The ventricular rhythm on the ECG is normal. ECG intervals and waves are normal. Heart rate

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Definition and essence of the method

To understand the essence of an electrocardiogram, you need to know what exactly is recorded by a device called an electrocardiograph. The ECG records the electrical activity of the heart, which changes cyclically in accordance with the onset of diastole and systole. The electrical activity of the human heart may seem like fiction, but this unique biological phenomenon exists in reality. In reality, the heart contains so-called cells of the conduction system, which generate electrical impulses that are transmitted to the muscles of the organ. It is these electrical impulses that cause the myocardium to contract and relax with a certain rhythm and frequency.

The electrical impulse propagates through the cells of the conduction system of the heart strictly sequentially, causing contraction and relaxation of the corresponding sections - the ventricles and atria. The electrocardiogram reflects precisely the total electrical potential difference in the heart.

decryption?

An electrocardiogram is recorded using a special device - an electrocardiograph, which can be multi-channel or single-channel. The speed depends on the modification and modernity of the device ECG records. Modern devices can be connected to a computer, which, with a special program, will analyze the recording and issue a final conclusion immediately after the procedure is completed.

Any cardiograph has special electrodes that are applied in a strictly defined order. There are four clothespins in red, yellow, green and black that are placed on both arms and both legs. If you go in a circle, then the clothespins are applied according to the rule “red-yellow-green-black”, from the right hand. It's easy to remember this sequence thanks to the student saying: "Every-Woman is an Eviler Trait." In addition to these electrodes, there are also chest electrodes, which are installed in the intercostal spaces.

As a result, the electrocardiogram consists of twelve waveforms, six of which are recorded from the chest electrodes, and are called chest leads. The remaining six leads are recorded from electrodes attached to the arms and legs, with three of them called standard and three more called enhanced. The chest leads are designated V1, V2, V3, V4, V5, V6, the standard ones are simply Roman numerals - I, II, III, and the reinforced leg leads - the letters aVL, aVR, aVF. Different leads of the cardiogram are necessary to create the most complete picture of the activity of the heart, since some pathologies are visible on the chest leads, others on the standard ones, and still others on the enhanced ones.

The person lies down on the couch, the doctor attaches the electrodes and turns on the device. While the ECG is being written, the person must be absolutely calm. We must not allow the appearance of any irritants that can distort the true picture of the work of the heart.

How to correctly perform an electrocardiogram followed by
transcript - video

The principle of decoding an ECG

All sharp and smooth convexities and concavities on the ECG line are called teeth. Each tooth is designated by a letter of the Latin alphabet. The P wave reflects contraction of the atria, the QRS complex – contraction of the ventricles of the heart, the T wave – relaxation of the ventricles. Sometimes after the T wave on the electrocardiogram there is another U wave, but it has no clinical and diagnostic role.

An ECG segment is considered to be a segment enclosed between adjacent teeth. For diagnosing heart pathology, the P – Q and S – T segments are of great importance. The interval on the electrocardiogram is a complex that includes a tooth and an interval. The P–Q and Q–T intervals are of great importance for diagnosis.

Often in the doctor’s report you can see small Latin letters, which also indicate teeth, intervals and segments. Small letters are used if the prong is less than 5 mm long. In addition, several R waves may appear in the QRS complex, which are usually designated R’, R”, etc. Sometimes the R wave is simply missing. Then the entire complex is designated by only two letters - QS. All this has important diagnostic significance.

ECG interpretation plan - general scheme for reading results

• position of the electrical axis of the heart;
• determining the correctness of the heart rhythm and conductivity of the electrical impulse (blockades, arrhythmias are identified);
• determining the regularity of contractions of the heart muscle;
• determination of heart rate;
• identifying the source of the electrical impulse (whether sinus rhythm is determined or not);
• analysis of the duration, depth and width of the atrial P wave and the P – Q interval;
• analysis of the duration, depth, width of the QRST ventricular wave complex;
• analysis of parameters of the RS – T segment and T wave;
• analysis of Q – T interval parameters.

In the conclusion on the electrocardiogram, the doctor must reflect the following parameters:

• sinus rhythm or not;
• rhythm regularity;
• heart rate (HR);
• position of the electrical axis of the heart.

Example of deciphering an electrocardiogram

Checking the regularity of heart contractions

Heart rate (HR) calculation

For example, if 4.8 large squares fit between two R teeth, then the heart rate, at a belt speed of 50 mm/s, will be equal to 600/4.8 = 125 beats per minute.

If the heart rate is abnormal, then the maximum and minimum heart rate is determined, also taking as a basis the maximum and minimum distances between the R waves.

Identifying the source of the rhythm

Decoding ECG - rhythms

In sinus rhythm on the electrocardiogram in lead II there is a P wave before each QRS complex, and it is always positive. In one lead, all P waves should have the same shape, length and width.

With atrial rhythm the P wave in leads II and III is negative, but is present before each QRS complex.

Atrioventricular rhythms are characterized by the absence of P waves on cardiograms, or the appearance of this wave after the QRS complex, and not before it, as is normal. With this type of rhythm, the heart rate is low, ranging from 40 to 60 beats per minute.

Ventricular rhythm characterized by an increase in the width of the QRS complex, which becomes large and quite frightening. The P waves and the QRS complex are completely unrelated to each other. That is, there is no strict correct normal sequence - the P wave, followed by the QRS complex. Ventricular rhythm is characterized by a decrease in heart rate - less than 40 beats per minute.

Detection of pathology of electrical impulse conduction through the structures of the heart

The normal duration of the P wave is up to 0.1 seconds, the P – Q interval is 0.12-0.2 seconds, the QRS complex is 0.06-0.1 seconds.

Electrical axis of the heart

The electrical axis of the heart can deviate under various pathological conditions. For example, hypertension leads to a deviation to the right; a conduction disorder (blockade) can shift it to the right or left.

Atrial P wave

• positive in I, II, aVF and chest leads (2, 3,4, 5, 6);
• negative in aVR;
• biphasic (part of the tooth lies in the positive region, and part in the negative) in III, aVL, V1.

Pathological forms of the P wave may indicate the following pathologies:
1. Tall and sharp teeth in leads II, III, aVF appear with hypertrophy of the right atrium (“cor pulmonale”);
2. A P wave with two peaks and a large width in leads I, aVL, V5 and V6 indicates hypertrophy of the left atrium (for example, mitral valve disease).

P–Q interval

• I degree: simple lengthening of the P–Q interval while preserving all other complexes and waves.
• II degree: prolongation of the P–Q interval with partial loss of some QRS complexes.
• III degree: lack of connection between the P wave and QRS complexes. In this case, the atria work in their own rhythm, and the ventricles - in their own.

Ventricular QRST complex

QRS complex consists of three waves, Q, R and S, respectively. The Q wave is visible on the cardiogram in all leads except 1, 2 and 3 chest leads. A normal Q wave has an amplitude up to 25% of that of an R wave. The duration of the Q wave is 0.03 seconds. The R wave is recorded in absolutely all leads. The S wave is also visible in all leads, but its amplitude decreases from the 1st thoracic to the 4th, and in the 5th and 6th it may be completely absent. The maximum amplitude of this tooth is 20 mm.

The S–T segment is very important from a diagnostic point of view. It is by this tooth that myocardial ischemia can be detected, that is, a lack of oxygen in the heart muscle. Usually this segment runs along the isoline, in the 1st, 2nd and 3rd chest leads; it can rise up by a maximum of 2 mm. And in the 4th, 5th and 6th chest leads, the S-T segment can shift below the isoline by a maximum of half a millimeter. It is the deviation of the segment from the isoline that reflects the presence of myocardial ischemia.

T wave

Q-T interval

ECG interpretation - normal indicators

Normally, the rhythm should be only sinus, the heart rate of an adult is 60 - 90 beats per minute. The P wave is normally no more than 0.1 s, the P – Q interval is 0.12-0.2 seconds, the QRS complex is 0.06-0.1 seconds, Q – T is up to 0.4 s.

If the cardiogram is pathological, then it indicates specific syndromes and deviations from the norm (for example, partial blockade of the left bundle branch, myocardial ischemia, etc.). The doctor can also reflect specific violations and changes in the normal parameters of the waves, intervals and segments (for example, shortening of the P wave or Q-T interval, etc.).

Interpretation of ECG in children and pregnant women

In pregnant women, there may be a slight deviation of the electrical axis of the heart by later gestation due to compression by the growing uterus. In addition, sinus tachycardia often develops, that is, an increase in heart rate to 110 - 120 beats per minute, which is functional state, and goes away on its own. An increase in heart rate is associated with a greater volume of circulating blood and increased workload. Due to increased workload on the heart, pregnant women may experience overload various departments organ. These phenomena are not a pathology - they are associated with pregnancy and will go away on their own after childbirth.

Decoding the electrocardiogram during a heart attack

In the process of development of myocardial infarction, four stages are distinguished, which have different manifestations on ECG:

• acute;
• acute;
• subacute;
• cicatricial.

Sometimes it is possible to detect the phase of myocardial ischemia preceding the acute phase, which is characterized by high T waves.

Acute stage A heart attack lasts 2–3 weeks. During this period, a wide and high-amplitude Q wave and a negative T wave are recorded on the ECG.

Subacute stage lasts up to 3 months. The ECG shows a very large negative T wave with a huge amplitude, which gradually normalizes. Sometimes a rise in the S-T segment is detected, which should have leveled off by this period. This is an alarming symptom, as it may indicate the formation of a cardiac aneurysm.

Scar stage heart attack is final, since connective tissue is formed at the damaged site, incapable of contraction. This scar is recorded on the ECG as a Q wave, which will remain for life. Often the T wave is smoothed, has a low amplitude, or is completely negative.

Interpretation of the most common ECGs

Ectopic rhythm means not sinus - which can be either a pathology or a norm. The norm is ectopic rhythm when there is a congenital malformation of the conduction system of the heart, but the person does not present any complaints and does not suffer from other cardiac pathologies. In other cases, an ectopic rhythm indicates the presence of blockades.

Changes in repolarization processes on the ECG reflects a violation of the process of relaxation of the heart muscle after contraction.

Sinus rhythm– this is a normal heart rhythm healthy person.

Sinus or sinusoidal tachycardia means that a person has a correct and regular rhythm, but an increased heart rate - more than 90 beats per minute. In young people under 30 years of age, this is a variant of the norm.

Sinus bradycardia- this is a low heart rate - less than 60 beats per minute against the background of a normal, regular rhythm.

Nonspecific ST-T changes mean that there are minor deviations from the norm, but their cause may be completely unrelated to heart pathology. Must pass full examination. Such nonspecific ST-T changes can develop with an imbalance of potassium, sodium, chlorine, magnesium ions, or various endocrine disorders, often during menopause in women.

Biphasic R wave in combination with other signs of a heart attack indicates damage to the anterior wall of the myocardium. If no other signs of a heart attack are detected, then a biphasic R wave is not a sign of pathology.

QT prolongation may indicate hypoxia (lack of oxygen), rickets, or overexcitation nervous system in a child, which is a consequence of birth trauma.

Myocardial hypertrophy means that the muscular wall of the heart is thickened and works under enormous load. This can lead to the formation of:

• heart failure;
• arrhythmias.

Moderate diffuse changes in the myocardium mean that tissue nutrition is impaired and cardiac muscle dystrophy has developed. This is a fixable condition: you need to see a doctor and undergo an adequate course of treatment, including normalizing your diet.

Deviation of the electrical axis of the heart (EOS) left or right is possible with hypertrophy of the left or right ventricle, respectively. EOS can deviate to the left in obese people, and to the right - in thin people, but in this case this is a variant of the norm.

Left type ECG– EOS deviation to the left.

NBPNG– an abbreviation for “incomplete right bundle branch block.” This condition can occur in newborns and is a normal variant. In rare cases, RBBB can cause arrhythmia, but generally does not lead to the development negative consequences. Block of the Hiss bundle branch is quite common in people, but if there are no complaints about the heart, then it is not at all dangerous.

BPVLNPG– an abbreviation meaning “blockade of the anterior branch of the left bundle branch.” Reflects a violation of the conduction of electrical impulses in the heart, and leads to the development of arrhythmias.

Small growth of the R wave in V1-V3 may be a sign of a heart attack interventricular septum. To accurately determine whether this is the case, it is necessary to do another ECG study.

CLC syndrome(Klein-Levy-Kritesco syndrome) is a congenital feature of the conduction system of the heart. May cause the development of arrhythmias. This syndrome does not require treatment, but it is necessary to be regularly examined by a cardiologist.

Short ECG voltage often recorded with pericarditis ( large volume connective tissue in the heart, replacing muscle tissue). In addition, this sign may be a reflection of exhaustion or myxedema.

Metabolic changes are a reflection of insufficient nutrition of the heart muscle. It is necessary to be examined by a cardiologist and undergo a course of treatment.

Conduction slowdown means that nerve impulse passes through the tissues of the heart more slowly than normal. This condition itself does not require special treatment - it may be a congenital feature of the conduction system of the heart. Regular monitoring by a cardiologist is recommended.

Blockade 2 and 3 degrees reflects a serious disturbance of cardiac conduction, which is manifested by arrhythmia. In this case, treatment is necessary.

Rotation of the heart by the right ventricle forward May be indirect sign development of hypertrophy. In this case, it is necessary to find out its cause and undergo a course of treatment, or adjust your diet and lifestyle.

Price of an electrocardiogram with interpretation

If you want to receive a thorough and detailed conclusion on the electrocardiogram, a doctor’s explanation of all the parameters and changes, it is better to contact a private clinic that provides similar services. Here the doctor will be able not only to write a conclusion after deciphering the cardiogram, but also to calmly talk to you, taking his time to explain all the points of interest. However, the cost of such a cardiogram with interpretation in a private medical center ranges from 800 rubles to 3,600 rubles. You should not assume that bad specialists work in an ordinary clinic or hospital - it’s just that a doctor in a public institution, as a rule, has a very large amount of work, so he simply does not have time to talk with each patient in great detail.

A normal ECG consists primarily of P, Q, R, S and T waves.
Between the individual teeth are the PQ, ST and QT segments, which have important clinical significance.
The R wave is always positive, and the Q and S waves are always negative. The P and T waves are normally positive.
The spread of excitation in the ventricle on the ECG corresponds to the QRS complex.
When they talk about restoring myocardial excitability, they mean the ST segment and the T wave.

Normal ECG usually consists of waves P, Q, R, S, T and sometimes U. These designations were introduced by Einthoven, the founder of electrocardiography. He chose these letter symbols randomly from the middle of the alphabet. The Q, R, and S waves together form the QRS complex. However, depending on the lead in which the ECG is recorded, there may be no Q, R, or S waves. There are also intervals PQ and QT and segments PQ and ST, connecting individual teeth and having a specific meaning.

Same part of the curve ECG can be called differently, for example, the atrial wave can be called a wave or P wave. Q, R and S can be called a Q wave, an R wave and an S wave, and P, T and U can be called a P wave, a T wave and a U wave. In this book for convenience, P, Q, R, S and T, with the exception of U, we will call teeth.

Positive teeth are located above the isoelectric line (zero line), and negative ones are below the isoelectric line. The P and T waves and the U wave are positive. These three waves are normally positive, but in pathology they can also be negative.

Q and S waves always negative, and the R wave is always positive. If the second wave R or S is not recorded, it is designated as R" and S".

QRS complex begins with the Q wave and lasts until the end of the S wave. This complex is usually split. In the QRS complex, high waves are designated by a capital letter, and low ones by a lowercase letter, for example, qrS or qRs.

The moment of the end of the QRS complex is indicated point J.

Accurate for a beginner tooth recognition and segments is very important, so we discuss them in detail. Each of the teeth and complexes is shown in a separate figure. For a better understanding, the main features of these teeth and their clinical significance are shown next to the pictures.

After describing the individual teeth and segments ECG and corresponding explanations, we will familiarize ourselves with the quantitative assessment of these electrocardiographic indicators, in particular the height, depth and width of the teeth and their main deviations from normal values.

The P wave is normal

The P wave, which is a wave of atrial excitation, normally has a width of up to 0.11 s. The height of the P wave changes with age, but normally should not exceed 0.2 mV (2 mm). Usually, when these parameters of the P wave deviate from the norm, we are talking about atrial hypertrophy.

PQ interval normal

The PQ interval, which characterizes the time of excitation to the ventricles, is normally 0.12 ms, but should not exceed 0.21 s. This interval lengthens with AV block and shortens with WPW syndrome.

The Q wave is normal

The Q wave in all leads is narrow and its width does not exceed 0.04 s. The absolute value of its depth is not standardized, but the maximum is 1/4 of the corresponding R wave. Sometimes, for example, with obesity, a relatively deep Q wave is recorded in lead III.
A deep Q wave primarily raises suspicion of MI.

The R wave is normal

The R wave has the greatest amplitude among all ECG waves. A high R wave is normally recorded in the left chest leads V5 and V6, but its height in these leads should not exceed 2.6 mV. A taller R wave indicates LV hypertrophy. Normally, the height of the R wave should increase when moving from lead V5 to lead V6. If there is a sharp decrease in the height of the R wave, MI should be excluded.

Sometimes the R wave is split. In these cases, it is designated by uppercase or lowercase letters (for example, R wave or r wave). An additional wave R or r is designated, as already mentioned, as R" or r" (for example, in lead V1.

The S wave is normal

The depth of the S wave is characterized by significant variability depending on the abduction, body position of the patient and his age. With ventricular hypertrophy, the S wave is unusually deep, for example, with LV hypertrophy - in leads V1 and V2.

The QRS complex is normal

The QRS complex corresponds to the spread of excitation through the ventricles and normally should not exceed 0.07-0.11 s. An expansion of the QRS complex (but not a decrease in its amplitude) is considered pathological. It is observed, first of all, with blockades of the legs of the PG.

J point is normal

The J point corresponds to the point at which the QRS complex ends.

ST segment is normal

Normally, the ST segment is located on the isoelectric line; in any case, it does not deviate significantly from it. Only in leads V1 and V2 can it be above the isoelectric line. With a significant rise in the ST segment, fresh MI should be excluded, while its decrease indicates ischemic heart disease.

The T wave is normal

The T wave has important clinical significance. It corresponds to the restoration of myocardial excitability and is usually positive. Its amplitude should not be less than 1/7 of the R wave in the corresponding lead (for example, in leads I, V5 and V6). With clearly negative T waves, combined with a decrease in the ST segment, MI and ischemic heart disease should be excluded.

QT interval is normal

The width of the QT interval depends on heart rate; it does not have constant absolute values. Prolongation of the QT interval is observed with hypocalcemia and long QT syndrome.

Cardiology
Chapter 5. Analysis of the electrocardiogram

V. Conduction disorders. Block of the anterior branch of the left bundle branch, block of the posterior branch of the left bundle branch, complete block of the left bundle branch, block of the right bundle branch, 2nd degree AV block and complete AV block.

G. Arrhythmias see chap. 4.

VI. Electrolyte disturbances

A. Hypokalemia. Prolongation of the PQ interval. Widening of the QRS complex (rare). Pronounced U wave, flattened inverted T wave, ST segment depression, slight prolongation of the QT interval.

B. Hyperkalemia

Lightweight(5.5 x 6.5 meq/l). Tall peaked symmetrical T wave, shortening of the QT interval.

Moderate(6.5 x 8.0 meq/l). Decreased P wave amplitude; prolongation of the PQ interval. Widening of the QRS complex, decreased amplitude of the R wave. Depression or elevation of the ST segment. Ventricular extrasystole.

Heavy(911 meq/l). Absence of the P wave. Expansion of the QRS complex (up to sinusoidal complexes). Slow or accelerated idioventricular rhythm, ventricular tachycardia, ventricular fibrillation, asystole.

IN. Hypocalcemia. Prolongation of the QT interval (due to ST segment prolongation).

G. Hypercalcemia. Shortening of the QT interval (due to shortening of the ST segment).

VII. Action medicines

A. Cardiac glycosides

Therapeutic effect. Prolongation of the PQ interval. Oblique depression of the ST segment, shortening of the QT interval, changes in the T wave (flattened, inverted, biphasic), pronounced U wave. Decrease in heart rate with atrial fibrillation.

Toxic effect. Ventricular extrasystole, AV block, atrial tachycardia with AV block, accelerated AV nodal rhythm, sinoatrial block, ventricular tachycardia, bidirectional ventricular tachycardia, ventricular fibrillation.

A. Dilated cardiomyopathy. Signs of enlargement of the left atrium, sometimes of the right. Low amplitude of the waves, pseudo-infarction curve, blockade of the left bundle branch, anterior branch of the left bundle branch. Nonspecific changes in the ST segment and T wave. Ventricular extrasystole, atrial fibrillation.

B. Hypertrophic cardiomyopathy. Signs of enlargement of the left atrium, sometimes of the right. Signs of left ventricular hypertrophy, pathological Q waves, pseudo-infarction curve. Nonspecific changes in the ST segment and T waves. With apical hypertrophy of the left ventricle, giant negative T waves in the left precordial leads. Supraventricular and ventricular rhythm disturbances.

IN. Amyloidosis of the heart. Low amplitude of the waves, pseudo-infarction curve. Atrial fibrillation, AV block, ventricular arrhythmias, sinus node dysfunction.

G. Duchenne myopathy. Shortening the PQ interval. High R wave in leads V 1, V 2; deep Q wave in leads V 5, V 6. Sinus tachycardia, atrial and ventricular extrasystole, supraventricular tachycardia.

D. Mitral stenosis. Signs of left atrium enlargement. Hypertrophy of the right ventricle and deviation of the electrical axis of the heart to the right are observed. Often atrial fibrillation.

E. Mitral valve prolapse. T waves are flattened or negative, especially in lead III; ST segment depression, slight prolongation of the QT interval. Ventricular and atrial extrasystole, supraventricular tachycardia, ventricular tachycardia, sometimes atrial fibrillation.

AND. Pericarditis. Depression of the PQ segment, especially in leads II, aVF, V 2 V 6. Diffuse elevation of the ST segment with convexity upward in leads I, II, aVF, V 3 V 6. Sometimes there is depression of the ST segment in lead aVR (in rare cases, in leads aVL, V 1, V 2). Sinus tachycardia, atrial rhythm disturbances. ECG changes go through 4 stages:

ST segment elevation, normal T wave;

the ST segment descends to the isoline, the amplitude of the T wave decreases;

ST segment on isoline, T wave inverted;

ST segment on isoline, T wave normal.

Z. Large pericardial effusion. Low wave amplitude, alternation of the QRS complex. Pathognomonic sign complete electrical alternans (P, QRS, T).

AND. Dextrocardia. The P wave is negative in lead I. The QRS complex is inverted in lead I, R/S< 1 во всех грудных отведениях с уменьшением амплитуды комплекса QRS от V 1 к V 6 . Инвертированный зубец T в I отведении.

TO. Atrial septal defect. Signs of enlargement of the right atrium, less often the left; prolongation of the PQ interval. RSR" in lead V 1; the electrical axis of the heart is deviated to the right with a defect of the ostium secundum type, to the left with a defect of the ostium primum type. Inverted T wave in leads V 1, V 2. Sometimes atrial fibrillation.

L. Pulmonary artery stenosis. Signs of enlargement of the right atrium. Right ventricular hypertrophy with a high R wave in leads V 1, V 2; deviation of the electrical axis of the heart to the right. Inverted T wave in leads V 1, V 2.

M. Sick sinus syndrome. Sinus bradycardia, sinoatrial block, AV block, sinus arrest, bradycardia-tachycardia syndrome, supraventricular tachycardia, atrial fibrillation/flutter, ventricular tachycardia.

IX. Other diseases

A. COPD. Signs of enlargement of the right atrium. Deviation of the electrical axis of the heart to the right, displacement of the transition zone to the right, signs of right ventricular hypertrophy, low amplitude of the waves; ECG type S I S II S III. T wave inversion in leads V 1, V 2. Sinus tachycardia, AV nodal rhythm, conduction disturbances, including AV block, slowing intraventricular conduction, bundle branch block.

B. TELA. Syndrome S I Q III T III, signs of overload of the right ventricle, transient complete or incomplete blockade of the right bundle branch, displacement of the electrical axis of the heart to the right. T wave inversion in leads V 1, V 2; nonspecific changes in the ST segment and T wave. Sinus tachycardia, sometimes atrial rhythm disturbances.

IN. Subarachnoid hemorrhage and other central nervous system lesions. Sometimes - pathological Q wave. High wide positive or deep negative T wave, elevation or depression of the ST segment, pronounced U wave, pronounced prolongation of the QT interval. Sinus bradycardia, sinus tachycardia, AV nodal rhythm, ventricular extrasystole, ventricular tachycardia.

G. Hypothyroidism. Prolongation of the PQ interval. Low amplitude of the QRS complex. Flattened T wave. Sinus bradycardia.

D. CRF. ST segment prolongation (due to hypocalcemia), tall symmetrical T waves (due to hyperkalemia).

E. Hypothermia. Prolongation of the PQ interval. Notch in the terminal part of the QRS complex (Osborne wave see). Prolongation of the QT interval, T wave inversion. Sinus bradycardia, atrial fibrillation, AV nodal rhythm, ventricular tachycardia.

THE EX . The main types of pacemakers are described by a three-letter code: the first letter indicates which chamber of the heart is being paced (A A trium atrium, V V entricle ventricle, D D ual both atrium and ventricle), the second letter the activity of which chamber is perceived (A, V or D), the third letter indicates the type of response to the perceived activity (I I nhibition blocking, T T riggering launch, D D ual both). Thus, in the VVI mode, both the stimulating and sensing electrodes are located in the ventricle, and when spontaneous ventricular activity occurs, its stimulation is blocked. In DDD mode, two electrodes (stimulating and sensing) are located in both the atrium and ventricle. Response type D means that when spontaneous atrial activity occurs, its stimulation will be blocked, and after a programmed period of time (AV interval) a stimulus will be issued to the ventricle; when spontaneous ventricular activity occurs, on the contrary, ventricular stimulation will be blocked, and atrial stimulation will start after the programmed VA interval. Typical modes of single-chamber pacemaker VVI and AAI. Typical modes of dual-chamber pacemaker DVI and DDD. Fourth letter R ( R ate-adaptive means that the pacemaker is capable of increasing the pacing rate in response to changes in physical activity or load-dependent physiological parameters (for example, QT interval, temperature).

A. General principles of ECG interpretation

Assess the nature of the rhythm (own rhythm with periodic activation of the stimulator or imposed).

Determine which chamber(s) are being stimulated.

Determine the activity of which chamber(s) is perceived by the stimulator.

Determine programmed pacemaker intervals (VA, VV, AV intervals) from atrial (A) and ventricular (V) pacing artifacts.

Determine the EX mode. It must be remembered that ECG signs of a single-chamber pacemaker do not exclude the possibility of the presence of electrodes in two chambers: thus, stimulated contractions of the ventricles can be observed with both single-chamber and dual-chamber pacemaker, in which ventricular stimulation follows at a certain interval after the P wave (DDD mode) .

Eliminate imposition and detection violations:

A. imposition disorders: there are stimulation artifacts that are not followed by depolarization complexes of the corresponding chamber;

b. detection disturbances: there are pacing artifacts that must be blocked for normal detection of atrial or ventricular depolarization.

B. Individual EX modes

AAI. If the natural rhythm frequency becomes less than the programmed pacemaker frequency, then atrial stimulation is started at a constant AA interval. When spontaneous atrial depolarization (and its normal detection) occurs, the pacemaker time counter is reset. If spontaneous atrial depolarization does not recur after the specified AA interval, atrial pacing is initiated.

VVI. When spontaneous ventricular depolarization (and its normal detection) occurs, the pacemaker time counter is reset. If, after a predetermined VV interval, spontaneous ventricular depolarization does not recur, ventricular pacing is initiated; V otherwise The time counter is reset again and the whole cycle starts over. In adaptive VVIR pacemakers, the rhythm frequency increases with increasing level of physical activity (up to a given upper limit Heart rate).

DDD. If the intrinsic rate becomes less than the programmed pacemaker rate, atrial (A) and ventricular (V) pacing is initiated at the specified intervals between pulses A and V (AV interval) and between a V pulse and the subsequent A pulse (VA interval). When spontaneous or induced ventricular depolarization (and its normal detection) occurs, the pacemaker time counter is reset and the VA interval begins to count. If spontaneous atrial depolarization occurs during this interval, atrial pacing is blocked; otherwise, an atrial impulse is issued. When spontaneous or induced atrial depolarization (and its normal detection) occurs, the pacemaker time counter is reset and the AV interval begins to count. If spontaneous ventricular depolarization occurs during this interval, ventricular pacing is blocked; otherwise, a ventricular impulse is issued.

IN. Pacemaker dysfunction and arrhythmias

Violation of imposition. The stimulation artifact is not followed by a depolarization complex, although the myocardium is not in the refractory stage. Causes: displacement of the stimulating electrode, cardiac perforation, increased stimulation threshold (during myocardial infarction, taking flecainide, hyperkalemia), damage to the electrode or violation of its insulation, disturbances in pulse generation (after defibrillation or due to depletion of the power source), as well as incorrectly set pacemaker parameters.

Detection failure. The pacemaker time counter is not reset when its own or imposed depolarization of the corresponding chamber occurs, which leads to the occurrence of an incorrect rhythm (the imposed rhythm is superimposed on its own). Reasons: low amplitude of the perceived signal (especially with ventricular extrasystole), incorrectly set pacemaker sensitivity, as well as the reasons listed above (see). Often it is enough to reprogram the sensitivity of the pacemaker.

Pacemaker hypersensitivity. At the expected point in time (after the appropriate interval has passed), no stimulation occurs. T waves (P waves, myopotentials) are misinterpreted as R waves and the pacemaker timer is reset. If the T wave is detected incorrectly, the VA interval begins counting from it. In this case, the sensitivity or refractory period of detection must be reprogrammed. You can also set the VA interval to start from the T wave.

Blocking by myopotentials. Myopotentials arising from arm movements may be misinterpreted as potentials from the myocardium and block stimulation. In this case, the intervals between the imposed complexes become different, and the rhythm becomes incorrect. Most often, such disorders occur when using unipolar pacemakers.

Circular tachycardia. An imposed rhythm with the maximum frequency for the pacemaker. Occurs when retrograde atrial excitation after ventricular stimulation is sensed by the atrial electrode and triggers ventricular stimulation. This is typical for a two-chamber pacemaker with detection of atrial excitation. In such cases, it may be sufficient to increase the detection refractory period.

Tachycardia induced by atrial tachycardia. An imposed rhythm with the maximum frequency for the pacemaker. It is observed if atrial tachycardia (for example, atrial fibrillation) occurs in patients with a dual-chamber pacemaker. Frequent atrial depolarization is sensed by the pacemaker and triggers ventricular pacing. In such cases, they switch to the VVI mode and eliminate the arrhythmia.

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. Left-hand side The heart is more developed than the right one, since 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 in an 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 for 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 is prescribed using mobile device. It continuously 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 in the frontal plane is determined; 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, and 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.

With 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.

ECG or electrocardiography is a diagnostic procedure during which a graphical recording of the electrical activity of the heart muscle is carried out. Decoding the ECG is the prerogative of a cardiologist or therapist. An ordinary patient, receiving the results of an electrocardiogram, sees only incomprehensible teeth that do not tell him anything.

The conclusion written on the back of the ECG tape also consists of continuous medical terms and only a specialist can explain their meaning. We hasten to reassure the most impressionable patients. If during the examination dangerous conditions are diagnosed (heart rhythm disturbances, suspicion of myocardial infarction), the patient is immediately hospitalized. In case of pathological changes of unknown etiology, the cardiologist will refer the patient for additional examination, which may include Holter monitoring, ultrasound of the heart, or load tests(veloergometry).

ECG of the heart: the essence of the procedure

An electrocardiogram is the simplest and available method functional diagnostics work of the heart. Today, every emergency cardiac care team is equipped with portable electrocardiographs that read information about myocardial contraction and record electrical impulses of the heart on a recorder tape. At the clinic, all patients undergoing a comprehensive medical examination are referred for an ECG procedure.

During the procedure, the following parameters are assessed:

1. Condition of the heart muscle (myocardium). When deciphering the cardiogram, an experienced doctor sees whether there are inflammation, damage, thickening in the structure of the myocardium, and assesses the consequences of electrolyte imbalance or hypoxia (oxygen starvation).
2. The correctness of the heart rhythm and the state of the heart system that conducts electrical impulses. All this is reflected graphically on the cardiogram tape.

When the heart muscle contracts, spontaneous electrical impulses occur, the source of which is in the sinus node. The path of each impulse passes along the nerve pathways of all parts of the myocardium, prompting it to contract. The period when the impulse passes through the myocardium of the atria and ventricles, causing them to contract, is called systole. The period of time when there is no impulse and the heart muscle contracts - diastole.

The ECG method consists precisely in recording these electrical impulses. The operating principle of the electrocardiograph is based on capturing the difference in electrical discharges occurring in different parts of the heart during systole (contraction) and diastole (relaxation) and transferring them to a special tape in the form of a graph. The graphic image looks like a series of pointed teeth or hemispherical peaks with spaces between them. When deciphering an ECG, the doctor pays attention to such graphic indicators as:

• teeth;
• intervals;
• segments.

Their location, peak height, duration of intervals between contractions, direction and sequence are assessed. Each line on the cardiogram tape must correspond to certain parameters. Even a slight deviation from the norm may indicate a dysfunction of the heart muscle.

ECG normal indicators with interpretation

The electrical impulse passing through the heart is reflected on the cardiogram tape in the form of a graph with teeth and intervals, above which you can see the Latin letters P, R, S, T, Q. Let's find out what they mean.

Teeth (peaks above the isoline):

P - processes of atrial systole and diastole;

Q, S - excitation of the septum between the ventricles of the heart;

R - Ventricular excitation;

T - ventricular relaxation.

Segments (areas including an interval and a tooth):

QRST - duration of ventricular contraction;

ST - period of complete excitation of the ventricles;

TP - duration of cardiac diastole.

Intervals (sections of the cardiogram lying on the isoline):

PQ is the time of propagation of an electrical impulse from the atrium to the ventricle.

When decrypting ECG of the heart Be sure to indicate the number of heart beats per minute or heart rate (HR). Normally, for an adult, this value ranges from 60 to 90 beats/min. In children, the rate depends on age. Thus, the heart rate in newborns is 140-160 beats per minute, and then gradually decreases.

Interpretation of the myocardial ECG takes into account such a criterion as the conductivity of the heart muscle. On the graph it shows the process of momentum transfer. Normally, they are transmitted sequentially, while the order of the rhythm remains unchanged.

When interpreting the ECG results, the doctor must pay attention to the sinus rhythm of the heart. By this indicator one can judge the coherence of the work of various parts of the heart and the correct sequence of systolic and diastolic processes. To more accurately imagine the work of the heart, let’s look at the breakdown of ECG indicators with a table of normative values.

ECG interpretation in adults

ECG interpretation in children

ECG results with interpretation help the doctor make the correct diagnosis and prescribe necessary treatment. Let us dwell in more detail on the description of such important indicators such as heart rate, myocardial conditions and cardiac muscle conductivity.

Heart Rate Options

Sinus rhythm

If you see this inscription in the description of the electrocardiogram, and the heart rate value is within the normal range (60-90 beats/min), this means that there are no malfunctions in the functioning of the heart muscle. The rhythm set by the sinus node is responsible for the health and well-being of the conduction system. And if there are no deviations in the rhythm, then your heart is an absolutely healthy organ. Pathological is the rhythm set by the atria, ventricular or atrioventricular parts of the heart.

With sinus arrhythmia, impulses leave the sinus node, but the intervals between contractions of the heart muscle are different. The cause of this condition may be physiological changes in the body. Therefore, sinus arrhythmia is often diagnosed in adolescents and young adults. In every third case, such deviations require monitoring by a cardiologist to prevent the development of more dangerous heart rhythm disorders.

Tachycardia

This is a condition in which the heart rate exceeds 90 beats/min. Sinus tachycardia can be physiological and pathological. In the first case, an increase in heart rate occurs in response to physical or psychological stress, consumption of alcohol, caffeine-containing or energy drinks. After the load disappears, the heart rate quickly returns to normal.

Pathological tachycardia is diagnosed when a rapid heartbeat is observed at rest. The reason for this condition may be infectious diseases, extensive blood loss, anemia, cardiomyopathy or endocrine pathologies, in particular thyrotoxicosis.

Bradycardia

This is a slowing of the heart rate to less than 50 beats/min. Physiological bradycardia occurs during sleep and is also often diagnosed in people who are professionally involved in sports.

Pathological slowing of heart rate is observed with weakness of the sinus node. In this case, the heart rate can slow down to 35 beats/min, which is accompanied by hypoxia (insufficient oxygen supply to the tissues of the heart) and fainting conditions. In this case, the patient is recommended to undergo surgery to implant a cardiac pacemaker, which replaces the sinus node and ensures a normal rhythm of heart contractions.

Extrasystole

This is a condition in which extraordinary cardiac contractions occur, accompanied by a double compensatory pause. The patient experiences dips in heart rhythm, which he describes as chaotic, rapid or slow beats. At the same time, there is a tingling sensation in the chest, a feeling of emptiness in the stomach and a fear of death.

Extrasystoles can be functional (caused by hormonal imbalances, panic attacks) or organic, occurring against the background of heart diseases (cardiopathy, myocarditis, coronary artery disease, heart defects).

Paroxysmal tachycardia

This term refers to a paroxysmal increase in heart rate that can persist for a short time or last several days. In this case, the heart rate can increase to 125 beats/min, with equal time intervals between heart contractions. Reason pathological condition There are disturbances in the circulation of impulses in the conduction system of the heart.

Arrhythmia atrial fibrillation

Severe pathology, which manifests itself as atrial flutter (atrial fibrillation). It may manifest itself in attacks or acquire a permanent form. The intervals between contractions of the heart muscle can be of different durations, since the rhythm is set not by the sinus node, but by the atria. The contraction frequency often increases to 300-600 beats/min, while full contraction of the atria does not occur, the ventricles are not sufficiently filled with blood, which worsens cardiac output and leads to oxygen starvation of organs and tissues.

An attack of atrial fibrillation begins with a strong cardiac impulse, after which a rapid, irregular heartbeat begins. The patient experiences severe weakness, dizziness, sweating, shortness of breath, and may sometimes lose consciousness. The end of the attack is indicated by normalization of the rhythm, accompanied by the urge to urinate and copious discharge of urine. An attack of atrial fibrillation is treated with medications (tablets, injections). In the absence of timely assistance, the risk of developing dangerous complications (stroke, thromboembolism) increases.

Conduction disorders

An electrical impulse, originating in the sinus node, spreads through the conduction system, stimulating the ventricles and atria to contract. But if a pulse delay occurs in any part of the conduction system, then the pumping function the entire heart muscle. Such failures in the conduction system are called blockades. Most often they develop as a result of functional disorders or are a consequence of alcohol or drug intoxication of the body. There are several types of blockades:

• AV blockade is characterized by a delay in excitation in the atrioventricular node. Moreover, the less often the ventricles contract, the more severe the circulatory disorders. The most severe is the 3rd degree, which is also called transverse blockade. In this condition, the contractions of the ventricles and atria are in no way interconnected.


• Sinoatrial block - accompanied by difficulty in the exit of the impulse from the sinus node. Over time, this condition leads to weakness of the sinus node, which is manifested by a decrease in heart rate, weakness, shortness of breath, dizziness, and fainting.
• Violation of ventricular conduction. In the ventricles, the impulse spreads along the branches, legs and trunk of the bundle of His. The blockade can manifest itself at any of these levels and is expressed by the fact that excitation does not occur simultaneously, since due to conduction disturbances one of the ventricles is delayed. In this case, the blockade of the ventricles can be permanent or intermittent, complete or partial.

The causes of conduction disturbances are various cardiac pathologies (heart defects, ischemic heart disease, cardiomyopathies, tumors, coronary disease, endocarditis).

Myocardial conditions

ECG interpretation gives an idea of ​​the state of the myocardium. For example, under the influence of regular overload, certain areas of the heart muscle can thicken. These changes on the cardiogram are noted as hypertrophy.

Myocardial hypertrophy

Ventricular hypertrophy is often caused by various pathologies- arterial hypertension, heart defects, cardiomyopathies, COPD, cor pulmonale.

Atrial hypertrophy is provoked by conditions such as mitral or aortic valve stenosis, heart defects, hypertension, pulmonary pathologies, and chest deformation.

Disorders of nutrition and myocardial contractility

Ischemic disease. Ischemia is oxygen starvation of the myocardium. As a result inflammatory process(myocarditis), cardiosclerosis or dystrophic changes There are disturbances in the nutrition of the myocardium, which can lead to oxygen starvation of tissues. The same diffuse changes of a reversible nature develop with disturbances in the water-electrolyte balance, with exhaustion of the body or long-term use diuretics. Oxygen starvation is expressed in ischemic changes, coronary syndrome, stable or unstable angina. The doctor selects treatment taking into account the option coronary disease hearts.

Myocardial infarction. If there are symptoms of a developing heart attack, the patient is urgently hospitalized. The main signs of myocardial infarction on the cardiogram are:

• high T-wave;
• absence or pathological shape of the Q wave;
• ST segment elevation.

If such a picture is present, the patient is immediately sent from the diagnostic room to the hospital ward.

How to prepare for an ECG?

To results diagnostic examination were as reliable as possible, you need to properly prepare for the ECG procedure. Before taking a cardiogram, it is unacceptable to:

• drink alcohol, energy drinks or drinks containing caffeine;
• worry, worry, be under stress;
• smoke;
• use stimulant medications.

It should be understood that excessive anxiety can lead to signs of false tachycardia (rapid heartbeat) appearing on the ECG tape. Therefore, before entering the office for the procedure, you need to calm down and relax as much as possible.

Try not to do an ECG after a heavy lunch; it is better to come for an examination on an empty stomach or after a light snack. You should not go to the cardiology room immediately after active training and high physical exertion, otherwise the result will be unreliable and you will have to undergo the ECG procedure again.

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What is an ECG?

Electrocardiography is a method used to record electrical currents that occur during contractions and relaxations of the heart muscle. An electrocardiograph is used to conduct the study. Using this device, it is possible to record electrical impulses that come from the heart and convert them into a graphic drawing. This image is called an electrocardiogram.

Electrocardiography reveals disturbances in the functioning of the heart and disruptions in the functioning of the myocardium. In addition, after decoding the results of the electrocardiogram, some non-cardiac diseases can be detected.

How does an electrocardiograph work?

The electrocardiograph consists of a galvanometer, amplifiers and a recorder. Weak electrical impulses that arise in the heart are read by electrodes and then amplified. The galvanometer then receives data on the nature of the pulses and transmits them to the recorder. In the recorder, graphic images are printed on special paper. The graphs are called cardiograms.

How is an ECG done?

Electrocardiography is performed according to established rules. Below is the procedure for taking an ECG:

• The person removes metal jewelry, removes clothing from the legs and upper body, and then assumes a horizontal position.
• The doctor treats the contact points between the electrodes and the skin, and then places the electrodes in certain places on the body. Next, he fixes the electrodes on the body with clips, suction cups and bracelets.
• The doctor attaches the electrodes to the cardiograph, after which the impulses are recorded.
• A cardiogram is recorded, which is the result of electrocardiography.

Separately, it should be said about the leads used for ECG. The following leads are used:

• 3 standard leads: one of them is located between the right and left arms, the second - between the left leg and right hand, the third - between the left leg and left hand.
• 3 limb leads with enhanced character.
• 6 leads located on the chest.

In addition, additional leads can be used if necessary.

After the cardiogram is recorded, it is necessary to decipher it. This will be discussed further.

Decoding the cardiogram

Conclusions about diseases are made on the basis of heart parameters obtained after deciphering the cardiogram. Below is the procedure for deciphering the ECG:

1. The heart rhythm and myocardial conductivity are analyzed. To do this, the regularity of contractions of the heart muscle and the frequency of myocardial contractions are assessed, and the source of excitation is determined.
2. The regularity of heart contractions is determined as follows: the R-R intervals between successive cardiac cycles are measured. If the measured R-R intervals are the same, then a conclusion is made about the regularity of contractions of the heart muscle. If the duration of the R-R intervals is different, then a conclusion is drawn about the irregularity of heart contractions. If a person exhibits irregular contractions of the myocardium, then a conclusion is drawn about the presence of arrhythmia.
3. Heart rate is determined by a certain formula. If a person’s heart rate exceeds the norm, then a conclusion is drawn about the presence of tachycardia, but if a person’s heart rate is below normal, then a conclusion is drawn about the presence of bradycardia.
4. The point from which the excitation comes is determined as follows: the movement of contraction in the cavities of the atria is assessed and the relationship of the R waves to the ventricles is established (according to the QRS complex). The nature of the heart rhythm depends on the source that causes the excitation.

The following heart rhythm patterns are observed:

1. The sinusoidal nature of the heart rhythm, in which the P waves in the second lead are positive and are located in front of the ventricular QRS complex, and the P waves in the same lead have an indistinguishable shape.
2. Atrial rhythm of the heart, in which the P waves in the second and third leads are negative and are located in front of the unchanged QRS complexes.
3. The ventricular nature of the heart rhythm, in which there is deformation of the QRS complexes and loss of connection between the QRS (complex) and the P waves.

Cardiac conductivity is determined as follows:

1. Measurements of P wave length, PQ interval length, and QRS complex are assessed. Exceeding the normal duration of the PQ interval indicates that the conduction velocity in the corresponding cardiac conduction section is too low.
2. The rotations of the myocardium around the longitudinal, transverse, anterior and posterior axes are analyzed. To do this, the position of the electrical axis of the heart in the general plane is assessed, after which the presence of rotations of the heart along one or another axis is determined.
3. The atrial P wave is analyzed. To do this, the amplitude of the P wave is assessed and the duration of the P wave is measured. Afterwards, the shape and polarity of the P wave are determined.
4. The ventricular complex is analyzed. For this purpose, the QRS complex, RS-T segment, QT interval, T wave are assessed.

When assessing the QRS complex, the following is done: the characteristics of the Q, S and R waves are determined, the amplitude values ​​of the Q, S and R waves in a similar lead and the amplitude values ​​of the R/R waves in different leads are compared.

At the time of evaluation of the RS-T segment, the nature of the displacement of the RS-T segment is determined. The displacement can be horizontal, oblique and oblique.

During the period of analysis of the T wave, the nature of the polarity, amplitude and shape are determined. The QT interval is measured by the time from the beginning of the QRT complex to the end of the T wave. When assessing the QT interval, do the following: analyze the interval from the starting point of the QRS complex to the end point of the T wave. To calculate the QT interval, use the Bezzet formula: the QT interval is equal to the product of the R-R interval and a constant coefficient.

The coefficient for QT depends on gender. For men, the constant coefficient is 0.37, and for women – 0.4.

A conclusion is made and the results are summed up.

At the end of the ECG, the specialist draws conclusions about the frequency of contractile function of the myocardium and cardiac muscle, as well as the source of excitation and the nature of the heart rhythm and other indicators. In addition, an example is given of the description and characteristics of the P wave, QRS complex, RS-T segment, QT interval, T wave.

Based on the conclusion, a conclusion is made that the person has heart disease or other ailments of the internal organs.

Electrocardiogram norms

The table with ECG results has a visual appearance, consisting of rows and columns. In the 1st column, the rows list: heart rate, examples of contraction frequency, QT intervals, examples of axis displacement characteristics, P wave indicators, PQ indicators, examples of QRS indicator. ECG is performed in the same way in adults, children and pregnant women, but the norm is different.

The ECG norm for adults is presented below:

• heart rate in a healthy adult: sinus;
• P wave index in a healthy adult: 0.1;
• heart rate in a healthy adult: 60 beats per minute;
• QRS indicator in a healthy adult: from 0.06 to 0.1;
• QT score in a healthy adult: 0.4 or less;
• RR in a healthy adult: 0.6.

If deviations from the norm are observed in an adult, a conclusion is drawn about the presence of a disease.

The norms of cardiogram indicators in children are presented below:

• P wave index in a healthy child: 0.1 or less;
• heart rate in a healthy child: 110 or less beats per minute in children under 3 years of age, 100 or less beats per minute in children under 5 years of age, no more than 90 beats per minute in adolescent children;
• QRS indicator in all children: from 0.06 to 0.1;
• QT score in all children: 0.4 or less;
• PQ indicator for all children: if the child is under 14 years old, then an example of the PQ indicator is 0.16, if the child is from 14 to 17 years old, then the PQ indicator is 0.18, after 17 years normal indicator PQ is 0.2.

If any deviations from the norm are detected in children when interpreting the ECG, then treatment should not be started immediately. Some heart problems improve with age in children.

But in children, heart disease can also be congenital. It is possible to determine whether a newborn child will have a heart pathology at the stage of fetal development. For this purpose, electrocardiography is performed on women during pregnancy.

The normal electrocardiogram indicators in women during pregnancy are presented below:

• heart rate in a healthy adult child: sinus;
• P wave index in all healthy women during pregnancy: 0.1 or less;
• heart muscle contraction frequency in all healthy women during pregnancy: 110 or less beats per minute in children under 3 years of age, 100 or less beats per minute in children under 5 years of age, no more than 90 beats per minute in adolescent children;
• QRS indicator for all expectant mothers during pregnancy: from 0.06 to 0.1;
• QT index in all expectant mothers during pregnancy: 0.4 or less;
• PQ indicator for all expectant mothers during pregnancy: 0.2.

It is worth noting that during different periods of pregnancy, ECG readings may differ slightly. In addition, it should be noted that performing an ECG during pregnancy is safe for both the woman and the developing fetus.

Additionally

It is worth saying that under certain circumstances, electrocardiography can give an inaccurate picture of a person’s health status.

If, for example, a person subjected himself to severe physical activity, then when deciphering the cardiogram, an erroneous picture may be revealed.

This is explained by the fact that during physical activity the heart begins to work differently than at rest. During physical activity, the heart rate increases, and some changes in the rhythm of the myocardium may be observed, which is not observed at rest.

It is worth noting that the work of the myocardium is affected not only by physical stress, but also by emotional stress. Emotional stress, like physical stress, disrupts the normal course of myocardial function.

At rest, the heart rhythm normalizes and the heartbeat evens out, so before electrocardiography you must be at rest for at least 15 minutes.

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1 What is an electrocardiograph?

The device, which records the electrical activity of the heart, began to be used 150 years ago. Since then, it has been improved several times, but the principles of operation remain the same. It is a recording of electrical impulses written on paper.

Without an electrocardiograph it is impossible to imagine diagnosing heart diseases. Normality or pathology is determined primarily by the ECG of the heart.

Every patient who has undergone such a diagnostic procedure wants to know what these long zigzags on the paper tape mean. Only a specialist can fully decipher and make a conclusion about the ECG. But elementary basic knowledge and ideas about cardiac rhythm, conductivity, normality and pathology in the heart are within the capabilities of an ordinary person.

The human heart has 4 chambers: two atria, two ventricles. The ventricles bear the main burden of pumping blood. The heart is divided into right and left sections (atrium and ventricle). The right ventricle provides pulmonary circulation, and the left one performs a greater load - it pushes blood to big circle blood circulation Therefore, the left ventricle has a more powerful thickened muscle wall. But the ventricle also suffers more often. Despite the functional difference, the right and left departments work like a well-coordinated mechanism.

The heart, as a hollow muscular organ, is heterogeneous in its morphological structure. It has contracting elements (myocardium) and non-contracting elements (nerve and vascular bundles, valves, fatty tissue). Each element has its own degree of electrical response.

An electrocardiograph records the electrical currents that occur when the heart muscle contracts or relaxes.

This device captures them and converts them into a graphic drawing.

This is an electrocardiogram of the heart.

What does an electrocardiograph consist of:

• galvanometer;
• amplifier;
• registrar

The electrical impulses of the heart are quite weak, so they are first read by electrodes and then amplified. The galvanometer receives this information and transmits it directly to the recorder. From it, a graphic image is displayed on a special paper - graphs, ECG results.

The electrocardiogram is measured with the patient lying down. To identify ischemic disease, cardiac arrhythmias and latent cardiovascular pathologies, an ECG with a load is performed - bicycle ergometry. It can be used to measure the heart’s tolerance to physical activity and clarify the diagnosis.

Bicycle ergometry also allows you to effectively monitor and correct drug therapy with coronary heart disease.

2 Teeth, leads, intervals

Without understanding these concepts, you can figure it out on your own (even general outline) with an electrocardiogram will be impossible.

Any cardiogram with normal or pathological changes reflects 2 main processes: depolarization (passage of an impulse through the myocardium, activation), and repolarization (excited myocardium comes to a state of rest, relaxation).

Each wave in the ECG is assigned a Latin letter:

• P - depolarization (activation) of the atria;
• group of QRS waves - ventricular depolarization (activation);
• T - ventricular repolarization (relaxation);
• U - repolarization (relaxation) in the distal parts of the ventricular conduction system.

If the prong points upward, it is a positive prong. If it's down, it's negative. Moreover, the Q and S waves are always negative, S - after the positive R wave.

And some useful information about the leads. There are 3 standard leads with which the potential difference between two points of the electric field that are distant from the heart (on the limbs) is recorded:

• the first is located between the right and left hands;
• the second runs from the left leg and right arm;
• the third runs from the left leg and left arm.

If necessary, additional leads are used: bipolar and unipolar chest leads (Table 1).

3 Heart rate analysis, myocardial conductivity

At the next stage, the recording needs to be decrypted. A conclusion about pathology or normality is made based on the parameters, and they are set in a certain order. The first priority is to determine the analysis of heart rate with myocardial conduction. The regularity and frequency of myocardial contractions is assessed. R-R interval between cycles the norm should be the same or with a slight variation of up to 10%.

These are regular cuts. If it is different, then this suggests disturbances in the form of arrhythmia. An ECG specialist calculates the heart rate using the formula: HR = 60/R-R (distance between the peaks of the highest teeth). This is how tachycardia or bradycardia is determined.

The nature of the rhythm is determined by the location of the points of the QRS complex:

1. 1. Sinus rhythm - the P wave in the second lead is positive, goes ahead of the ventricular QRS complex, and in all leads the P waves are of the same shape.
2. 2. Atrial rhythm - in the second and third leads the P wave is negative and located before the unchanged QRS complexes.
3. 3. Ventricular nature of the heart rhythm - the QRS complex is deformed and the connection between it and the P wave is disrupted.

Myocardial conductivity is determined by measuring the length of the P wave and the P interval with the QRS complex. If the PQ interval exceeds the norm, this indicates a low speed of impulse transmission.

Afterwards, an analysis of the rotation of the myocardium along a certain axis is carried out: longitudinal, transverse, posterior, anterior.

Atrial activation is analyzed by the atrial P wave. Its amplitude, duration, shape, and polarity are assessed.

Ventricular activation is assessed by the QRS complex, RS-T segment, RS-T interval and T wave.

QRS complex assessment:

• characteristics of teeth;
• comparison of the amplitude values ​​of the waves in different leads.

The QT interval (from QRS to T) measures the sum of the processes of depolarization and repolarization. This is electrical cardiac systole.

4 Data processing

Decoding the cardiogram in adults. Reading ECG norm:

1. 1. The Q wave is no more than 3 mm deep.
2. 2. QT (interval of duration of gastric contractions) 390-450 ms. If longer - ischemia, atherosclerosis, myocarditis, rheumatism. If the interval is shorter - hypercalcemia (increased calcium levels in the blood).
3. 3. Normally, the S wave is always lower than the R wave. If there are deviations, this may indicate disturbances in the functioning of the right ventricle. An R wave below the S wave indicates left ventricular hypertrophy.
4. 4. QRS waves show how the biopotential passes through the septum and myocardium. Normal if the Q wave does not exceed 40 ms in width and no more than a third of the R wave

Normal indicators are in table 2.

Interpretation of ECG in children. Norm:

1. 1. Heart rate up to three years of age: 100-110 beats per minute, 3-5 years 100, teenagers 60-90.
2. 2. Wave P - up to 0.1 s.
3. 3. QRS reading 0.6-0.1 s.
4. 4. There is no change in the electrical axis.
5. 5. Sinus rhythm.

A child's heart cardiogram may reveal notching, thickening, or splitting of the R wave. The specialist pays attention to the location and amplitude. Most often this age characteristics: moderate tachycardia, bradycardia.

There may also be an atrial rhythm on the ECG of the child on the right. This is not considered a pathology.

5 Why may the values ​​differ?

It happens that one patient’s ECG data over a short period may show different data. This happens most often due to technical problems. Perhaps the resulting cardiogram was incorrectly stitched together or the Roman numerals were read incorrectly.

Incorrect cutting of the graph when one of the teeth is lost can cause an error.

The cause may be electrical appliances operating nearby. Alternating current and its fluctuations can be reflected in the electrocardiogram by repeating waves.

The patient should be comfortable and completely relaxed. If there is anxiety and discomfort, the data is distorted. Many people are sure that no preliminary preparation is needed to undergo an ECG. This is not true. The patient should go to the procedure well-rested and preferably on an empty stomach. A light breakfast is allowed. If the procedure is scheduled during the day, it is better not to eat anything 2 hours before it. You should avoid tonic and energy drinks. The body must be clean, without any care products. A greasy film on the surface will have a bad effect on the contact between the electrode and the skin.

Before lying down for the procedure, you need to sit quietly for a few minutes. eyes closed and breathe evenly. This will calm the pulse and allow the device to give objective readings.

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The need for an electrocardiographic examination is due to the manifestation of certain symptoms:

• the presence of synchronous or periodic heart murmurs;
• syncope signs (fainting, short-term loss of consciousness);
• attacks of convulsive seizures;
• paroxysmal arrhythmia;
• manifestations of coronary artery disease (ischemia) or infarction conditions;
• the appearance of heart pain, shortness of breath, sudden weakness, cyanosis skin in patients with cardiac diseases.

ECG studies are used to diagnose systemic diseases, monitor patients under anesthesia or before surgery. Before clinical examination of patients who have crossed the 45-year mark.

An ECG examination is mandatory for persons undergoing a medical examination (pilots, drivers, machinists, etc.) or associated with hazardous work.

The human body has high electrical conductivity, which allows the potential energy of the heart to be read from its surface. Electrodes connected to various parts of the body help with this. In the process of excitation of the heart muscle by electrical impulses, the voltage difference oscillates between certain lead points, which is recorded by electrodes located on the body - on the chest and limbs.

A certain movement and amount of tension during systole and diastole (contraction and relaxation) of the heart muscle changes, the tension fluctuates, and this is recorded on a chart paper tape with a curved line - teeth, convexity and concavity. Electrodes placed on the limbs (standard leads) create signals and form the tops of triangular teeth.

Six leads located on the chest display cardiac activity in a horizontal position - from V1 to V6.

On the limbs:

• Lead (I) – displays the voltage level in the intermediate circuit of the electrodes located on the left and right wrist (I=LR+PR).
• (II) – records on the tape the electrical activity in the circuit – ankle of the left leg + wrist of the right hand).
• Lead (III) – characterizes the voltage in the chain of fixed electrodes of the wrist of the left hand and ankle of the left leg (LR + LN).

If necessary, additional leads are installed, reinforced ones - “aVR”, “aVF” and “aVL”.

The general principles of deciphering a cardiac cardiogram are based on the readings of the elements of the cardiography curve on the chart tape.

The teeth and bulges on the diagram are indicated by capital letters of the Latin alphabet - “P”, “Q”, “R”, “S”, “T”

1. The convexity (wave or concavity) of the “P” reflects the function of the atria (their excitation), and the entire complex of the upward-pointing wave is the “QRS”, the greatest spread of the impulse through the cardiac ventricles.
2. The “T” convexity characterizes the restoration of the potential energy of the myocardium (the middle layer of the heart muscle).
3. When deciphering ECGs in adults, special attention is paid to the distance (segment) between adjacent elevations - “P-Q” and “S-T”, which reflect the delay of electrical impulses between the cardiac ventricles and the atrium, and the “TR” segment - relaxation of the heart muscle in the interval (diastole) .
4. The intervals on the cardiographic line include both elevations and segments. For example - “P-Q” or “Q-T”.

Each element on graphic image indicates certain processes occurring in the heart. It is by the indicators of these elements (length, height, width), location relative to the isoline, features, according to the various locations of electrodes (leads) on the body that the doctor can identify the affected areas of the myocardium, based on the readings of the dynamic aspects of the energy of the heart muscle.

Interpretation of ECG - the norm in adults, table

Analysis of the result ECG interpretation is carried out by assessing data in a certain sequence:

• Determination of heart rate indicators. With the same interval between the “R” teeth, the indicators correspond to the norm.
• The heart rate is calculated. This is determined simply - the ECG recording time is distributed by the number of cells of the interval between the “R” teeth. With a good cardiogram of the heart, the frequency of contractions of the heart muscle should be within the limits not exceeding 90 beats/min. A healthy heart should have sinus rhythm, it is determined mainly by the elevation of “P”, reflecting the excitation of the atria. In terms of wave motion, this normal indicator is 0.25 mV with a duration of 100 ms.
• The norm for the size of the depth of the “Q” wave should not be more than 0.25% of the fluctuations in the elevation of “R” and the width of 30 ms.
• The latitude of oscillations of the “R” elevation, during normal heart function, can be displayed with a large range ranging from 0.5-2.5 mV. And the activation time of excitation above the zone of the right cardiac chamber - V1-V2 is 30 ms. Above the left chamber zone – V5 and V6, it corresponds to 50 ms.
• According to the maximum length of the “S” wave, its normal dimensions at the greatest abduction cannot cross the threshold of 2.5 mV.
• The amplitude of the oscillations of the “T” elevation, which reflects the restorative cellular processes of the initial potential in the myocardium, should be equal to ⅔ of the oscillations of the “R” wave. The normal interval (width) of the "T" elevation can vary (100-250) ms.
• The normal width of the ventricular excitation complex (QRS) is 100 ms. It is measured by the interval between the beginning of the “Q” and the end of the “S” teeth. The normal amplitude of the duration of the “R” and “S” waves is determined by the electrical activity of the heart. The maximum duration should be within 2.6 mV.