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.

The electrical axis of the heart (EOS) is a concept that implies the activity of conducting nerve excitations synthesized and executed in the heart.

This indicator is characterized by the sum of the conduction of electrical signals through the cavities of the heart that occurs during any contraction of the heart tissue.

The electrical axis of the heart is one of the characteristics determined on an ECG. To make a diagnosis, additional hardware tests are necessary.

During an electrocardiogram study, the device records nerve excitations emitted by different parts of the heart by applying electrocardiograph sensors to different parts of the chest.

To calculate the direction of the EOS, doctors use a coordinate system, comparing the location of the heart with it. Due to the projection of electrodes onto it, the EOS angle is calculated.

In places where the zone of the heart muscle in which the electrode is installed emits stronger nerve excitations, that is where the EOS angle is located.

Why is the normal conduction of electrical excitations of the heart so important?

The fibers that make up the heart perfectly conduct nervous excitations, and with their multitude they create the cardiac system, where they conduct these nervous excitations.

The initial functioning of the heart muscle begins in the sinus node, with the appearance of nervous excitation. Next, the nerve signal is transported to the ventricular node, which transmits the signal to the His bundle, through which the signal propagates further.

The location of the latter is localized in the septum separating the two ventricles, where it branches into the anterior and posterior legs.

The nerve conduction system is very important for the healthy functioning of the heart, since, thanks to electrical impulses, it sets the normal rhythm of heart contractions, which determines the healthy functioning of the body.

If deviations appear in the signal conduction structure, then significant deviations in the position of the EOS are possible.

How is the electrical axis of the heart determined?

It is up to the attending physician to identify the location of the EOS, deciphering the ECG, using diagrams and tables, and finding the alpha angle.

This angle is formed from two straight lines. One of them is the 1st lead axis, and the second is the vector line of the electrical axis of the heart.

Location features include:

Another way to identify the electrical axis of the heart is to compare QRS complexes, the main task of which is the synthesis of nerve excitations and contraction of the ventricles.

The definition indicators are given below:

To accurately determine the height of the teeth, if they are at approximately the same level, use the following method:

• Determine QRS complexes in leads 1 and 3;
• The height of the R-waves of the 1st lead is summed up;
• A similar operation is performed with the R-waves of the 3rd lead;
• The resulting sums are inserted into a specific table, and the place where the data joins is identified, corresponding to a certain corner radius. Having identified normal alpha angle values, you can easily determine the location of the EOS.

You can also determine the position of the electrical axis using a pencil. This method is not accurate enough, and is used in many cases by students.

To determine in this way, apply the back of a pencil to the results of the electrocardiogram in the places of three leads and determine the highest R-wave.

After this, the sharp side of the pencil is directed to the R-wave, to the lead where it is largest.

Normal EOS indicators

The boundaries of normal levels of the electrical axis of the heart are determined by studying the electrocardiogram.

In weight ratio, the right ventricle is larger than the left. Therefore, in the latter, nervous excitations are much stronger, which directs EOS towards it.

If you compare the heart with the coordinate system, then its position will be in the range from thirty to seventy degrees.

This location is normal for the axis. But its position can vary from zero to ninety degrees, which varies from the personal parameters of the human body:

• Horizontal. In most cases, it is registered in people of short stature, but with a wide sternum;
• Vertical. It is predominantly registered in people of tall stature but thin build.

When fixing the electrical axis of the heart, the above-described positions are rarely observed. Semi-horizontal and semi-vertical axis positions are recorded in the majority of cases.

All of the above locations are normal indicators. Rotations of the heart as projected onto the coordinate system will help determine the location of the heart and diagnose possible diseases.

The results of the electrocardiogram may record rotations of the EOS around the coordinate axis, which may be normal.

Such cases are considered individually, depending on the patient’s symptoms, condition, complaints and the results of other examinations.

Violations of the norm indicators are deviations to the left or right.

Normal indicators in children

For infants, a clear axis shift is noted on the ECG; during growth, it normalizes. For the period of one year from birth, the indicator is usually located vertically. Normalization of the position is characterized by enlargement and development of the left ventricle.

In children of school and preschool age, the normal electrical axis of the heart predominates; vertical and very rarely horizontal are also found.

• Standards for children:
• Infants - from ninety to one hundred and seventy degrees;
• Children from one to three years old - vertical position of the axis;

Adolescent children – normal axis position.

For what purpose is EOS determined?

The disease is not diagnosed based on the displacement of the electrical axis of the heart alone. This factor is one of the parameters on the basis of which abnormalities in the body can be diagnosed.

In certain pathologies, axis deviation is most characteristic.

• These include:
• Primary damage to the heart muscle, not associated with inflammatory, tumor, ischemic lesions;
• Heart failure;
• Heart defects.

What does EOS shift to the right mean?

Complete blockade of the posterior branch of the His bundle also leads to disruption of the electrical axis to the right. If a right-sided displacement is registered, a pathological increase in the size of the right ventricle, which is responsible for supplying blood to the lungs for oxygen saturation, is possible.

This disease is caused by narrowing of the pulmonary artery and tricuspid valve insufficiency.

Pathological growth of the right ventricle occurs with ischemia and/or heart failure, and other diseases that do not occur under the influence of inflammatory and ischemic processes.

What does EOS shift to the left mean?

When determining the displacement of the electrical axis to the left side, it may indicate a pathological enlargement of the left ventricle, as well as its overload.

This pathological condition, in most cases, is provoked by the following influencing factors:

• Persistent increase in blood pressure, which causes the ventricle to contract much more strongly. This process leads to the fact that it grows in weight and, accordingly, in size;
• Ischemic attacks;
• Heart failure;
• Primary heart lesions, not associated with ischemic and inflammatory processes;
• Left ventricular valve damage. It is caused by a narrowing of the largest vessel in the human body - the aorta, in which the normal ejection of blood from the left ventricle is disrupted, and insufficiency of its valve, when some part of the blood is thrown back into the left ventricle;
• For people involved in sports at a professional level. In this case, you need to consult a sports doctor about further sports activities.

Violation of the normal boundaries of the electrical axis can be either a congenital indicator or an acquired one. In most situations, heart defects are consequences of fever caused by rheumatism.

Also, displacements of the electrical axis to the left side can appear when the conduction of nerve excitations inside the ventricles is shifted, and the anterior bundle branch block is blocked.

Symptoms

A separate displacement of the EOS does not entail any symptoms. But since it occurs as a consequence of some pathological condition, the symptoms correspond to the disease present in the body.

The most common symptoms are:

If you detect the slightest symptoms, you should consult a cardiologist. Timely diagnosis and effective treatment can save the patient's life.

Diagnostics

To diagnose diseases associated with a violation of the electrical axis of the heart, it is necessary to conduct several hardware studies, in addition to an ECG, to confirm the diagnosis.

These include:

• Ultrasound examination (ultrasound). It is a method that provides a large amount of information about the condition of the heart, in which structural abnormalities in the heart can be determined. During this examination, a visual picture of the condition of the heart is displayed on the screen, which will help diagnose enlargement. The method is safe and painless, which makes it accessible to any category of people, including infants and pregnant women;
• Daily electrocardiogram. Allows you to determine the slightest disturbances in the functioning of the heart using an electrocardiograph throughout the day;
• MRI of the heart– is a very complex type of safe research and is very effective. Many people mistakenly think that it is associated with ionizing radiation, but this is not the case. The basis of MRI is a magnetic field, as well as radiofrequency pulses. During the examination, the patient is placed in a special device - a tomograph;
• Load tests (treadmill, bicycle ergometry). A treadmill is a test performed while exercising on a special type of treadmill. A bicycle ergometer is a similar test method, but using a special bicycle;
• X-ray of the sternum. When carrying out this research method, the patient is irradiated with x-rays. The results help determine heart enlargement;
• Coronography.

  The choice of research method belongs to the attending physician, depending on the patient’s complaints and symptoms.

  Treatment

  All the diseases listed in this article can be diagnosed by just one violation of the electrical axis. If displacement is detected, it is necessary to consult a cardiologist and conduct additional studies.

  Registration of a violation in one direction or another does not require treatment.

  It normalizes after the initial pathological condition is eliminated. And only by eliminating it will the electrical axis indicators return to normal.

  What could be the consequences?

  The onset of complications depends on the disease that provoked the deviation of the electrical axis.

  Due to insufficient blood supply to the heart (ischemia), the following complications can progress:

  • Tachycardia. A pathological increase in heart rate occurs when the myocardium does not have enough blood volume to function healthy, which it tries to compensate for in a large number of contractions;
  • Death of heart tissue. The progression of a heart attack as a result of prolonged oxygen starvation, provoked by insufficient blood supplies to the heart, is inevitable;
  • Failure of circulation in the body. Against the background of circulatory failures in the body, blood stagnation, tissue death of vital organs, gangrene and other irreversible complications may progress;
  • Violation of the heart structure;
  • Fatal outcome. Extensive myocardial infarction and other serious complications can lead to rapid death.

  To prevent the development of severe complications and to prevent possible unexpected death, if symptoms are detected, you should immediately go to the hospital.

  Examinations will help doctors correctly diagnose the disease and prescribe effective therapy or surgery.

The greatest electrical activity of the ventricular myocardium is detected during the period of their excitation. In this case, the resultant of the resulting electrical forces (vector) occupies a certain position in the frontal plane of the body, forming an angle  (it is expressed in degrees) relative to the horizontal zero line (I standard lead). The position of this so-called electrical axis of the heart (EOS) is assessed by the size of the QRS complex waves in standard leads, which makes it possible to determine the angles and, accordingly, the position of the electrical axis of the heart. Angle is considered positive if it is located below the horizontal line, and negative if it is located above. This angle can be determined by geometric construction in Einthoven’s triangle, knowing the size of the QRS complex teeth in two standard leads. In practice, special tables are used to determine the angle  (they determine the algebraic sum of the teeth of the QRS complex in standard leads I and II, and then find the angle  using the table). There are five options for the location of the heart axis: normal, vertical position (intermediate between the normal position and the levogram), deviation to the right (pravogram), horizontal (intermediate between the normal position and the levogram), deviation to the left (levogram).

All five options are schematically presented in Fig. 23–9.

Rice.23–9 .Optionsdeviationselectricalaxeshearts. They are assessed by the size of the main (maximum amplitude) waves of the QRS complex in leads I and III. PR - right hand, LR - left hand, LN - left leg.

 Normogram(normal position of the EOS) is characterized by an anglefrom +30° to +70°. ECG signs:

 the R wave prevails over the S wave in all standard leads;

 maximum R wave in standard lead II;

 in aVL and aVF R waves also predominate, and in aVF it is usually higher than in aVL.

Normogram formula: R II >R I >R III.

 Verticalposition characterized by an angle from +70° to +90°. ECG signs:

 equal amplitude of the R waves in standard leads II and III (or in lead III slightly lower than in lead II);

 the R wave in standard lead I is small, but its amplitude exceeds the amplitude of the S wave;

 The QRS complex in aVF is positive (high R wave predominates), and in aVL it is negative (deep S wave predominates).

Formula: R II R III >R I, R I >S I.

 Phramogram. Deviation of the EOS to the right (pravogram) - anglemore than +90°. ECG signs:

 the R wave is maximum in standard lead III, in leads II and I it progressively decreases;

 the QRS complex in lead I is negative (the S wave predominates);

 in aVF a high R wave is characteristic, in aVL - a deep S wave with a small R wave;

Formula: R III >R II >R I, S I >R I.

 Horizontalposition characterized by an anglefrom +30° to 0°. ECG signs:

 the R waves in leads I and II are almost the same, or the R wave in lead I is slightly higher;

 in standard lead III, the R wave has a small amplitude, the S wave exceeds it (on inspiration, the r wave increases);

 in aVL the R wave is high, but slightly smaller than the S wave;

 in aVF the R wave is not high, but exceeds the S wave.

Formula: R I R II >R III, S III >R III, R aVF >S aVF.

 Levogram. Deviation of the EOS to the left (levogram) - angle less than 0° (up to –90°). ECG signs:

 the R wave in lead I exceeds the R waves in standard leads II and III;

 the QRS complex in lead III is negative (the S wave predominates; sometimes the r wave is completely absent);

 in aVL the R wave is high, almost equal to or greater than the R wave in standard lead I;

 in aVF the QRS complex resembles that in standard lead III.

Formula: R I >R II >R III, S III >R III, R aVF

Papproximate grade provisions electrical axes hearts. To remember the differences between the right-hand and left-hand grammars, students use a witty schoolboy technique, which consists of the following. When examining your palms, bend the thumb and index fingers, and the remaining middle, ring and little fingers are identified with the height of the R wave. “Read” from left to right, like an ordinary line. Left hand - levogram: the R wave is maximum in standard lead I (the first highest finger is the middle finger), in lead II it decreases (ring finger), and in lead III it is minimal (little finger). The right hand is a right hand, where the situation is reverse: the R wave increases from lead I to lead III (as does the height of the fingers: little finger, ring finger, middle finger).

Causes of deviation of the electrical axis of the heart. The position of the electrical axis of the heart depends on both cardiac and extracardiac factors.

 In people with a high diaphragm and/or a hypersthenic constitution, the EOS takes on a horizontal position or even a levogram appears.

 In tall, thin people with low standing, the diaphragm of the EOS is normally located more vertically, sometimes up to the right angle.

Deviation of EOS is most often associated with pathological processes. As a result of the predominance of myocardial mass, i.e. ventricular hypertrophy, the EOS deviates towards the hypertrophied ventricle. However, if during left ventricular hypertrophy the deviation of the EOS to the left almost always occurs, then for its deviation to the right the right ventricle must be significantly hypertrophied, since its mass in a healthy person is 6 times less than the mass of the left ventricle. Nevertheless, it must immediately be pointed out that, despite the classical ideas, at present, EOS deviation is not considered a reliable sign of ventricular hypertrophy.

The electrical axis of the heart is a term that means the electrical activity of the organ, that is, the total indicator of its average vector during depolarization. This is an indicator of the electrical processes of the heart.

This concept is used in cardiology and in functional diagnostics. Determination of the direction of EOS is carried out using an ECG.

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.

Impulses travel through the conduction system of the heart. It consists of atypical fibers that are located in certain areas of the organ.

This system begins in the sinus node. The impulse then passes to the atria and ventricles and to the bundle of His.

When any disturbances occur in the conduction system, the EOS changes its direction.

Axis location

In a healthy person, the left ventricle has a larger mass than the right.

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.

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.

As for individual characteristics, it is noted that in people who are tall and have a thin build, the EOS is in a semi-vertical position, and in people who are shorter and have a stocky build, the EOS is in a semi-horizontal position.

The pathological condition looks like a sharp deviation to the left or right.

Reasons for rejection

When the EOS deviates sharply to the left, this may mean that there are certain diseases, namely LV hypertrophy.

In this condition, the cavity stretches and increases in size. Sometimes this occurs due to overload, but it can also be a consequence of a disease.

Diseases that cause hypertrophy are:

In addition to hypertrophy, the main causes of axis deviation to the left are conduction disorders inside the ventricles and during blockades of various types.

Quite often, with such a deviation, blockade of the left leg of His, namely its anterior branch, is diagnosed.

As for the pathological deviation of the heart axis sharply to the right, this may mean that there is RV hypertrophy.

This pathology can be caused by the following diseases:

As well as diseases characteristic of LV hypertrophy:

• cardiac ischemia;
• chronic heart failure;
• cardiomyopathy;
• complete blockade of the left leg of His (posterior branch).

When the electrical axis of the heart is sharply deviated to the right in a newborn, this is considered normal.

We can conclude that the main cause of pathological displacement to the left or right is ventricular hypertrophy.

And the greater the degree of this pathology, the more EOS is rejected. A change in the axis is simply an ECG sign of some disease.

It is important to carry out timely identification of these indications and diseases.

Deviation of the heart axis does not cause any symptoms; symptoms manifest themselves from hypertrophy, which disrupts the hemodynamics of the heart. The main symptoms are headaches, chest pain, swelling of the limbs and face, suffocation and shortness of breath.

If cardiac symptoms occur, you should immediately undergo electrocardiography.

Determination of ECG signs

This is the position at which the axis is within the range of 70-900.

On the ECG this is expressed as tall R waves in the QRS complex. In this case, the R wave in lead III exceeds the wave in lead II. In lead I there is an RS complex, in which S has a greater depth than the height of R.

In this case, the position of the alpha angle is within the range of 0-500. The ECG shows that in standard lead I the QRS complex is expressed as R-type, and in lead III its form is S-type. The S wave has a depth greater than the height R.

With blockade of the posterior branch of the left leg of His, the alpha angle has a value greater than 900. On the ECG, the duration of the QRS complex may be slightly increased. There is a deep S wave (aVL, V6) and a high R wave (III, aVF).

With blockade of the anterior branch of the left leg of His, the values ​​will be from -300 or more. On the ECG, signs of this are a late R wave (lead aVR). Leads V1 and V2 may have a small r wave. In this case, the QRS complex is not expanded, and the amplitude of its waves is not changed.

Blockade of the anterior and posterior branches of the left leg of His (complete block) - in this case, the electrical axis is sharply deviated to the left and can be located horizontally. On the ECG in the QRS complex (leads I, aVL, V5, V6), the R wave is widened and its apex is jagged. Near the high R wave there is a negative T wave.

It should be concluded that the electrical axis of the heart can be moderately deviated. If the deviation is sharp, then this may mean the presence of serious cardiac diseases.

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 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 QRS 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(see section ""). And vice versa, if in any limb lead the complex QRS two-phase, average electrical axis of the complex QRS 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 R.S., therefore, the EOS should be perpendicular to lead I.

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 QRS would be in it negative. In Fig. 5-3 there is a positive complex in lead aVF QRS(high prong R), so the axis must have an angle of +90°.

Rice. 5-4.

The QRS angle is -30°.

Method No. 3 QRS Another example is in Fig. 5-4. At a quick glance, the average electrical axis of the complex horizontal R.S.. , since in leads I and aVL the complexes are positive, and in leads aVF, III and aVR they are predominantly negative. The exact electrical axis of the heart can be determined by lead II with a biphasic complex Hence QRS, 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 would be positive..

So the axis angle is -30°

Method number 4 QRS The next example is in Fig. 5-5. Complex R positive in leads II, III and aVF, so the EOS is relatively vertical. Teeth have equal heights in leads I and III - hence QRS, the average electrical axis of the complex

should be located between these two leads at an angle of +60°.

Rice. 5-5.

QRS angle +60°. QRS Method No. 5 According to Fig. 5-5 average electrical axis of the complex R.S. can be calculated differently. 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 R.

Consider the example in Fig. 5-6.

Rice. 5-6.

QRS angle -90°. QRS EOS is directed from leads II, III, aVF to leads aVR and aVL, where the complexes R positive. Because the teeth 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 - R.S. 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.

QRS angle -60°. R.S. Method No. 6 Since in lead aVR there is a two-phase complex-type, EOS should be located QRS perpendicular QRS 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 you can also R calculate from lead I , where the amplitude of the tooth equal to the amplitude of the tooth

S Lead II. The axis should be located between the positive pole of lead I (0°) and the negative pole of lead II (-120°); The axis angle is -60°. QRS These examples show QRS basic rules for determining the average electrical axis of the complex R. 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 , where the amplitude of the tooth close to biphasic, or in two leads, where the amplitudes of the waves

(or R or , where the amplitude of the tooth) are approximately equal. QRS For example, if the amplitudes of the teeth R.S. or QR in two leads are only approximately equal, the average electrical axis of the complex R 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 ( , where the amplitude of the tooth) with teeth And 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 ( R(or teeth R Q , where the amplitude of the tooth) of different amplitudes, the axis is not exactly perpendicular to this lead. If the tooth And more than a tooth R(or prong , where the amplitude of the tooth or And), the axis points are less than 90° from the lead. If the tooth

less than a tooth QRS:

1. , the axis points are more than 90° away from this lead. QRS located in the middle between the axes of the two limb leads with high teeth R equal amplitude.
2. , the axis points are more than 90° away from this lead. QRS directed at an angle of 90° to any limb lead with a biphasic complex ( QR or R.S.) and to a lead that has relatively high teeth R.