Currently in clinical practice widely used electrocardiography method(ECG). The ECG reflects the processes of excitation in the heart muscle - the occurrence and spread of excitation.

There are various ways to tap the electrical activity of the heart, which differ from each other in the location of the electrodes on the surface of the body.

Heart cells, coming into a state of excitation, become a source of current and cause the appearance of a field in the environment surrounding the heart.

In veterinary practice, electrocardiography is used different systems leads: application of metal electrodes to the skin in the chest, heart, limbs and tail.

Electrocardiogram(ECG) is a periodically repeating curve of the biopotentials of the heart, reflecting the process of excitation of the heart that originates in the sinus (sinoatrial) node and spreads throughout the heart, recorded using an electrocardiograph (Fig. 1).

Rice. 1. Electrocardiogram

Its individual elements - teeth and intervals - received special names: teeth R,Q, R, S, T intervals R,PQ, QRS, QT, R.R.; segments PQ, ST, TP, characterizing the occurrence and spread of excitation along the atria (P), interventricular septum (Q), gradual excitation of the ventricles (R), maximum excitation of the ventricles (S), repolarization of the ventricles (S) of the heart. The P wave reflects the process of depolarization of both atria, a complex QRS- depolarization of both ventricles, and its duration is the total duration of this process. Segment ST and wave G correspond to the phase of ventricular repolarization. Interval duration PQ determined by the time it takes for the excitation to pass through the atria. The duration of the QR-ST interval is the duration of the “electrical systole” of the heart; it may not correspond to the duration of mechanical systole.

Indicators of good heart fitness and great potential functional capabilities for the development of lactation in highly productive cows are low or medium heart rate and high voltage of ECG waves. High heart rate with a high voltage of the ECG waves, this is a sign of a heavy load on the heart and a decrease in its potential. Reducing tooth voltage R and T, increasing intervals P- Q and Q-T indicate a decrease in the excitability and conductivity of the cardiac system and low functional activity of the heart.

Elements of ECG and principles of its general analysis

— a method for recording the potential difference of the electric dipole of the heart in certain areas of the human body. When the heart is excited, an electric field arises that can be registered on the surface of the body.

Vectorcardiography - method for studying the magnitude and direction of the integral electrical vector of the heart during cardiac cycle, the value of which is constantly changing.

Teleelectrocardiography (radioelectrocardiography electrotelecardiography)- a method of recording an ECG, in which the recording device is significantly removed (from several meters to hundreds of thousands of kilometers) from the person being examined. This method is based on the use of special sensors and receiving and transmitting radio equipment and is used when conventional electrocardiography is impossible or undesirable, for example, in sports, aviation and space medicine.

Holter monitoring— daily ECG monitoring with subsequent analysis of rhythm and other electrocardiographic data. Daily monitoring An ECG, along with a large amount of clinical data, makes it possible to identify heart rate variability, which in turn is an important criterion for the functional state of the cardiovascular system.

Ballistocardiography - a method for recording micro-oscillations of the human body caused by the ejection of blood from the heart during systole and the movement of blood through large veins.

Dynamocardiography - a method for recording the displacement of the center of gravity of the chest, caused by the movement of the heart and the movement of blood mass from the cavities of the heart into the vessels.

Echocardiography (ultrasound cardiography)- a method for studying the heart, based on recording ultrasonic vibrations reflected from the surfaces of the walls of the ventricles and atria at their border with the blood.

Auscultation- a method for assessing sound phenomena in the heart on the surface of the chest.

Phonocardiography - a method of graphically recording heart sounds from the surface of the chest.

Angiocardiography - x-ray method examination of the cavities of the heart and great vessels after their catheterization and the introduction of radiocontrast substances into the blood. A variation of this method is coronary angiography - X-ray contrast examination of the heart vessels directly. This method is the “gold standard” in diagnosis coronary disease hearts.

Rheography- a method for studying the blood supply to various organs and tissues, based on recording changes in the total electrical resistance of tissues when an electric current of high frequency and low strength passes through them.

The ECG is represented by waves, segments and intervals (Fig. 2).

P wave V normal conditions characterizes the initial events of the cardiac cycle and is located on the ECG in front of the waves of the ventricular complex QRS. It reflects the dynamics of excitation of the atrial myocardium. Prong R it is symmetrical, has a flattened apex, its amplitude is maximum in lead II and is 0.15-0.25 mV, duration is 0.10 s. The ascending part of the wave reflects depolarization mainly of the myocardium of the right atrium, the descending part - of the left atrium. Normal tooth R positive in most leads, negative in lead aVR, in III and V1 in leads it can be biphasic. Changing the normal location of the tooth R on the ECG (before the complex QRS) observed in cardiac arrhythmias.

The processes of repolarization of the atrial myocardium are not visible on the ECG, since they are superimposed on the higher amplitude waves of the QRS complex.

IntervalPQ measured from the beginning of the tooth R before the beginning of the tooth Q. It reflects the time elapsed from the onset of atrial excitation to the onset of ventricular excitation or other in words, the time spent on conducting excitation through the conduction system to the ventricular myocardium. Its normal duration is 0.12-0.20 s and includes the time of atrioventricular delay. Increasing the duration of the intervalPQmore than 0.2 s may indicate a disturbance in the conduction of excitation in the area of ​​the atrioventricular node, the His bundle or its branches and is interpreted as evidence that a person has signs of 1st degree conduction block. If an adult has an intervalPQless than 0.12 s, this may indicate the existence of additional pathways for excitation between the atria and ventricles. Such people are at risk of developing arrhythmias.

Rice. 2. Normal values ​​of ECG parameters in lead II

Complex of teethQRS reflects the time (normally 0.06-0.10 s) during which the structures of the ventricular myocardium are consistently involved in the process of excitation. In this case, the papillary muscles and the outer surface are the first to be excited. interventricular septum(a spike appears Q lasting up to 0.03 s), then the bulk of the ventricular myocardium (tooth duration 0.03-0.09 s) and lastly the myocardium of the base and the outer surface of the ventricles (tooth 5, duration up to 0.03 s). Since the mass of the myocardium of the left ventricle is significantly greater than the mass of the right, changes in electrical activity, specifically in the left ventricle, dominate in the ventricular complex of ECG waves. Since the complex QRS reflects the process of depolarization of the powerful mass of the ventricular myocardium, then the amplitude of the teeth QRS usually higher than the wave amplitude R, reflecting the process of depolarization of a relatively small mass of atrial myocardium. Prong amplitude R fluctuates in different leads and can reach up to 2 mV in I, II, III and aVF leads; 1.1 mV V aVL and up to 2.6 mV in the left chest leads. Teeth Q And S in some leads they may not appear (Table 1).

Table 1. Limits of normal values ​​of the amplitude of ECG waves in standard lead II

ECG waves	Minimum norm, mV	Maximum norm, mV

SegmentST is registered after the complex ORS. It is measured from the end of the tooth S before the beginning of the tooth T. At this time, the entire myocardium of the right and left ventricles is in a state of excitation and the potential difference between them practically disappears. Therefore, the ECG recording becomes almost horizontal and isoelectric (normally, segment deviation is allowed ST from the isoelectric line no more than 1 mm). Bias ST a greater value can be observed with myocardial hypertrophy, during heavy physical activity and indicates insufficiency of blood flow in the ventricles. Significant deviation ST from the baseline, recorded in several ECG leads, may be a harbinger or evidence of the presence of myocardial infarction. Duration ST in practice it is not assessed, since it significantly depends on the heart rate.

T wave reflects the process of ventricular repolarization (duration - 0.12-0.16 s). The amplitude of the T wave is highly variable and should not exceed 1/2 the amplitude of the wave R. The G wave is positive in those leads in which the wave is of significant amplitude R. In leads in which the tooth R low amplitude or not detected, a negative wave may be recorded T(leads AVR and VI).

IntervalQT reflects the duration of “ventricular electrical systole” (the time from the beginning of their depolarization to the end of repolarization). This interval is measured from the beginning of the tooth Q to the end of the tooth T. Normally, at rest, it lasts 0.30-0.40 s. Interval duration FROM depends on heart rate, tone of autonomic centers nervous system, hormonal levels, the effects of certain medications. Therefore, changes in the duration of this interval are monitored to prevent overdose of certain cardiac medications.

ProngU is not a permanent element of the ECG. It reflects trace electrical processes observed in the myocardium of some people. It did not receive any diagnostic value.

ECG analysis is based on assessing the presence of waves, their sequence, direction, shape, amplitude, measuring the duration of waves and intervals, position relative to the isoline and calculating other indicators. Based on the results of this assessment, a conclusion is made about the heart rate, the source and correctness of the rhythm, the presence or absence of signs of myocardial ischemia, the presence or absence of signs of myocardial hypertrophy, the direction of the electrical axis of the heart and other indicators of cardiac function.

For the correct measurement and interpretation of ECG indicators, it is important that it be recorded qualitatively under standard conditions. A high-quality ECG recording is one in which there is no noise and no shift in the recording level from the horizontal and the standardization requirements are met. An electrocardiograph is an amplifier of biopotentials, and to set a standard gain on it, select its level such that applying a calibration signal of 1 mV to the input of the device leads to a deviation of the recording from the zero or isoelectric line by 10 mm. Compliance with the amplification standard allows you to compare ECGs recorded on any type of device and express the amplitude of the ECG waves in millimeters or millivolts. To correctly measure ECG wave durations and intervals, recordings must be made at standard chart paper, writing device, or monitor screen speeds. Most modern electrocardiographs will allow you to record ECG at three standard speeds: 25, 50 and 100 mm/s.

Having visually checked the quality and compliance with the standardization requirements of the ECG recording, we begin to evaluate its indicators.

The amplitude of the teeth is measured using the isoelectric, or zero, line as the reference point. The first is recorded in the case of the same potential difference between the electrodes (PQ - from the end of the P wave to the beginning of Q, the second - in the absence of a potential difference between the output electrodes (TP interval)). Teeth directed upward from the isoelectric line are called positive, and those directed downward are called negative. A segment is an ECG section between two waves; an interval is a section that includes a segment and one or more waves adjacent to it.

An electrocardiogram can be used to judge the location of excitation in the heart, the sequence in which the parts of the heart are covered by excitation, and the speed of excitation. Consequently, one can judge the excitability and conductivity of the heart, but not the contractility. In some heart diseases, there may be a disconnect between the excitation and contraction of the heart muscle. In this case, the pumping function of the heart may be absent in the presence of recorded myocardial biopotentials.

RR interval

The duration of the cardiac cycle is determined by the interval R.R., which corresponds to the distance between the tops of adjacent teeth R. The proper value (norm) of the interval QT calculated using Bazett's formula:

Where TO - coefficient equal to 0.37 for men and 0.40 for women; R.R.— duration of the cardiac cycle.

Knowing the duration of the cardiac cycle, it is easy to calculate the heart rate. To do this, it is enough to divide the time interval of 60 s by the average duration of the intervals R.R..

Comparing the duration of a series of intervals R.R. a conclusion can be made about the correctness of the rhythm or the presence of arrhythmia in the heart.

A comprehensive analysis of standard ECG leads also allows us to identify signs of insufficiency of blood flow, metabolic disorders in the heart muscle and diagnose a number of heart diseases.

Heart sounds- sounds occurring during systole and diastole are a sign of the presence of heart contractions. The sounds generated by the beating heart can be examined by auscultation and recorded by phonocardiography.

Auscultapia (listening) can be performed directly with the ear attached to the chest, and with the help of instruments (stethoscope, phonendoscope) that amplify or filter sound. During auscultation, two tones are clearly audible: the first sound (systolic), which occurs at the beginning of ventricular systole, and the second sound (diastolic), which occurs at the beginning of ventricular diastole. The first tone during auscultation is perceived as lower and longer (represented by frequencies of 30-80 Hz), the second - higher and shorter (represented by frequencies of 150-200 Hz).

The formation of the first tone is caused by sound vibrations caused by the slamming of the AV valves, the trembling of the tendon threads associated with them when they are stretched, and the contraction of the ventricular myocardium. The opening of the semilunar valves may make some contribution to the origin of the last part of the first tone. The first sound is heard most clearly in the area of ​​the apex beat of the heart (usually in the 5th intercostal space on the left, 1-1.5 cm to the left of the midclavicular line). Listening to its sound at this point is especially informative for assessing the condition of the mitral valve. To assess the condition of the tricuspid valve (overlapping the right AV orifice), listening to 1 tone at the base of the xiphoid process is more informative.

The second tone is better heard in the 2nd intercostal space to the left and right of the sternum. The first part of this tone is caused by the slamming of the aortic valve, the second - by the pulmonary valve. The sound of the pulmonary valve is better heard on the left, and the aortic valve on the right.

With pathology of the valve apparatus, aperiodic sound vibrations occur during heart operation, which create noise. Depending on which valve is damaged, they are superimposed on a certain heart sound.

A more detailed analysis of sound phenomena in the heart is possible using a recorded phonocardiogram (Fig. 3). To record a phonocardiogram, an electrocardiograph is used, complete with a microphone and an amplifier of sound vibrations (phonocardiographic attachment). The microphone is installed at the same points on the body surface where auscultation is performed. For a more reliable analysis of heart sounds and murmurs, the phonocardiogram is always recorded simultaneously with the electrocardiogram.

Rice. 3. Synchronously recorded ECG (top) and phonocardogram (bottom).

On the phonocardiogram, in addition to the I and II tones, the III and IV tones, which are usually not audible by the ear, can be recorded. The third tone appears as a result of vibrations of the ventricular wall during their rapid filling with blood during the diastole phase of the same name. The fourth sound is recorded during atrial systole (presystole). The diagnostic value of these tones has not been determined.

The appearance of the first tone healthy person is always recorded at the beginning of ventricular systole (period of tension, end of the phase of asynchronous contraction), and its complete registration coincides in time with the recording of the waves of the ventricular complex on the ECG QRS. The initial low-frequency oscillations of the first tone, small in amplitude (Fig. 1.8, a), are sounds that occur during contraction of the ventricular myocardium. They are recorded almost simultaneously with the Q wave on the ECG. The main part of the first tone, or the main segment (Fig. 1.8, b), is represented by high-frequency sound vibrations of large amplitude that occur when the AV valves close. The beginning of registration of the main part of the first tone is delayed in time by 0.04-0.06 from the beginning of the tooth Q on ECG (Q- I tone in Fig. 1.8). End part I tone (Fig. 1.8, c) represents small amplitude sound vibrations that occur when the aortic valves open and pulmonary artery and sound vibrations of the walls of the aorta and pulmonary artery. The duration of the first tone is 0.07-0.13 s.

The beginning of the second sound under normal conditions coincides in time with the beginning of ventricular diastole, delaying by 0.02-0.04 s to the end of the G wave on the ECG. The tone is represented by two groups of sound oscillations: the first (Fig. 1.8, a) is caused by the closure of the aortic valve, the second (P in Fig. 3) is caused by the closure of the pulmonary valve. The duration of the second tone is 0.06-0.10 s.

If the ECG elements are used to judge the dynamics of electrical processes in the myocardium, then the phonocardiogram elements are used to judge mechanical phenomena in the heart. The phonocardiogram provides information about the state of the heart valves, the beginning of the phase of isometric contraction and relaxation of the ventricles. The duration of the “mechanical systole” of the ventricles is determined by the distance between the first and second sounds. An increase in the amplitude of the second tone may indicate high blood pressure in the aorta or pulmonary trunk. However, at present, more detailed information about the state of the valves, the dynamics of their opening and closing and other mechanical phenomena in the heart is obtained by ultrasound examination hearts.

Ultrasound of the heart

Ultrasound examination (ultrasound) of the heart, or echocardiography, is an invasive method for studying the dynamics of changes in the linear dimensions of the morphological structures of the heart and blood vessels, allowing one to calculate the rate of these changes, as well as changes in the volumes of the cavities of the heart and blood during the cardiac cycle.

The method is based on physical property high-frequency sounds in the range of 2-15 MHz (ultrasound) pass through liquid media, tissues of the body and heart, while being reflected from the boundaries of any changes in their density or from the boundaries of organs and tissues.

A modern ultrasound (US) echocardiograph includes such units as an ultrasound generator, an ultrasound emitter, a receiver of reflected ultrasound waves, visualization and computer analysis. The ultrasound emitter and receiver are structurally combined in a single device called an ultrasound sensor.

An echocardiographic examination is carried out by sending short series of ultrasound waves generated by the device from the sensor into the body in certain directions. Part of the ultrasound waves, passing through the tissues of the body, is absorbed by them, and the reflected waves (for example, from the interfaces of the myocardium and blood; valves and blood; walls of blood vessels and blood) propagate in the opposite direction to the body surface, are captured by the sensor receiver and converted into electrical signals. After computer analysis of these signals, an ultrasound image of the dynamics is formed on the display screen mechanical processes, occurring in the heart during the cardiac cycle.

Based on the results of calculating the distances between the working surface of the sensor and the interfaces of various tissues or changes in their density, it is possible to obtain many visual and digital echocardiographic indicators of heart function. Among these indicators are the dynamics of changes in the size of the heart cavities, the size of the walls and septa, the position of the valve leaflets, the size of the internal diameter of the aorta and large vessels; identifying the presence of compactions in the tissues of the heart and blood vessels; calculation of end-diastolic, end-systolic, stroke volumes, ejection fraction, rate of blood expulsion and blood filling of the cavities of the heart, etc. Ultrasound of the heart and blood vessels is currently one of the most common, objective methods for assessing the state of the morphological properties and pumping function of the heart.

Equipment for recording electrocardiogram

Electrocardiography - a method of graphically recording changes in the difference in cardiac potentials that occur during the processes of myocardial excitation.

The first registration of an electrocardiosignal, the prototype of a modern ECG, was undertaken by V. Einthoven in 1912 . in Cambridge. After this, the ECG recording technique was intensively improved. Modern electrocardiographs allow both single-channel and multi-channel ECG recording.

In the latter case, several different electrocardiographic leads (from 2 to 6-8) are simultaneously recorded, which significantly reduces the study period and makes it possible to obtain more accurate information about the electrical field of the heart.

Electrocardiographs consist of an input device, a biopotential amplifier and a recording device. The potential difference that occurs on the surface of the body when the heart is excited is recorded using a system of electrodes attached to different areas bodies. Electrical vibrations are converted into mechanical displacements of the electromagnet armature and are recorded in one way or another on a special moving paper tape. Now they use directly both mechanical recording using a very light pen, to which ink is applied, and thermal recording of ECG using a pen, which, when heated, burns the corresponding curve onto special thermal paper.

Finally, there are capillary-type electrocardiographs (mingographs), in which ECG recording is carried out using a thin stream of splashing ink.

A gain calibration of 1 mV, causing a 10 mm deflection of the recording system, allows comparison of ECGs recorded from a patient in different times and/or different devices.

Tape transport mechanisms in all modern electrocardiographs provide paper movement at different speeds: 25, 50, 100 mm s -1, etc. Most often in practical electrocardiology, the ECG recording speed is 25 or 50 mm s -1 (Fig. 1.1).

Rice. 1.1. ECG recorded at a speed of 50 mm·s -1 (a) and 25 mm·s -1 (b). The calibration signal is shown at the beginning of each curve

Electrocardiographs must be installed in a dry room at a temperature not lower than 10 and not higher than 30 ° C. The electrocardiograph must be grounded during operation.

Electrocardiographic leads

Changes in the potential difference on the body surface that occur during heart activity are recorded using various ECG lead systems. Each lead records the potential difference that exists between two specific points in the electrical field of the heart at which the electrodes are installed. Thus, different electrocardiographic leads differ from each other, first of all, in the areas of the body at which the potential difference is measured.

Electrodes installed at each of the selected points on the body surface are connected to the galvanometer of the electrocardiograph. One of the electrodes is connected to the positive pole of the galvanometer (positive or active lead electrode), the second electrode is connected to its negative pole (negative lead electrode).

Today in clinical practice, the most widely used are 12 ECG leads, the recording of which is mandatory for each electrocardiographic examination of a patient: 3 standard leads, 3 enhanced unipolar limb leads and 6 chest leads.

Standard leads

Three standard leads form an equilateral triangle (Einthoven's triangle), the vertices of which are the right and left arms, as well as the left leg with electrodes installed on them. The hypothetical line connecting the two electrodes involved in the formation of the electrocardiographic lead is called the lead axis. The axes of standard leads are the sides of Einthoven’s triangle (Fig. 1. 2).

Rice. 1.2. Formation of three standard limb leads

Perpendiculars drawn from the geometric center of the heart to the axis of each standard lead divide each axis into two equal parts. The positive part faces the positive (active) lead electrode, and the negative part faces the negative electrode. If the electromotive force (EMF) of the heart at some point in the cardiac cycle is projected onto the positive part of the lead axis, a positive deviation (positive R, T, P waves) is recorded on the ECG, and if it is negative, negative deviations are recorded on the ECG (Q waves, S, sometimes negative T or even P waves). To record these leads, electrodes are placed on the right hand (red marking) and left (yellow marking), as well as the left leg (green marking). These electrodes are connected in pairs to the electrocardiograph to record each of the three standard leads. Standard limb leads are recorded in pairs by connecting electrodes:

Lead I - left (+) and right (-) hand;

Lead II - left leg (+) and right arm (-);

Lead III - left leg (+) and left arm (-);

The fourth electrode is installed on the right leg to connect the ground wire (black marking).

The signs “+” and “-” here indicate the corresponding connection of the electrodes to the positive or negative poles of the galvanometer, that is, the positive and negative pole of each lead are indicated.

Reinforced limb leads

Strengthened limb leads were proposed by Goldberg in 1942 . They record the potential difference between one of the limbs on which the active positive electrode of a given lead is installed (right arm, left arm or leg) and the average potential of the other two limbs. The so-called combined Goldberg electrode, which is formed by connecting two limbs through additional resistance, is used as a negative electrode in these leads. Thus, aVR is an enhanced abduction from the right hand; aVL—increased abduction from the left arm; aVF - increased abduction from the left leg (Fig. 1.3).

The designation of enhanced limb leads comes from the first letters of the English words: “ a "- augmented (enhanced); "V" - voltage (potential); "R" - right (right); “L” - left (left); "F" - foot (leg).

Rice. 1.3. Formation of three reinforced unipolar limb leads. Below - Einthoven's triangle and the location of the axes of three reinforced unipolar limb leads

Six-axis coordinate system (according to BAYLEY)

Standard and enhanced unipolar limb leads make it possible to record changes in the EMF of the heart in the frontal plane, that is, in the one in which Einthoven’s triangle is located. For a more accurate and visual determination of various deviations of the EMF of the heart in this frontal plane, in particular to determine the position of the electrical axis of the heart, the so-called six-axis coordinate system was proposed (Bayley, 1943). It can be obtained by combining the axes of three standard and three reinforced leads from the limbs, drawn through the electrical center of the heart. The latter divides the axis of each lead into positive and negative parts, directed, respectively, to the positive (active) or negative electrodes (Fig. 1.4).

Rice. 1.4. Formation of a six-axis coordinate system (according to Bayley)

The direction of the axes is measured in degrees. The reference point (0°) is conventionally taken to be a radius drawn strictly horizontally from the electrical center of the heart to the left towards the active positive pole of standard lead I. The positive pole of standard lead II is located at an angle of +60 °, lead aVF - +90 °, standard lead III - +120 °, aVL - - 30 °, and aVR - -150 °. Lead axis aVL is perpendicular to axis II of standard lead, axis I of standard lead is perpendicular to axis aVF, and axis aVR is perpendicular to axis III of standard lead.

chest leads

Unipolar chest leads proposed by Wilson in 1934 ., record the potential difference between the active positive electrode installed at certain points on the surface of the chest and the negative combined Wilson electrode. This electrode is formed by connecting three limbs (right and left arms, as well as left leg) through additional resistances, the combined potential of which is close to zero (about 0.2 mV). To record an ECG, 6 generally accepted positions of the active electrode are used on the anterior and lateral surface of the chest, which in combination with the combined Wilson electrode form 6 chest leads (Fig. 1.5):

lead V 1 - in the fourth intercostal space along the right edge of the sternum;

lead V 2 - in the fourth intercostal space along the left edge of the sternum;

lead V 3 - between positions V 2 and V 4, approximately at the level of the fourth rib along the left parasternal line;

lead V 4 - in the fifth intercostal space along the left midclavicular line;

lead V 5 - at the same horizontal level as V 4, along the left anterior axillary line;

lead V 6 - along the left mid-axillary line at the same horizontal level as the electrodes of leads V 4 and V 5.

Rice. 1.5. Chest electrode placement

Thus, 12 electrocardiographic leads (3 standard, 3 enhanced unipolar limb leads and 6 chest leads) are most widely used.

Electrocardiographic deviations in each of them reflect the total EMF of the entire heart, that is, they are the result of the simultaneous influence on this lead of a changing electrical potential in the left and right parts of the heart, in the anterior and posterior walls of the ventricles, in the apex and base of the heart.

Additional leads

It is sometimes advisable to expand the diagnostic capabilities of electrocardiographic examination by using some additional leads. They are used in cases where the usual program for recording 12 generally accepted ECG leads does not allow one to reliably diagnose a particular electrocardiographic pathology or requires clarification of some changes.

The method of recording additional chest leads differs from the method of recording 6 generally accepted chest leads only in the localization of the active electrode on the surface of the chest. A combined Wilson electrode is used as an electrode connected to the negative pole of the cardiograph.

Rice. 1.6. Location of additional chest electrodes

Leads V7-V9. The active electrode is installed along the posterior axillary (V 7), scapular (V 8) and paravertebral (V 9) lines at the horizontal level on which the electrodes V 4 -V 6 are located (Fig. 1.6). These leads are usually used for more accurate diagnosis focal changes in the myocardium in the posterobasal regions of the LV.

Leads V 3R—V6R. The chest (active) electrode is placed on right half chest in positions symmetrical to the usual locations of electrodes V 3 -V 6. These leads are used to diagnose right heart hypertrophy.

Neb leads. Bipolar chest leads, proposed in 1938 by Nab, record the potential difference between two points located on the surface of the chest. To record three Neb leads, electrodes designed to record three standard limb leads are used. The electrode, usually placed on the right arm (red marking), is placed in the second intercostal space along the right edge of the sternum. The electrode from the left leg (green marking) is moved to the position of chest lead V 4 (at the apex of the heart), and the electrode located on the left arm (yellow marking) is placed at the same horizontal level as the green electrode, but along the posterior axillary line . If the electrocardiograph lead switch is in position I of the standard lead, record the Dorsalis lead (D).

By moving the switch to standard leads II and III, the Anterior (A) and Inferior (I) leads are recorded, respectively. Neb leads are used to diagnose focal changes in the myocardium back wall(lead D), anterior lateral wall (lead A) and upper sections anterior wall (lead I).

ECG recording technique

To obtain a high-quality ECG recording, you must adhere to some rules for its registration.

Conditions for conducting an electrocardiographic study

The ECG is recorded in a special room, remote from possible sources of electrical interference: electric motors, physiotherapy and X-ray rooms, electrical distribution panels. The couch should be at a distance of at least 1.5-2 m from the electrical wires.

It is advisable to shield the couch by placing a blanket under the patient with a sewn-in metal mesh, which must be grounded.

The study is carried out after a 10-15 minute rest and no earlier than 2 hours after eating. The patient should be undressed to the waist, the legs should also be freed from clothing.

An ECG is usually recorded in a supine position, which allows for maximum muscle relaxation.

Application of electrodes

On inner surface 4 plate electrodes are applied to the legs and forearms in their lower third using rubber bands, and one or more (for multi-channel recording) chest electrodes are installed on the chest using a rubber suction bulb. To improve the quality of the ECG and reduce the amount of inductive currents, good contact of the electrodes with the skin should be ensured. To do this, it is necessary: ​​1) first degrease the skin with alcohol in the areas where the electrodes are applied; 2) in case of significant hairiness of the skin, moisten the places where the electrodes are applied soap solution; 3) use electrode paste or generously moisten the skin in the areas where the electrodes are applied with a 5-10% sodium chloride solution.

Connecting wires to electrodes

Each electrode, installed on the limbs or on the surface of the chest, is connected to a wire coming from the electrocardiograph and marked with a certain color. The generally accepted marking of input wires is: right hand - red; left hand - yellow; left leg - green, right leg(patient grounding) - black; chest electrode - white. If you have a 6-channel electrocardiograph that allows you to simultaneously record an ECG in 6 chest leads, a wire with a red color on the tip is connected to electrode V 1; to the electrode V 2 - yellow, V 3 - green, V 4 - brown, V 5 - black and V 6 - blue or purple. The markings of the remaining wires are the same as in single-channel electrocardiographs.

Selecting the electrocardiograph gain

Before you start recording an ECG, you must set the same amplification of the electrical signal on all channels of the electrocardiograph. For this purpose, each electrocardiograph has the ability to supply a standard calibration voltage (1 mV) to the galvanometer. Typically, the gain of each channel is selected so that a voltage of 1 mV causes a deflection of the galvanometer and recording system equal to 10 mm . To do this, in the position of the lead switch “0”, the gain of the electrocardiograph is adjusted and the calibration millivolt is recorded. If necessary, you can change the gain: reduce if the amplitude of the ECG waves is too large (1 mV = 5 mm) or increase if their amplitude is small (1 mV = 15 or 20 mm).

ECG recording

ECG recording is carried out during quiet breathing, as well as at the height of inspiration (in lead III). First, an ECG is recorded in standard leads (I, II, III), then in enhanced leads from the limbs (aVR, aVL and aVF) and chest (V 1 -V 6). At least 4 cardiac PQRST cycles are recorded in each lead. ECG is recorded, as a rule, at a paper speed of 50 mm·s -1. A lower speed (25 mm·s -1) is used when longer ECG recordings are required, for example, to diagnose rhythm disturbances.

Immediately after the end of the study, the patient’s last name, first name and patronymic, year of birth, date and time of the study are recorded on a paper tape.

Normal ECG

P wave

The P wave reflects the process of depolarization of the right and left atria. Normally, in the frontal plane, the average resulting vector of atrial depolarization (vector P) is located almost parallel to axis II of the standard lead and is projected onto the positive parts of the axes of leads II, aVF, I and III. Therefore, in these leads, a positive P wave is usually recorded, having a maximum amplitude in leads I and II.

In lead aVR, the P wave is always negative, since the P vector is projected onto the negative part of the axis of this lead. Since the axis of lead aVL is perpendicular to the direction of the average resulting vector P, its projection onto the axis of this lead is close to zero; in most cases, a biphasic or low-amplitude P wave is recorded on the ECG.

With a more vertical location of the heart in the chest (for example, in people with an asthenic physique), when the P vector is parallel to the axis of lead aVF (Fig. 1.7), the amplitude of the P wave increases in leads III and aVF and decreases in leads I and aVL. The P wave in aVL may even become negative.

Rice. 1.7. Formation of the P wave in the limb leads

On the contrary, with a more horizontal position of the heart in the chest (for example, in hypersthenics), the P vector is parallel to the I axis of the standard lead. In this case, the amplitude of the P wave increases in leads I and aVL. P aVL becomes positive and decreases in leads III and aVF. In these cases, the projection of vector P onto axis III of the standard lead is zero or even has a negative value. Therefore, the P wave in lead III can be biphasic or negative (more often with left atrial hypertrophy).

Thus, in a healthy person in leads I, II and aVF the P wave is always positive, in leads III and aVL it can be positive, biphasic or (rarely) negative, and in lead aVR the P wave is always negative.

In the horizontal plane, the average resulting vector P usually coincides with the direction of the axes of the chest leads V 4 -V 5 and is projected onto the positive parts of the axes of leads V 2 -V 6, as shown in Fig. 1.8. Therefore, in a healthy person, the P wave in leads V 2 -V 6 is always positive.

Rice. 1.8. Formation of the P wave in the precordial leads

The direction of the average vector P is almost always perpendicular to the axis of lead V 1, at the same time, the direction of the two moment depolarization vectors is different. The first initial moment vector of atrial excitation is oriented forward, towards the positive electrode of lead V 1, and the second final moment vector (smaller in magnitude) is directed back, towards negative pole leads V 1. Therefore, the P wave in V 1 is often biphasic (+-).

The first positive phase of the P wave in V 1, due to the excitation of the right and partially left atria, is greater than the second negative phase of the P wave in V 1, reflecting the relatively short period of final excitation of only the left atrium. Sometimes the second negative phase of the P wave in V 1 is weakly expressed and the P wave in V 1 is positive.

Thus, in a healthy person, a positive P wave is always recorded in chest leads V 2 -V 6, and in lead V 1 it can be biphasic or positive.

The amplitude of P waves normally does not exceed 1.5-2.5 mm, and the duration is 0.1 s.

Interval P‒ Q(R)

The P-Q(R) interval is measured from the beginning of the P wave to the beginning of the ventricular QRS complex (Q or R wave). It reflects the duration of AV conduction, that is, the time of excitation propagation through the atria, AV node, His bundle and its branches (Fig. 1.9). The P-Q(R) interval does not follow with the PQ(R) segment, which is measured from the end of the P wave to the beginning of Q or R

Rice. 1.9. P-Q(R) interval

The duration of the P-Q(R) interval ranges from 0.12 to 0.20 s and in a healthy person depends mainly on heart rate: the higher it is, the shorter the P-Q(R) interval.

Ventricular QRS complex T

The ventricular QRST complex reflects the complex process of propagation (QRS complex) and extinction (RS-T segment and T wave) of excitation throughout the ventricular myocardium. If the amplitude of the QRS complex waves is large enough and exceeds 5 mm , they are denoted by capital letters of the Latin alphabet Q, R, S, if small (less than 5 mm ) — lowercase letters q, r, s.

The R wave refers to any positive wave that is part of the QRS complex. If there are several such positive teeth, they are designated respectively as R, Rj, Rjj, etc. The negative wave of the QRS complex immediately preceding the R wave is designated Q (q), and the negative wave immediately following the R wave is S (s).

If only a negative deviation is recorded on the ECG, and the R wave is completely absent, the ventricular complex is designated as QS. The formation of individual waves of the QRS complex in different leads can be explained by the existence of three moment vectors of ventricular depolarization and their different projections on the axes of the ECG leads.

Q wave

In most ECG leads, the formation of the Q wave is caused by the initial moment vector of depolarization between the ventricular septum, lasting up to 0.03 s. Normally, the Q wave can be recorded in all standard and enhanced unipolar limb leads and in the chest leads V 4 -V 6. The amplitude of the normal Q wave in all leads except aVR does not exceed 1/4 the height of the R wave, and its duration is 0.03 s. In lead aVR in a healthy person, a deep and wide Q wave or even a QS complex may be recorded.

R wave

The R wave in all leads, with the exception of the right chest leads (V 1, V 2) and lead aVR, is caused by the projection on the lead axis of the second (middle) QRS moment vector, or conventionally the 0.04 s vector. The 0.04 s vector reflects the process of further propagation of excitation throughout the myocardium of the RV and LV. But, since the LV is a more powerful part of the heart, vector R is oriented to the left and down, that is, towards the LV. In Fig. Figure 1.10a shows that in the frontal plane, a vector of 0.04 s is projected onto the positive parts of the axes of leads I, II, III, aVL and aVF and onto the negative part of the lead axis aVR. Therefore, in all limb leads, with the exception of aVR, high R waves are formed, and with a normal anatomical position of the heart in the chest, the R wave in lead II has the maximum amplitude. In lead aVR, as mentioned above, a negative deviation always predominates - the S, Q or QS wave, caused by the projection of the 0.04 s vector onto the negative part of the axis of this lead.

With a vertical position of the heart in the chest, the R wave becomes maximum in leads aVF and II, and with a horizontal position of the heart - in standard lead I. In the horizontal plane, the vector of 0.04 s usually coincides with the direction of the axis of lead V 4. Therefore, the R wave in V 4 exceeds the R waves in the other chest leads in amplitude, as shown in Fig. 1.10b. Thus, in the left chest leads (V 4 -V 6), the R wave is formed as a result of the projection of the main torque vector of 0.04 s onto the positive parts of these leads.

Rice. 1.10. Formation of the R wave in the limb leads

The axes of the right chest leads (V 1, V 2) are usually perpendicular to the direction of the main torque vector of 0.04 s, so the latter has almost no effect on these leads. The R wave in leads V 1 and V 2, as shown above, is formed as a result of the projection onto the axis of these leads of the initial momentary choice (0.02 s) and reflects the spread of excitation along the interventricular septum.

Normally, the amplitude of the R wave gradually increases from lead V 1 to lead V 4, and then again decreases slightly in leads V 5 and V 6. The height of the R wave in the limb leads usually does not exceed 20 mm, and in the chest leads - 25 mm. Sometimes in healthy people, the r wave in V 1 is so weakly expressed that the ventricular complex in lead V 1 takes on the appearance of QS.

For comparative characteristics The time of propagation of the excitation wave from the endocardium to the epicardium of the RV and LV is usually determined by the so-called interval of internal deviation (intrinsical defl ection) in the right (V 1, V 2) and left (V 5, V 6) chest leads, respectively. It is measured from the beginning of the ventricular complex (Q or R wave) to the apex of the R wave in the corresponding lead, as shown in Fig. 1.11.

Rice. 1.11. Measuring the internal deviation interval

In the presence of split R waves (complexes of the RSRj or qRsrj type), the interval is measured from the beginning of the QRS complex to the top of the last R wave.

Normally, the interval of internal deviation in the right chest lead (V 1) does not exceed 0.03 s, and in the left chest lead V 6 -0.05 s.

S wave

In a healthy person, the amplitude of the S wave in different ECG leads fluctuates within wide limits, not exceeding 20 mm.

With a normal position of the heart in the chest in the limb leads, the S amplitude is small, except in lead aVR. In the chest leads, the S wave gradually decreases from V 1, V 2 to V 4, and in leads V 5, V 6 it has a small amplitude or is absent.

The equality of the R and S waves in the chest leads (transition zone) is usually recorded in lead V 3 or (less often) between V 2 and V 3 or V 3 and V 4.

The maximum duration of the ventricular complex does not exceed 0.10 s (usually 0.07-0.09 s).

The amplitude and ratio of positive (R) and negative waves (Q and S) in various leads largely depend on the rotation of the heart axis around its three axes: anteroposterior, longitudinal and sagittal.

Segment RS—T

The RS-T segment is a segment from the end of the QRS complex (the end of the R or S wave) to the beginning of the T wave. It corresponds to the period of full coverage of both ventricles by excitation, when the potential difference between different parts of the heart muscle is absent or small. Therefore, normally in standard and enhanced unipolar limb leads, the electrodes of which are located at a great distance from the heart, the RS-T segment is located on the isoline and its displacement up or down does not exceed 0.5 mm . In the chest leads (V 1 -V 3), even in a healthy person, a slight shift of the RS-T segment upwards from the isoline is often noted (no more than 2 mm).

In the left chest leads, the RS-T segment is more often recorded at the level of the isoline - the same as in standard leads (± 0.5 mm).

The transition point of the QRS complex to the RS-T segment is designated as j. Deviations of point j from the isoline are often used to quantitatively characterize the displacement of the RS-T segment.

T wave

The T wave reflects the process of rapid terminal repolarization of the ventricular myocardium (phase 3 of transmembrane PD). Normally, the total resulting vector of ventricular repolarization (vector T) usually has almost the same direction as the average vector of ventricular depolarization (0.04 s). Therefore, in most leads where a high R wave is recorded, the T wave has a positive value, projecting onto the positive parts of the axes of electrocardiographic leads (Fig. 1.12). In this case, the largest R wave corresponds to the largest T wave in amplitude, and vice versa.

Rice. 1.12. Formation of the T wave in the limb leads

In lead aVR, the T wave is always negative.

In the normal position of the heart in the chest, the direction of the T vector is sometimes perpendicular to axis III of the standard lead, and therefore a biphasic (+/-) or low-amplitude (smoothed) T wave in III can sometimes be recorded in this lead.

With a horizontal position of the heart, the T vector can be projected even onto the negative part of the axis of lead III and a negative T wave in III is recorded on the ECG. However, in lead aVF the T wave remains positive.

When the heart is located vertically in the chest, the T vector is projected onto the negative part of the aVL lead axis and a negative T wave in aVL is recorded on the ECG.

In the precordial leads, the T wave usually has its maximum amplitude in lead V4 or V3. The height of the T wave in the precordial leads usually increases from V 1 to V 4, and then decreases slightly in V 5 -V 6. In lead V 1, the T wave can be biphasic or even negative. Normally, T in V 6 is always greater than T in V 1.

The amplitude of the T wave in the limb leads in a healthy person does not exceed 5-6 mm, and in the chest leads - 15-17 mm. The duration of the T wave ranges from 0.16 to 0.24 s.

Q-T interval (QRST)

The Q-T interval (QRST) is measured from the beginning of the QRS complex (Q or R wave) to the end of the T wave. The Q-T interval (QRST) is called ventricular electrical systole. During electrical systole, all parts of the ventricles of the heart are excited. The duration of the QT interval primarily depends on the heart rate. The higher the rhythm frequency, the shorter the proper QT interval. Normal duration the Q-T interval is determined by the formula Q-T=K√R-R, where K is a coefficient equal to 0.37 for men and 0.40 for women; R-R is the duration of one cardiac cycle. Since the duration of the Q-T interval depends on the heart rate (lengthening as it slows down), for assessment it must be adjusted relative to the heart rate, therefore the Bazett formula is used for calculations: QТс = Q-T/√R-R.

Sometimes on the ECG, especially in the right precordial leads, immediately after the T wave, a small positive U wave is recorded, the origin of which is still unknown. There are suggestions that the U wave corresponds to a period of short-term increase in the excitability of the ventricular myocardium (exaltation phase), which occurs after the end of the LV electrical systole.

O.S. Sychev, N.K. Furkalo, T.V. Getman, S.I. Deyak "Fundamentals of electrocardiography"

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

What is ECG

Electrocardiography is a method of examining the electrophysiological functioning of the heart muscle. When diagnosing, a special device is used that records the slightest changes in its activity, and then displays them in graphic representation. Conduction, contraction frequency, hypertrophic changes, scarring and other changes in myocardial function can all be detected using an ECG.

During the diagnostic process, special electrodes record the contraction of the heart, namely the bioelectric potentials that arise. Electrical excitation covers different departments cardiac muscle at different times, therefore, a potential difference is recorded between the non-excited and excited sections. It is this data that is captured by electrodes placed on the body.

The video below will tell you about the indicators and features of the ECG in a simple and accessible form:

Who is it prescribed to?

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

1. Scheduled examination. Necessary for different categories persons, including teenagers, pregnant women, athletes, before surgical interventions or in the presence of any diseases (lung and gastrointestinal diseases, thyroid gland, diabetes).
2. For the diagnosis of secondary or primary diseases as a preventive measure or to identify possible complications.
3. Carrying out monitoring during the treatment period or after its completion if any diseases are detected.

An electrocardiogram is performed if there are indications for using this diagnostic method. It is also required when passing medical examination drivers, draft commission, when sent for treatment to a sanatorium. For pregnant women, the test is done at least 2 times: at the time of registration and before giving birth.

Why do it?

Diagnostics helps to determine the early stages of cardiac dysfunction, as well as the prerequisites for the development of serious pathologies. An electrocardiogram is capable of detecting the slightest changes occurring in the heart: thickening of its walls, changes in the normal dimensions inside its cavities, and its location, size, etc. This greatly affects the accuracy of the prognosis and the selection of appropriate treatment, not to mention the importance of timely prevention.

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

Types of diagnostics

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

• At rest. Standard method, used in most cases. If the diagnosis at this stage does not provide accurate data, they resort to other types of ECG.
• With load. This type of examination involves the use of physical (bicycle ergometry, treadmill test) or medicinal load. This also includes inserting a sensor through the esophagus to electrically stimulate the heart. This technique makes it possible to identify diseases that are not detected at rest.
• . A small device is installed in the chest area, which monitors cardiac activity throughout the day. Heart function is recorded during everyday activities, which is one of the advantages of the study.
• Transesophageal ECG performed with low information content of electrocardiography through the chest wall.

Indications for testing

You should contact the clinic for an examination if:

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

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

Contraindications for

Special contraindications that could cause refusal conducting an ECG, No. Difficulties in carrying out the procedure are observed only in certain categories of citizens (high degree of hair growth, obesity, chest injuries). The data is distorted in persons with an installed pacemaker.

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

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

If a transesophageal ECG is necessary, then contraindications are, accordingly, pathologies of the esophagus.

Safety of the procedure

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

How to prepare for a cardiac ECG

No special preparation is required before the test.

• You can take food and water without restricting yourself in front of it.
• But you should give up energy drinks, including coffee.
• It is also better to leave cigarettes and alcohol aside before the examination so as not to distort the data.

How does the session work?

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

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

Throughout the entire period of the study, which usually lasts no longer than 10 minutes, the patient does not feel discomfort, everything passes in a calm state and without discomfort. After this, all that remains is to wait for the received data to be decrypted. This procedure is also performed by a doctor, and then he transmits the results to the treating doctor’s office or directly into the hands of the visitor. If pathologies requiring immediate treatment are identified, he may be sent to a hospital, but if there are none, the patient is sent home.

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

Results and their interpretation

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

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

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

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

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

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

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

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

When assessing the T wave, you need to pay attention to its polarity, shape, and amplitude.
Then it is measured QT interval and is compared with the proper value determined using a special table.

Normal ECG

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

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

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

Heart rhythm disturbance

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

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

Arrhythmias are divided into the following main groups.

Based on a violation of impulse formation:

1. violations of the automatism of the sinus node (sinus tachycardia, bradycardia, arrhythmia);
2. ectopic (non-sinus) rhythms caused by the predominance of automatism of non-sinus centers (escaping, accelerated ectopic rhythms, migration of the pacemaker);
3. ectopic rhythms caused by the re-entry mechanism (paroxysmal tachycardia, fibrillation and flutter of the atria and ventricles).

Based on conductivity disorders:

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

Electrocardiographic signs of these disorders are varied and complex.

Hypertrophy of the heart

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

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

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

Myocardial blood supply disorders

In some cases, an ECG can be used to assess the blood supply to the heart muscle. Especially great value This method was acquired in the diagnosis of myocardial infarction: an acute disturbance of blood flow in the coronary vessels, accompanied by necrosis (necrosis) of a section of the heart muscle, followed by the formation of scar changes in this area.

The ECG during the course of myocardial infarction has a natural dynamics, which makes it possible to monitor the development of the process, determine its prevalence and identify complications. Using an ECG, the localization of myocardial infarction is also determined.

Other ECG changes

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

Video course “Everyone can do an ECG”, lesson 1 - “The conduction system of the heart, electrodes”

Video course “Everyone can do an ECG”, lesson 2 - “Tines, segments, intervals”

Video course “Everyone Can Do an ECG,” Lesson 3 - “ECG Analysis Algorithm”

A cardiac cardiogram displays the activity of the biopotential of the heart muscle. With its help, you can identify abnormalities in the functioning of the organ and prescribe appropriate treatment in a timely manner. You can decipher the heart cardiogram yourself by familiarizing yourself with its designations and their meanings.

Using a cardiogram, you can determine the rhythm and frequency of heart contractions, the functioning of the conduction system, and whether any part of the organ is affected oxygen starvation, identify aneurysm and previous heart attacks. The teeth on the electrocardiogram have the following meanings:

• P is an indicator of the passage of an electrical signal through the atria. Normally, the value is up to 2.5 mm in height.
• Q – indicates status upper lobe hearts. Often instruments do not register it, or it is negative - this is the norm. If the indicator is strongly expressed, this indicates the presence of cardiac problems.
• R - reflects the activity of the outer part of the ventricles and the lower part of the heart. The interval norm is 0.03 s. If the value does not correspond to the specified value, the presence of myocardial hypertrophy is likely.
• S – reflects the completion of excitation processes in the ventricles of the heart. The normal value is up to 20 mm.
• The PR interval shows the speed with which excitation spreads from the atria to the ventricles. The natural indicator is 0.12-0.2 s.
• T - helps to diagnose ischemic diseases. The norm is from 0.16 to 0.24 s., positive. Indicates restoration of the biopotential of the heart muscle.
• TP – intermediate interval between contractions. Normal duration is 0.4 s.
• ST – indicates the activity of both ventricles. Permissible deviations: 0.5-1 mm down or up.
• QRS – reflects the work of the ventricles.

R-R interval shows the rhythm of contraction of the heart muscle. The duration of the intervals should be the same, maximum difference is 10%. Other indicators indicate cardiac arrhythmias.

Terminology of the electrocardiogram conclusion:

• Normal heart rate (heart rate) is 60-90 beats per minute. Deviations from the norm, in the absence of other signs, do not indicate the presence of pathology and may be a consequence of natural causes, for example, anxiety.
• The EOS (electrical axis of the heart) determines the location of the organ in the chest. It can be located normally, vertically, horizontally, with a deviation to the right or left. If the heart deviates to the left or is horizontal, hypertension can be assumed. The heart may deviate to the right when chronic diseases lungs. The vertical location of the heart is found in asthenic people, while in obese people it is horizontal.
• A regular sinus rhythm indicates normal heart function. A non-sinus rhythm indicates cardiac pathology.
• Sinus arrhythmia, not related to breathing, is a sign of disease.

These are the main indicators, list possible deviations in the work of the heart muscle is quite large.

For an ECG in a child aged 1 to 12 months, heart rate fluctuations are considered normal; the standard is 137 beats per minute. The location of the EOS is vertical. For children aged 1 to 6 years, the heart rate is 96-127 beats per minute. Characterized by normal, vertical and horizontal position. Children from 7 to 15 years old have a heart rate of 66-89 beats per minute and a normal or vertical position of the EOS.