Electrocardiography (ECG): basics of theory, removal, analysis, detection of pathologies. How to properly prepare for an ECG and decipher its results Methodology for the procedure

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Almost every person who has undergone an electrocardiogram is interested in the meaning of different teeth and the terms written by the diagnostician. Although only a cardiologist can give a full interpretation of the ECG, everyone can easily figure out whether he has a good cardiogram of the heart or there are some deviations.

Indications for an ECG

A non-invasive study - an electrocardiogram - is performed in the following cases:

• Complaints of the patient about high blood pressure, retrosternal pain and other symptoms indicating cardiac pathology;
• Deterioration of well-being of a patient with a previously diagnosed cardiovascular disease;
• Deviations in laboratory tests blood - high cholesterol, prothrombin;
• In the complex of preparation for the operation;
• Detection of endocrine pathology, diseases of the nervous system;
• After severe infections with a high risk of heart complications;
• For prophylactic purposes in pregnant women;
• Examination of the health status of drivers, pilots, etc.

ECG decoding - numbers and Latin letters

Full-scale interpretation of the cardiogram of the heart includes an assessment heart rate, the work of the conduction system and the state of the myocardium. For this, the following leads are used (electrodes are installed in a certain order on the chest and limbs):

• Standard: I - left / right wrist on the hands, II - right wrist and ankle area on the left leg, III - left ankle and wrist.
• Reinforced: aVR - right wrist and joint left upper/lower limbs, aVL - left wrist and joint left ankle and right wrist, aVF - left ankle zone and joint potential of both wrists.
• Thoracic (potential difference located on chest electrode with a suction cup and the combined potentials of all limbs): V1 - electrode in the IV intercostal space along the right border of the sternum, V2 - in the IV intercostal space to the left of the sternum, V3 - on the IV rib along the left parasternal line, V4 - V intercostal space along the left midclavicular line , V5 - V intercostal space along the anterior axillary line on the left, V6 - V intercostal space along the mid-axillary line on the left.

Additional pectorals - located symmetrically to the left pectoral with additional V7-9.

One cardiac cycle on the ECG is represented by the PQRST graph, which records electrical impulses in the heart:

• P wave - displays atrial excitation;
• QRS complex: Q wave - the initial phase of depolarization (excitation) of the ventricles, R wave - the actual process of ventricular excitation, S wave - the end of the depolarization process;
• wave T - characterizes the extinction of electrical impulses in the ventricles;
• ST segment - describes the complete recovery of the initial state of the myocardium.

When decoding ECG indicators, the height of the teeth and their location relative to the isoline, as well as the width of the intervals between them, matters.

Sometimes a U impulse is registered behind the T wave, indicating the parameters of the electric charge carried away with the blood.

Interpretation of ECG indicators - the norm in adults

On the electrocardiogram, the width (horizontal distance) of the teeth - the duration of the period of excitation of relaxation - is measured in seconds, the height in leads I-III - the amplitude of the electrical impulse - in mm. A normal cardiogram in an adult looks like this:

• The heart rate is normal heart rate within 60-100/min. The distance from the tops of adjacent R waves is measured.
• EOS - the electric axis of the heart is the direction of the total angle of the electric force vector. The normal indicator is 40-70º. Deviations indicate the rotation of the heart around its own axis.
• P wave - positive (directed upwards), negative only in lead aVR. Width (excitation duration) - 0.7 - 0.11 s, vertical size - 0.5 - 2.0 mm.
• Interval PQ - horizontal distance 0.12 - 0.20 s.
• The Q wave is negative (below the isoline). The duration is 0.03 s, the negative value of the height is 0.36 - 0.61 mm (equal to ¼ of the vertical dimension of the R wave).
• The R wave is positive. Its height is important - 5.5 -11.5 mm.
• Tooth S - negative height 1.5-1.7 mm.
• QRS complex - horizontal distance 0.6 - 0.12 s, total amplitude 0 - 3 mm.
• The T wave is asymmetric. Positive height 1.2 - 3.0 mm (equal to 1/8 - 2/3 of the R wave, negative in aVR lead), duration 0.12 - 0.18 s (more than the duration of the QRS complex).
• ST segment - runs at the level of the isoline, length 0.5 -1.0 s.
• U wave - height indicator 2.5 mm, duration 0.25 s.

Abbreviated results of ECG decoding in adults and the norm in the table:

In the usual conduct of the study (recording speed - 50 mm / s), the decoding of the ECG in adults is performed according to the following calculations: 1 mm on paper when calculating the duration of the intervals corresponds to 0.02 sec.

A positive P wave (standard leads) followed by a normal QRS complex indicates normal sinus rhythm.

ECG norm in children, decoding

Cardiogram parameters in children are somewhat different from those in adults and vary depending on age. Decryption ECG of the heart in children, the norm:

• Heart rate: newborns - 140 - 160, by 1 year - 120 - 125, by 3 years - 105 -110, by 10 years - 80 - 85, after 12 years - 70 - 75 per minute;
• EOS - corresponds to adult indicators;
• sinus rhythm;
• tooth P - does not exceed 0.1 mm in height;
• the length of the QRS complex (often not particularly informative in diagnosis) - 0.6 - 0.1 s;
• PQ interval - less than or equal to 0.2 s;
• Q wave - non-permanent parameters, negative values ​​in lead III are acceptable;
• P wave - always above the isoline (positive), the height in one lead may fluctuate;
• wave S - negative indicators of non-constant value;
• QT - no more than 0.4 s;
• the duration of the QRS and the T wave are equal, they are 0.35 - 0.40.

An example of an ECG with arrhythmia

By deviations in the cardiogram, a qualified cardiologist can not only diagnose the nature of a heart disease, but also fix the location of the pathological focus.

Arrhythmias

Distinguish the following violations of cardiac rhythm:

1. Sinus arrhythmia - the length of the RR intervals fluctuates with a difference of up to 10%. It is not considered a pathology in children and young people.
2. Sinus bradycardia is a pathological decrease in the frequency of contractions to 60 per minute or less. The P wave is normal, PQ from 12 s.
3. Tachycardia - heart rate 100 - 180 per minute. In adolescents - up to 200 per minute. The rhythm is right. With sinus tachycardia, the P wave is slightly higher than normal, with ventricular tachycardia - QRS - length indicator above 0.12 s.
4. Extrasystoles - extraordinary contractions of the heart. Single on a conventional ECG (on a daily Holter - no more than 200 per day) are considered functional and do not require treatment.
5. Paroxysmal tachycardia is a paroxysmal (several minutes or days) increase in the frequency of heart beats up to 150-220 per minute. It is characteristic (only during an attack) that the P wave merges with the QRS. The distance from the R wave to the P height from the next contraction is less than 0.09 s.
6. Atrial fibrillation - irregular atrial contraction with a frequency of 350-700 per minute, and ventricles - 100-180 per minute. There is no P wave, fine-coarse-wave oscillations along the entire isoline.
7. Atrial flutter - up to 250-350 per minute of atrial contractions and regular reduced ventricular contractions. The rhythm can be correct, on the ECG there are sawtooth atrial waves, especially pronounced in standard leads II - III and chest V1.

EOS Position Deviation

A change in the total EOS vector to the right (more than 90º), a higher S wave height compared to the R wave indicate a pathology of the right ventricle and blockade of the His bundle.

When the EOS is shifted to the left (30-90º) and the pathological ratio of the height of the S and R teeth is diagnosed, left ventricular hypertrophy, blockade of the leg of the n. His. EOS deviation indicates a heart attack, pulmonary edema, COPD, but it also happens in the norm.

Conduction system disruption

The following pathologies are most often recorded:

• 1 degree atrioventricular (AV-) block - PQ distance more than 0.20 s. After each R, a QRS follows naturally;
• Atrioventricular blockade 2 tbsp. - a gradually lengthening PQ throughout the ECG sometimes displaces the QRS complex (Mobitz type 1 deviation) or a complete prolapse of the QRS is recorded against the background of PQ equal length(Mobitz 2);
• Complete blockade of the AV node - atrial HR is higher than the ventricular FR. PP and RR are the same, PQ are different lengths.

Selected heart diseases

The results of the ECG decoding can provide information not only about what happened heart disease, but also pathologies of other organs:

1. Cardiomyopathy - atrial hypertrophy (usually left), low-amplitude teeth, partial blockade of p. Gis, atrial fibrillation or extrasystoles.
2. Mitral stenosis - the left atrium and right ventricle are enlarged, the EOS is rejected to the right, often atrial fibrillation.
3. Prolapse mitral valve- T wave flattened/negative, some QT prolongation, depressive ST segment. Various rhythm disturbances are possible.
4. Chronic obstruction of the lungs - EOS to the right of the norm, low-amplitude teeth, AV blockade.
5. CNS damage (including subarachnoid hemorrhage) - pathological Q, wide and high-amplitude (negative or positive) T wave, pronounced U, long QT duration of rhythm disturbance.
6. Hypothyroidism - long PQ, low QRS, flat T wave, bradycardia.

Quite often, an ECG is performed to diagnose myocardial infarction. At the same time, each of its stages corresponds to characteristic changes in the cardiogram:

• ischemic stage - peaked T with a sharp apex is fixed 30 minutes before the onset of necrosis of the heart muscle;
• stage of damage (changes are recorded in the first hours up to 3 days) - ST in the form of a dome above the isoline merges with the T wave, shallow Q and high R;
• acute stage (1-3 weeks) - the worst cardiogram of the heart during a heart attack - the preservation of domed ST and the transition of the T wave to negative values, a decrease in R height, pathological Q;
• subacute stage (up to 3 months) - comparison of ST with isoline, preservation of pathological Q and T;
• scarring stage (several years) - pathological Q, negative R, smoothed T wave gradually comes to normal.

Do not sound the alarm if you found in the ECG handed out pathological changes. It should be remembered that some deviations from the norm occur in healthy people.

If the electrocardiogram revealed any pathological processes in the heart, you will definitely be assigned a consultation with a qualified cardiologist.

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 field team has a portable and lightweight electrocardiograph capable of reading information by fixing on the recorder the electrical impulses of the heart muscle - myocardium at the time of contraction.

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 peak value, the age of the patient, the presence or absence of aggravating factors, etc.

ECG of the heart for diabetics who, in addition to diabetes there are also late cardiovascular complications, which makes it possible to assess the severity of the disease and intervene in time in order to delay the further progression of the disease, which can lead to serious consequences in the form of myocardial infarction, thromboembolism pulmonary artery 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 for a pregnant woman will be somewhat different, since a natural shift occurs in the process of fetal growth internal organs 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

1. Drinking alcohol or any other strong drinks (including energy drinks, etc.)
2. Overeating (best taken on an empty stomach or a light snack before going out)
3. Smoking
4. Use medicines heart stimulants or suppressants, or drinks (such as coffee)
5. Physical activity
6. 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 pick up 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, look 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 ECG 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 affects 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.

ECG norm 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 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:

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.

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 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 right leg 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 it starts chain reaction because the work of one department depends on the work of other departments. 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 kidney 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 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 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, some kind of blockade 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 same interval teeth P-P. 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 portable device, capable for a long period of time to fix the signals coming through the electrodes on the magnetic tape.

On a conventional stationary device, it is quite difficult to notice some intermittent 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.

Painless symptoms are usually the basis for this type of analysis. coronary disease heart, 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, do 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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Pathology of cardio-vascular system is one of the most common problems affecting people of all ages. Timely treatment and diagnostics of the circulatory system can significantly reduce the risk of developing dangerous diseases.

To date, the most effective and easily accessible method of studying the work of the heart is an electrocardiogram.

When examining the results of the examination of the patient, doctors pay attention to such components of the ECG as:

• teeth;
• intervals;
• Segments.

Not only their presence or absence is assessed, but also their height, duration, location, direction and sequence.

There are strict normal parameters for each line on the ECG tape, the slightest deviation from which may indicate violations in the work of the heart.

ECG analysis

The entire set of ECG lines is examined and measured mathematically, after which the doctor can determine some parameters of the heart muscle and its conduction system: heart rate, heart rate, pacemaker, conduction, electrical axis of the heart.

To date, all these indicators are investigated by high-precision electrocardiographs.

Sinus rhythm of the heart

This is a parameter that reflects the rhythm of heart contractions that occur under the influence of the sinus node (normal). It shows the coherence of the work of all parts of the heart, the sequence of processes of tension and relaxation of the heart muscle.

The rhythm is very easy to identify by the tallest R waves: if the distance between them is the same throughout the entire recording or deviates by no more than 10%, then the patient does not suffer from arrhythmia.

heart rate

The number of beats per minute can be determined not only by counting the pulse, but also by the ECG. To do this, you need to know the speed at which the ECG was recorded (usually 25, 50 or 100mm / s), as well as the distance between the highest teeth (from one peak to another).

By multiplying the recording time of one mm by length of segment R-R you can get your heart rate. Normally, its performance ranges from 60 to 80 beats per minute.

Source of excitation

The autonomic nervous system of the heart is designed in such a way that the process of contraction depends on the accumulation nerve cells in one of the areas of the heart. Normally, this is the sinus node, the impulses from which diverge throughout nervous system hearts.

In some cases, other nodes (atrial, ventricular, atrioventricular) can take on the role of the pacemaker. This can be determined by examining the P wave is inconspicuous, located just above the isoline.

You can read detailed and comprehensive information about the symptoms of cardiosclerosis of the heart.

Conductivity

This is a criterion showing the process of momentum transfer. Normally, impulses are transmitted sequentially from one pacemaker to another, without changing the order.

Electric axis

An indicator based on the process of excitation of the ventricles. Mathematical analysis of Q, R, S waves in leads I and III allows you to calculate a certain resulting vector of their excitation. This is necessary to establish the functioning of the branches of the His bundle.

The obtained angle of inclination of the axis of the heart is estimated by the value: 50-70° normal, 70-90° deviation to the right, 50-0° deviation to the left.

In cases where there is a tilt of more than 90° or more than -30°, there is a serious malfunction in the bundle of His.

Teeth, segments and intervals

Teeth - ECG sections lying above the isoline, their meaning is as follows:

• P- reflects the processes of contraction and relaxation of the atria.
• Q, S- reflect the processes of excitation of the interventricular septum.
• R- the process of excitation of the ventricles.
• T- the process of relaxation of the ventricles.

Intervals are sections of the ECG lying on the isoline.

• PQ- reflects the propagation time of the impulse from the atria to the ventricles.

Segments - sections of the ECG, including an interval and a wave.

• QRST- the duration of the contraction of the ventricles.
• ST- the time of complete excitation of the ventricles.
• TP is the time of electrical diastole of the heart.

Norm in men and women

The decoding of the ECG of the heart and the norms of indicators in adults are presented in this table:

Healthy Childhood Outcomes

Deciphering the results of ECG measurements in children and their norm in this table:

Dangerous diagnoses

What dangerous conditions can be determined by the ECG readings during decoding?

Extrasystole

This phenomenon characterized by irregular heartbeat. A person feels a temporary increase in the frequency of contractions, followed by a pause. It is associated with the activation of other pacemakers, sending along with the sinus node an additional burst of impulses, which leads to an extraordinary contraction.

If extrasystoles appear no more than 5 times per hour, then they cannot cause significant harm to health.

Arrhythmia

Characterized change in the frequency of sinus rhythm when pulses arrive at different frequencies. Only 30% of these arrhythmias require treatment, because can lead to more serious illnesses.

In other cases, this may be a manifestation of physical activity, a change in hormonal levels, the result of a fever and does not threaten health.

Bradycardia

It occurs when the sinus node is weakened, unable to generate impulses with the proper frequency, as a result of which the heart rate also slows down, up to 30-45 beats per minute.

Tachycardia

The opposite phenomenon, characterized by an increase in heart rate over 90 beats per minute. In some cases, temporary tachycardia occurs under the influence of strong physical exertion and emotional stress, as well as during illnesses associated with fever.

Conduction disorder

In addition to the sinus node, there are other underlying pacemakers of the second and third orders. Normally, they conduct impulses from the first-order pacemaker. But if their functions weaken, a person may feel weakness, dizziness caused by depression of the heart.

It is also possible to lower blood pressure, because the ventricles will contract less frequently or arrhythmically.

Many factors can lead to disruption in the work of the heart muscle itself. Tumors develop, muscle nutrition is disrupted, and depolarization processes fail. Most of these pathologies require serious treatment.

Why there might be differences in performance

In some cases, when re-analyzing the ECG, deviations from previously obtained results are revealed. With what it can be connected?

• different time of day. Usually, an ECG is recommended to be done in the morning or afternoon, when the body has not yet had time to be influenced by stress factors.
• Loads. It is very important that the patient is calm while recording the ECG. The release of hormones can increase heart rate and distort performance. In addition, before the examination, it is also not recommended to engage in heavy physical labor.
• meal. Digestive processes affect blood circulation, and alcohol, tobacco and caffeine can affect heart rate and pressure.
• electrodes. Improper overlap or accidental shifting can seriously change the performance. Therefore, it is important not to move during the recording and degrease the skin in the area where the electrodes are applied (the use of creams and other skin products before the examination is highly undesirable).
• Background. Sometimes other devices can interfere with the operation of the electrocardiograph.

Additional examination methods

Halter

Method long-term study of the work of the heart, made possible by a portable compact tape recorder that is capable of recording results on magnetic tape. The method is especially good when it is necessary to investigate recurrent pathologies, their frequency and time of occurrence.

Treadmill

Unlike a normal resting ECG, this method based on results analysis after physical activity . It is most commonly used for risk assessment. possible pathologies not detected on a standard ECG, as well as when prescribing a course of rehabilitation to patients who have had a heart attack.

Phonocardiography

Allows analyze heart sounds and murmurs. Their duration, frequency and time of occurrence correlate with the phases of cardiac activity, which makes it possible to assess the functioning of the valves, the risks of developing endocarditis and rheumatic heart disease.

A standard ECG is a graphic representation of the work of all parts of the heart. Its accuracy can be affected by many factors, so doctor's advice should be followed.

The examination reveals most of the pathologies of the cardiovascular system, however, additional tests may be required for an accurate diagnosis.

Finally, we suggest watching a video course on decoding “ECG for everyone”:

R-R interval- an indicator of the duration of the cardiac cycle, measured in any leads. Sinus rhythm is considered correct if the fluctuations in the R-R intervals do not exceed 0.1 s. The heart rate in 1 min is determined by dividing 60 s by the duration of the R-R interval (in seconds).

Q-T interval(QRS-T) corresponds to the duration of the electrical systole of the ventricles; usually measured in standard lead II from the beginning of the complex to the end of the T wave. In physiological helovia, its value depends on the sex of the person under study and the heart rate. Due for the lannsgo patient Q-T duration(according to gender and rhythm frequency) can be calculated by the formula: Q-T = K * R-R, where K is an empirically found constant equal to 0.39 for women, 0.37 for men. The proper value "on Q-T is given ~ in the table.

Grade duration ventricular electrical systole at different heart rates is facilitated if the duration of the ventricular phase ( Q-T value) calculate as a percentage of the duration of the entire cardiac cycle according to the formula: SC \u003d (Q-T * 100) / R-R%. The resulting value is called a systolic indicator (L. I. Fogelson and A Chernobrov, 1927).

Electrical axis of the heart and location options. The electromotive force of the heart has a certain value and voltage, that is, it is a vector quantity. Its vector in space depends both on the position in the chest and on the electrical properties of its departments. In the process of depolarization, the moment vector of the heart is constantly changing as the excitation passes through various layers and departments of the heart. The direction of the electromotive force can be determined for any single moment of the cardiac cycle. However, in practical work usually determine its main (average) direction during the period of depolarization of the ventricles (according to the QRS complex). The projection of this vector onto the frontal plane is called the electrical axis of the heart. Its direction is usually expressed by the angle a, which is formed by the intersection of the electric axis with horizontal line, corresponding to the line I of assignment. In this case, the angles located below the horizontal are taken with a plus sign (+), and above - with a minus sign (-).

Regulations the electrical axis of the heart are shown in the figure:
- the normal position of the electrical axis corresponds to the angle a, the value of which ranges from +30 to -70 °. In this case, RII>RI>RIII, RI,II,III>SI,II,III;
- its horizontal position - angle a, the value of which varies from + 30 ° to 0 °.

In this case, the tooth RI> RII> RIII, RavF> Savf;

Deviation of the electrical axis of the heart to the left - angle a, the value of which ranges from 0 ° to -90 °. In this case RI>RII>RIII,RavF - its vertical position - the angle a, the value of which varies from + 70 to + 80 °. In this case
- deviation of the electric axis to the right - angle a, which is greater than +90°. In this case, RIIi>Rii>Ri Based on the ratio teeth of the QRS complex in standard and enhanced unipolar leads, you can determine a number of angle a values ​​that are useful in practical work:

If RI = RII, SIII = RIII, then the angle a is +30°;
- if RII=RIII, SI=RI, then the angle a is equal to + 90°;
- if RI=RIII, then angle a is +60°;
- if RI > RII and SIII > RIII, and RII = SII, then the angle a is equal to -30°.

For exact definition direction of the electrical axis of the heart various schemes and tables are proposed. The Dieda scheme is shown in fig. 5. With its help, the angle a is calculated based on the ratio of the magnitude of the amplitude of the teeth of the QRS complex in leads I and III. In this case, the algebraic sum of the amplitudes of the teeth of the QRS complex. put on the axis I of the lead (from zero towards + or -), and the sum of the amplitudes of QRSIII - on the axis of the III lead. Then, from the point corresponding to the sum of the QRSI amplitudes, a perpendicular is drawn to the axis I of the lead, and from the point, which corresponds to the sum of the QRSIII amplitudes, to the axis III of the lead. The intersection of two perpendiculars is the second point of the electric axis, and the center of the system is the first. By connecting these points with a straight line, a vector representing the electrical network is obtained. The angle between the electrical axis and the horizontal line corresponding to the axis I of the lead is the angle a.

Registration of an electrocardiogram is a method of studying electrical signals generated during the activity of the muscles of the heart. To record electrocardiogram data, 10 electrodes are used: 1 zero on the right leg, 3 standard ones from the extremities and 6 in the heart area.

The result of the removal of electrical indicators, the work of various departments of the body, is the creation of an electrocardiogram.

Its parameters are recorded on a special roll paper. Paper movement speed is available in 3 options:

• 25 mm.sec;
• 50 mm.sec;
• 100 mm.sec;

There are electronic sensors that can record ECG parameters on HDD system unit and, if necessary, display this data on the monitor or print it on the required paper sizes.

Interpretation of the recorded electrocardiogram.

The specialist cardiologist gives the result of the analysis of the parameters of the electrocardiogram. The doctor deciphers the record by establishing the duration of the intervals between the various elements of the recorded indicators. An explanation of the features of the electrocardiogram contains many points:

Normal ECG.

Consideration of a standard cardiogram of the heart is represented by the following indicators:

Electrocardiogram in case of myocardial infarction.

Myocardial infarction occurs due to exacerbation of coronary disease, when the internal cavity is significantly narrowed coronary artery heart muscle. If this violation is not eliminated within 15 - 20 minutes, the death of the muscle cells of the heart, which receive oxygen and nutrients from this artery, occurs. This circumstance creates significant disturbances in the functioning of the heart and is a severe and serious threat to life. In the event of a heart attack of the heart, an electrocardiogram will help identify the site of necrosis. The specified cardiogram contains markedly manifested deviations in the electrical signals of the heart muscle:

Heart rhythm disorder.

A disorder in the rhythm of contraction of the heart muscles is detected when shifts appear on the electrocardiogram:

Hypertrophy of the heart.

An increase in the volume of the heart muscles is an adaptation of the body to new conditions of functioning. The changes that appear on the electrocardiogram are determined by a high bioelectric force, a characteristic muscle area, a delay in the movement of bioelectric impulses in its thickness, the appearance of signs oxygen starvation.

Conclusion.

Electrocardiographic indicators of cardiac pathology are diverse. Reading them is a complex activity that requires special training and improvement of practical skills. A specialist characterizing an ECG needs to know the basic principles of the physiology of the heart, various versions of cardiograms. He needs to have skills in the ability to determine anomalies in the activity of the heart. Calculate impact medicines and other factors, the occurrence of differences in the structure of the teeth and intervals of the ECG. Therefore, the interpretation of the electrocardiogram should be entrusted to a specialist who has encountered in his practice with various options for shortcomings in the work of the heart.

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