Normal cardiogram. What is an ECG, how to decipher it yourself

The heart is the most important human organ. When it is dysfunctional, the entire body suffers. To identify various cardiovascular pathologies, the electrocardiography method is used. Here they use a device that records the electrical impulses of the heart - an electrocardiograph. Decoding the ECG allows you to see the main deviations in the functioning of the organ on a graphical curve, which in most cases helps to make a diagnosis without additional research, prescribe the necessary treatment.

What concepts are used when decoding

Decoding an ECG is a rather complex process that requires deep knowledge from a specialist. During the assessment of the heart condition, the cardiogram parameters are measured mathematically. In this case, such concepts as , frequency are used heart beats, electrical conductivity and electrical axis, pacemakers and some others. By assessing these indicators, the doctor can clearly determine some parameters of the functioning of the heart.

Heart rate

Heart rate is a specific number of heart beats over a certain period of time. Typically an interval of 60 seconds is taken. On a cardiogram, heart rate is determined by measuring the distance between the tallest teeth (R - R). The recording speed of the graphic curve is usually 100 mm/s. By multiplying the recording length of one mm by the duration of the segment R – R, the heart rate is calculated. U healthy person the number of heart contractions should be 60 - 80 beats per minute.

Sinus rhythm

Another concept included in the interpretation of the ECG is the sinus rhythm of the heart. During normal functioning of the heart muscle, electrical impulses arise in a special node, then spread to the area of ​​the ventricle and atrium. The presence of sinus rhythm indicates normal functioning of the heart.

The cardiogram of a healthy person should show the same distance between the R waves throughout the entire recording. A deviation of 10% is allowed. Such indicators indicate the absence of arrhythmia in a person.

Conduction Pathways

This concept defines a process such as the propagation of electrical impulses through the tissues of the heart muscle. Normally, impulses are transmitted in a certain sequence. Violation of the order of their transfer from one pacemaker to another indicates organ dysfunction and the development of various blockades. These include sinoatrial, intraatrial, atrioventricular, intraventricular blocks, as well as Wolff-Parkinson-White syndrome.

On an ECG, a specialist can see a violation of cardiac conduction

Electrical axis of the heart

When deciphering a cardiogram of the heart, the concept of the electrical axis of the heart is taken into account. This term is widely used in cardiological practice. When interpreting an ECG, this concept allows a specialist to see what is happening in the heart. In other words, the electrical axis is the totality of all biological and electrical changes within an organ.

An electrocardiogram allows you to visualize what is happening in a specific area of ​​the heart muscle using a graphic image obtained by transmitting impulses from electrodes to a special device.

The position of the electrical axis is determined by the doctor using special diagrams and tables or by comparing the QRS complexes, which are responsible for the process of excitation and contraction of the cardiac ventricles.

If ECG indicators indicate that the R wave in lead III has a smaller amplitude than in lead I, we're talking about about deviation of the cardiac axis to the left. If in lead III the R wave has a greater amplitude than in lead I, it is customary to speak of axis deviation to the right. Normal indicators in the cardiogram table - the R wave is the highest in lead II.

Teeth and intervals

On the cardiogram itself obtained during the study, the waves and intervals are not indicated. They are needed only for the specialist doing the decryption.

Prongs:

  • P – determines the beginning of contraction of the atrium;
  • Q, R, S – belong to the same type, coincide with the contraction of the ventricles;
  • T – time of inactivity of the ventricles of the heart, that is, their relaxation;
  • U - rarely noted on the cardiogram; there is no consensus on its origin.

For ease of interpretation, the cardiogram is divided into intervals. On the tape you can see straight lines that run clearly in the middle of the tooth. They are called isolines or segments. When making a diagnosis, indicators of the P – Q and S – T segments are usually taken into account.

In turn, one interval consists of segments and teeth. The length of the interval also helps assess the overall picture of heart function. The intervals P - Q and Q - T have diagnostic significance.

Reading a cardiogram

How to decipher a cardiogram of the heart? This question is asked by many patients who have had to deal with the electrocardiography procedure. It is very difficult to do this yourself, because decrypting data has a lot of nuances. And if you read certain disturbances in the activity of the heart in your cardiogram, this does not at all mean the presence of this or that disease.


A cardiologist reads a cardiogram

Prongs

In addition to taking into account the intervals and segments, it is important to monitor the height and duration of all teeth. If their fluctuations do not deviate from the norm, this indicates healthy functioning of the heart. If the amplitude is deviated, we are talking about pathological conditions.

Norm of waves on an ECG:

  • P – should have a duration of no more than 0.11 s., a height within 2 mm. If these indicators are violated, the doctor can make a conclusion about a deviation from the norm;
  • Q – should not be higher than a quarter of the R wave, wider than 0.04 s. Particular attention should be paid to this tooth; its deepening often indicates the development of myocardial infarction in a person. In some cases, tooth distortion occurs in people with severe obesity;
  • R – when deciphered, it can be traced in leads V5 and V6, its height should not exceed 2.6 mV;
  • S is a special tooth for which there are no clear requirements. Its depth depends on many factors, for example, weight, gender, age, body position of the patient, but when the tooth is too deep, we can talk about ventricular hypertrophy;
  • T – must be at least a seventh of the R wave.

In some patients, after the T wave on the cardiogram, a U wave appears. This indicator is rarely taken into account when making a diagnosis and does not have any clear standards.

Intervals and segments also have their own normal values. If these values ​​are violated, the specialist usually gives a referral to the person for further research.

Normal indicators:

  • The ST segment should normally be located directly on the isoline;
  • The QRS complex should not last more than 0.07 - 0.11 s. If these indicators are violated, various pathologies of the heart are usually diagnosed;
  • the PQ interval should last from 0.12 milliseconds to 0.21 seconds;
  • The QT interval is calculated taking into account the heart rate of a particular patient.

Important! The ST segment in leads V1 and V2 sometimes runs slightly above the baseline. The specialist must take this feature into account when deciphering the ECG.

Decryption features

To record a cardiogram, special sensors are attached to a person’s body, which transmit electrical impulses to an electrocardiograph. In medical practice, these impulses and the paths they take are called leads. Basically, 6 main leads are used during the study. They are designated by the letters V from 1 to 6.

The following rules for deciphering a cardiogram can be distinguished:

  • In lead I, II or III, you need to determine the location of the highest region of the R wave, and then measure the gap between the next two waves. This number should be divided by two. This will help determine the regularity of your heart rate. If the gap between the R waves is the same, this indicates normal contraction of the heart.
  • After this, you need to measure each tooth and interval. Their standards are described in the article above.

Most modern devices automatically measure your heart rate. When using older models, this has to be done manually. It is important to consider that the ECG recording speed is usually 25 – 50 mm/s.

Heart rate is calculated using a special formula. At an ECG recording speed of 25 mm per second, it is necessary to multiply the R - R interval distance by 0.04. In this case, the interval is indicated in millimeters.

At a speed of 50 mm per second, the R - R interval must be multiplied by 0.02.

For ECG analysis, 6 of 12 leads are usually used, since the next 6 duplicate the previous ones.

Normal values ​​in children and adults

In medical practice, there is a concept of an electrocardiogram norm, which is typical for each age group. Due to anatomical features body in newborns, children and adults, the study indicators are somewhat different. Let's take a closer look at them.

ECG norms for adults can be seen in the figure.

Children's body different from an adult. Due to the fact that the organs and systems of the newborn are not fully formed, electrocardiography data may differ.

In children, the mass of the right ventricle of the heart prevails over the left ventricle. Newborns often have a high R wave in lead III and a deep S wave in lead I.

The ratio of the P wave to the R wave in adults is normally 1:8; in children, the P wave is tall, often more pointed, in relation to R is 1:3.

Due to the fact that the height of the R wave is directly related to the volume of the ventricles of the heart, its height is lower than in adults.

In newborns, the T wave is sometimes negative and may be lower.

The PQ interval appears shortened, since in children the speed of impulses through the conduction system of the heart is higher. This also explains the shorter QRS complex.

IN preschool age electrocardiogram indicators change. During this period, a deviation of the electrical axis of the heart to the left is still observed. The mass of the ventricles increases, and accordingly, the ratio of the P wave to the R wave decreases. The force of ventricular contraction increases, the R wave becomes higher, the speed of impulse transmission through the conduction system decreases, which entails an increase in the QRS complex and PQ interval.

Children should normally have the following indicators:

Important! Only after 6–7 years do the complexes, teeth and intervals acquire the size that is characteristic of an adult.

What affects the accuracy of indicators

Sometimes the results of a cardiogram may be erroneous and differ from previous studies. Errors in results are often associated with many factors. These include:

  • incorrectly attached electrodes. If the sensors are poorly attached or become dislodged during an ECG, the test performance can be seriously affected. That is why the patient is recommended to lie still during the entire period of taking the electrocardiogram;
  • extraneous background. The accuracy of the results is often influenced by extraneous devices in the room, especially when the ECG is performed at home using mobile equipment;
  • smoking, drinking alcohol. These factors affect blood circulation, thereby changing the cardiogram parameters;
  • meal. Another reason that affects blood circulation and, accordingly, the correctness of indicators;
  • emotional experiences. If the patient is worried during the study, this may affect the heart rate and other indicators;
  • Times of Day. When conducting a study at different times of the day, the indicators may also differ.

The specialist must take into account the above-described nuances when interpreting the ECG; if possible, they should be excluded.

Dangerous diagnoses

Diagnostics using electrical cardiography helps to identify many cardiac pathologies in a patient. Among them are arrhythmia, bradycardia, tachycardia and others.

Cardiac conduction disorder

Normally, the electrical impulse of the heart passes through the sinus node, but sometimes a person has other pacemakers. In this case, symptoms may be completely absent. Sometimes conduction disturbances are accompanied by rapid fatigue, dizziness, weakness, jumps blood pressure and other signs.

At asymptomatic Special therapy is often not required, but the patient must undergo regular examinations. Many factors can negatively affect the functioning of the heart, which entails disruption of depolarization processes, decreased myocardial nutrition, development of tumors and other complications.

Bradycardia

A common type of arrhythmia is bradycardia. The condition is accompanied by a decrease in heart rate below normal (less than 60 beats per minute). Sometimes such a rhythm is considered normal, which depends on the individual characteristics of the body, but more often bradycardia indicates the development of one or another heart pathology.

Features of ECG in a patient with bradycardia can be seen in the figure.

There are several types of disease. With a hidden course of bradycardia without obvious clinical signs Therapy is usually not required. In patients with pronounced symptoms, the underlying pathology causing the disorder is treated heart rate.

Extrasystole

Extrasystole is a condition accompanied by untimely contraction of the heart. In the patient, extrasystole causes a sensation of a strong cardiac impulse, a sensation of cardiac arrest. At the same time, the patient experiences fear, anxiety, and panic. The prolonged course of this condition often leads to impaired blood flow, entailing angina pectoris, fainting, paresis and others. dangerous symptoms.

It is believed that with extrasystole no more than 5 times per hour there is no danger to health, but if attacks occur more often, appropriate treatment should be carried out.

Sinus arrhythmia

The peculiarity of this disorder is that when the heart rate changes, the work of the organ remains coordinated, the sequence of contractions of the heart parts remains normal. Sometimes a healthy person has ECG sinus arrhythmia can be observed under the influence of factors such as food intake, anxiety, and physical activity. In this case, the patient does not experience any symptoms. Arrhythmia is considered physiological.

In other situations, this disorder may indicate pathologies such as coronary heart disease, myocardial infarction, myocarditis, cardiomyopathy, and heart failure.

Patients may experience symptoms such as headaches, dizziness, nausea, heart rhythm disturbances, shortness of breath, chronic fatigue. Treatment of sinus arrhythmia involves getting rid of the underlying pathology.


Norm and signs of arrhythmia on a cardiogram

Important! In children, sinus arrhythmia often occurs in adolescence, may be associated with hormonal imbalances.

Tachycardia

With tachycardia, the patient experiences an increase in heart rate, that is, more than 90 beats per minute. Normally, tachycardia develops in people after strong physical activity, sometimes stress can cause palpitations. In a normal state, the rhythm is normalized without consequences for health.

It is important to note that tachycardia is not an independent disease and does not occur on its own. This disorder always acts as a secondary symptom of some pathology. This means that treatment should be aimed at the disease causing the increased heart rate.

One of the forms coronary disease, occurring in the acute stage - myocardial infarction. The condition is accompanied by the death of myocardial tissue, often leading to irreversible consequences.

The course of a heart attack usually occurs in several stages, each of which is characterized by changes in ECG parameters:

  • the early stage lasts 6–7 days. In the first few hours, the cardiogram shows a high T wave. Over the next three days, the ST interval increases, the T wave goes down. With timely treatment at this stage, it is possible to completely restore myocardial function;
  • the appearance of dead areas. The cardiogram shows an increase and widening of the Q wave. Medical therapy here involves restoration of areas with tissue necrosis;
  • subacute period. This stage lasts from 10 to 30 days. Here the cardiogram begins to return to normal. Scars appear at the site of the affected areas of the myocardium;
  • scarring stage. Its duration takes from 30 days or more, accompanied by complete scarring of the tissue. Sometimes patients experience cardiosclerosis and other changes.

In the picture you can see the change in ECG indicators during the disease.


Cardiogram indicators for myocardial infarction at different stages

Electrocardiography is a complex, but at the same time very informative diagnostic method, used in medical practice for decades. It is quite difficult to independently decipher the graphic image obtained during the study. Data interpretation should be carried out by a qualified physician. This will help to accurately diagnose and prescribe appropriate treatment.

The electrocardiogram reflectselectrical processes onlyin the myocardium: depolarization (excitation) and repolarization (restoration) of myocardial cells.

Ratio ECG intervals With phases of the cardiac cycle(ventricular systole and diastole).

Normally, depolarization leads to contraction of the muscle cell, and repolarization leads to relaxation.

To simplify further, instead of “depolarization-repolarization” I will sometimes use “contraction-relaxation”, although this is not entirely accurate: there is a concept “ electromechanical dissociation“, in which depolarization and repolarization of the myocardium do not lead to its visible contraction and relaxation.

Elements of a normal ECG

Before moving on to deciphering the ECG, you need to understand what elements it consists of.

Waves and intervals on the ECG.

It's interesting that abroad P-Q interval usually calledP-R.

Any ECG consists of waves, segments and intervals.

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

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

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

INTERVALS
The interval consists of tooth (complex of teeth) and segment. Thus, interval = tooth + segment. The most important are the P-Q and Q-T intervals.

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

QRS complex waves

Since the ventricular myocardium is more massive than the atrial myocardium and has not only walls, but also a massive interventricular septum, the spread of excitation in it is characterized by the appearance of a complex complex QRS on the ECG.

How to do it right highlight the teeth in it?

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

The R wave (r) is called any positive(upward) wave that is part of the QRS complex. If there are several teeth, subsequent teeth indicate strokes: R, R’, R”, etc.

Negative (downward) wave of the QRS complex, located before the R wave, is denoted as Q(q), and after - like S(s). If there are no positive waves at all in the QRS complex, then the ventricular complex is designated as QS.

Variants of the QRS complex.

Normal:

Q wave reflects depolarization of the interventricular septum (the interventricular is excitedforged partition)

R wave - depolarizationbulk of the ventricular myocardium ( the apex of the heart and adjacent areas are excited)

S wave - depolarization basal (i.e. near the atria) sections of the interventricular septum ( the base of the heart is excited)

R wave V1, V2 reflects excitation of the interventricular septum,

A R V4, V5, V6 - stimulation of the muscles of the left and right ventricles.

Necrosis of areas of the myocardium (for example, withmyocardial infarction ) causes the Q wave to widen and deepen, so close attention is always paid to this wave.

ECG analysis

General scheme of ECG decoding

  1. Checking the correctness of ECG registration.
  2. Heart rate and conduction analysis:
    • assessment of heart rate regularity,
    • heart rate (HR) counting,
    • determination of the source of excitation,
    • conductivity assessment.
  3. Determination of the electrical axis of the heart.
  4. Analysis of the atrial P wave and P-Q interval.
  5. Analysis of the ventricular QRST complex:
    • QRS complex analysis,
    • analysis of the RS - T segment,
    • T wave analysis,
    • Q-T interval analysis.
  6. Electrocardiographic report.

Normal electrocardiogram.

1) Checking the correctness of ECG registration

At the beginning of each ECG tape there must be calibration signal- the so-called reference millivolt. To do this, at the beginning of the recording, a standard voltage of 1 millivolt is applied, which should display a deviation of 10 mm. Without a calibration signal, the ECG recording is considered incorrect.

Normally, in at least one of the standard or enhanced limb leads, the amplitude should exceed 5 mm, and in chest leads - 8 mm. If the amplitude is lower, it is called reduced ECG voltage, which occurs in some pathological conditions.

2) Heart rate and conduction analysis:

  1. assessment of heart rate regularity

    Rhythm regularity is assessed by R-R intervals. If the teeth are at an equal distance from each other, the rhythm is called regular, or correct. Variation in the duration of individual R-R intervals no more ± 10% from their average duration. If the rhythm is sinus, it is usually regular.

  2. heart rate (HR) counting

    The ECG film has large squares printed on it, each of which contains 25 small squares (5 vertical x 5 horizontal).

    To quickly calculate heart rate with the correct rhythm, count the number of large squares between two adjacent teeth R - R.

    At belt speed 50 mm/s: HR = 600 / (number of large squares).
    At belt speed 25 mm/s: HR = 300 / (number of large squares).

    At a speed of 25 mm/s, each small cell is equal to 0.04 s,

    and at a speed of 50 mm/s - 0.02 s.

    This is used to determine the duration of the teeth and intervals.

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

  3. determination of the excitation source

    In other words, they are looking for where pacemaker, which causes contractions of the atria and ventricles.

    Sometimes this is one of the most difficult stages, because various disorders of excitability and conduction can be very confusingly combined, which can lead to incorrect diagnosis and incorrect treatment.

SINUS rhythm (this is a normal rhythm, and all other rhythms are pathological).
The source of excitation is in sinoatrial node.

Signs on the ECG:

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

P wave in sinus rhythm.

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

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

P wave during atrial rhythm.

Rhythms from the AV connection. If the pacemaker is in the atrioventricular ( atrioventricular node) node, then the ventricles are excited as usual (from top to bottom), and the atria - retrograde (i.e. from bottom to top).

At the same time, on the ECG:

  • P waves may be absent because they are superimposed on normal QRS complexes,
  • P waves can be negative, located after the QRS complex.

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

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

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

Ventricular, or IDIOVENTRICULAR, rhythm

In this case, the source of rhythm is the ventricular conduction system.

Excitation spreads through the ventricles in the wrong way and is therefore slower. Features of idioventricular rhythm:

  • QRS complexes are widened and deformed (they look “scary”). Normally, the duration of the QRS complex is 0.06-0.10 s, therefore, with this rhythm, the QRS exceeds 0.12 s.
  • there is no pattern between QRS complexes and P waves because the AV junction does not release impulses from the ventricles, and the atria can be excited from sinus node, as normal.
  • Heart rate less than 40 beats per minute.

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

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

To assess conductivity, measure:

  • P wave duration (reflects the speed of impulse transmission through the atria),normal up to 0.1 s.
  • duration of the P - Q interval (reflects the speed of impulse conduction from the atria to the ventricular myocardium); interval P - Q = (wave P) + (segment P - Q). Normal 0.12-0.2 s .
  • duration of the QRS complex (reflects the spread of excitation through the ventricles). Normally 0.06-0.1 s.
  • interval of internal deviation in leads V1 and V6. This is the time between the onset of the QRS complex and the R wave. Normally in V1 up to 0.03 s and in V6 up to 0.05 s. Used mainly to recognize bundle branch blocks and to determine the source of excitation in the ventricles in the case of ventricular extrasystole(extraordinary contraction of the heart).

Measuring the internal deviation interval.

3) Determination of the electrical axis of the heart.

4) Analysis of the atrial P wave.

  • Normally, in leads I, II, aVF, V2 - V6, the P wavealways positive.
  • In leads III, aVL, V1, the P wave can be positive or biphasic (part of the wave is positive, part is negative).
  • In lead aVR, the P wave is always negative.
  • Normally, the duration of the P wave does not exceed0.1 s, and its amplitude is 1.5 - 2.5 mm.

Pathological deviations of the P wave:

  • Pointed high P waves of normal duration in leads II, III, aVF are characteristic of right atrial hypertrophy, for example, with “pulmonary heart”.
  • Split with 2 apexes, widened P wave in leads I, aVL, V5, V6 is characteristic ofleft atrial hypertrophy, for example, with mitral valve defects.

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

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

4) P-Q interval analysis:

normal 0.12-0.20 s.

An increase in this interval occurs when the conduction of impulses through the atrioventricular node is impaired ( atrioventricular block, AV block).

There are 3 degrees of AV block:

  • I degree - the P-Q interval is increased, but each P wave has its own QRS complex ( no loss of complexes).
  • II degree - QRS complexes partially fall out, i.e. Not all P waves have their own QRS complex.
  • III degree - complete blockade of conduction in the AV node. The atria and ventricles contract at their own rhythm, independently of each other. Those. idioventricular rhythm occurs.

5) Analysis of the ventricular QRST complex:

  1. QRS complex analysis.

    The maximum duration of the ventricular complex is 0.07-0.09 s(up to 0.10 s).

    The duration increases with any bundle branch block.

    Normally, the Q wave can be recorded in all standard and enhanced limb leads, as well as in V4-V6.

    The amplitude of the Q wave normally does not exceed 1/4 R wave height, and the duration is 0.03 s.

    In lead aVR, there is normally a deep and wide Q wave and even a QS complex.

    The R wave, like the Q wave, can be recorded in all standard and enhanced limb leads.

    From V1 to V4, the amplitude increases (in this case, the r wave of V1 may be absent), and then decreases in V5 and V6.

    The S wave can have very different amplitudes, but usually no more than 20 mm.

    The S wave decreases from V1 to V4, and may even be absent in V5-V6.

    In lead V3 (or between V2 - V4) “ transition zone” (equality of R and S waves).

  2. RS - T segment analysis

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

    Normally, the S-T segment is located in the limb leads on the isoline ( ± 0.5 mm).

    In leads V1-V3, the S-T segment may shift upward (no more than 2 mm), and in leads V4-V6 - downward (no more than 0.5 mm).

    The point at which the QRS complex transitions to the S-T segment is called the point j(from the word junction - connection).

    The degree of deviation of point j from the isoline is used, for example, to diagnose myocardial ischemia.

  3. T wave analysis.

    The T wave reflects the process of repolarization of the ventricular myocardium.

    In most leads where a high R is recorded, the T wave is also positive.

    Normally, the T wave is always positive in I, II, aVF, V2-V6, with T I > T III, and T V6 > T V1.

    In aVR the T wave is always negative.

  4. Q-T interval analysis.

    The Q-T interval is called electrical ventricular systole, because at this time all parts of the ventricles of the heart are excited.

    Sometimes after the T wave there is a small U wave, which is formed due to short-term increased excitability of the ventricular myocardium after their repolarization.

6) Electrocardiographic report.
Should include:

  1. Source of rhythm (sinus or not).
  2. Regularity of rhythm (correct or not). Usually sinus rhythm is normal, although respiratory arrhythmia is possible.
  3. Position of the electrical axis of the heart.
  4. Presence of 4 syndromes:
    • rhythm disturbance
    • conduction disturbance
    • hypertrophy and/or overload of the ventricles and atria
    • myocardial damage (ischemia, dystrophy, necrosis, scars)

Interference on the ECG

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

Three types of ECG interference(explained below).

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

ECG analysis algorithm: determination method and basic standards

Good afternoon, dear teapot. If you were looking for a site where you can improve your ECG skills at least a little, then you have come to the right place. The site contains more than 100 ECGs with examples of transcripts, mainly in theory assignments. I strongly recommend that you start from the beginning and if you study diligently, then within 1-2 weeks you will be able to distinguish normality from pathology. Of course, this will only be possible if you are a beginner with a medical education.

Here for you I will analyze an example of the first ECG I came across. In order for you to understand the amount of work that remains to be mastered. You will also be able to evaluate the quality of the ECG images collected by me as part of this project.

Decoding an ECG for dummies - an example.

The conclusion looks like this: Sinus rhythm, heart rate=62/min, AV block I stage, Incomplete blockade right bundle branch. Nonspecific disturbance of repolarization in the lateral wall area.

How we determined it.

  1. Sinus rhythm - here in the second lead there is a P wave, it is positive and follows each ventricular complex at the same distance.
  2. Heart rate— There are 49 cells between the RR teeth (3000/49≈62).
  3. AV block I stage — PR > 0.2, which indicates the presence of an AV block.
  4. Incomplete right bundle branch block - the ventricular complex is expanded (0.13 s) there is a characteristic rsr V1 complex.
  5. Nonspecific disturbance of repolarization in the lateral wall area. — T waves in leads V5-V6 are smoothed.

This ECG is not too complicated if you follow the ECG interpretation plan and know how to use a ruler, but also of course know the theory. I made sure not to overload you with this very theory. Each section provides only the information that a “non-cardiologist” doctor needs for a high-quality interpretation of the ECG at an acceptable level.

Complete right bundle branch block (RBBB). The patient is 62 years old, with complaints of cough, clinical picture of acute bronchitis. No acute coronary pathology was detected.

Atrial extrasystole. A 73-year-old female patient came to the clinic due to worsening hypertension. He does not feel any interruptions in his heart function, emergency treatment not required.

Atrial flutter

Atrial flutter, regular form 2:1, heart rate 130 per minute. A 66-year-old patient has been experiencing palpitations for 1 month. Previously, rhythm disturbances were not detected.

Atrial flutter, irregular shape, heart rate 104 per minute. The same patient after intravenous administration of 10 mg verapamil.

Paroxysmal supraventricular tachycardia

Paroxysmal supraventricular tachycardia. A 66-year-old female patient complains of general weakness and palpitations for 1 hour. There is a history of repeated paroxysms of PSVT. The paroxysm was stopped by an intravenous bolus of ATP 10 mg.

Sinus bradycardia

Sinus bradycardia. Heart rate 42 per minute. A 54-year-old patient complains of general weakness, dizziness, nausea, and vomiting. BP 60/30. Toxic effect of ethanol. After intravenous administration of 0.5 ml of atropine, heart rate increased to 64 per minute.

Atrial fibrillation

Atrial fibrillation, normosystole, heart rate 82 per minute. An 83-year-old female patient presented with pain in the chest vertebrogenic genesis. History: IHD. Permanent form of atrial fibrillation. There are no dynamics with the previous ECG. No rhythm or heart rate correction is required.

Acute myocardial infarction

Acute anterolateral myocardial infarction. The patient is 72 years old, the duration of the pain attack is 8 hours. A typical attack of anginal pain, accompanied by sweating and weakness. Nitrates have no effect. Treatment according to the standard of acute coronary syndrome with ST segment elevation; pain syndrome was relieved after administration of morphine. She was hospitalized at the vascular center for coronary angiography and further treatment.

An electrocardiograph (ECG) is a device that allows you to evaluate cardiac activity, as well as diagnose the condition of this organ. During the examination, the doctor receives data in the form of a curve. How to read an ECG waveform? What types of teeth are there? What changes are visible on the ECG? Why do doctors need this diagnostic method? What does the ECG show? These are not all the questions that interest people who are faced with electrocardiography. First you need to know how the heart works.

The human heart consists of two atria and two ventricles. The left side of the heart is more developed than the right, as it bears a greater load. It is this ventricle that most often suffers. Despite the difference in size, both sides of the heart must work stably and harmoniously.

Learning to read an electrocardiogram on your own

How to read an ECG correctly? This is not as difficult to do as it might seem at first glance. First you should look at the cardiogram. It is printed on special paper that has cells, and two types of cells are clearly visible: large and small.

The ECG conclusion is read from these cells. teeth, cells? These are the main parameters of the cardiogram. Let's try to learn how to read an ECG from scratch.

The meaning of cells (cells)

There are two types of cells on the paper for printing the examination result: large and small. All of them consist of vertical and horizontal guides. The vertical ones are voltage, and the horizontal ones are time.

Large squares consist of 25 small cells. Each small cell is equal to 1 mm and corresponds to 0.04 seconds in the horizontal direction. Large squares equal 5 mm and 0.2 seconds. In the vertical direction, a centimeter of strip is equal to 1 mV of voltage.

Prongs

There are five teeth in total. Each of them displays the work of the heart on a graph.

  1. P - ideally, this wave should be positive in the range from 0.12 to two seconds.
  2. Q - negative wave, shows the condition of the interventricular septum.
  3. R - displays the state of the ventricular myocardium.
  4. S - negative wave, shows the completion of processes in the ventricles.
  5. T - positive wave, indicates restoration of potential in the heart.

All ECG waves have their own reading characteristics.

P wave

All waves of the electrocardiogram have a certain significance for making the correct diagnosis.

The very first tooth of the graph is called P. It indicates the time between heartbeats. To measure it, it is best to isolate the beginning and end of the tooth and then count the number of small cells. Normally, the P wave should be between 0.12 and two seconds.

However, measuring this indicator in only one area will not give accurate results. To make sure that the heartbeat is even, it is necessary to determine the P wave interval in all parts of the electrocardiogram.

R wave

Knowing how to read an ECG the easy way, you can understand whether there are heart pathologies. The next important peak on the chart is R. It is easy to find - it is the highest peak on the chart. This will be the positive tooth. Its highest part is marked on the cardiogram as R, and its lower parts as Q and S.

The QRS complex is called the ventricular or sinus complex. In a healthy person, the sinus rhythm on the ECG is narrow and high. The ECG R waves are clearly visible in the figure, they are the highest:

Between these peaks, the number of large squares indicates this indicator is calculated using the following formula:

300/number of large squares = heart rate.

For example, there are four full squares between the peaks, then the calculation will look like this:

300/4=75 heart beats per minute.

Sometimes the cardiogram shows a prolongation of the QRS complex by more than 0.12 s, which indicates a blockade of the His bundle.

PQ tooth spacing

PQ is the interval from the P wave to the Q wave. It corresponds to the time of excitation through the atria to the ventricular myocardium. PQ interval norm in different ages various. Usually it is 0.12-0.2 s.

With age, the interval increases. Thus, in children under 15 years of age, PQ can reach 0.16 s. Between the ages of 15 and 18 years, PQ increases to 0.18 s. In adults, this figure is equal to a fifth of a second (0.2).

When the interval lengthens to 0.22 s, they speak of bradycardia.

QT wave interval

If this complex is longer, then we can assume ischemic heart disease, myocarditis or rheumatism. With the shortened type, hypercalcemia may be observed.

ST interval

Normally, this indicator is located at the level of the midline, but can be two cells higher than it. This segment shows the process of restoring depolarization of the heart muscle.

In rare cases, the indicator may rise three cells above the midline.

Norm

The transcript of the cardiogram should normally look like this:

  • The Q and S segments must always be below the midline, i.e. negative.
  • The R and T waves should normally be located above the midline, i.e. they will be positive.
  • The QRS complex should be no wider than 0.12 s.
  • Heart rate should be between 60 and 85 beats per minute.
  • There should be sinus rhythm on the ECG.
  • The R should be higher than the S wave.

ECG for pathologies: sinus arrhythmia

How to read an ECG when various pathologies? One of the most common heart diseases is sinus rhythm disorder. It can be pathological and physiological. The latter type is usually diagnosed in people involved in sports and with neuroses.

With sinus arrhythmia, the cardiogram has the following form: sinus rhythms are preserved, fluctuations in the R-R intervals are observed, but during breath holding the graph is smooth.

With pathological arrhythmia, preservation of the sinus impulse is observed constantly, regardless of breath holding, while wave-like changes are observed at all R-R intervals.

Manifestation of a heart attack on an ECG

When myocardial infarction occurs, changes in the ECG are pronounced. Signs of pathology are:

  • increase in heart rate;
  • ST segment is elevated;
  • there is a fairly persistent depression in the ST leads;
  • The QRS complex increases.

In case of a heart attack, the main means of recognizing zones of necrosis of the heart muscle is a cardiogram. It can be used to determine the depth of organ damage.

During a heart attack, the ST segment will be elevated and the R wave will be depressed, giving the ST a cat's back shape. Sometimes, with pathology, changes in the Q wave can be observed.

Ischemia

When it occurs, you can see in which part it is located.

  • The location of ischemia at the anterior wall of the left ventricle. Diagnosed with symmetrical pointed T-waves.
  • Location at the epicardium of the left ventricle. The T-wave is pointed, symmetrical, and directed downward.
  • Transmural type of left ventricular ischemia. T is pointed, negative, symmetrical.
  • Ischemia of the left ventricular myocardium. T is smoothed, slightly raised upward.
  • Heart damage is indicated by the state of the T wave.

Changes in the ventricles

ECG shows changes in the ventricles. Most often they appear in the left ventricle. This type of cardiogram occurs in people with long-term additional stress, for example, obesity. With this pathology, there is a deviation of the electrical axis to the left, against the background of which the S wave becomes higher than R.

Holter method

How can you learn to read an ECG if it is not always clear which waves are located and how they are located? In such cases, continuous recording of the cardiogram using a mobile device is prescribed. It constantly records ECG data on a special tape.

This examination method is necessary in cases where classical ECG fails to detect pathologies. During a Holter diagnosis, a detailed diary is necessarily kept, where the patient records all his actions: sleep, walks, sensations during activities, all activities, rest, symptoms of the disease.

Typically, data recording occurs within 24 hours. However, there are times when it is necessary to take readings for up to three days.

ECG interpretation schemes

  1. The conductivity and rhythm of the heart are analyzed. To do this, the regularity of heart contractions is assessed, the number of heart rates is calculated, and the conduction system is determined.
  2. Axial rotations are detected: the position of the electric axis is determined in frontal plane; around the transverse, longitudinal axis.
  3. The R wave is analyzed.
  4. QRS-T is analyzed. In this case, the state of the QRS complex, RS-T, T wave, as well as the Q-T interval are assessed.
  5. A conclusion is made.

The duration of the R-R cycle indicates the regularity and normality of the heart rhythm. When assessing heart function, more than one is assessed R-R gap, that's all. Normally, deviations within 10% of the norm are allowed. In other cases, an incorrect (pathological) rhythm is determined.

To establish pathology, the QRS complex and a certain period of time are taken. It counts the number of times a segment is repeated. Then the same period of time is taken, but further on the cardiogram, it is calculated again. If at equal periods of time the number of QRS is the same, then this is the norm. With different quantities, pathology is assumed, and they focus on the P waves. They must be positive and stand before the QRS complex. Throughout the entire graph, the shape of P should be the same. This option indicates a sinus rhythm of the heart.

At atrial rhythms the P wave is negative. Behind it is the QRS segment. In some people, the P wave on the ECG may be absent, completely merging with the QRS, which indicates pathology of the atria and ventricles, which the impulse reaches simultaneously.

Ventricular rhythm is shown on the electrocardiogram as a deformed and widened QRS. In this case, the connection between P and QRS is not visible. There are large distances between the R waves.

Cardiac conduction

The ECG determines cardiac conduction. The P wave determines the atrial impulse; normally this indicator should be 0.1 s. The P-QRS interval reflects the overall conduction velocity through the atria. The norm of this indicator should be within 0.12 to 0.2 s.

The QRS segment shows conduction through the ventricles; the normal range is 0.08 to 0.09 s. As the intervals increase, cardiac conduction slows down.

Patients do not need to know what the ECG shows. A specialist should understand this. Only a doctor can correctly decipher the cardiogram and make the correct diagnosis, taking into account the degree of deformation of each individual tooth or segment.

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