Sinusitis

Electrocardiography (ECG): basic theory, recording, analysis, detection of pathologies. Decoding ECG indicators ECG norm in adults decoding example

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

The result of taking electrical indicators, the work of various parts of the organ, is the creation of an electrocardiogram.

Its parameters are recorded on special roll paper. The paper moving speed is available in 3 options:

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

There are electronic sensors that can record ECG parameters on the hard drive of the system unit and, if necessary, display this data on a monitor or print it on the required paper formats.

Decoding of the recorded electrocardiogram.

The results of the analysis of electrocardiogram parameters are given by a cardiologist. The recording is deciphered by the doctor by establishing the duration of the intervals between the various elements of the recorded indicators. An explanation of the features of the electrocardiogram contains many points:

Normal ECG readings.

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

Electrocardiogram in case of myocardial infarction.

Myocardial infarction occurs due to exacerbation of coronary artery disease, when the internal cavity of the coronary artery of the heart muscle narrows significantly. If this disorder is not corrected within 15–20 minutes, the death of the heart muscle cells that receive oxygen and nutrients from this artery occurs. This circumstance creates significant disturbances in the functioning of the heart and turns out to be a severe and serious threat to life. If a heart attack occurs, an electrocardiogram will help identify the location of necrosis. The indicated cardiogram contains noticeably manifested deviations in the electrical signals of the heart muscle:

Heart rhythm disorder.

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

Hypertrophy of the heart.

An increase in the volume of the heart muscles is an adaptation of the organ to new operating conditions. Changes appearing on the electrocardiogram are determined by high bioelectric strength, a characteristic muscle area, a delay in the movement of bioelectric impulses in its thickness, and the appearance of signs of oxygen starvation.

Conclusion.

Electrocardiographic indicators of heart pathology are varied. Reading them is a complex activity that requires special training and improvement of practical skills. A specialist characterizing an ECG needs to know the basic principles of cardiac physiology and various versions of cardiograms. He needs to have skills in identifying abnormalities in cardiac activity. Calculate the impact of medications and other factors on the occurrence of differences in the structure of ECG waves and intervals. Therefore, the interpretation of the electrocardiogram should be entrusted to a specialist who has encountered in his practice various types of deficiencies in the functioning of the heart.

Main objectives of the survey

The ECG procedure is a way to determine the electrical activity of the heart muscle. Its biological potentials are recorded by special electrodes. The resulting data is displayed graphically on the device’s monitor or printed on paper. Electrocardiography allows you to determine:

Conductivity of the heart muscle and the frequency of its contractions.
The sizes of the atria (the sections into which blood flows from the veins) and the ventricles (the sections that receive blood from the atria and pump it into the arteries).
The presence of disturbances in the conduction of electrical impulses - blockade.
Level of blood supply to the myocardium.

No special preparation is required to conduct an ECG examination. With its help, it is possible to identify not only disturbances in the functional activity of the heart, but also pathological processes in blood vessels, lung tissue and endocrine glands.

An electrocardiogram is considered the main method that can diagnose dangerous diseases such as congenital and acquired heart defects, arrhythmia, heart failure, myocardial infarction

Methods for conducting electrocardiographic studies

In order to make an accurate diagnosis, practicing cardiologists use a comprehensive examination of the heart, including several methods.

Classic ECG

The most common method for studying the direction of electrical impulses and their strength. This simple procedure lasts no more than 5 minutes, during which time the ECG can show:

cardiac conduction disturbance;
the presence of an inflammatory process in the serous membrane - pericarditis;
the condition of the heart chambers and hypertrophy of their walls.

The disadvantage of this technique is that it is performed while the patient is at rest. It is impossible to record those pathological changes that manifest themselves during physical and psycho-emotional stress. In this case, when diagnosing the disease, the doctor takes into account the main clinical signs and the results of other studies.

Daily ECG monitoring

Long-term recording of indicators makes it possible to detect disturbances in the functional activity of the patient’s heart during sleep, stress, walking, physical activity, and running. Holter ECG helps an experienced specialist in studying the causes of irregular heart rhythm and identifying the early stages of ischemia - insufficient blood flow to the myocardium.

Stress test

Monitoring the work of the heart muscle during physical stress (exercise on a treadmill or exercise bike). This method is used if the patient has periodic cardiac disturbances, which the ECG does not show at rest. The exercise test provides the doctor with the opportunity to:

find the reasons for the deterioration of the patient’s condition during physical stress;
detect the source of sudden changes in blood pressure and sinus rhythm disturbances - the most important indicator of the normal functioning of the heart;
monitor the patient's condition after heart attacks or surgery.

The data shown by a cardiac cardiogram allows you to select the most appropriate medications and monitor the results of therapy.

Indications for ECG

Practitioners prescribe this diagnostic procedure if the patient has complaints about:

increased blood pressure (BP) parameters;
difficulty breathing;
shortness of breath even at rest;
discomfort in the chest in the projection of the heart;
frequent loss of consciousness;
causeless disturbance of heart rhythm.

The procedure is also carried out for chronic diseases of the musculoskeletal system that occur with damage to the cardiovascular system, restoration of the body after focal damage to the brain as a result of a violation of its blood supply - stroke. ECG registration can be performed routinely or urgently.

For the purpose of prevention, functional diagnostics are prescribed to assess professional suitability (athletes, sailors, drivers, pilots, etc.), persons who have crossed the 40-year mark, as well as patients with arterial hypertension, obesity, hypercholesterolemia, rheumatism, and chronic infectious diseases. A planned cardiogram is carried out to assess cardiac activity before any operation, during pregnancy, after complex medical procedures.

Urgent implementation of the procedure is required when:

painful sensations in the heart and behind the sternum;
sudden shortness of breath;
prolonged pain in the upper abdomen and spine;
persistent increase in blood pressure;
chest injury;
fainting;
the appearance of weakness of unknown etiology;
arrhythmias;
severe pain in the lower jaw and neck.

Contraindications

Conventional cardiography does not cause harm to the human body - the equipment records only cardiac impulses and does not affect other tissues and organs. That is why diagnostic testing can be done often for an adult, a child, and a pregnant woman. But it is not recommended to prescribe a stress ECG for:

stage III hypertension;
severe coronary circulatory disorders;
exacerbation of thrombophlebitis;
acute stage of myocardial infarction;
thickening of the heart walls;
diabetes mellitus;
severe infectious and inflammatory diseases.

How to prepare for the procedure?

The patient does not need to perform complex preparatory measures. To obtain accurate results of the study, you should get a good night's sleep, limit smoking, reduce physical activity, avoid stressful situations and food loads, and avoid drinking alcohol.

Performing an ECG

Heartbeats are recorded by a qualified nurse in the functional diagnostics room. The procedure consists of several stages:

The patient bares his legs, forearms, chest, wrists and lies down on the couch, arms extended along the body and legs straightened at the knees.
The skin of the areas where the cardiograph electrodes are applied is treated with a special gel.
Cuffs and suction cups with wires are attached: red - on the right arm, yellow - on the left arm, green - on the left leg, black - on the right leg, 6 electrodes - on the chest.
The device is turned on, the operating principle of which is based on reading the rhythm of contractions of the heart muscle and recording any disturbances in its functioning in the form of a graphic image.

If it is necessary to take an additional ECG, the healthcare worker may ask the patient to hold his breath for 10-15 seconds. The received cardiogram record indicates the patient’s data (full name and age), its description is carried out by an experienced cardiologist.

Decoding the final data

ECG results are considered the basis for diagnosing cardiovascular pathologies. When interpreting them, such indicators as the systolic (stroke) volume of blood, which is pumped into the ventricles and released into the great vessels, the minute volume of blood circulation, and the frequency of contractions of the heart muscle in 1 minute, are taken into account.

The sequence algorithm for assessing the functional activity of the heart consists of:

Studying the rhythm of contractions - assessing the duration of intervals and identifying disturbances in the conduction of electrical impulses (blockade).
Analysis of ST segments and detection of pathological Q waves.
Study of P waves reflecting atrial contraction.
Study of the walls of the ventricles in order to identify their compaction.
Determination of the electrical axis of the heart.
Study of T waves, reflecting repolarization (restoration) of muscle tissue after contractions.

ECG analysis consists of the main indicators, schematically depicted on a graphic tape: elevations or depressions with sharp ends above a straight line - teeth; segments that connect the teeth - segments; distance from tooth to segment – interval

After analyzing the characteristics of the cardiogram, the attending physician has an idea of the clinical picture of cardiac activity, for example, a change in the width of the intervals and the shape of all convex and concave teeth is observed when the conduction of the cardiac impulse slows down, a mirror-inverted curve of the T wave and a decrease in the ST segment indicates damage to the cells of the muscle layer hearts.

When interpreting an ECG, contractions of the heart muscle are assessed by studying the amplitude and direction of their electric fields in 3 standard leads, 3 enhanced (unipolar) leads, 6 leads from the chest area - I, II, III, avR, avL and avF . Based on the results of these elements, the electrical axis of the heart is assessed, the location of the heart and the presence of disturbances in the passage of electrical impulses through the heart muscle (blockades) are assessed.

Normal cardiogram of an adult

Normal ECG of a child

The location and duration of the segments comply with generally accepted standards. Some study indicators depend on age:

the electrical axis has an angle from 45° to 70°, in a newborn baby it is deviated to the left, until the age of 14 it is located vertically;
heart rate is sinus, in a newborn up to 135 beats/min, in a teenager – 75-85.

Pathological disorders of the heart

If the final study data contains changed parameters, this is a reason for a more detailed examination of the patient. There are several types of deviations in ECG results:

borderline - some indicators slightly do not correspond to the norm;
low-amplitude (decrease in the amplitude of the waves in all leads) – characterizes myocardial dystrophy;
pathological - cardiac dysfunction requires immediate medical attention.

However, not all altered results should be taken as evidence of serious problems with the functioning of the heart muscle. For example, a reduction in the horizontal distance of teeth and segments, as well as rhythm disturbances, can be recorded after physical and psycho-emotional stress. In such cases, the diagnostic procedure should be repeated.

The photo shows an example of a cardiogram with deviations - ventricular extrasystole

Only a qualified specialist can “read” an ECG and draw appropriate conclusions! An inexperienced patient should not independently diagnose the disease and take medications. In the table we indicate an approximate interpretation of pathological electrocardiography:

Deviations	Disease, pathology	Interpretation
Heart rhythm disturbance	Bradycardia	Pulse less than 60 beats/min, PQ segments> 0.12", P wave in N (normal)
Heart rhythm disturbance	Tachycardia	Heart rate up to 180 beats/min, P wave directed upward, QRS> 0.12"
Changing the position of the EOS (electrical axis of the heart)	Bundle branch block	The S wave is highly elevated relative to R, the axis is deviated to the right by >90°
	Left ventricular hypertrophy – observed with pulmonary edema and infarction	The R and S teeth are very high, the axis is deflected to the left from 40° to 90°
Cardiac conduction disorders	AV I degree (atrioventricular block)	Duration of the PQ interval >0.2", the T wave changes with the ventricular complex
	AB II degree	PQ is constantly increased and completely replaces ORS
	Complete AV block	Change in atrial systole, equal sizes of P and R waves
Other pathological changes	Mitral valve prolapse (loss)	The T wave is directed downward, QT segment prolongation and ST depression are observed
	Underfunction of the thyroid gland – hypothyroidism	Bradycardia, T wave is flat, PQ segment is lengthened, QRS is low
	Ischemia	T angle is sharp and high
	Heart attack	The ST segment and the T wave are dome-shaped, the height of R is increased, the Q is shallow

How many times a year is the procedure done?

The classical technique simply records the impulses transmitted by the heart muscle. The equipment does not have any negative impact on the human body. That is why it is possible to monitor heart activity using electrocardiography for both children and adults. Some caution is exercised only when prescribing a stress ECG. The shelf life of the examination results is 30 days.

Thanks to this safe technique, serious cardiovascular pathologies can be detected in a timely manner and the success of treatment measures can be monitored. In public medical institutions, ECG is free; to perform it, the patient must receive a referral from the attending physician. In private clinical diagnostic centers, examination is paid - its cost depends on the procedure method and the level of qualifications of specialists.

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 is 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.

P wave. Features: the first low tooth of a semicircular shape that appears after the isoelectric line. Meaning: atrial stimulation.
Q wave. Features: the first negative small wave, following the P wave and the end of the PQ segment. Meaning: the beginning of ventricular excitation.
R wave. Features: The first positive wave after the Q wave or the first positive wave after the P wave if there is no Q wave. Meaning: excitation of the ventricles.
S wave. Features: The first negative small wave after the R wave. Meaning: excitation of the ventricles.
QRS complex. Features: Typically a split complex following the P wave and PQ interval. Meaning: Spread of excitation through the ventricles.
Point J. Corresponds to the point at which the QRS complex ends and the ST segment begins.

T wave. Features: The first positive semicircular wave appearing after the QRS complex. Meaning: Restoration of ventricular excitability.
Wave U. Features: Positive small wave appearing immediately after the T wave. Significance: Aftereffect potential (after restoration of ventricular excitability).
Zero (isoelectric) line. Features: The distance between individual waves, such as between the end of a T wave and the beginning of the next R wave. Meaning: The baseline against which the depth and height of ECG waves are measured.
PQ interval. Features: time from the beginning of the P wave to the beginning of the Q wave. Value: time of excitation from the atria to the AV node and further through the PG and its legs.

PQ segment. Features: time from the end of the P wave to the beginning of the Q wave. Significance: has no clinical significance ST segment. Features: time from the end of the S wave to the beginning of the T wave. Value: time from the end of the spread of excitation through the ventricles to the beginning of restoration of ventricular excitability. QT interval. Features: time from the beginning of the Q wave to the end of the T wave. Value: time from the beginning of the propagation of excitation to the end of restoration of excitability of the ventricular myocardium (ventricular electrical systole).

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.

Many will be surprised to learn that even the healthiest and strongest heart does not work exactly like a Swiss watch. Heart rate variability(also called cycle length variability or R-R interval variability) is the phenomenon of changing the time between two successive heartbeats.

Even when a person is at rest and his pulse is quite stable, his R-R intervals(intervals between heartbeats
abbreviations) can differ greatly from each other.

A variety of factors influence heart rate variability:

cardiovascular health
level of psychological stress
quality of sleep and rest and other parameters.

What should a “good” rhythm variability be?

Anything related to heart rate is of interest to us from a training perspective. Studying heart rate variability allows you to understand how your body adapts to training.

A low resting heart rate usually indicates a strong and healthy heart, so should low variability indicate health and fitness? No, that's not true at all! Low heart rate variability indicates health problems, stress, excessive exercise, and high heart rate variability indicates that your autonomic nervous system adapts well to changing conditions of the external and internal environment.

That is, if this parameter increases over time, it means your form is growing.

Now R-R intervals are of increasing interest to researchers; for example, it was found that the intervals between contractions were reduced in groups with diseases such as coronary heart disease, fibromyalgia, diabetes, congestive heart failure and even depression.

How to measure HRV?

One of the options is, of course, to do an ECG and see a cardiologist. But for athletes, it is not the individual results of the study that are more important, but rather their dynamics, so you will have to visit the doctor regularly!

However, this is not the only way to get the desired data.

To measure HRV at home you need:

Run the test when you first wake up and follow the on-screen instructions. The data will be automatically saved in the watch and then added to your Polar Flow profile.

Try to always perform the test under similar conditions - for example, immediately after waking up without getting out of bed, after a day of rest, and if you have had enough sleep at night. Otherwise, additional factors will influence the results.

You can analyze the test data using the Polar Flow service.

Do not forget that the results of the orthostatic test are also influenced by the current state of health, previous exercise, stress level and amount of sleep.

Pathology of the cardiovascular system is one of the most common problems that affects people of all ages. Timely treatment and diagnosis of the circulatory system can significantly reduce the risk of developing dangerous diseases.

Today, the most effective and easily accessible method for studying the functioning of the heart is an electrocardiogram.

When studying the results of a patient's examination, Doctors pay attention to such components of the ECG as:

Teeth;
Intervals;
Segments.

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

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

Cardiogram analysis

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

Today, all these indicators are studied by high-precision electrocardiographs.

Sinus rhythm of the heart

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

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

Heart rate

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

Multiplying the recording duration of one mm by length of segment R-R, you can get the heart rate. Normally, its indicators range from 60 to 80 beats per minute.

Excitation source

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

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

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

Conductivity

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

Electric axis

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

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

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

Teeth, segments and intervals

Waves are sections of the ECG lying above the isoline, their meaning is as follows:

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

Intervals are ECG sections lying on the isoline.

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

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

QRST– duration of ventricular contraction.
ST– time of complete excitation of the ventricles.
TP– time of electrical diastole of the heart.

Normal for men and women

Interpretation of the ECG of the heart and normal indicators in adults are presented in this table:

Healthy Childhood Outcomes

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

Dangerous diagnoses

What dangerous conditions can be determined by ECG readings during interpretation?

Extrasystole

This phenomenon characterized by abnormal heart rhythm. The person feels a temporary increase in contraction frequency followed by a pause. It is associated with the activation of other pacemakers, which, along with the sinus node, send an additional volley of impulses, which leads to an extraordinary contraction.

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

Arrhythmia

Characterized by change in sinus rhythm periodicity when pulses arrive at different frequencies. Only 30% of such arrhythmias require treatment, because can provoke more serious diseases.

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

Bradycardia

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

Tachycardia

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

Conduction disturbance

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

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

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

Why there might be differences in performance

In some cases, when re-analyzing the ECG, deviations from previously obtained results are revealed. What could this be connected with?

Different times of day. Typically, an ECG is recommended to be done in the morning or afternoon, when the body has not yet been exposed to stress factors.
Loads. It is very important that the patient is calm when recording an ECG. The release of hormones can increase heart rate and distort indicators. In addition, it is also not recommended to engage in heavy physical labor before the examination.
Eating. Digestive processes affect blood circulation, and alcohol, tobacco and caffeine can affect heart rate and blood pressure.
Electrodes. Incorrect application or accidental displacement can seriously change the indicators. Therefore, it is important not to move during recording and to degrease the skin in the area where the electrodes are applied (the use of creams and other skin products before the examination is highly undesirable).
Background. Sometimes extraneous devices can affect the operation of the electrocardiograph.

Additional examination techniques

Holter

Method long-term study of heart function, possible thanks to a portable compact tape recorder that is capable of recording results on magnetic film. The method is especially good when it is necessary to study periodically occurring pathologies, their frequency and time of appearance.

Treadmill

Unlike a conventional ECG, which is recorded at rest, this method is based on the analysis of the results after physical activity. Most often, this is used to assess the risk of possible pathologies not detected on a standard ECG, as well as when prescribing a course of rehabilitation for patients who have suffered a heart attack.

Phonocardiography

Allows analyze heart sounds and murmurs. Their duration, frequency and time of occurrence are correlated with the phases of cardiac activity, which makes it possible to assess the functioning of the valves and the risks of developing endo- and rheumatic carditis.

A standard ECG is a graphical representation of the work of all parts of the heart. Many factors can affect its accuracy, so the doctor's recommendations should be followed.

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

Finally, we suggest watching a video course on decoding “An ECG can be done by everyone”: