Determination of the position of the electrical axis of the heart. Calculation of the electrical axis Heart axis according to Bailey

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What exactly does the ECG machine record? The electrocardiograph records total electrical activity of the heart

, or more precisely, the difference in electrical potential (voltage) between 2 points. Where in the heart a potential difference arises ? It's simple. At rest, myocardial cells are charged negatively from the inside and positively charged from the outside, while a straight line (= isoline) is recorded on the ECG tape. When an electrical impulse (excitation) arises and propagates in the conduction system of the heart, cell membranes move from a resting state to an excited state, changing polarity to the opposite (the process is called depolarization ). In this case, 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 and into the cell. After depolarization, after a certain time, the cells enter a resting state, restoring their original polarity (minus inside, plus outside), this process is called.

repolarization The electrical impulse sequentially spreads throughout the parts of the heart, causing depolarization of myocardial cells. During depolarization, part of the cell becomes 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). EMF of the heart is a tricky but important thing, so let’s return to it a little lower. Schematic location of the cardiac EMF vector
(in the center)

at one point in time.

ECG leads As stated above, the electrocardiograph records voltage (electrical potential difference) between 2 points , that is, in some lead

. In other words, the ECG device records on paper (screen) the magnitude of the projection of the electromotive force of the heart (cardiac emf) onto any lead. A standard ECG is recorded in:

• 3 12 leads standard
• 3 (I, II, III), reinforced
• from the limbs (aVR, aVL, aVF), and 6 infant

1) (V1, V2, V3, V4, V5, V6).(suggested by Einthoven in 1913).
I - between the left hand and the right hand,
II - between the left leg and right arm,
III - between the left leg and left arm.

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

Multichannel portable electrocardiograph.
All electrodes and suction cups differ in color and location.

2) Reinforced 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, recording of these leads is done by simply switching the handle on a single-channel cardiograph (i.e., there is no need to rearrange the electrodes).

aVR- enhanced abduction from the right hand (short for augmented voltage right - enhanced potential on the right).
aVL- increased abduction from the left hand (left - left)
aVF- increased 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 chest electrode placement points are located sequentially along the anterolateral surface of the chest from the midline of the body to the left arm.

I don’t indicate too much detail, because it is not necessary for non-specialists. The principle itself is important (see figure).
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 - along the left mid-axillary line at the level of the apex of the heart.

Location of 6 chest electrodes when recording ECG.

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

• according to Neb(between points on the surface of the chest),
• V7 - V9(continuation of chest leads to the left half of the back),
• V3R - V6R(mirror reflection of chest leads V3 - V6 on the right half of the chest).

Lead meaning

For reference: quantities can be scalar and vector. Scalar quantities haveonly the size (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 was it invented? so many leads? EMF of the heart is vector EMF of the heart in a three-dimensional world(length, width, height) taking into account time. On a flat ECG film we can see only 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 cardiac EMF. First 6 leads(3 standard and 3 reinforced from the limbs) reflect the EMF of the heart in the so-called frontal plane(see figure) 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.

The relative position of standard and enhanced leads in the frontal plane.
But there is an error in the picture:
aVL and lead III are NOT on the same 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 makes it possible to clarify the localization of the pathological focus (for example, myocardial infarction): interventricular septum, apex of the heart, lateral parts of the left ventricle, etc.

When analyzing 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 you study the second part of the series, you will return to it, and it will become much clearer.

Electrical axis of the heart (EOS)

If you draw circle and through its center draw lines corresponding to the directions of three standard and three reinforced limb leads, 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, from which the location of the pathological focus and the electrical axis of the heart can be assessed.

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

Electrical axis of the heart- this is a 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. The electrical axis of the heart is expressed quantitatively angle α between the axis itself and the positive (right) half of the axis of standard lead I, located horizontally.

It is clearly seen that the same EMF of the heart in projections
gives different waveforms for different leads.

Determination rules the positions of the EOS in the frontal plane are as follows: electrical axis of the heart matches with that of the first 6 leads in which the highest positive teeth, And perpendicular the lead in which the size of the positive teeth 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.

Variants of the position of the electrical axis of the heart:

• normal: 30° > α< 69°,
• vertical: 70° > α< 90°,
• horizontal: 0° > α < 29°,
• sharp axis deviation to the right: 91° > α< ±180°,
• sharp axis deviation to the left: 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 matches his anatomical axis(for thin people it is directed more vertically from the average values, and for obese people it is more horizontal). For example, when hypertrophy(proliferation) of the right ventricle, the axis of the heart deviates to the right. At conduction disorders the electrical axis of the heart may deviate sharply to the left or right, which in itself is a diagnostic sign. For example, with a complete block of the anterior branch of the left bundle branch, a sharp deviation of the electrical axis of the heart to the left (α ≤ −30°) is observed, and a sharp deviation of the posterior branch to the right (α ≥ +120°).

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

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

The electrocardiogram reflects electrical processes only in the myocardium: depolarization (excitation) and repolarization (restoration) 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, instead of “depolarization-repolarization” I will sometimes use “contraction-relaxation”, 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 earlier.

Elements of a normal ECG

Before moving on to decoding the ECG, you need to understand 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.

Any ECG consists of teeth, segments And intervals.

TEETH- these are convexities and concavities on the electrocardiogram.
The following waves are distinguished on the ECG:

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

SEGMENTS
A segment on an ECG is called straight line segment(isolines) between two adjacent teeth. The most important segments are P-Q and S-T. For example, the P-Q segment is formed due to a delay in the 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.

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

QRS complex waves

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 do it right highlight the teeth in it?

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

The R wave (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. Negative (downward) wave of the QRS complex, located before the R wave, is denoted as Q(q), and after - like 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, tooth R- the bulk of the ventricular myocardium, tooth S- basal (i.e. near the atria) sections of the interventricular septum. The R V1, V2 wave 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 the Q wave to widen and deepen, so close attention is always paid to this wave.

ECG analysis

General ECG decoding diagram

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

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

Determination of the electrical axis of the heart.

Analysis of the atrial P wave and P-Q interval.

Analysis of the ventricular QRST complex:

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

Electrocardiographic report.

Normal electrocardiogram.

1) Checking the correct ECG registration

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

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

2) Heart rate and conduction analysis:

1. 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 regular.

1. heart rate counting(heart rate)

The ECG film has large squares printed on it, each of which contains 25 small squares (5 vertical x 5 horizontal). To quickly calculate heart rate with the correct rhythm, count the number of large squares between two adjacent teeth R - R.

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

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

If the rhythm is incorrect, it is usually considered maximum and minimum heart rate according to the duration of the smallest and largest R-R interval, respectively.

1. determination of the excitation source

In other words, they are looking for where pacemaker, which causes contractions of the atria and ventricles. Sometimes this is one of the most difficult stages, because various disorders of excitability and conduction can be very confusingly combined, which can lead to incorrect diagnosis and incorrect treatment. To correctly determine the source of excitation on an 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. Signs on the ECG:

• in standard lead II, the P waves are always positive and are located before each QRS complex,
• P waves in the same lead have the same shape at all times.

P wave in sinus rhythm.

ATRIAL rhythm. If the source of excitation is located in the lower parts of the atria, then the excitation wave propagates to the atria from bottom to top (retrograde), therefore:

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

P wave during atrial rhythm.

Rhythms from the AV connection. 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 can be negative, located after the QRS complex.

Rhythm from the AV junction, superimposition of the P wave on the QRS complex.

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

Heart rate with a rhythm from the AV junction is less than sinus rhythm and is approximately 40-60 beats per minute.

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

• QRS complexes are widened and deformed (they 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 be excited from the sinus node, as normal.
• Heart rate is less than 40 beats per minute.

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

1. conductivity assessment.
   To properly account for conductivity, the recording speed is taken into account.

To assess conductivity, measure:

• duration P wave(reflects the speed of impulse transmission through the atria), normally up to 0.1 s.
• duration interval P - Q(reflects the speed of impulse conduction from the atria to the ventricular myocardium); interval P - Q = (wave P) + (segment P - Q). Fine 0.12-0.2 s.
• duration QRS complex(reflects the spread of excitation through the ventricles). Fine 0.06-0.1 s.
• internal deviation interval in leads V1 and V6. This is the time between the beginning of the QRS complex and the R wave. Normal in V1 up to 0.03 s and in V6 up to 0.05 s. Used mainly 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).

Measuring the internal deviation interval.

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

4) Atrial P wave analysis.
Normally, in leads I, II, aVF, V2 - V6, the 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 0.1 s, 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 “pulmonary heart”.
• Split with 2 apexes, widened P wave in leads I, aVL, V5, V6 is characteristic of left atrial hypertrophy, for example, with mitral valve defects.

Formation of the P wave (P-pulmonale) with hypertrophy of the right atrium.

Formation of the P wave (P-mitrale) with hypertrophy of the left atrium.

P-Q interval: fine 0.12-0.20 s.
An increase in this interval occurs when the conduction of impulses through the atrioventricular node is impaired ( 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 conduction in the AV node. The atria and ventricles contract at their own rhythm, independently of each other. Those. idioventricular rhythm occurs.

5) Ventricular QRST analysis:

1. QRS complex analysis.

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

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

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

The S wave can have 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) “ transition zone” (equality of R and S waves).

1. RS - T segment analysis

The S-T segment (RS-T) is a segment from the end of the QRS complex to the beginning of the T wave. The S-T segment is especially carefully analyzed in case of coronary artery disease, since it reflects the lack of oxygen (ischemia) in the myocardium.

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

The point at which the QRS complex transitions 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.

1. 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.

1. Q-T interval analysis.

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

6) Electrocardiographic report.
Should include:

1. Source of rhythm (sinus or not).
2. Regularity of rhythm (correct or not). Usually sinus rhythm is normal, although respiratory arrhythmia is possible.
3. Position of the electrical axis of the heart.
4. Presence of 4 syndromes:

• rhythm disturbance
• conduction disturbance
• hypertrophy and/or overload of the ventricles and atria
• myocardial damage (ischemia, dystrophy, necrosis, scars)

Examples of conclusions(not quite complete, but real):

Sinus rhythm with heart rate 65. Normal position of the electrical axis of the heart. No pathology was identified.

Sinus tachycardia with heart rate 100. Single supraventricular extrasystole.

Sinus rhythm with heart rate 70 beats/min. Incomplete blockade of the right bundle branch. Moderate metabolic changes in the myocardium.

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

Interference on the ECG

Due to frequent questions in the comments about the type of ECG, I’ll tell you about interference which may appear on the electrocardiogram:

Three types of ECG interference(explained below).

Interference on an ECG in the lexicon of health workers is called tip-off:
a) inrush currents: network pickup in the form of regular oscillations with a frequency of 50 Hz, corresponding to the frequency of alternating electric current in the outlet.
b) " swimming"(drift) of the isoline due to poor contact of the electrode with the skin;
c) interference caused by muscle tremors(irregular frequent vibrations are visible).

The resulting vector of all bioelectrical oscillations of the heart muscle is called the electrical axis. Most often it coincides with the anatomical one. This indicator is used when analyzing ECG data to assess the predominance of one part of the heart, which may be an indirect sign of myocardial hypertrophy.

Read in this article

Normal electrical axis of the heart

The direction of the heart axis is calculated in degrees. To do this, they use such a concept as the alpha angle. It is formed by a horizontal line that is drawn through the electrical center of the heart. To determine it, the axis of the first ECG lead is shifted to the Einthoven center. This is a triangle, its vertices are the hands spread out to the side and the left foot.

In a healthy person, the electrical axis fluctuates between 30 and 70 degrees. This is due to the fact that the left ventricle is more developed than the right, therefore, more impulses come from it. This position of the heart occurs with a normosthenic physique, and the ECG is called a normogram.

Position deviations

A change in the direction of the heart axis on an electrocardiogram is not always a sign of pathology. Therefore, for making a diagnosis, its deviations are of auxiliary importance and are used for the preliminary formulation of the conclusion.

Right

Pravogramma (alpha 90 - 180) on the ECG occurs with an increase in the mass of the myocardium of the right ventricle. The following diseases lead to this condition:

• chronic obstructive pulmonary diseases;
• bronchitis;
• bronchial asthma;
• narrowing of the pulmonary artery trunk, mitral orifice;
• circulatory failure with congestion in the lungs;
• cessation of the passage of impulses (blockade) of the left Hiss leg;
• thrombosis of pulmonary vessels;
• cirrhosis of the liver.

Cardiomyopathy is one of the causes of deviation of the heart axis to the right

Left

A left-side shift of the electrical axis (alpha from 0 to minus 90) occurs quite often. Leads to him. This may be due to the following conditions:

How to determine by ECG

In order to identify the position of the axis, it is necessary to examine two leads aVL and aVF. You need to measure the tooth in them R. Normally, its amplitude is equal. If it is high in aVL and absent in aVF, then the position is horizontal; in vertical it will be the other way around.

There will be an axis deviation to the left if R in the first standard lead is greater than S in the third. Pravogram - S1 exceeds R3, and if R2, R1, R3 are arranged in descending order, then this is a sign of a normogram. For a more detailed study, special tables are used.

Additional Research

If the ECG reveals an axis shift to the right or left, then the following additional examination methods are used to clarify the diagnosis:

If there is only a pathological alpha angle, and no other manifestations are detected on the ECG, the patient does not experience difficulty breathing, the pulse and blood pressure are normal, then this condition does not require any further action. This may be due to an anatomical feature.

A more unfavorable sign is pravogramma with lung diseases, as well as levogramma combined with hypertension.

In these cases, the displacement of the heart axis can be used to judge the degree of progression of the underlying pathology. If the diagnosis is unknown, and there is a significant axis deviation with cardiac symptoms, then the patient should be fully examined to identify the cause of this phenomenon.

The displacement of the electrical axis can be to the left or to the right, depending on which of the heart ventricles the activity predominates.

Such changes in the ECG are an indirect sign of myocardial hypertrophy and are considered in conjunction with other indicators. If there are complaints about heart function, additional examination is required. In young children, pravogram is a physiological condition that does not require intervention.

The rules for how an ECG is done are quite simple. The decoding of indicators in adults differs from that which is normal in children and during pregnancy. How often can an ECG be done? How to prepare, including for women. Can this be done for colds and coughs?

The T wave on the ECG is determined to identify pathologies of cardiac activity. It can be negative, high, biphasic, smoothed, flat, reduced, and depression of the coronary T wave can also be detected. Changes can also be in the ST, ST-T, QT segments. What is an alternation, discordant, absent, double-humped tooth.

The heart needs to be examined under different circumstances, including at 1 year of age. The ECG norm in children differs from that in adults. How is an ECG done for children, deciphering the indicators? How to prepare? How often can you do it and what should you do if your child is afraid?

As a result of increased load on the heart, right ventricular hypertrophy can develop in both adults and children. Signs are visible on the ECG. There may also be combined hypertrophy - of the right and left ventricles, right atrium and ventricle. In each case, it is decided individually how to treat the pathology.

The electrical axis of the heart (EOS) is the first word that every person sees when they have a transcript of the cardiogram in their hands. When a specialist next to them adds that the EOS is in a normal position, the person being examined has nothing to worry about his health. But what if the axis takes a different position or has deviations?

What is EOS?

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

1. Atria.
2. Ventricles.
3. Bundle of His.

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

The placement of the axis is calculated by dividing the circle drawn around the triangle by degrees. The direction of the vector gives the specialist an approximate idea of ​​the location of the heart in the chest.

The concept of EOS norm

The position of the EOS depends on:

• The speed and correctness of impulse movement 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:

• Vertical.
• Horizontal.
• Intermediate
• Normal.

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

In an intermediate position, the vector ranges from +15 to +60 degrees.

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

Correct placement of EOS in children

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

Children's EOS standards:

• Up to a year – the passage of the axis is between +90 – +170 degrees.
• From one to three years - vertical EOS.
• 6-16 – stabilization of indicators to adult standards.

Measuring indicators using electrocardiography

ECG signs in the analysis of EOS are determined by the rightogram and the leftogram.

A rightogram is finding 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.

Phramogram

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

Levogram

Why does deviation occur?

When the axis is deviated to the left, this means that the patient has left ventricular hypertrophy.

The causes of the disease include:

1. Hypertension. Especially in cases of frequent increases in blood pressure.
2. Ischemic diseases.
3. Chronic heart failure.
4. Cardiomyopathy. This disease is the growth of the heart muscle in a mass and expansion of its cavities.
5. Pathology of the aortic valve. They can be congenital or acquired. They provoke blood flow disturbances and LV reloading.

Important! Very often, hypertrophy worsens in people who spend a lot of time on varied sports activities.

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

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

ECG for “cor pulmonale”

Vertical position of the EOS

A vertical position is characterized by a range of +70 – +90º. Characteristic of tall, thin people with a narrow sternum. According to anatomical indicators, with such a physique, the heart seems to be “hanging.”

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

Horizontal position of the EOS

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

On the cardiogram, the highest positive waves appear in aVL, and negative ones in aVF.

Horizontal position of the EOS

EOS deviation to the left

The deviation of the electrical axis to the left is the location of the vector in the range of 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. In some people, such indicators are provoked by deep exhalation.

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

Reasons why the axis deviates to the left:

• LV hypertrophy.
• Disruption or blockage of the His bundle.
• Myocardial infarction.
• Myocardial dystrophy.
• Heart defects.
• Violation of CM contractions.
• Myocarditis.
• Cardiosclerosis.
• Calcium accumulations in the organ, 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.

Reasons for EOS deviation to the right

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

1. Damage to the pancreas by infarction.
2. The simultaneous occurrence of coronary artery disease and hypertension - they deplete the heart with a vengeance and provoke failure.
3. Pulmonary diseases of a chronic nature.
4. Incorrect passage of electrical impulses along the right branch of the His bundle.
5. Pulmonary emphysema.
6. Severe strain on the pancreas caused by obstruction of the pulmonary artery.
7. Dextrocardia.
8. Mitral heart disease, which provokes pulmonary hypertension and stimulates the work of the pancreas.
9. A thrombotic block 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.

Because of these pathologies, the specialist determines on electrocardiography that the EOS is deviated to the right.

EOS deviation to the right

What to do if the axis is deviated?

If you are diagnosed with a pathological deviation of the axis, the specialist must resort to new studies. Each ailment that provokes displacement of the EOS is accompanied by several symptoms that require careful analysis. Most often they resort to ultrasound diagnostics of the heart.

Finally

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. An opinion on it can only be made by a qualified specialist, since a deviation does not always mean the presence of heart problems.

More:

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Let us mentally place the resulting vector of ventricular excitation inside Einthoven’s triangle. The angle formed by the direction of the resulting vector and the I axis of the standard lead is the desired alpha angle.

The value of the alpha angle is found using special tables or diagrams, having previously determined on the electrocardiogram the algebraic sum of the teeth of the ventricular complex (Q + R + S) in standard leads I and III. Finding the algebraic sum of the teeth of the ventricular complex is quite simple: measure in millimeters the size of each tooth of one ventricular QRS complex, taking into account that the Q and S waves have a minus sign (-), since they are below the isoelectric line, and the K wave has a plus sign (+ ). If any wave on the electrocardiogram is missing, then its value is equal to zero (0).

Next, by comparing the found algebraic sum of the teeth for standard leads I and III, the value of the alpha angle is determined from the table. In our case, it is equal to minus 70°. Table for determining the position of the electrical axis of the heart (according to Diede)

Alpha Angle Determination Table

If the alpha angle is within 50-70°, we speak of a normal position of the electrical axis of the heart (the electrical axis of the heart is not deviated), or a normogram. When the electrical axis of the heart deviates to the right, the alpha angle will be determined within 70-90°. In everyday life, this position of the electrical axis of the heart is called a rightogram.

If the alpha angle is greater than 90° (for example, 97°), it is considered that this ECG shows a block of the posterior branch of the left bundle branch. Determining the alpha angle within 50-0° speaks of a deviation of the electrical axis of the heart to the left, or a levogram. A change in the alpha angle within 0 - minus 30° indicates a sharp deviation of the electrical axis of the heart to the left or, in other words, a sharp leftogram. And finally, if the value of alpha is less than minus 30° (for example, minus 45°), they speak of blockade of the anterior branch of the left bundle branch.

Limits of deviation of the electrical axis of the heart

Determination of the deviation of the electrical axis of the heart by the alpha angle using tables and diagrams is carried out mainly by doctors in functional diagnostics offices, where the corresponding tables and diagrams are always at hand. However, it is possible to determine the deviation of the electrical axis of the heart without the necessary tables. In this case, the deviation of the electrical axis is determined by analyzing the R and S waves in standard leads I and III. In this case, the concept of the algebraic sum of the teeth of the ventricular complex of the QRS complex is replaced visually with the concept of “defining tooth”, comparing the R and S waves in absolute value. They speak of an “R-type ventricular complex,” meaning that in this ventricular complex the K wave is higher. On the contrary, in the “S-type ventricular complex,” the defining wave of the QRS complex is the S wave.

Comparison of K waves and 3rd QRS complex

If on the electrocardiogram in the first standard lead the ventricular complex is represented by the R-type, and the QRS complex in the third standard lead has an S-type shape, then in this case the electrical axis of the heart is deviated to the left (levogram).

Schematically, this condition is written as RI-SIII.

Levogram 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.

Visual determination of the electrical axis of the heart

Pravogram 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.

Normal position of the electrical axis of the heart

(normogram) The figure shows that the amplitude of the R wave in standard lead II is the greatest. In turn, the K wave in standard lead I exceeds the RIII wave. Under this condition of the ratio of the R waves in various standard leads, we have a normal position of the electrical axis of the heart (the electrical axis of the heart is not deviated). A short notation for this condition is RII>RI>RIII.

For example, in Fig. 5-3 high teeth visible R in leads II, III, aVF, which is considered as a sign of the vertical position of the EOS (vertical average electrical axis QRS).

Rice. 5-3.

The QRS angle is +90°. R In addition, the height of the teeth R is the same in leads II and III. In Fig. 5-3 teeth height QRS in three leads (II, III and aVF) is the same; in this case, the EOS is directed to the middle lead aVF (+90°). Therefore, a simple assessment of the electrocardiogram can assume that directed between positive poles

leads II and III to the positive pole aVF (+90°).

Method No. 2 In Fig. 5-3 the direction of the EOS can be calculated in another way. Remember that if the wave is perpendicular to the axis of any lead, it is recorded two-phase complex R.S. or QR QRS(see section ""). And vice versa, if in any limb lead the complex QRS two-phase, average electrical axis of the complex complex should be directed at an angle of 90° to this lead. Look again at Fig. 5-3. Do you see any biphasic complexes? It is obvious that in lead I there is a two-phase complex

, therefore, the EOS should be perpendicular to lead I. QRS Since lead I in the six-axis diagram corresponds to 0°, the electrical axis lies at right angles to 0° (angle QRS can be -90° or +90°). If the axis angle were -90°, the depolarization would be directed from the positive pole of lead aVF and the complex would be in it negative QRS. In Fig. 5-3 there is a positive complex in lead aVF R(high prong

), so the axis must have an angle of +90°.

Rice. 5-4.

The QRS angle is -30°. QRS Method No. 3 Another example is in Fig. 5-4. At a quick glance, the average electrical axis of the complex complex. horizontal, the axis should be directed at right angles to lead II. It is located at an angle of +60° in a six-axis system, so the axis angle can be -30° or +150°. If it were +150°, in leads II, III, aVF complexes QRS would be positive. So the axis angle is -30°.

Method No. 4

The next example is in Fig. 5-5. Complex QRS positive in leads II, III and aVF, so the EOS is relatively vertical. Teeth R have equal heights in leads I and III - hence, the average electrical axis of the complex QRS should be located between these two leads at an angle of +60°.

Rice. 5-5.

QRS angle +60°.

Method No. 5 QRS According to Fig. 5-5 average electrical axis of the complex can be calculated differently complex taking into account the two-phase complex-type in lead aVL R.

. The axis should be perpendicular to lead aVL (-30°), i.e. at an angle of -120° or +60°. Obviously the axis angle is +60°. The EOS should be directed to lead II with a high tooth

Consider the example in Fig. 5-6.

Rice. 5-6. QRS QRS angle -90°. R EOS is directed from leads II, III, aVF to leads aVR and aVL, where the complexes positive. Because the teeth complex have equal heights in leads aVR and aVL, the axis should be located exactly between these leads at an angle of -90°. In addition, in lead I -

two-phase complex

. In this case, the axis should be located perpendicular to lead I (0°), i.e. The axis angle can be -90° or +90°. Since the axis is directed from the positive pole of lead aVF to its negative pole, the axis angle should be -90°.

Look at fig. 5-7.

Rice. 5-7. complex QRS angle -60°. Method number 6 Since in lead aVR there is a two-phase complex QRS-type, EOS should be located QRS perpendicular axis of this lead. The lead axis angle aVR is -150°, so the average electrical axis of the complex in this case it should be -60° or +120°. It is clear that the axis angle is -60°, since in lead aVL the complex is positive, and in lead III it is negative. In Fig. 5-7 average electrical axis of the complex R you can also S calculate from lead I

, where the amplitude of the tooth equal to the amplitude of the tooth QRS . However, such a definition may be approximate. An error of 10-15° has no significant clinical significance. Thus, it is possible to determine the electrical axis of the heart by the lead where the complex QRS close to biphasic, or in two leads, where the amplitudes of the waves R(or S) are approximately equal.

For example, if the amplitudes of the teeth R R.S. S in two leads are only approximately equal, the average electrical axis of the complex QRS does not lie exactly between these leads. The axis is deviated towards the lead with a larger amplitude. In the same way, if there is a two-phase complex in the lead ( complex R.S. or) with teeth R And S(or teeth Q And R) of different amplitudes, the axis is not exactly perpendicular to this lead. If the tooth R more than a tooth S(or prong Q), the axis points are less than 90° from the lead. If the tooth R less than a tooth S R.S. Q, the axis points are more than 90° away from this lead.

Rules for determining the average electrical axis of the complex QRS:

1. The average electrical axis of the complex QRS located in the middle between the axes of the two limb leads with high teeth R equal amplitude.
2. The average electrical axis of the complex QRS directed at an angle of 90° to any limb lead with a biphasic complex ( or R.S. complex) and to a lead that has relatively high teeth R.