Electrocardiography is a method of graphic recording of the potential difference in the electric field of the heart that occurs during its activity. Registration is carried out using an apparatus - an electrocardiograph. It consists of an amplifier capable of capturing very low voltage currents; a galvanometer that measures the magnitude of the voltage; power systems; recording device; electrodes and wires connecting the patient to the device. The recorded waveform is called an electrocardiogram (ECG). Registration of the potential difference of the electric field of the heart from two points on the surface of the body is called abduction. As a rule, an ECG is recorded in twelve leads: three - bipolar (three standard leads) and nine - unipolar (three unipolar enhanced leads from the limbs and 6 unipolar chest leads). With bipolar leads, two electrodes are connected to the electrocardiograph, with unipolar leads, one electrode (indifferent) is combined, and the second (different, active) is placed at a selected point on the body. If the active electrode is placed on a limb, the lead is said to be unipolar, reinforced from the limb; if this electrode is placed on the chest - unipolar chest lead.
To register an ECG in standard leads (I, II and III), cloth napkins moistened with saline are placed on the limbs, on which metal plates of electrodes are placed. One electrode with a red wire and one relief ring is placed on the right, the second - with a yellow wire and two relief rings - on the left forearm and the third - with a green wire and three relief rings - on the left shin. To register the leads, two electrodes are connected in turn to the electrocardiograph. To record lead I, the electrodes of the right and left hands are connected, lead II - the electrodes of the right hand and left leg, lead III - the electrodes of the left hand and left foot. Switching leads is done by turning the knob. In addition to the standard ones, unipolar reinforced leads are removed from the limbs. If the active electrode is located on the right hand, the lead is designated as aVR or uP, if on the left hand - aVL or uL, and if on the left leg - aVF or yN.
Rice. 1. The location of the electrodes during registration of the anterior chest leads (indicated by the numbers corresponding to their serial numbers). Vertical stripes crossing the numbers correspond to the anatomical lines: 1 - right sternal; 2 - left sternal; 3 - left parasternal; 4-left midclavicular; 5-left anterior axillary; 6 - left middle axillary.
When registering unipolar chest leads, the active electrode is placed on the chest. ECG is recorded in the following six positions of the electrode: 1) at the right edge of the sternum in the IV intercostal space; 2) at the left edge of the sternum in the IV intercostal space; 3) along the left parasternal line between the IV and V intercostal spaces; 4) along the midclavicular line in the V intercostal space; 5) along the anterior axillary line in the 5th intercostal space and 6) along the midaxillary line in the 5th intercostal space (Fig. 1). Unipolar chest leads are denoted by the Latin letter V or Russian - GO. Less often, bipolar chest leads are recorded, in which one electrode was located on the chest, and the other on the right arm or left leg. If the second electrode was located on the right hand, the chest leads were designated in Latin letters CR or in Russian - ГП; when the second electrode was placed on the left leg, the chest leads were designated in Latin letters CF or in Russian - GN.
The ECG of healthy people differs in variability. It depends on age, physique, etc. However, normally, certain teeth and intervals can always be distinguished on it, reflecting the sequence of excitation of the heart muscle (Fig. 2). According to the available time stamp (on photographic paper, the distance between two vertical stripes is 0.05 seconds, on graph paper at a speed of 50 mm / s, 1 mm is 0.02 seconds, at a speed of 25 mm / s - 0.04 seconds. ) you can calculate the duration of the teeth and intervals (segments) of the ECG. The height of the teeth is compared with the standard mark (when a pulse of 1 mV is applied to the device, the recorded line should deviate from the initial position by 1 cm). Myocardial excitation begins with the atria, and an atrial P wave appears on the ECG. Normally, it is small: 1-2 mm high and 0.08-0.1 sec long. The distance from the beginning of the P wave to the Q wave (P-Q interval) corresponds to the propagation time of excitation from the atria to the ventricles and is equal to 0.12-0.2 sec. During excitation of the ventricles, the QRS complex is recorded, and the magnitude of its teeth in different leads is expressed differently: the duration of the QRS complex is 0.06-0.1 sec. The distance from the S wave to the beginning of the T wave is the S-T segment, normally located at the same level with the P-Q interval and its displacement should not exceed 1 mm. With the extinction of excitation in the ventricles, a T wave is recorded. The interval from the beginning of the Q wave to the end of the T wave reflects the process of excitation of the ventricles (electrical systole). Its duration depends on the heart rate: with an increase in the rhythm, it shortens, with a slowdown, it lengthens (on average, it is 0.24-0.55 seconds). The heart rate is easy to calculate from the ECG, knowing how long one cardiac cycle lasts (the distance between two R waves) and how many such cycles are contained in a minute. The T-R interval corresponds to the diastole of the heart, the device at this time records a straight (so-called isoelectric) line. Sometimes, after the T wave, a U wave is recorded, the origin of which is not entirely clear.
Rice. 2. Electrocardiogram of a healthy person.
In pathology, the size of the teeth, their duration and direction, as well as the duration and location of ECG intervals (segments), can vary significantly, which gives reason to use electrocardiography in the diagnosis of many heart diseases. With the help of electrocardiography, various cardiac arrhythmias are diagnosed (see), inflammatory and degenerative lesions of the myocardium are reflected on the ECG. Electrocardiography plays a particularly important role in the diagnosis of coronary insufficiency and myocardial infarction.
According to the ECG, you can determine not only the presence of a heart attack, but also find out which wall of the heart is affected. In recent years, to study the potential difference of the electric field of the heart, the method of teleelectrocardiography (radioelectrocardiography), based on the principle of wireless transmission of the electric field of the heart using a radio transmitter, has been used. This method allows you to register an ECG during physical activity, in motion (for athletes, pilots, astronauts).
Electrocardiography (Greek kardia - heart, grapho - write, write down) - a method of recording electrical phenomena that occur in the heart during its contraction.
The history of electrophysiology, and consequently, electrocardiography, begins with the experience of L. Galvani, who discovered in 1791 electrical phenomena in the muscles of animals. Matteucci (S. Matteucci, 1843) established the presence of electrical phenomena in the excised heart. Dubois-Reymond (E. Dubois-Reymond, 1848) proved that the excited part of both nerves and muscles is electronegative with respect to the resting part. Kelliker and Muller (A. Kolliker, N. Muller, 1855), applying a frog neuromuscular preparation consisting of the sciatic nerve connected to the gastrocnemius muscle to the contracting heart, received a double contraction during heart contraction: one at the beginning of systole and the other (non-constant ) at the beginning of diastole. Thus, the electromotive force (EMF) of a naked heart was recorded for the first time. Waller (A. D. Waller, 1887) was the first to register the EMF of the heart from the surface of the human body using a capillary electrometer. Waller believed that the human body is a conductor surrounding the source of EMF - the heart; different points of the human body have potentials of different magnitudes (Fig. 1). However, the recording of the EMF of the heart obtained by a capillary electrometer did not accurately reproduce its fluctuations.
Rice. 1. Scheme of the distribution of isopotential lines on the surface of the human body, due to the electromotive force of the heart. The numbers indicate the magnitude of the potentials.
An accurate record of the EMF of the heart from the surface of the human body - an electrocardiogram (ECG) - was made by Einthoven (W. Einthoven, 1903) using a string galvanometer built on the principle of devices for receiving transatlantic telegrams.
According to modern concepts, excitable tissue cells, in particular myocardial cells, are covered with a semi-permeable membrane (membrane), permeable to potassium ions and impermeable to anions. Positively charged potassium ions, which are in excess in cells compared to their environment, are retained on the outer surface of the membrane by negatively charged anions located on its inner surface, which is impermeable to them.
Thus, a double electric layer appears on the shell of a living cell - the shell is polarized, and its outer surface is positively charged in relation to the inner content, which is negatively charged.
This transverse potential difference is the resting potential. If microelectrodes are applied to the outer and inner sides of the polarized membrane, then a current appears in the outer circuit. Recording the resulting potential difference gives a monophasic curve. When excitation occurs, the membrane of the excited area loses its semi-impermeability, depolarizes, and its surface becomes electronegative. Registration by two microelectrodes of the potentials of the outer and inner shells of the depolarized membrane also gives a monophasic curve.
Due to the potential difference between the surface of the excited depolarized area and the surface of the polarized, at rest, an action current arises - an action potential. When excitation covers the entire muscle fiber, its surface becomes electronegative. Termination of excitation causes a wave of repolarization, and the resting potential of the muscle fiber is restored (Fig. 2).
Rice. 2. Schematic representation of the polarization, depolarization and repolarization of the cell.
If the cell is at rest (1), then electrostatic equilibrium is observed on both sides of the cell membrane, consisting in the fact that the surface of the cell is electropositive (+) with respect to its inner side (-).
The excitation wave (2) instantly breaks this balance, and the surface of the cell becomes electronegative with respect to its inner side; this phenomenon is called depolarization or, more correctly, inversion polarization. After the excitation has passed through the entire muscle fiber, it becomes completely depolarized (3); its entire surface has the same negative potential. This new equilibrium does not last long, because the wave of excitation is followed by a wave of repolarization (4), which restores the polarization of the resting state (5).
The process of excitation in a normal human heart - depolarization - proceeds as follows. Arising in the sinus node located in the right atrium, the excitation wave propagates at a speed of 800-1000 mm per 1 sec. beam-like along the muscle bundles, first of the right and then the left atrium. The duration of excitation coverage of both atria is 0.08-0.11 sec.
First 0.02 - 0.03 sec. only the right atrium is excited, then 0.04 - 0.06 sec - both atria and the last 0.02 - 0.03 sec - only the left atrium.
Upon reaching the atrioventricular node, the spread of excitation slows down. Then, with a large and gradually increasing speed (from 1400 to 4000 mm in 1 sec.), It is directed along the bundle of His, its legs, their branches and ramifications, and reaches the final endings of the conductor system. Having reached the contractile myocardium, excitation with a significantly reduced speed (300-400 mm per 1 sec.) Spreads through both ventricles. Since the peripheral branches of the conduction system are scattered mainly under the endocardium, the inner surface of the heart muscle comes into excitation first of all. The further course of excitation of the ventricles is not associated with the anatomical location of the muscle fibers, but is directed from the inner surface of the heart to the outer. The time of occurrence of excitation in the muscle bundles located on the surface of the heart (subepicardial) is determined by two factors: the time of excitation of the branches of the conduction system closest to these bundles and the thickness of the muscle layer that separates the subepicardial muscle bundles from the peripheral branches of the conduction system.
First of all, the interventricular septum and the right papillary muscle are excited. In the right ventricle, excitation first covers the surface of its central part, since the muscular wall in this place is thin and its muscle layers are in close contact with the peripheral branches of the right leg of the conduction system. In the left ventricle, the apex is the first to be excited, since the wall separating it from the peripheral branches of the left leg is thin. For various points on the surface of the right and left ventricles of a normal heart, the excitation period begins at a strictly defined time, and most of the fibers on the surface of the thin-walled right ventricle and only a small number of fibers on the surface of the left ventricle come into excitation first of all due to their proximity to the peripheral branches of the conduction system (Fig. .3).
Rice. 3. Schematic representation of the normal excitation of the interventricular septum and the outer walls of the ventricles (according to Sodi-Pallares et al.). Excitation of the ventricles begins on the left side of the septum in its middle part (0.00-0.01 sec.) and then can reach the base of the right papillary muscle (0.02 sec.). After that, the subendocardial muscle layers of the outer wall of the left (0.03 sec.) and right (0.04 sec.) ventricles are excited. The basal parts of the outer walls of the ventricles are excited last (0.05-0.09 sec.).
The process of cessation of excitation of the muscle fibers of the heart - repolarization - cannot be considered fully understood. The process of atrial repolarization coincides for the most part with the process of depolarization of the ventricles and partly with the process of their repolarization.
The process of ventricular repolarization is much slower and in a slightly different sequence than the process of depolarization. This is explained by the fact that the duration of excitation of muscle bundles of the surface layers of the myocardium is less than the duration of excitation of subendocardial fibers and papillary muscles. Recording the process of depolarization and repolarization of the atria and ventricles from the surface of the human body and gives a characteristic curve - ECG, reflecting the electrical systole of the heart.
The recording of the EMF of the heart is currently being done by slightly different methods than those recorded by Einthoven. Einthoven recorded the current generated by connecting two points on the surface of the human body. Modern devices - electrocardiographs - directly record the voltage caused by the electromotive force of the heart.
The voltage caused by the heart, equal to 1-2 mV, is amplified by radio tubes, semiconductors or a cathode ray tube up to 3-6 V, depending on the amplifier and recording device.
The sensitivity of the measuring system is set in such a way that a potential difference of 1 mV gives a deviation of 1 cm. The recording is made on photographic paper or film or directly on paper (ink writing, thermal recording, inkjet recording). The most accurate results are recorded on photographic paper or film and inkjet recording.
To explain the peculiar form of the ECG, various theories of its genesis have been proposed.
A.F. Samoilov considered the ECG as the result of the interaction of two monophasic curves.
Given that when two microelectrodes register the outer and inner surfaces of the membrane in states of rest, excitation and damage, a monophasic curve is obtained, M. T. Udelnov believes that the monophasic curve reflects the main form of myocardial bioelectric activity. The algebraic sum of the two monophasic curves gives the ECG.
Pathological ECG changes are due to shifts in monophasic curves. This theory of ECG genesis is called differential.
The outer surface of the cell membrane in the period of excitation can be represented schematically as consisting of two poles: negative and positive.
Directly before the excitation wave, in any place of its propagation, the cell surface is electropositive (polarization state at rest), and immediately after the excitation wave, the cell surface is electronegative (depolarization state; Fig. 4). These electric charges of opposite signs, grouped in pairs on one and the other side of each place covered by the excitation wave, form electric dipoles (a). Repolarization also creates an incalculable number of dipoles, but unlike the above dipoles, the negative pole is in front and the positive pole is behind in relation to the direction of wave propagation (b). If depolarization or repolarization is completed, the surface of all cells has the same potential (negative or positive); dipoles are completely absent (see Fig. 2, 3 and 5).
Rice. 4. Schematic representation of electrical dipoles during depolarization (a) and repolarization (b), arising from both sides of the excitation wave and the repolarization wave as a result of a change in the electrical potential on the surface of myocardial fibers.
Rice. 5. Scheme of an equilateral triangle according to Einthoven, Far and Warth.
A muscle fiber is a small bipolar generator producing a small (elementary) emf - an elementary dipole.
At each moment of the systole of the heart, depolarization and repolarization of a huge number of myocardial fibers located in different parts of the heart occur. The sum of the formed elementary dipoles creates the corresponding value of the EMF of the heart at each moment of systole. Thus, the heart represents, as it were, one total dipole, which changes its magnitude and direction during the cardiac cycle, but does not change the location of its center. The potential at different points on the surface of the human body has a different value depending on the location of the total dipole. The sign of the potential depends on which side of the line perpendicular to the axis of the dipole and drawn through its center, this point is located: on the side of the positive pole, the potential has a + sign, and on the opposite side - a - sign.
Most of the time of excitation of the heart, the surface of the right half of the trunk, right arm, head and neck has a negative potential, and the surface of the left half of the trunk, both legs and left arm has a positive potential (Fig. 1). This is a schematic explanation of the genesis of the ECG according to the dipole theory.
EMF of the heart during the electrical systole changes not only its magnitude, but also its direction; therefore, it is a vector quantity. The vector is depicted as a straight line segment of a certain length, the size of which, with certain data of the recording apparatus, indicates the absolute value of the vector.
The arrow at the end of the vector indicates the direction of the EMF of the heart.
The emf vectors of individual heart fibers that have arisen simultaneously are summarized according to the rule of vector addition.
The total (integral) vector of two vectors located in parallel and directed in the same direction is equal in absolute value to the sum of its constituent vectors and is directed in the same direction.
The total vector of two vectors of the same size, located in parallel and directed in opposite directions, is equal to 0. The total vector of two vectors directed at an angle to each other is equal to the diagonal of the parallelogram built from its constituent vectors. If both vectors form an acute angle, then their total vector is directed towards its component vectors and is greater than any of them. If both vectors form an obtuse angle and, therefore, are directed in opposite directions, then their total vector is directed towards the largest vector and is shorter than it. Vector analysis of the ECG consists in determining the spatial direction and magnitude of the total EMF of the heart at any moment of its excitation by the ECG teeth.
One of the leading causes of death among the population worldwide is cardiovascular disease. Over the past decades, this figure has declined significantly due to the emergence of more modern methods of examination, treatment, and, of course, new drugs.
Electrocardiography (ECG) is a method of recording the electrical activity of the heart, one of the first research methods, which for a long time remained practically the only one in this field of medicine. About a century ago, in 1924, Willem Einthoven received the Nobel Prize in Medicine, he designed the apparatus with which the ECG was recorded, named its teeth and determined the electrocardiographic signs of certain heart diseases.
Many research methods with the advent of more modern developments are losing their relevance, but this does not apply to electrocardiography. Even with the advent of imaging techniques (, CT, etc.), ECG for decades continues to be the most common, very informative, and in some places the only available method for examining the heart. Moreover, over the century of its existence, neither the device itself nor the method of its use has changed significantly.
Indications and contraindications
An ECG may be prescribed to a person for the purpose of a preventive examination, as well as if any heart disease is suspected.Electrocardiography is a unique examination method that helps to make a diagnosis or becomes the starting point for drawing up a plan for further examination of the patient. In any case, the diagnosis and treatment of any heart disease begins with an ECG.
ECG is an absolutely safe and painless method of examination for people of all ages; there are no contraindications to conventional electrocardiography. The study takes only a few minutes and does not require any special preparation.
But there are so many indications for electrocardiography that it is simply impossible to list them all. The main ones are the following:
- general examination during medical examination or medical commission;
- assessment of the state of the heart in various diseases (atherosclerosis, lung disease, etc.);
- differential diagnosis for retrosternal pain and (often have a non-cardiac cause);
- suspicion of, as well as control of the course of this disease;
- diagnosis of cardiac arrhythmias (24-hour Holter ECG monitoring);
- violation of electrolyte metabolism (hyper- or hypokalemia, etc.);
- drug overdose (for example, cardiac glycosides or antiarrhythmic drugs);
- diagnosis of non-cardiac diseases (pulmonary embolism), etc.
The main advantage of the ECG is that the study can be performed outside the hospital, many ambulances are equipped with electrocardiographs. This makes it possible for a doctor at home in a patient to detect myocardial infarction at its very beginning, when damage to the heart muscle is just beginning and is partially reversible. After all, treatment in such cases begins even during the transportation of the patient to the hospital.
Even in cases where the ambulance is not equipped with this device and the ambulance doctor does not have the opportunity to perform a study at the prehospital stage, the first diagnostic method in the emergency room of a medical institution will be an ECG.
Interpretation of the ECG in adults
In most cases, cardiologists, therapists, emergency doctors work with electrocardiograms, but a functional diagnostics doctor is a specialist in this field. Deciphering an ECG is not an easy task, which is beyond the power of a person who does not have the appropriate qualifications.
Usually, five waves can be distinguished on the ECG of a healthy person, recorded in a certain sequence: P, Q, R, S and T, sometimes a U wave is recorded (its nature is not known for sure today). Each of them reflects the electrical activity of the myocardium of different parts of the heart.
When registering an ECG, several complexes are usually recorded, corresponding to contractions of the heart. In a healthy person, all the teeth in these complexes are located at the same distance. The difference in the intervals between the complexes indicates .
In this case, in order to accurately establish the form of arrhythmia, Holter monitoring of the ECG may be necessary. Using a special small portable device, the cardiogram is recorded continuously for 1-7 days, after which the resulting record is processed using a computer program.
- The first P wave reflects the process of depolarization (excitation coverage) of the atria. According to its width, amplitude and shape, the doctor may suspect hypertrophy of these chambers of the heart, a violation of the conduction of an impulse through them, suggest that the patient has organ defects and other pathologies.
- The QRS complex reflects the process of excitation coverage of the ventricles of the heart. Deformation of the shape of the complex, a sharp decrease or increase in its amplitude, the disappearance of one of the teeth can indicate a variety of diseases: myocardial infarction (with the help of ECG it is possible to establish its localization and prescription), scars, conduction disorders (blockade of the bundle legs), etc.
- The last T wave is determined by ventricular repolarization (relatively speaking, relaxation), the deformation of this element may indicate electrolyte disturbances, ischemic changes, and other pathologies of the heart.
The sections of the ECG connecting the various teeth are called "segments". Normally, they lie on the isoline, or their deviation is not significant. Between the teeth there are intervals (for example, PQ or QT), which reflect the time of passage of an electrical impulse through the heart, in a healthy person they have a certain duration. Lengthening or shortening of these intervals is also a significant diagnostic feature. Only a qualified doctor can see and evaluate all changes on the ECG.
In deciphering an ECG, every millimeter is important, sometimes even half a millimeter is decisive in choosing a treatment strategy. Very often, an experienced doctor can make an accurate diagnosis using an electrocardiogram without using additional research methods, and in some cases its information content exceeds the data of other types of research. In fact, this is a screening method of examination in cardiology, which allows to detect or at least suspect heart disease in the early stages. That is why the electrocardiogram will remain one of the most popular diagnostic methods in medicine for many years to come.
Which doctor to contact
For a referral to an ECG, you need to contact a general practitioner or cardiologist. The analysis of the cardiogram and the conclusion on it is given by the doctor of functional diagnostics. The ECG report itself is not a diagnosis and should be considered by the clinician in conjunction with other patient data.
Basics of electrocardiography in educational video:
Video course "ECG for everyone", lesson 1:
Video course "ECG for everyone", lesson 2.
An electrocardiogram (ECG) is an instrumental diagnostic method that determines pathological processes in the heart by recording cardiac electrical impulses. A graphical representation of the activity of the cardiac muscles under the influence of electrical impulses enables the cardiologist to detect the presence or development of cardiac pathologies in time.
ECG decoding indicators help to determine with great certainty:
- Frequency and rhythm of cardiac contraction;
- Timely diagnose acute or chronic processes in the heart muscle;
- Disorders of the conducting system of the heart and its independent rhythmic contractions;
- See hypertrophic changes in its departments;
- To reveal violations in the water-electrolyte balance and non-cardiac pathologies (cor pulmonale) throughout the body.
The need for an electrocardiographic examination is due to the manifestation of certain symptoms:
- the presence of synchronous or periodic murmurs in the heart;
- syncopal signs (fainting, short-term loss of consciousness);
- attacks of convulsive seizures;
- paroxysmal arrhythmia;
- manifestations of coronary artery disease (ischemia) or infarct conditions;
- the appearance of pain in the heart, shortness of breath, sudden weakness, cyanosis of the skin in patients with cardiac diseases.
An ECG study is used to diagnose systemic diseases, monitor patients under anesthesia or before surgery. Before medical examination of patients who have crossed the 45-year milestone.
An ECG examination is mandatory for persons undergoing a medical commission (pilots, drivers, machinists, etc.) or associated with hazardous production.
The human body has a high electrical conductivity, which allows you to read the potential energy of the heart from its surface. Electrodes connected to various parts of the body help with this. In the process of excitation of the heart muscle by electrical impulses, the voltage difference fluctuates between certain points of abduction, which is recorded by electrodes located on the body - on the chest and limbs.
A certain movement and magnitude of tension during the period of systole and diastole (contraction and relaxation) of the heart muscle changes, the tension fluctuates, and this is fixed on a chart paper tape by a curved line - teeth, convexity and concavity. Signals are created and the tops of triangular teeth are formed by electrodes placed on the limbs (standard leads).
Six leads located on the chest display heart activity in a horizontal position - from V1 to V6.
On the limbs:
- Lead (I) - displays the voltage level in the intermediate circuit of the electrodes placed on the left and right wrists (I=LR+PR).
- (II) - fixes on the tape the electrical activity in the circuit - the ankle of the left leg + the wrist of the right hand).
- Lead (III) - characterizes the voltage in the circuit of the fixed electrodes of the wrist of the left hand and the ankle of the left leg (LR + LN).
If necessary, additional leads are installed, reinforced - "aVR", "aVF" and "aVL".
Deciphering the ECG diagram, photo
The general principles for deciphering the cardiogram of the heart are based on the indications of the elements of the cardiography curve on the chart tape.
The teeth and bulges in the diagram are indicated by capital letters of the Latin alphabet - “P”, “Q”, “R”, “S”, “T”
- The convexity (tooth or concavity) "P" displays the function of the atria (their excitation), and the entire complex of the upwardly directed wave - "QRS", the greatest spread of the impulse through the heart ventricles.
- The bulge "T" characterizes the restoration of the potential energy of the myocardium (the middle layer of the heart muscle).
- Particular attention when deciphering the ECG in adults is given to the distance (segment) between adjacent elevations - "P-Q" and "ST", displaying the delay in electrical impulses between the heart ventricles and the atrium, and the "TR" segment - relaxation of the heart muscle in the interval (diastole) .
- The intervals on the cardiographic line include both hills and segments. For example - "P-Q" or "Q-T".
Each element on the graphic image indicates certain processes occurring in the heart. It is by the indicators of these elements (length, height, width), location relative to the isoline, features, according to the various locations of the electrodes (leads) on the body, that the doctor can identify the affected areas of the myocardium, based on the indications of the dynamic aspects of the energy of the heart muscle.
Deciphering the ECG - the norm in adults, table
The analysis of the result of the ECG decoding is carried out by evaluating the data in a certain sequence:
- Determination of heart rate indicators. With the same interval between the "R" teeth, the indicators correspond to the norm.
- The rate of heart contraction is calculated. It is determined simply - the ECG recording time is distributed by the number of cells in the interval between the "R" teeth. With a good cardiogram of the heart, the frequency of contractions of the heart muscle should be within the limits not exceeding 90 beats / min. A healthy heart should have a sinus rhythm, it is determined mainly by the elevation of the "P", reflecting the excitation of the atria. For wave motion, this norm indicator is 0.25 mV with a duration of 100 ms.
- The norm of the size of the depth of the "Q" tooth should not be more than 0.25% of the fluctuations in the height of the "R" and the width of 30 ms.
- The fluctuation width "R" of the elevation, during normal heart function, can be displayed with a large range ranging from 0.5-2.5 mV. And the activation time of excitation over the zone of the right heart chamber - V1-V2 is 30 ms. Above the zone of the left chamber - V5 and V6, it corresponds to 50 ms.
- According to the maximum length of the “S” wave, its dimensions in the norm with the largest lead cannot cross the threshold of 2.5 mV.
- The amplitude of the "T" fluctuations of the elevation, which reflects the restorative cellular processes of the initial potential in the myocardium, should be equal to ⅔ of the fluctuations of the "R" wave. The normal interval (width) "T" of elevation can vary (100-250) ms.
- The normal ventricular firing complex (QRS) width is 100 ms. It is measured by the interval of the beginning of the "Q" and the end of the "S" of the teeth. The normal amplitude of the duration of the "R" and "S" waves is determined by the electrical activity of the heart. The maximum duration should be within 2.6 mV.
| ECG decoding in adults is the norm in the table | |
| Indicator | Meaning |
| QRS | 0.06-0.1 s |
| P | 0.07-0.11 s |
| Q | 0.03 s |
| T | 0.12-0.28 s |
| PO | 0.12-0.2 s |
| heart rate | 60-80 beats minute |
Deciphering the ECG in children, the norm of indicators
The electrocardiogram in children, as practice shows, is not much different from the norm in adult patients. But certain physiological age characteristics can change some indicators. In particular, the heart rate. In young children, up to 3 years, they can be from 100 to 110 contractions / minute. But, already at puberty, it is equal to adult indicators (60-90).
Normally, when deciphering the ECG of the heart in children, the passage of electrical impulses through the parts of the heart (in the interval of elevations P, QRS, T) varies 120-200 ms.
The indicator of ventricular excitation (QRS) is determined by the width of the interval between the "Q" and "S" waves and should not cross the boundaries of 60-100 ms.
Particular attention is paid to the size (excitation activity) of the right ventricle (V1-V2). In children, this figure is higher than in the left ventricle. With age, the indicators return to normal.
- Quite often on the ECG in babies there are thickenings, splitting or notches on the "R" hills. Such a symptom in the cardiogram of adults indicates tachycardia and bradycardia, and in children it is quite a common condition.
But there are indications of a bad cardiogram hearts, which indicate the presence or progression of pathological processes in the heart. Much depends on the individual performance of the child. In addition, interruption or slowing of the normal heart rate is seen in children with chest pain, dizziness, frequent signs of blood pressure instability or impaired coordination.
If during an ECG examination of a child, an excess of the heart rate of more than 110 beats / min is diagnosed. - this is an alarming signal that speaks of the development of tachycardia.
It is necessary to immediately reduce physical activity in a child and protect him from nervous overexcitation. In children, these symptoms may be temporary, but if you do not take action, tachycardia will develop into a permanent problem.
Example ECG - Atrial tachycardia
An electrocardiogram is the most accessible, common way to make a diagnosis, even in conditions of emergency intervention in an ambulance situation.
Now every cardiologist in the mobile team has a portable and lightweight electrocardiograph capable of reading information by fixing the electrical impulses of the heart muscle - myocardium at the moment of contraction on the recorder.
Deciphering the ECG is within the power of every even a child, given the fact that the patient understands the basic canons of the heart. Those same teeth on the tape are the peak (response) of the heart to contraction. The more often they are, the faster the myocardial contraction occurs, the smaller they are, the slower the heartbeat occurs, and in fact the transmission of the nerve impulse. However, this is just a general idea.
To make a correct diagnosis, it is necessary to take into account the time intervals between contractions, the height of the peak value, the age of the patient, the presence or absence of aggravating factors, etc.
An ECG of the heart for diabetics who, in addition to diabetes, also have late cardiovascular complications, allows us to assess the severity of the disease and intervene in time in order to delay further progression of the disease, which can lead to serious consequences in the form of myocardial infarction, pulmonary embolism and etc.
If the pregnant woman had a bad electrocardiogram, then repeated studies are prescribed with possible daily monitoring.
However, it is worth considering the fact that the values on the tape in a pregnant woman will be somewhat different, since in the process of fetal growth, a natural displacement of the internal organs occurs, which are displaced by the expanding uterus. Their heart occupies a different position in the chest area, therefore, there is a shift in the electrical axis.
In addition, the longer the period, the greater the load experienced by the heart, which is forced to work harder in order to satisfy the needs of two full-fledged organisms.
However, you should not worry so much if the doctor, according to the results, reported the same tachycardia, since it is she who can most often be false, provoked either intentionally or out of ignorance by the patient himself. Therefore, it is extremely important to properly prepare for this study.
In order to correctly pass the analysis, it is necessary to understand that any excitement, excitement and experience will inevitably affect the results. Therefore, it is important to prepare yourself in advance.
Invalid
- Drinking alcohol or any other strong drinks (including energy drinks, etc.)
- Overeating (best taken on an empty stomach or a light snack before going out)
- Smoking
- Use of medicines that stimulate or suppress heart activity, or drinks (such as coffee)
- Physical activity
- Stress
It is not uncommon for a patient, being late to the treatment room at the appointed time, to become very worried or frantically rush to the cherished office, forgetting about everything in the world. As a result, his leaf was mottled with frequent sharp teeth, and the doctor, of course, recommended that his patient re-examine. However, in order not to create unnecessary problems, try to calm yourself as much as possible before entering the cardiology room. Moreover, nothing bad will happen to you there.
When the patient is invited, it is necessary to undress behind the screen to the waist (women take off their bra) and lie down on the couch. In some treatment rooms, depending on the alleged diagnosis, it is also required to free the body from below the torso to the underwear.
After that, the nurse applies a special gel to the abduction sites, to which he attaches electrodes, from which multi-colored wires are stretched to the reading machine.
Thanks to special electrodes, which the nurse places at certain points, the slightest cardiac impulse is captured, which is recorded by means of a recorder.
After each contraction, called depolarization, a tooth is displayed on the tape, and at the moment of transition to a calm state - repolarization, the recorder leaves a straight line.
Within a few minutes, the nurse will take a cardiogram.
The tape itself, as a rule, is not given to patients, but is transferred directly to a cardiologist who deciphers. With notes and transcripts, the tape is sent to the attending physician or transferred to the registry so that the patient can pick up the results himself.
But even if you pick up a cardiogram tape, you will hardly be able to understand what is depicted there. Therefore, we will try to slightly open the veil of secrecy so that you can at least a little bit appreciate the potential of your heart.
ECG interpretation
Even on a blank sheet of this type of functional diagnostics, there are some notes that help the doctor with decoding. The recorder, on the other hand, reflects the transmission of an impulse that passes through all parts of the heart over a certain period of time.
To understand these scribbles, it is necessary to know in what order and how exactly the impulse is transmitted.
The impulse, passing through different parts of the heart, is displayed on the tape in the form of a graph, which conditionally displays marks in the form of Latin letters: P, Q, R, S, T
Let's see what they mean.
P value
The electrical potential, going beyond the sinus node, transmits excitation primarily to the right atrium, in which the sinus node is located.
At this very moment, the reading device will record the change in the form of a peak of excitation of the right atrium. After the conduction system - the interatrial bundle of Bachmann passes into the left atrium. Its activity occurs at the moment when the right atrium is already fully covered by excitation.
On the tape, both of these processes appear as the total value of excitation of both right and left atria and are recorded as a P peak.
In other words, the P peak is a sinus excitation that travels along the conduction pathways from the right to the left atria.
Interval P - Q
Simultaneously with the excitation of the atria, the impulse that has gone beyond the sinus node passes along the lower branch of the Bachmann bundle and enters the atrioventricular junction, which is otherwise called atrioventricular.
This is where the natural delay occurs. Therefore, a straight line appears on the tape, which is called isoelectric.
In evaluating the interval, the time it takes for the impulse to pass through this connection and subsequent departments plays a role.
The count is in seconds.
Complex Q, R, S
After the impulse, passing along the conducting paths in the form of a bundle of His and Purkinje fibers, reaches the ventricles. This whole process is presented on the tape as a QRS complex.
The ventricles of the heart are always excited in a certain sequence, and the impulse travels this path in a certain amount of time, which also plays an important role.
Initially, the septum between the ventricles is covered by excitation. This takes about 0.03 sec. A Q wave appears on the chart, extending just below the main line.
After the impulse for 0.05. sec. reaches the apex of the heart and adjacent areas. A high R wave forms on the tape.
After that, it moves to the base of the heart, which is reflected in the form of a falling S wave. This takes 0.02 seconds.
Thus, the QRS is an entire ventricular complex with a total duration of 0.10 seconds.
S-T interval
Since myocardial cells cannot be in excitation for a long time, there comes a moment of decline when the impulse fades. By this time, the process of restoring the original state that prevailed before the excitement starts.
This process is also recorded on the ECG.
By the way, in this case, the initial role is played by the redistribution of sodium and potassium ions, the movement of which gives this same impulse. All this is called in one word - the process of repolarization.
We will not go into details, but only note that this transition from excitation to extinction is visible from the S to the T wave.
ECG norm
These are the main designations, looking at which one can judge the speed and intensity of the beating of the heart muscle. But in order to get a more complete picture, it is necessary to reduce all the data to some single standard of the ECG norm. Therefore, all devices are configured in such a way that the recorder first draws control signals on the tape, and only then begins to capture electrical vibrations from the electrodes connected to the person.
Typically, such a signal is equal in height to 10 mm and 1 millivolt (mV). This is the same calibration, control point.
All measurements of the teeth are made in the second lead. On the tape, it is indicated by the Roman numeral II. The R wave must correspond to the control point, and based on it, the rate of the remaining teeth is calculated:
- height T 1/2 (0.5 mV)
- depth S - 1/3 (0.3 mV)
- height P - 1/3 (0.3 mV)
- depth Q - 1/4 (0.2 mV)
The distance between teeth and intervals is calculated in seconds. Ideally, one looks at the width of the P wave, which is equal to 0.10 sec, and the subsequent length of the teeth and intervals is equal to 0.02 sec each time.
Thus, the width of the P wave is 0.10±0.02 sec. During this time, the impulse will cover both atria with excitation; P - Q: 0.10±0.02 sec; QRS: 0.10±0.02 sec; for passing a full circle (excitation passing from the sinus node through the atrioventricular connection to the atria, ventricles) in 0.30 ± 0.02 sec.
Let's look at a few normal ECGs for different ages (in a child, in adult men and women)
It is very important to take into account the age of the patient, his general complaints and condition, as well as current health problems, since even the slightest cold can affect the results.
Moreover, if a person goes in for sports, then his heart “gets used” to work in a different mode, which is reflected in the final results. An experienced doctor always takes into account all relevant factors.
ECG norm of a teenager (11 years old). For an adult, this will not be the norm.
The norm of the ECG of a young man (age 20 - 30 years).
The description of the resulting diagram is made according to a certain template:
- An assessment of the heart rate is carried out with the measurement of heart rate (heart rate) at the norm: the rhythm is sinus, the heart rate is 60-90 beats per minute.
- Calculation of intervals: Q-T at a rate of 390 - 440 ms.
This is necessary to estimate the duration of the contraction phase (they are called systoles). In this case, Bazett's formula is used. An extended interval indicates coronary heart disease, atherosclerosis, myocarditis, etc. A short interval may be associated with hypercalcemia.
- Assessment of the electrical axis of the heart (EOS)
This parameter is calculated from the isoline, taking into account the height of the teeth. In a normal heart rhythm, the R wave should always be higher than S. If the axis deviates to the right, and S is higher than R, then this indicates disorders in the right ventricle, with a deviation to the left in leads II and III - left ventricular hypertrophy.
- Q-R-S Complex Assessment
Normally, the interval should not exceed 120 ms. If the interval is distorted, then this may indicate various blockades in the conductive pathways (peduncles in the bundles of His) or conduction disturbances in other areas. According to these indicators, hypertrophy of the left or right ventricles can be detected.
- an inventory of the S-T segment is being conducted
It can be used to judge the readiness of the heart muscle to contract after its complete depolarization. This segment should be longer than the Q-R-S complex.
What do Roman numerals on an ECG mean?
Each point to which the electrodes are connected has its own meaning. It captures electrical vibrations and the recorder reflects them on the tape. In order to correctly read the data, it is important to correctly install the electrodes on a specific area.
For example:
- the potential difference between two points of the right and left hand is recorded in the first lead and is denoted by I
- the second lead is responsible for the potential difference between the right arm and left leg - II
- the third between the left hand and left foot - III
If we mentally connect all these points, then we get a triangle, named after the founder of electrocardiography, Einthoven.
In order not to confuse them with each other, all electrodes have wires of different colors: red is attached to the left hand, yellow to the right, green to the left leg, black to the right leg, it acts as a ground.
This arrangement refers to a bipolar lead. It is the most common, but there are also single-pole circuits.
Such a single-pole electrode is indicated by the letter V. The recording electrode, mounted on the right hand, is indicated by the sign VR, on the left, respectively, VL. On the leg - VF (food - leg). The signal from these points is weaker, so it is usually amplified, there is an “a” mark on the tape.
The chest leads are also slightly different. The electrodes are attached directly to the chest. Receiving impulses from these points is the strongest, clearest. They don't require amplification. Here the electrodes are arranged strictly according to the agreed standard:
| designation | electrode attachment point |
| V1 | in the 4th intercostal space at the right edge of the sternum |
| V2 | in the 4th intercostal space at the left edge of the sternum |
| V3 | midway between V2 and V4 |
| V4 | |
| V5 | in the 5th intercostal space on the mid-clavicular line |
| V6 | at the intersection of the horizontal level of the 5th intercostal space and the midaxillary line |
| V7 | at the intersection of the horizontal level of the 5th intercostal space and the posterior axillary line |
| V8 | at the intersection of the horizontal level of the 5th intercostal space and the mid-scapular line |
| V9 | at the intersection of the horizontal level of the 5th intercostal space and the paravertebral line |
The standard study uses 12 leads.
How to identify pathologies in the work of the heart
When answering this question, the doctor pays attention to the diagram of a person and, according to the main designations, he can guess which particular department began to fail.
We will display all the information in the form of a table.
| designation | myocardial department |
| I | anterior wall of the heart |
| II | total display I and III |
| III | posterior wall of the heart |
| aVR | right side wall of the heart |
| aVL | left anterior-lateral wall of the heart |
| aVF | posterior inferior wall of the heart |
| V1 and V2 | right ventricle |
| V3 | interventricular septum |
| V4 | apex of the heart |
| V5 | anterior-lateral wall of the left ventricle |
| V6 | lateral wall of the left ventricle |
Considering all of the above, you can learn how to decipher the tape at least according to the simplest parameters. Although many serious deviations in the work of the heart will be visible to the naked eye, even with this set of knowledge.
For clarity, we will describe some of the most disappointing diagnoses so that you can simply visually compare the norm and deviations from it.
myocardial infarction
Judging by this ECG, the diagnosis will be disappointing. Here, from the positive, only the duration of the Q-R-S interval, which is normal.
In leads V2 - V6 we see ST elevation.
This is the result acute transmural ischemia(AMI) of the anterior wall of the left ventricle. Q waves are seen in the anterior leads.
On this tape, we see a conduction disturbance. However, even with this fact, acute anterior-septal myocardial infarction against the background of blockade of the right leg of the bundle of His.
The right chest leads dismantle the S-T elevation and positive T waves.
Rimm - sinus. Here, there are high regular R waves, the pathology of the Q waves in the posterolateral sections.
Visible deviation ST in I, aVL, V6. All this indicates a posterolateral myocardial infarction with coronary heart disease (CHD).
Thus, the signs of myocardial infarction on the ECG are:
- tall T wave
- elevation or depression of the S-T segment
- pathological Q wave or its absence
Signs of myocardial hypertrophy
Ventricular
For the most part, hypertrophy is characteristic of those people whose heart has experienced additional stress for a long time as a result of, say, obesity, pregnancy, some other disease that negatively affects the non-vascular activity of the whole organism as a whole or individual organs (in particular, lungs, kidneys).
The hypertrophied myocardium is characterized by several signs, one of which is an increase in the time of internal deflection.
What does it mean?
Excitation will have to spend more time passing through the cardiac departments.
The same applies to the vector, which is also larger, longer.
If you look for these signs on the tape, then the R wave will be higher in amplitude than normal.
A characteristic symptom is ischemia, which is the result of insufficient blood supply.
Through the coronary arteries to the heart there is a blood flow, which, with an increase in the thickness of the myocardium, encounters an obstacle on the way and slows down. Violation of the blood supply causes ischemia of the subendocardial layers of the heart.
Based on this, the natural, normal function of the pathways is disrupted. Inadequate conduction leads to failures in the process of excitation of the ventricles.
After that, a chain reaction is launched, because the work of other departments depends on the work of one department. If there is hypertrophy of one of the ventricles on the face, then its mass increases due to the growth of cardiomyocytes - these are cells that are involved in the process of transmitting a nerve impulse. Therefore, its vector will be larger than the vector of a healthy ventricle. On the tape of the electrocardiogram, it will be noticeable that the vector will be deviated towards the localization of hypertrophy with a shift in the electrical axis of the heart.
The main features include a change in the third chest lead (V3), which is something like a transshipment, transition zone.
What kind of zone is this?
It includes the height of the R tooth and the depth S, which are equal in their absolute value. But when the electrical axis changes as a result of hypertrophy, their ratio will change.
Consider specific examples
In sinus rhythm, left ventricular hypertrophy is clearly visible with characteristic high T waves in the chest leads.
There is nonspecific ST depression in the inferolateral region.
EOS (electrical axis of the heart) deviated to the left with an anterior hemiblock and prolongation of the QT interval.
High T waves indicate that a person has, in addition to hypertrophy, also hyperkalemia most likely developed against the background of renal failure and, which are characteristic of many patients who have been ill for many years.
In addition, a longer QT interval with ST depression indicates hypocalcemia that progresses in advanced stages (chronic renal failure).
This ECG corresponds to an elderly person who has serious kidney problems. He is on the edge.
atrial
As you already know, the total value of atrial excitation on the cardiogram is shown by the P wave. In case of failures in this system, the width and / or height of the peak increases.
With right atrial hypertrophy (RAA), P will be higher than normal, but not wider, since the peak of the excitation of the PP ends before the excitation of the left. In some cases, the peak takes on a pointed shape.
With HLP, there is an increase in the width (more than 0.12 seconds) and height of the peak (double-hump appears).
These signs indicate a violation of the conduction of the impulse, which is called intra-atrial blockade.
blockades
Blockades are understood as any failures in the conduction system of the heart.
A little earlier, we looked at the path of the impulse from the sinus node through the conducting paths to the atria, at the same time, the sinus impulse rushes along the lower branch of the Bachmann bundle and reaches the atrioventricular junction, passing through it, it undergoes a natural delay. Then it enters the conduction system of the ventricles, presented in the form of His bundles.
Depending on the level at which the failure occurred, a violation is distinguished:
- intra-atrial conduction (sinus impulse block in the atria)
- atrioventricular
- intraventricular
Intraventricular conduction
This system is presented in the form of a trunk of His, divided into two branches - the left and right legs.
The right leg "supplies" the right ventricle, inside which it branches into many small networks. It appears as one wide bundle with branches inside the muscles of the ventricle.
The left leg is divided into anterior and posterior branches, which "adjoin" the anterior and posterior wall of the left ventricle. Both of these branches form a network of smaller branches within the LV musculature. They are called Purkinje fibers.
Blockade of the right leg of the bundle of His
The course of the impulse first covers the path through the excitation of the interventricular septum, and then the first unblocked LV is involved in the process, through its normal course, and only after that the right one is excited, to which the impulse reaches the distorted path through the Purkinje fibers.
Of course, all this will affect the structure and shape of the QRS complex in the right chest leads V1 and V2. At the same time, on the ECG we will see bifurcated peaks of the complex, similar to the letter "M", in which R is the excitation of the interventricular septum, and the second R1 is the actual excitation of the pancreas. S, as before, will be responsible for the excitation of the left ventricle.
On this tape we see incomplete RBBB and 1st degree AB block, there are also p ubtsovye changes in the posterior diaphragmatic region.
Thus, the signs of blockade of the right leg of the bundle of His are as follows:
- elongation of the QRS complex in standard lead II for more than 0.12 sec.
- an increase in the time of the internal deflection of the right ventricle (on the graph above, this parameter is presented as J, which is more than 0.02 sec in the right chest leads V1, V2)
- deformation and splitting of the complex into two "humps"
- negative T wave
Blockade of the left leg of the bundle of His
The course of excitation is similar, the impulse reaches the LV through detours (it does not pass along the left leg of the His bundle, but through the network of Purkinje fibers from the pancreas).
Characteristic features of this phenomenon on the ECG:
- widening of the ventricular QRS complex (more than 0.12 sec)
- an increase in the time of internal deviation in the blocked LV (J is greater than 0.05 sec)
- deformation and bifurcation of the complex in leads V5, V6
- negative T wave (-TV5, -TV6)
Blockade (incomplete) of the left leg of the bundle of His
It is worth paying attention to the fact that the S wave will be “atrophied”, i.e. he will not be able to reach the isoline.
Atrioventricular block
There are several degrees:
- I - slow conduction is characteristic (heart rate is normal within 60 - 90; all P waves are associated with the QRS complex; P-Q interval is more than normal 0.12 sec.)
- II - incomplete, divided into three options: Mobitz 1 (heart rate slows down; not all P waves are associated with the QRS complex; the P-Q interval changes; periodicals appear 4:3, 5:4, etc.), Mobitz 2 (also most, but the interval P - Q is constant; periodicity 2:1, 3:1), high-grade (significantly reduced heart rate; periodicity: 4:1, 5:1; 6:1)
- III - complete, divided into two options: proximal and distal
Well, we will go into details, but only note the most important:
- the time of passage through the atrioventricular junction is normally 0.10±0.02. Total, no more than 0.12 sec.
- reflected on the interval P - Q
- here there is a physiological impulse delay, which is important for normal hemodynamics
AV block II degree Mobitz II
Such violations lead to failures of intraventricular conduction. Usually people with such a tape have shortness of breath, dizziness, or they quickly overwork. In general, this is not so scary and is very common even among relatively healthy people who do not particularly complain about their health.
Rhythm disturbance
Signs of arrhythmia are usually visible to the naked eye.
When excitability is disturbed, the response time of the myocardium to the impulse changes, which creates characteristic graphs on the tape. Moreover, it should be understood that not in all cardiac departments the rhythm can be constant, taking into account the fact that there is, say, one of the blockades that inhibits the transmission of impulses and distorts signals.
So, for example, the following cardiogram indicates atrial tachycardia, and the one below it indicates ventricular tachycardia with a frequency of 170 beats per minute (LV).
The sinus rhythm with a characteristic sequence and frequency is correct. Its characteristics are as follows:
- frequency of P waves in the range of 60-90 per minute
- RR spacing is the same
- the P wave is positive in the II standard lead
- P wave is negative in lead aVR
Any arrhythmia indicates that the heart is working in a different mode, which cannot be called regular, habitual and optimal. The most important thing in determining the correctness of the rhythm is the uniformity of the interval of the P-P waves. Sinus rhythm is correct when this condition is met.
If there is a slight difference in the intervals (even 0.04 sec, not exceeding 0.12 sec), then the doctor will already indicate a deviation.
The rhythm is sinus, irregular, since the RR intervals differ by no more than 0.12 sec.
If the intervals are more than 0.12 seconds, then this indicates an arrhythmia. It includes:
- extrasystole (most common)
- paroxysmal tachycardia
- flicker
- flutter, etc.
Arrhythmia has its own focus of localization, when a rhythm disturbance occurs in certain parts of the heart (in the atria, ventricles) on the cardiogram.
The most striking sign of atrial flutter is high-frequency impulses (250 - 370 beats per minute). They are so strong that they overlap the frequency of sinus impulses. There will be no P waves on the ECG. In their place, sharp, sawtooth low-amplitude “teeth” (no more than 0.2 mV) will be visible on lead aVF.
ECG Holter
This method is otherwise abbreviated as HM ECG.
What it is?
Its advantage is that it is possible to carry out daily monitoring of the work of the heart muscle. The reader itself (recorder) is compact. It is used as a portable device capable of recording signals from electrodes on a magnetic tape for a long period of time.
On a conventional stationary device, it is quite difficult to notice some periodically occurring jumps and malfunctions in the work of the myocardium (given the asymptomaticity) and the Holter method is used to make sure the diagnosis is correct.
The patient is invited to keep a detailed diary on his own after medical instructions, since some pathologies can manifest themselves at a certain time (the heart “collapses” only in the evenings and then not always, in the mornings something “presses” on the heart).
While observing, a person writes down everything that happens to him, for example: when he was at rest (sleep), overworked, ran, quickened his pace, worked physically or mentally, was nervous, worried. At the same time, it is also important to listen to yourself and try to describe as clearly as possible all your feelings, symptoms that accompany certain actions, events.
The time of data collection usually lasts no longer than a day. For such daily monitoring of the ECG allows you to get a clearer picture and determine the diagnosis. But sometimes the data collection time can be extended to several days. It all depends on the person's well-being and the quality and completeness of previous laboratory tests.
Usually, the basis for prescribing this type of analysis is the painless symptoms of coronary heart disease, latent hypertension, when doctors have suspicions, doubts about any diagnostic data. In addition, they can prescribe it when prescribing new drugs for the patient that affect the functioning of the myocardium, which are used in the treatment of ischemia or if there is an artificial pacemaker, etc. This is also done in order to assess the patient's condition in order to assess the degree of effectiveness of the prescribed therapy, and so on.
How to prepare for HM ECG
Usually there is nothing complicated in this process. However, it should be understood that other devices, especially emitting electromagnetic waves, can affect the device.
Interaction with any metal is also not desirable (rings, earrings, metal buckles, etc. should be removed). The device must be protected from moisture (complete body hygiene under the shower or bath is unacceptable).
Synthetic fabrics also negatively affect the results, as they can create static voltage (they become electrified). Any such “splash” from clothes, bedspreads and other things distorts the data. Replace them with natural ones: cotton, linen.
The device is extremely vulnerable and sensitive to magnets, you should not stand near a microwave oven or an induction hob, avoid being near high-voltage wires (even if you drive a car through a small section of the road over which high-voltage lines lie).
How is data collected?
Usually, the patient is given a referral, and at the appointed time he comes to the hospital, where the doctor, after some theoretical introductory course, installs electrodes on certain parts of the body, which are connected by wires to a compact recorder.
The registrar itself is a small device that captures any electromagnetic vibrations and remembers them. It fastens on the belt and hides under the clothes.
Men sometimes have to shave in advance some parts of the body on which the electrodes are attached (for example, to “free” the chest from hair).
After all preparations and installation of equipment, the patient can go about his usual activities. He should merge into his daily life as if nothing had happened, though not forgetting to take notes (it is extremely important to indicate the time of manifestation of certain symptoms and events).
After the period set by the doctor, the “subject” returns to the hospital. The electrodes are removed from it and the reading device is taken away.
The cardiologist, using a special program, will process the data from the recorder, which, as a rule, is easily synchronized with a PC and will be able to make a specific inventory of all the results obtained.
Such a method of functional diagnostics as an ECG is much more effective, since thanks to it even the slightest pathological changes in the work of the heart can be noticed, and it is widely used in medical practice in order to identify life-threatening diseases in patients like a heart attack.
It is especially important for diabetics with cardiovascular late complications that have developed against the background of diabetes mellitus to undergo it periodically at least once a year.
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To determine the diagnosis, one of the most indispensable aids of a doctor is a cardiogram. With its help, important heart diseases such as myocardial infarction or arrhythmia can be detected. And at the same time, it is inexpensive and accessible to everyone, and the method of its construction is based on a careful study of the bioelectrical activity of the heart muscles. Now we will teach anyone to read a cardiogram.
1.
During ECG recording, it is important to avoid all kinds of interference and guidance currents, the minivolt should not exceed ten millimeters
2.
The heart rate is determined by the frequency of contractions of the heart and their regularity, conduction and the source of excitation are determined. This is determined by comparing the duration of the R-R intervals. If the heart rate rhythm is correct, this is calculated by dividing 60 by the R-R interval per second.
3.
The algebraic axis of the heart is calculated by determining the sum of the amplitudes of the QRS waves at any points of the limb leads.
4.
Carefully examine the atrial scar R. Measure along the isoline from the top of the tooth its amplitude, it should be no more than twenty-five millimeters. Measure the distance from the beginning to the end, if the person is healthy, it will not exceed 0.1 second.
5.
The PQ interval is an indicator of the rate of impulse supply from the atrium to the ventricles. Its interval must be between 0.12 and 0.1 seconds. You also need to analyze the ventricular QRS complex, measuring the amplitude of the complex and the duration of each of its teeth.
6. Analyze the T wave. It reflects the relaxation phase of the heart muscle. It is necessary to determine its polarity, amplitude and shape. When a person is healthy, this wave is positive and has the same polarity as the wave responsible for the ventricular complex. Its shape should be gently rising and have a steeply falling knee.
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