Normal ecg film. Interpretation of ecg indicators in adults

Electrocardiography is a method of measuring the potential difference that occurs under the influence of electrical impulses of the heart. The result of the study is presented in the form of an electrocardiogram (ECG), which reflects the phases of the cardiac cycle and the dynamics of the heart.

During the heartbeat, the sinus node, located near the right atrium, generates electrical impulses that travel along the nerve pathways, contracting the myocardium (heart muscle) of the atria and ventricles in a certain sequence.

After the contraction of the myocardium, the impulses continue to propagate through the body in the form of an electric charge, resulting in a potential difference - a measurable value that can be determined using the electrodes of an electrocardiograph.

Features of the procedure

In the process of recording an electrocardiogram, leads are used - electrodes are applied according to a special scheme. In order to fully display the electrical potential in all parts of the heart (anterior, posterior and lateral walls, interventricular septa), 12 leads are used (three standard, three reinforced and six chest), in which the electrodes are located on the arms, legs and in certain areas of the chest.

During the procedure, the electrodes register the strength and direction of electrical impulses, and the recording device records the resulting electromagnetic oscillations in the form of teeth and a straight line on special paper for recording ECG at a certain speed (50, 25 or 100 mm per second).

Two axes are used on a paper registration tape. The horizontal X-axis shows the time and is indicated in millimeters. With the help of a time interval on graph paper, you can track the duration of the processes of relaxation (diastole) and contraction (systole) of all parts of the myocardium.

The vertical Y-axis is an indicator of the strength of the impulses and is indicated in millivolts - mV (1 small cell = 0.1 mV). By measuring the difference in electrical potentials, pathologies of the heart muscle are determined.

Also on the ECG leads are indicated, on each of which the work of the heart is recorded in turn: standard I, II, III, chest V1-V6 and enhanced standard aVR, aVL, aVF.

ECG indicators

The main indicators of the electrocardiogram, characterizing the work of the myocardium, are teeth, segments and intervals.

The serrations are all sharp and rounded protuberances recorded along the vertical Y-axis, which can be positive (upward), negative (downward), and biphasic. There are five main teeth that are necessarily present on the ECG graph:

• P - is recorded after the occurrence of an impulse in the sinus node and a consistent contraction of the right and left atria;
• Q - is recorded when an impulse appears from the interventricular septum;
• R, S - characterize contractions of the ventricles;
• T - indicates the process of relaxation of the ventricles.

Segments are sections with straight lines, indicating the time of tension or relaxation of the ventricles. There are two main segments in the electrocardiogram:

• PQ is the duration of ventricular excitation;
• ST is relaxation time.

An interval is a section of an electrocardiogram consisting of a wave and a segment. When examining the PQ, ST, QT intervals, the propagation time of excitation in each atrium, in the left and right ventricles is taken into account.

ECG norm in adults (table)

Using the table of norms, you can conduct a consistent analysis of the height, intensity, shape and length of the teeth, intervals and segments to identify possible deviations. Due to the fact that the passing impulse propagates unevenly through the myocardium (due to the different thickness and size of the cardiac chambers), the main parameters of the norm of each element of the cardiogram are distinguished.

Based on information obtained from deciphering the ECG, we can draw conclusions about the features of the heart muscle:

• normal operation of the sinus node;
• operation of the conducting system;
• frequency and rhythm of heart contractions;
• the state of the myocardium - blood circulation, thickness in different areas.

ECG decoding algorithm

There is an ECG decoding scheme with a consistent study of the main aspects of the heart:

• sinus rhythm;
• rhythm regularity;
• conductivity;
• analysis of teeth and intervals.

Sinus rhythm - a uniform rhythm of the heartbeat, due to the appearance of an impulse in the AV node with a gradual contraction of the myocardium. The presence of sinus rhythm is determined by deciphering the ECG according to the P wave.

Also in the heart are additional sources of excitation that regulate the heartbeat in violation of the AV node. Non-sinus rhythms appear on the ECG as follows:

• Atrial rhythm - P waves are below the isoline;
• AV-rhythm - on the electrocardiogram P are absent or go after the QRS complex;
• Ventricular rhythm - in the ECG there is no pattern between the P wave and the QRS complex, while the heart rate does not reach 40 beats per minute.

When the occurrence of an electrical impulse is regulated by non-sinus rhythms, the following pathologies are diagnosed:

• Extrasystole - premature contraction of the ventricles or atria. If an extraordinary P wave appears on the ECG, as well as with deformation or a change in polarity, atrial extrasystole is diagnosed. With nodal extrasystole, P is directed downward, absent, or located between the QRS and T.
• Paroxysmal tachycardia (140-250 beats per minute) on the ECG can be represented as an overlay of the P wave on the T, standing behind the QRS complex in II and III standard leads, as well as an extended QRS.
• Flutter (200-400 beats per minute) of the ventricles is characterized by high waves with hardly discernible elements, and with atrial flutter, only the QRS complex is released, and sawtooth waves are present at the site of the P wave.
• Flicker (350-700 beats per minute) on the ECG is expressed as non-uniform waves.

Heart rate

Decryption ECG of the heart necessarily contains heart rate indicators and is recorded on the tape. To determine the indicator, you can use special formulas depending on the recording speed:

• at a speed of 50 millimeters per second: 600 / (number of large squares in the interval R-R);
• at a speed of 25 mm per second: 300 / (number of large squares between R-R),

Also, the numerical indicator of the heartbeat can be determined by small cells interval R-R if the cardiogram tape was recorded at a speed of 50 mm/s:

• 3000/number of small cells.

The normal heart rate for an adult is 60 to 80 beats per minute.

Rhythm regularity

Normally, the R-R intervals are the same, but an increase or decrease by no more than 10% of the average value is allowed. Changes in the regularity of the rhythm and increased/decreased heart rate may occur as a result of impaired automatism, excitability, conduction, and myocardial contractility.

In case of violation of the function of automatism in the heart muscle, the following indicators of intervals are observed:

• tachycardia - heart rate is in the range of 85-140 beats per minute, a short relaxation period (TP interval) and a short RR interval;
• bradycardia - heart rate decreases to 40-60 beats per minute, and the distance between RR and TP increases;
• arrhythmia - different distances are kept between the main intervals of the heartbeat.

Conductivity

For the rapid transmission of an impulse from the source of excitation to all parts of the heart, there is a special conduction system (SA- and AV-nodes, as well as the bundle of His), the violation of which is called blockade.

There are three main types of blockade - sinus, intra-atrial and atrioventricular.

With sinus blockade, the ECG shows a violation of the transmission of the impulse to the atria in the form of periodic loss of PQRST cycles, while the distance between R-R increases significantly.

Intraatrial blockade is expressed as a long P wave (more than 0.11 s).

Atrioventricular blockade is divided into several degrees:

• I degree - prolongation of the P-Q interval for more than 0.20 s;
• II degree - periodic loss of QRST with an uneven change in time between complexes;
• III degree - the ventricles and atria contract independently of each other, as a result of which there is no connection between P and QRST in the cardiogram.

Electric axle

EOS displays the sequence of impulse transmission through the myocardium and can normally be horizontal, vertical and intermediate. In deciphering the ECG, the electrical axis of the heart is determined by the location of the QRS complex in two leads - aVL and aVF.

In some cases, axis deviation occurs, which in itself is not a disease and occurs due to an increase in the left ventricle, but, at the same time, may indicate the development of pathologies of the heart muscle. As a rule, the EOS deviates to the left due to:

• ischemic syndrome;
• pathology of the valvular apparatus of the left ventricle;
• arterial hypertension.

Axis tilt to the right is observed with an increase in the right ventricle with the development of the following diseases:

• stenosis pulmonary artery;
• bronchitis;
• asthma;
• pathology of the tricuspid valve;
• congenital defect.

Deviations

Violation of the duration of the intervals and the height of the waves are also signs of changes in the work of the heart, on the basis of which a number of congenital and acquired pathologies can be diagnosed.

Cardiology
Chapter 5

in. Conduction disorders. Blockade of the anterior branch of the left leg of the bundle of His, blockade of the posterior branch of the left leg of the bundle of His, complete blockade of the left leg of the bundle of His, blockade right leg bundle of His, AV blockade of the 2nd degree and complete AV blockade.

G. Arrhythmias see Ch. four.

VI. Electrolyte disorders

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

B. Hyperkalemia

Light(5.56.5 meq/l). High peaked symmetrical T wave, shortening of the QT interval.

Moderate(6.58.0 meq/l). Reducing the amplitude of the P wave; prolongation of the PQ interval. Expansion of the QRS complex, a decrease in the amplitude of the R wave. Depression or elevation of the ST segment. Ventricular extrasystole.

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

AT. Hypocalcemia. Prolongation of the QT interval (due to lengthening of the ST segment).

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

VII. Action medicines

BUT. cardiac glycosides

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

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

BUT. dilated cardiomyopathy. Signs of an increase in the left atrium, sometimes right. Low amplitude of the teeth, pseudo-infarction curve, blockade of the left leg of the bundle of His, the anterior branch of the left leg of the bundle of His. Nonspecific changes in the ST segment and T wave. Ventricular extrasystole, atrial fibrillation.

B. Hypertrophic cardiomyopathy. Signs of an increase in the left atrium, sometimes right. Signs of left ventricular hypertrophy, pathological Q waves, pseudoinfarction curve. Nonspecific changes in the ST segment and T wave. With apical hypertrophy of the left ventricle giant negative T waves in the left chest leads. Supraventricular and ventricular arrhythmias.

AT. amyloidosis of the heart. Low amplitude of the teeth, pseudo-infarction curve. Atrial fibrillation, AV block, ventricular arrhythmias, sinus node dysfunction.

G. Duchenne myopathy. Shortening of 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 enlargement of the left atrium. There is hypertrophy of the right ventricle, deviation of the electrical axis of the heart to the right. Often - atrial fibrillation.

E. Prolapse mitral valve. T waves are flattened or inverted, 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 ST-segment elevation with upward bulge in leads I, II, aVF, V 3 V 6 . Sometimes ST segment depression in lead aVR (in rare cases in leads aVL, V 1 , V 2). Sinus tachycardia, atrial arrhythmias. ECG changes go through 4 stages:

ST segment elevation, T wave normal;

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

ST segment on the isoline, T wave inverted;

the ST segment is on the isoline, the T wave is normal.

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

AND. Dextrocardia. The P wave is negative in lead I. QRS complex 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 an increase in the right atrium, less often 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. Stenosis of the pulmonary artery. Signs of enlargement of the right atrium. Right ventricular hypertrophy with 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

BUT. COPD. Signs of enlargement of the right atrium. Deviation of the electrical axis of the heart to the right, shift of the transition zone to the right, signs of right ventricular hypertrophy, low amplitude of the teeth; 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, intraventricular conduction delay, 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 block, 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.

AT. Subarachnoid hemorrhage and other CNS 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. HPN. ST segment elongation (due to hypocalcemia), high symmetrical T waves (due to hyperkalemia).

E. Hypothermia. Prolongation of the PQ interval. A notch at the end of the QRS complex (Osborn's 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 stimulated (A A trium atrium, V V entricle ventricle, D D ual and atrium and ventricle), the second letter which chamber activity 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 start, D D ual both). So, in the VVI mode, both the stimulating and sensing electrodes are located in the ventricle, and when spontaneous activity of the ventricle occurs, its stimulation is blocked. In DDD mode, both the atrium and the ventricle have two electrodes (stimulating and sensing). Response type D means that if spontaneous atrial activity occurs, its stimulation will be blocked, and after a programmed time interval (AV-interval), a stimulus will be given to the ventricle; if spontaneous ventricular activity occurs, on the contrary, ventricular pacing will be blocked, and atrial pacing will start after a programmed VA interval. Typical modes of a single-chamber pacemaker VVI and AAI. Typical two-chamber EKS modes DVI and DDD. The fourth letter R ( R ate-adaptive adaptive) means that the pacemaker is able to increase the pacing rate in response to changes in motor activity or load-dependent physiological parameters (eg, QT interval, temperature).

BUT. 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) is being stimulated.

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

Determine programmed pacer 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 ECS do not exclude the possibility of the presence of electrodes in two chambers: for example, stimulated contractions of the ventricles can be observed both with single-chamber and dual-chamber ECS, in which ventricular stimulation follows a certain interval after the P wave (DDD mode) .

Rule out violations of imposition and detection:

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 should be blocked if atrial or ventricular depolarization is normally detected.

B. Separate EKS modes

AAI. If the intrinsic rate falls below the programmed pacer rate, atrial pacing is initiated at a constant AA interval. With spontaneous atrial depolarization (and normal detection), the pacemaker time counter is reset. If spontaneous atrial depolarization does not recur after the set AA interval, atrial pacing is initiated.

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

DDD. If the intrinsic rate falls below the programmed pacemaker rate, atrial (A) and ventricular (V) pacing is initiated at the specified intervals between the A and V pulses (AV interval) and between the V pulse and the subsequent A pulse (VA interval). With spontaneous or forced ventricular depolarization (and its normal detection), the pacemaker time counter is reset and the VA interval begins. If spontaneous atrial depolarization occurs in this interval, atrial pacing is blocked; otherwise, an atrial impulse is delivered. With spontaneous or imposed atrial depolarization (and its normal detection), the pacemaker time counter is reset and the AV interval begins. If spontaneous ventricular depolarization occurs in this interval, then ventricular pacing is blocked; otherwise, a ventricular impulse is delivered.

AT. Pacemaker dysfunction and arrhythmias

Binding violation. 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, perforation of the heart, an increase in the stimulation threshold (with myocardial infarction, taking flecainide, hyperkalemia), damage to the electrode or violation of its insulation, disturbances in impulse generation (after defibrillation or due to depletion of the power source), as well as incorrectly set EKS parameters.

Detection violation. The pacer time counter is not reset when self or imposed depolarization of the corresponding chamber occurs, resulting in an abnormal rhythm (imposed rhythm superimposed on own). Reasons: low amplitude of the perceived signal (especially with ventricular extrasystole), incorrectly set pacemaker sensitivity, as well as the reasons listed above (see). It is often enough to reprogram the pacemaker sensitivity.

Hypersensitivity of the pacemaker. At the expected time (after the appropriate interval) no stimulation occurs. T waves (P waves, myopotentials) are misinterpreted as R waves and the pacemaker time counter is reset. In case of erroneous detection of the T wave, the VA interval starts from it. In this case, the sensitivity or refractory period of detection must be reprogrammed. You can also set the VA interval to the T wave.

Blocking by myopotentials. Myopotentials arising from hand movements can 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 violations occur when using unipolar pacemakers.

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

Tachycardia induced by atrial tachycardia. Imposed rhythm with the maximum rate for the pacemaker. It is observed if atrial tachycardia (eg, 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, switch to VVI mode and eliminate the arrhythmia.

Allows you to monitor the state of your heart and control the ECG. Follow the signs of a normal ECG. You do a study and in 30 seconds you receive an automatic conclusion about the state of your heart. If necessary, you can send the study to the doctor's control.

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ECG is the main method for diagnosing cardiac arrhythmias. This publication briefly presents signs of a normal ECG. ECG recording is carried out in a position convenient for the patient, breathing should be calm. For ECG registration, 12 main leads are most often used: 6 from the limbs and 6 from the chest. The project offers an analysis of microalternations in six leads (only electrodes applied to the limbs are used), which allow you to independently identify probable deviations in the work of the heart. Using the project, analysis is also possible for 12 leads. But at home, it is difficult for an unprepared person to correctly position the chest electrodes, which can lead to incorrect recording of the electrocardiogram. Therefore, the CARDIOVISOR device, which registers 12 leads, is purchased by cardiologists.

To obtain 6 standard leads, the electrodes are applied as follows:
. Lead I: left hand(+) and right hand (-)
. II lead: left leg (+) and right arm (-)
. III lead: left leg (+) and left arm (-)
. aVR - enhanced lead from right hand(short for augmented voltage right - enhanced potential on the right).
. aVL - enhanced abduction from the left hand
. aVF - enhanced abduction from the left leg

The figure shows an electrocardiogram obtained by a client in the website project

Each lead characterizes the work of a certain area of ​​the myocardium. Leads I and aVL reflect the potentials of the anterior and lateral wall of the left ventricle. III and aVF leads reflect the potentials of the lower diaphragmatic (posterior) wall of the left ventricle. Lead II is intermediate, confirms changes in the anterolateral or posterior wall of the left ventricle.

The heart consists of two atria and two ventricles. The mass of the atria is much smaller than the mass of the ventricles, so the electrical changes associated with atrial contraction are small. They are associated with the P wave. In turn, during depolarization of the ventricles, high-amplitude oscillations are recorded on the ECG - this is the QRS complex. The T wave is associated with the return of the ventricles to a resting state.

When analyzing an ECG, a strict sequence is followed:
. Heart rhythm
. Conductivity Intervals
. Electrical axis of the heart
. Description of QRS complexes
. Description of ST segments and T waves

Heart rate and heart rate

The heart rate is an important indicator of the work of the heart. Normally, the rhythm is sinus (the name is associated with the sinus node - the pacemaker, thanks to which the impulse is transmitted and the heart contracts). If the depolarization does not begin in the sinus node, then in this case they speak of arrhythmia and the rhythm is named after the department from which the depolarization begins. The heart rate (HR) is determined on the ECG by the distance between the R waves. The heart rhythm is considered normal if the duration of the R-R intervals is the same or has a slight variation (up to 10%). Normal heart rate is 60-80 beats per minute. The ECG machine draws paper at a speed of 25mm/s, so a large square (5mm) corresponds to 0.2 seconds (s) or 200 milliseconds (ms). Heart rate is measured by the formula
Heart rate = 60/R-R,
where R-R distance between the highest teeth associated with contraction of the ventricles.

The acceleration of the rhythm is called tachycardia, and the slowdown is called bradycardia.
ECG analysis should be carried out by a cardiologist. Using the CARDIOVISOR, the client of the project can take an ECG on his own, since all calculations are carried out by a computer program, and the patient sees the final result analyzed by the system.

Conductivity Intervals

By the intervals between the P-QRS-T waves, one can judge the conduction of an electrical impulse between the parts of the heart. Normally, the PQ interval is 120-200 ms (3-5 small squares). According to the PQ interval, one can judge the conduction of an impulse from the atria through the atrioventricular (atrioventricular) node to the ventricles. The QRS complex characterizes the excitation of the ventricles. The width of the QRS complex is measured from the beginning of the Q wave to the end of the S wave. Normally, this width is 60-100 ms. They also look at the nature of the teeth of this complex. Normally, the Q wave in duration should be no more than 0.04 s and not exceed 3 mm in depth. An abnormal Q wave may indicate myocardial infarction.

QT interval characterizes the total duration of systole (contraction) of the ventricles. QT includes the interval from the beginning of the QRS complex to the end of the T wave. Bazett's formula is often used to calculate the QT interval. This formula takes into account the dependence of the QT interval on the rhythm rate (QTc). Normally, the QTc interval is 390-450 ms. Prolongation of the QT interval indicates the development of coronary heart disease, atherosclerosis, rheumatism or myocarditis. Shortening of the QT interval may indicate hypercalcemia.
All intervals that reflect the conductivity of the electrical impulse are calculated by a special program, which allows you to get fairly accurate examination results that are visible in the diagnostic room mode of the system.

Electrical axis of the heart (EOS)

Determining the position of the electrical axis of the heart allows you to identify areas of violation of the conduction of the electrical impulse. The assessment of the position of the EOS is carried out by cardiologists. When using , data on the position of the electrical axis of the heart are calculated automatically and the patient can view the result in his diagnostic room. To determine the EOS look at the height of the teeth. Normally, the R wave should be larger than the S wave (counted from the isoline) in I, II and III leads. Axis deviation to the right (the S wave is larger than the R wave in lead I) indicates problems in the work of the right ventricle, and left axis deviation (the S wave is larger than the R wave in leads II and III) may indicate left ventricular hypertrophy.

Description of the QRS complex

The QRS complex arises due to the conduction of an impulse along the septum and myocardium of the ventricles and characterizes their work. Normally, there is no pathological Q wave (not wider than 20-40 ms and not deeper than 1/3 of the R wave). In lead aVR, the P wave is negative and the QRS complex is oriented downward from the isoelectric line. The width of the QRS complex normally does not exceed 120 ms. An increase in this interval may indicate blockade of the bundle branch of the His (conduction disturbance).

Picture. Negative P wave in aVR lead (red isoelectric line).

P wave morphology

The P wave reflects the propagation of an electrical impulse through both atria. The initial part of the P wave characterizes the activity of the right atrium, and the final part - the left atrium. Normally, the P wave should be positive in leads I and II, aVR is negative, usually positive in aVF and intermittent in leads III and aVL (may be positive, inverted, or biphasic). The width of the P wave is normally not less than 0.12 s (120 ms). With an increase in the width of the P wave, as well as its doubling, we can talk about a violation of the impulse conduction - atrioventricular blockade occurs (figure).

Picture. Doubling and increasing the width of the P-tooth

Description of ST segments and T waves

ST segment corresponds to the period when both ventricles are completely covered by excitation, measured from the end of the S to the beginning of the T-wave. The duration of ST depends on the pulse rate. Normally, the ST segment is located on the isoline, ST depression is allowed up to 0.5 mm, its rise in standard leads should not exceed 1 mm. Elevation of the ST segment is observed in acute infarction and pericarditis, and depression indicates myocardial ischemia or the influence of cardiac glycosides.

T wave characterizes the process of repolarization (return of the ventricles to their original state). During normal heart function, the T-wave is up in leads I and II, but in aVR, it will always be negative. A high and pointed T-wave is observed with hyperkalemia, and a flat and elongated tooth indicates the reverse process - hypokalemia. A negative T wave in leads I and II may indicate ischemia, infarction, hypertrophy of the right and left ventricles, or pulmonary embolism.

The main parameters that are used for ECG analysis by the standard method are described above. The project offers an ECG analysis based on the dispersion mapping method. It is based on the formation of an information-topological model of small ECG fluctuations - microalterations of the ECG signal. The analysis of these deviations makes it possible to detect pathology in the work of the heart at earlier stages, in contrast to the standard method of ECG analysis.

Rostislav Zhadeiko, especially for the project .

Electrocardiogram reflects only electrical processes in the myocardium: depolarization (excitation) and repolarization (recovery) 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, I will sometimes use “contraction-relaxation” instead of “depolarization-repolarization”, 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. I wrote a little more about this phenomenon before .

Elements of a normal ECG

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

Waves and intervals on the ECG. It is curious that abroad the P-Q interval is usually called P-R.

Every ECG is made up of teeth, segments and intervals.

TEETH are convexities and concavities on the electrocardiogram. The following teeth are distinguished on the ECG:

P(atrial contraction)

Q, R, S(all 3 teeth characterize the contraction of the ventricles),

T(ventricular 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 are P-Q segments and S-T. For example, the P-Q segment is formed due to a delay in 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.

Teeth, segments and intervals on ekg. Pay attention to large and small cells (about them below).

Waves of the QRS complex

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 pick out the teeth?

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

The tooth R (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. The negative (downward) wave of the QRS complex located before the R wave, denoted as Q (q), and after - as 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 tooth. Q reflects depolarization of the interventricular septum R- the bulk of the myocardium of the ventricles, tooth S- basal (i.e., near the atria) sections of the interventricular septum. The R wave V1, V2 reflects the excitation of the interventricular septum, and R V4, V5, V6 - the excitation of the muscles of the left and right ventricles. necrosis of areas of the myocardium (for example, with myocardial infarction ) causes widening and deepening of the Q wave, so this wave is always paid close attention.

ECG analysis

General ECG decoding scheme

Checking the correctness of ECG registration.

Analysis heart rate and conductivity:

assessment of the regularity of heart contractions,

counting the heart rate (HR),

determination of the source of excitation,

conductivity rating.

Determination of the electrical axis of the heart.

Analysis of atrial P wave and P-Q interval.

Analysis of the ventricular QRST complex:

• analysis of the QRS complex,

  analysis of the RS-T segment,

  T wave analysis,

  analysis of the interval Q - T.

Electrocardiographic conclusion.

Normal electrocardiogram.

1) Checking the correctness of the ECG registration

At the beginning of each ECG tape there should be calibration signal- so-called control millivolt. To do this, at the beginning of the recording, a standard voltage of 1 millivolt is applied, which should display on the tape a deviation of 10 mm. Without a calibration signal, the ECG recording is considered incorrect. Normally, in at least one of the standard or augmented limb leads, the amplitude should exceed 5 mm, and in the chest leads - 8 mm. If the amplitude is lower, it is called reduced EKG voltage which occurs in some pathological conditions.

Reference millivolt on the ECG (at the beginning of the recording).

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. The variation in the duration of individual R-R intervals is allowed no more than ±10% from their average duration. If the rhythm is sinus, it is usually correct.

heart rate count(HR)

Large squares are printed on the ECG film, each of which includes 25 small squares (5 vertical x 5 horizontal). For a quick calculation of heart rate with the correct rhythm, the number of large squares between two adjacent R-R teeth is counted.

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

On the overlying ECG, the R-R interval is approximately 4.8 large cells, which at a speed of 25 mm/s gives 300 / 4.8 = 62.5 bpm

At a speed of 25 mm/s each little cell is equal to 0.04s, and at a speed of 50 mm/s - 0.02 s. This is used to determine the duration of the teeth and intervals.

With an incorrect rhythm, they usually consider maximum and minimum heart rate according to the duration of the smallest and largest R-R interval, respectively.