum of teeth QRS is detected in lead aVL, which confirms the assumption made. Conclusion. Deviation of the electrical axis of the heart to the left. Angle a- -30 e.

Rice. 4.17, a. The ECG shows a deviation of the electrical axis of the heart to the right: high waves R m mVF and deep teeth 5, aVU and R in > R u > R l . Algebraic sum of the amplitudes of the teeth of the complex QRS equals zero in lead aVR. The electrical axis of the heart is located at an angle a+ 120 e and approximately coincides with axis III of the standard lead. This is confirmed by the fact that the maximum amplitude of the tooth R determined in lead Sh.

Conclusion, Deviation of the electrical axis of the heart to the right. Angle a= +120*.

Rice. 4.17, b. The ECG recorded high waves L w aVF and relatively deep waves L ", aVL, with ^ P >^ G > L^. The sum of the amplitudes of the waves QRS equal to zero in lead I. The electrical axis of the heart is located at an angle a = +90°, coinciding with the axis of lead aVR In lead aVF there is a maximum positive sum of wave amplitudes QRS which confirms this assumption. Conclusion. Vertical position of the electrical axis of the heart. Angle a - +90°.

Rice. 4.18, a. The ECG recorded high waves /?, hVL and deep waves L* H1 oVF, with /?,>/?,>/?,. In lead aVR, the algebraic sum of the teeth of the complex QRS equal to a bullet. The electrical axis of the heart most likely coincides with the negative half of the axis of standard lead III (the largest amplitude S U 1). Unlike an ECG, it depicts

Noah in Fig. 4.17, a, the electrical axis of the heart is not deviated to the right but

to the left, so angle a is approximately -60°. Conclusion. A sharp deviation of the electrical axis of the heart to the left. Angle a -60 e.

Rice. 4.18, 6. There is approximately a rotation of the heart axis to the left: high teeth I am aVL, deep serrations Sul aVF , and R J > R ll > R tll . There is no lead on the ECG in which the algebraic sum of the waves QRS is clearly equal to zero. However, the minimum algebraic sum of teeth QRS approaching zero, found in leads II and aVF , whose axes are located nearby, at an angle of 30* to each other. Moreover, the sum of the amplitudes of the teeth of the complex QRS in standard lead II it has a small positive value, and in lead aVF it has a small negative value. Consequently, a hypothetical line perpendicular to the electrical axis of the heart passes between the axes of leads II and aVF, and the electrical axis of the heart itself is accordingly located approximately at an angle a equal to - 15°, i.e., between the axes of leads I and aVL. Indeed, the maximum algebraic sum of teeth QRS found in leads I and aVL, which confirms the assumption made. Conclusion. Deviation of the electrical axis of the heart to the left. Angle a* - 15 e.

Rice. 4.19 A. There is approximately a rotation of the electrical axis of the heart to the left: high waves D, aVL, relatively deep waves S uv what does it have to do with R t > R n > R m . As in the previous example, it is impossible to identify a lead on the ECG in which the algebraic sum of the teeth QRS equal to zero. A hypothetical line perpendicular to the electrical axis of the heart probably runs between adjacent lead axes III and aVF , since the algebraic sum of the teeth QRS in these leads approaches zero, and the sum of the teeth in III lead indicates the predominance of the negative wave S, and in lead aVF - to the predominance of the wave R. Consequently, the electrical axis of the heart is most likely located at an angle a* +15°. Maximum positive algebraic sum of teeth QRS is detected in lead I, which confirms the assumption made. Conclusion. Horizontal position of the electrical axis of the heart. Angle a +15°.

Rice. 4.19, b. Approximately has a rotation of the electrical axis of the heart to the left: high teeth Rlt aVL, deep teeth 5 Ш, aVF, and R l > R ^> R Bl . In lead aVF, the algebraic sum of waves QRS equal to zero, i.e. the electrical axis is perpendicular to the axis of lead aVF. Therefore, we can assume that angle a is 0°. The maximum positive sum of waves is found in standard lead I, which confirms the assumption made. Conclusion. Horizontal position of the electrical axis of the heart. Angle ai 0°.