Examples of ecg. How to decipher a cardiogram of the heart. Decoding ECG

An ECG device was invented by an English scientist more than a century ago. He recorded the electrical activity of the heart muscle and recorded this data on a special paper tape. Naturally, throughout its existence it has been modernized several times, but the basic principle of operation, which is based on the recording of electrical impulses, has remained unchanged.

Now it is available in any hospital, ambulance teams and local therapists are equipped with it. A lightweight and mobile electrocardiograph helps save lives with its ability to quickly take an ECG. Speed and accuracy are important for patients with pulmonary embolism, myocardial infarction, bradycardia, and diseases that require emergency medical care.

Deciphering ECG readings is not a problem for an experienced doctor. Many cardiac diagnoses are established on the basis of this monitoring, and most of them unmistakably indicate cardiovascular pathologies.

What you need to know about ECG principles

An outsider, which is any cardiology patient, is not able to understand the incomprehensible teeth and peaks displayed by the electrocardiograph recorder. It is difficult for people without special education to understand what the doctor sees there, but the general principles of the heart’s functioning are quite clear to everyone.

Man is a mammal and his heart consists of 4 chambers. These are two atria with thin walls that perform auxiliary work, and two ventricles, which withstand the main loads. There are certain differences between the right and left side of the heart. It is easier for the body to supply blood to the pulmonary circulation through the right ventricle than to push blood into the systemic circulation through the left ventricle. Therefore, the left one is more developed, but there are more diseases that affect it. But despite this fundamental difference, human health largely depends on the coherence and uniformity of the work of all parts of the organ.

In addition, the parts of the heart differ in their structure and intensity of electrical activity. The myocardium, that is, contractile complexes, and nerves, valves, fatty tissue, vessels, in fact – irreducible elements, differ in the degree and speed of response to electrical impulses.

Cardiologists recognize cardiac pathologies due to their in-depth knowledge of the principles of heart function and the ability to interpret an electrocardiogram. The intervals, waves, and leads must be viewed in a single context that defines common heart conditions.

There are not so many specific functions of the heart; it has:

Automatically, that is, it spontaneously generates impulses that lead to its excitation.
Excitability, responsible for the possibility of cardiac activation under the influence of an exciting impulse.
Conductivity. The heart can ensure the conduction of an impulse from the place of its origin to the contractile structure involved in the process.
Contractility. This is the ability of the heart muscle to contract and relax under the control of the current impulse.
Tonicity. When the heart in diastole does not lose its shape and is able to provide constant activity according to the physiological cycle.

The calm state of the heart, called static polarization, is electrically neutral, and at the stage of generation and conduction of exciting impulses, implying an electrical process, characteristic biocurrents are formed.

How to decipher an ECG: what does the doctor focus on?

Carrying out an ECG procedure today is not difficult; any hospital is equipped with these devices. But what is included in the complex of manipulations and what is usually regarded as the norm of conditions? The technique of performing an electrocardiogram is familiar only to health workers who undergo an additional training cycle. The patient should know about the rules for preparing for an ECG. Before monitoring you need:

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Stop smoking, drinking coffee and alcohol.
Avoid taking medications.
Avoid strenuous physical activity before the procedure.

All this will affect the results of the electrocardiogram in the form of tachycardia or more serious disorders. The patient, who is in a calm state, undresses to the waist, takes off his shoes and lies down on the couch. The nurse treats the lead sites with a special solution, attaches the electrodes and takes readings. Then its data is transferred to a cardiologist for decoding.

Each wave on the ECG is designated as a capital Latin letter, P, Q, R, S, T, U.

P – atrial depolarization. When the QRS waves are complex, they speak of ventricular depolarization.
T – ventricular repolarization. A blurred U wave indicates repolarization of the distal portions of the conduction system.
If the teeth are directed upwards, then they are positive, those that are directed downwards are negative. The Q and S waves will always be negative, and the R waves will always be positive.

To collect data, 12 leads are used:

Standard: I, II, III.
Reinforced unipolar limb leads – three.
Reinforced unipolar chest - six.

In case of pronounced arrhythmia or abnormal position of the heart, there is a need to use additional chest leads, bipolar and unipolar (D, A, I).

When deciphering the results, the doctor measures the duration of the intervals between each of the ECG indicators. In this way, an assessment is made of the rhythm frequency, when the size and shape of the tooth in different leads determines the nature of the rhythm, the electrical phenomena occurring in the heart and the electrical activity of each section of the myocardium. In essence, an ECG demonstrates the complex functioning of the heart in a single period.

Detailed interpretation of the ECG: norm, pathologies and diseases

If a strict decoding is necessary, an analysis and calculation of the area of the teeth is carried out using additional leads, according to the vector theory. But in everyday practice, they much more often resort to such an indicator as the direction of the electrical axis. It is the total QRS vector. Naturally, each person has individual physiological characteristics of the structure of the chest, and the heart can be displaced from its usual location. In addition, the weight ratio of the ventricles and the intensity and velocity of conduction within them may also vary. Therefore, decoding requires a description of both the vertical and horizontal directions along this vector.

Decoding can only be carried out in a certain sequence, which helps to differentiate normal indicators from detected violations:

The heart rate is assessed and the heart rate is measured. A normal ECG is characterized by sinus rhythm with a heart rate of 60-80 beats/minute.
Intervals are calculated indicating the duration of systole (contraction phase). This is done using a special Bazett formula. Normal QT is 390/450 ms; if it lengthens, a diagnosis of ischemic heart disease, myocarditis, rheumatism, or atherosclerosis can be made. If the interval is shortened, hypercalcemia is suspected. The intervals reflect the conductivity of the impulses; it is calculated using special automatic programs, which only increases the diagnostic value of the results.
The position of the EOS is calculated from the isoline and is guided by the height of the teeth. Under normal conditions, the R wave will always be higher than the S wave. And if, on the contrary, with simultaneous deviation of the axis to the right, then functional failures in the right ventricle are assumed. With axis deviation to the left, respectively, to the left, provided that S is greater than R in leads II and III. This indicates left ventricular hypertrophy.
The QRS complex formed when impulses are carried out to the ventricular muscles is examined. The complex determines the functional load of the ventricles. In a normal state, there is no pathological Q wave, and the width of the entire complex does not exceed 120 ms. When this interval shifts, a diagnosis of complete or partial block of the bundle branches is made or conduction disorders are spoken of. Incomplete blockade of the right leg acts as an electrocardiographic indicator of hypertrophic changes in the right ventricle, and incomplete blockade of the left leg is evidence of hypertrophy of the left ventricle.
ST segments are described that reflect the period of restoration of the initial state of the heart muscle from the moment of its complete depolarization. Normally they are located along the isoline. And also the T wave, reflecting the process of ventricular repolarization. The process is directed upward, with asymmetry, and its amplitude should normally be below the T wave. It is longer in duration than the QRS complex.

A full transcript can only be carried out by a doctor, but if necessary, an ambulance paramedic can also do this.

Deviations from the norm: physiological aspects

This is an image of a normal cardiogram of a healthy person. His heart works smoothly, with a regular rhythm and correctly. But these indicators can change and vary under different physiological conditions. One such condition is pregnancy. In women carrying a child, the heart shifts somewhat relative to its normal anatomical location in the chest, and therefore the electrical axis also shifts. It all depends on the period, since every month increases the load on the heart. During pregnancy, all these changes will be displayed on the ECG, but will be regarded as a conditional norm.

The children's cardiogram is also different, the indicators of which change according to age as the child grows. And only after 12 years, the ECG of children begins to resemble the gastrointestinal tract of adults.

Sometimes situations arise when two ECGs for the same patient, taken even just a few hours apart, are strikingly different. Why is this happening? To get accurate results, you need to take into account many influencing factors:

A distorted ECG recording may be the result of a device malfunction or other technical problems. For example, if the results were incorrectly glued together by a healthcare worker. Please note that some Roman symbols look identical both inverted and in normal position. There are situations when the chart is cut incorrectly, which leads to the loss of the last or first tooth.
It is also important how well the patient prepared. Anything that stimulates the heart rate will certainly affect the ECG results. It is advisable to take a shower before the procedure, but you should not use body cosmetics. And during the process of taking a cardiogram, the patient should be in a relaxed state.
The possibility of incorrect placement of the electrodes cannot be ruled out.

It is best to trust electrocardiographs to check your heart; they carry out the analysis with maximum accuracy. To confirm the diagnosis found on the ECG, the doctor always prescribes several additional studies.

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

Atrial extrasystole. A 73-year-old female patient consulted due to worsening hypertension. He does not feel any interruptions in his heart function, and no emergency treatment is required.

Atrial flutter

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

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

Paroxysmal supraventricular tachycardia

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

Sinus bradycardia

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

Atrial fibrillation

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

Acute myocardial infarction

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

Registration of an electrocardiogram is a way to study the 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 result of the analysis of electrocardiogram parameters is 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 to 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.

Indications for an ECG

In clinical practice, there are several indications for electrocardiography:

severe chest pain;
constant fainting;
dyspnea;
exercise intolerance;
dizziness;
heart murmurs.

During a routine examination, an ECG is a mandatory diagnostic method. There may be other indications determined by the attending physician. If you experience any other alarming symptoms, consult your doctor immediately to determine their cause.

How to decipher a cardiogram of the heart?

A strict plan for deciphering an ECG consists of analyzing the resulting graph. In practice, only the total vector of the QRS complex is used. The work of the heart muscle is presented in the form of a continuous line with marks and alphanumeric designations. Any person can decipher an ECG with certain training, but only a doctor can make the correct diagnosis. ECG analysis requires knowledge of algebra, geometry and an understanding of letter symbols.

ECG indicators that need to be taken into account when interpreting the results:

intervals;
segments;
teeth.

There are strict indicators of normality on the ECG, and any deviation is already a sign of disturbances in the functioning of the heart muscle. Pathology can only be excluded by a qualified specialist - a cardiologist.

ECG interpretation in adults - the norm in the table

Cardiogram analysis

The ECG records cardiac activity in twelve leads: 6 limb leads (aVR, aVL, aVF, I, II, III) and six chest leads (V1-V6). The P wave reflects the process of excitation and relaxation of the atria. The Q, S waves show the depolarization phase of the interventricular septum. R - wave, indicating depolarization of the lower chambers of the heart, and T-wave - relaxation of the myocardium.

Electrocardiogram analysis

The QRS complex shows the time of ventricular depolarization. The time it takes for an electrical impulse to travel from the SA node to the AV node is measured by the PR interval.

Computers built into most ECG devices are capable of measuring the time it takes for an electrical impulse to travel from the SA node to the ventricles. These measurements can help your doctor evaluate your heart rate and certain types of heart block.

Computer programs can also interpret ECG results. And as artificial intelligence and programming improve, they are often more accurate. However, ECG interpretation has many subtleties, so human factors still remain an important part of the assessment.

There may be abnormalities in the electrocardiogram that do not affect the patient’s quality of life. However, there are standards for normal cardiac performance that are accepted by the international cardiological community.

Based on these standards, a normal electrocardiogram in a healthy person looks like this:

RR interval – 0.6-1.2 seconds;
P-wave – 80 milliseconds;
PR interval – 120-200 milliseconds;
PR segment – 50-120 milliseconds;
QRS complex – 80-100 milliseconds;
J-wave: absent;
ST segment – 80-120 milliseconds;
T-wave – 160 milliseconds;
ST interval – 320 milliseconds;
The QT interval is 420 milliseconds or less if the heart rate is sixty beats per minute.
ind.juice – 17.3.

Normal ECG

Pathological ECG parameters

The ECG in normal and pathological conditions is significantly different. Therefore, it is necessary to carefully approach the decoding of the heart cardiogram.

QRS complex

Any abnormality in the electrical system of the heart causes a prolongation of the QRS complex. The ventricles have greater muscle mass than the atria, so the QRS complex is significantly longer than the P wave. The duration, amplitude, and morphology of the QRS complex are useful in identifying cardiac arrhythmias, conduction abnormalities, ventricular hypertrophy, myocardial infarction, electrolyte abnormalities, and other disease conditions.

Q, R, T, P, U teeth

Abnormal Q waves occur when an electrical signal passes through damaged heart muscle. They are considered markers of previous myocardial infarction.

R-wave depression is also usually associated with myocardial infarction, but it can also be caused by left bundle branch block, WPW syndrome, or hypertrophy of the lower chambers of the heart muscle.

Table of ECG indicators is normal

T wave inversion is always considered an abnormal value on the ECG tape. Such a wave may be a sign of coronary ischemia, Wellens' syndrome, hypertrophy of the lower cardiac chambers, or a central nervous system disorder.

A P wave with increased amplitude may indicate hypokalemia and right atrial hypertrophy. Conversely, a P wave with reduced amplitude may indicate hyperkalemia.

U waves are most often observed with hypokalemia, but may also be present with hypercalcemia, thyrotoxicosis, or taking epinephrine, class 1A and 3 antiarrhythmic drugs. They are often found in congenital long QT syndrome and intracranial hemorrhage.

An inverted U wave may indicate pathological changes in the myocardium. Another U-wave can sometimes be seen on ECGs in athletes.

QT, ST, PR intervals

QTc prolongation causes premature action potentials during late phases of depolarization. This increases the risk of developing ventricular arrhythmias or fatal ventricular fibrillation. Higher rates of QTc prolongation are observed in women, older patients, hypertensive patients, and short people.

The most common causes of QT prolongation are hypertension and certain medications. The duration of the interval is calculated using the Bazett formula. With this symptom, the interpretation of the electrocardiogram should be performed taking into account the medical history. This measure is necessary to eliminate hereditary influence.

ST interval depression may indicate coronary ischemia, transmural myocardial infarction, or hypokalemia.

Characteristics of all indicators of electrocardiographic research

A prolonged PR interval (greater than 200 ms) may indicate first-degree heart block. Prolongation may be associated with hypokalemia, acute rheumatic fever, or Lyme disease. A short PR interval (less than 120 ms) may be associated with Wolff-Parkinson-White syndrome or Lown-Ganong-Levine syndrome. PR segment depression may indicate atrial injury or pericarditis.

Examples of heart rate descriptions and ECG interpretation

Normal sinus rhythm

Sinus rhythm is any heart rhythm in which the excitation of the heart muscle begins from the sinus node. It is characterized by correctly oriented P waves on the ECG. By convention, the term "normal sinus rhythm" includes not only normal P waves, but also all other ECG measurements.

ECG norm and interpretation of all indicators

ECG norm in adults:

heart rate from 55 to 90 beats per minute;
regular rhythm;
normal PR interval, QT and QRS complex;
The QRS complex is positive in almost all leads (I, II, AVF and V3-V6) and negative in aVR.

Sinus bradycardia

A heart rate less than 55 in sinus rhythm is called bradycardia. ECG interpretation in adults should take into account all parameters: sports, smoking, medical history. Because in some cases, bradycardia is a variant of the norm, especially in athletes.

Pathological bradycardia occurs with weak sinus node syndrome and is recorded on the ECG at any time of the day. This condition is accompanied by constant fainting, pallor and hyperhidrosis. In extreme cases, pacemakers are prescribed for malignant bradycardia.

Sinus bradycardia

Signs of pathological bradycardia:

heart rate less than 55 beats per minute;
sinus rhythm;
P waves are vertical, consistent, and normal in morphology and duration;
PR interval from 0.12 to 0.20 seconds;

Sinus tachycardia

A regular rhythm with a high heart rate (above 100 beats per minute) is commonly called sinus tachycardia. Note that normal heart rate varies depending on age; for example, in infants, the heart rate may reach 150 beats per minute, which is considered normal.

Advice! At home, severe coughing or pressing on the eyeballs can help with severe tachycardia. These actions stimulate the vagus nerve, which activates the parasympathetic nervous system, causing the heart to beat slower.

Sinus tachycardia

Signs of pathological tachycardia:

Heart rate is above one hundred beats per minute;
sinus rhythm;
P waves are vertical, consistent and normal in morphology;
PR interval fluctuates between 0.12-0.20 seconds and shortens with increasing heart rate;
QRS complex less than 0.12 seconds.

Atrial fibrillation

Atrial fibrillation is an abnormal heart rhythm characterized by rapid and irregular contraction of the atria. Most episodes are asymptomatic. Sometimes an attack is accompanied by the following symptoms: tachycardia, fainting, dizziness, shortness of breath or chest pain. The disease is associated with an increased risk of heart failure, dementia and stroke.

Atrial fibrillation

Signs of atrial fibrillation:

Heart rate is unchanged or accelerated;
P waves are absent;
electrical activity is chaotic;
RR intervals are irregular;
QRS complex less than 0.12 seconds (in rare cases, the QRS complex lengthens).

Important! Despite the above explanations with the decoding of the data, an ECG conclusion should only be made by a qualified specialist - a cardiologist or a general physician. Decoding the electrocardiogram and differential diagnosis requires higher medical education.

How to “read” myocardial infarction on an ECG?

Students starting to study cardiology often have a question: how to learn to read a cardiogram correctly and identify myocardial infarction (MI)? You can “read” a heart attack on a paper tape based on several signs:

ST segment elevation;
peaked T wave;
deep Q wave or lack thereof.

When analyzing electrocardiography results, these indicators are first identified, and then the others are dealt with. Sometimes the earliest sign of acute myocardial infarction is only a peaked T wave. In practice, this is quite rare because it appears only 3-28 minutes after the onset of a heart attack.