An electrocardiograph (ECG) is a device that allows you to evaluate cardiac activity, as well as diagnose the condition of this organ. When passing the examination, the doctor receives the data in the form of a curve. How to read an ECG curve? What types of teeth are there? What changes on the ECG are visible? Why do doctors need this diagnostic method? What does an ECG show? These are far from all the issues that interest people who have encountered electrocardiography. First you need to find out how the heart works .
The human heart consists of two atria and two ventricles. The left side of the heart is more developed than the right, since a large load falls on it. It is this ventricle that most often suffers. Despite the difference in size, both sides of the heart should work stably, harmoniously.
Learning to read an electrocardiogram yourself
How to read ECG correctly? This is not as difficult as it might seem at first glance. First you need to look at the cardiogram. It is printed on special paper with cells, and two types of cells are clearly visible: large and small.
An ECG report is read from these cells. What do ECG teeth, cells show ? These are the main parameters of the cardiogram. Let's try to learn to read an ECG from scratch.
The value of cells (cells)
On the paper for printing the result of the examination, there are two types of cells: large and small. All of them consist of vertical and horizontal guides. Vertical is voltage, and horizontal is time.
Large squares are made up of 25 small cells. Each small cell is 1 mm and corresponds to 0.04 seconds in the horizontal direction. Large squares are 5 mm and 0.2 seconds. In the vertical direction, the centimeter of the strip is 1 mV of voltage.
Battlements
To read the conclusion of the ECG, you need to know what teeth are and what they mean.
In total, five teeth are distinguished. Each of them on the graph displays the work of the heart.
- P - ideally, this tooth should be positive in the range from 0.12 to two seconds.
- Q - negative tooth, shows the state of the interventricular septum.
- R - displays the state of the ventricular myocardium.
- S - negative tooth, shows the completion of processes in the ventricles.
- T - a positive tooth, shows the restoration of potential in the heart.
All ECG teeth have their own reading characteristics.
Tooth P
All teeth of the electrocardiogram have a certain value for making the correct diagnosis.
The very first tooth of the graph is called R. It indicates the time between the heartbeats. To measure it, it is best to select the beginning and end of the tooth with vertical lines, and then count the number of small cells. Normally, the P wave should be in the range from 0.12 to two seconds.
However, measuring this indicator in only one area will not give accurate results. To make sure that the heartbeat is even, it is necessary to determine the interval of the P wave in all parts of the electrocardiogram.
R tooth
Knowing how to read the ECG in an easy way, you can understand if there are any pathologies of the heart. The next important prong of the graph is R. It is easy to find - it is the highest peak on the graph. This will be a positive tooth. Its highest part is noted on the cardiogram R, and its lower parts Q and S.
The QRS complex is called the ventricular, or sinus. In a healthy person, the sinus rhythm on the ECG is narrow, high. In the figure, the teeth of the ECG R are clearly visible, they are the highest:
Between these peaks, the number of large squares indicates a heart rate (HR). This indicator is calculated using the following formula:
300 / number of large squares = heart rate.
For example, between the peaks there are four full squares, then the calculation will look like this:
300/4 = 75 heartbeats per minute.
Sometimes the cardiogram shows an elongation of the QRS complex of more than 0.12 s, which indicates blockade of the bundle of His.
PQ spacing
PQ is the interval from the P wave to Q. It corresponds to the time of excitation in the atria to the ventricular myocardium. The norm of the PQ interval is different at different ages. Usually it is 0.12-0.2 s.
With age, the interval increases. So, in children under 15 years of age, PQ can reach 0.16 s. At the age of 15 to 18 years, PQ increases to 0.18 s. In adults, this indicator is equal to a fifth of a second (0.2).
With an extension of the interval to 0.22 s, they speak of bradycardia.
QT spacing
To know how to read the ECG correctly, you need to understand the intervals. After determining the teeth, proceed to the calculation of the QT interval. Normally, it is 400-450 ms.
If this complex is longer, then IHD, myocarditis or rheumatism can be assumed. With a shortened type, hypercalcemia can be noted.
ST interval
Normally, this indicator is located at the midline, but can be two cells above it. This segment shows the process of restoring depolarization of the heart muscle.
In rare cases, the indicator can rise three cells above the midline.
Norm
The decoding of the cardiogram should normally look like this:
- The Q and S segments must always be below the midline, i.e. negative.
- The R and T teeth should normally be above the midline, i.e. they will be positive.
- The QRS complex should be no wider than 0.12 s.
- Heart rate should be between 60 and 85 beats per minute.
- There should be a sinus rhythm on the ECG.
- R should be higher than tooth S.
ECG for pathologies: sinus arrhythmia
And how to read an ECG for various pathologies? One of the most common heart diseases is sinus rhythm disturbance. It can be pathological and physiological. The latter type is usually diagnosed in people involved in sports, with neurosis.
In case of sinus arrhythmia, the cardiogram has the following form: sinus rhythms are preserved, fluctuations in the RR intervals are observed, but during a breath-holding schedule is smooth.
In pathological arrhythmias, the conservation of sinus impulse is observed continuously, regardless of the holding of the breath, while wave-like changes are observed at all RR intervals.
The manifestation of a heart attack on an ECG
When a myocardial infarction occurs, ECG changes are pronounced. Signs of pathology are:
- increase in heart rate;
- ST segment increased;
- ST leads have a fairly persistent depression;
- the QRS complex is increasing.
With a heart attack, the main means of recognizing zones of necrosis of the heart muscle is a cardiogram. With its help, you can determine the depth of damage to the organ.
With a heart attack, an increase in the ST segment is observed on the graph, and the R wave will be lowered down, giving the ST a shape resembling a cat's back. Sometimes with pathology, changes in the Q wave can be observed.
Ischemia
If ischemia occurs on the ECG, you can see in which part it is located.
- The location of ischemia in the anterior wall of the left ventricle. It is diagnosed with symmetric pointed T-teeth.
- The location of the epicardium of the left ventricle. The T-tooth is pointed, symmetrical, directed downward.
- Transmural type of left ventricular ischemia. T is pointed, negative, symmetrical.
- Ischemia in the left ventricular myocardium. T flattened, slightly raised up.
- Damage to the heart by coronary disease is displayed by the state of the T wave.
Ventricular changes
An ECG shows changes in the ventricles. Most often they appear in the left ventricle. This type of cardiogram is found in people with prolonged additional load, for example, with obesity. With this pathology, the electric axis deviates to the left, against which the S wave becomes higher than R.
Holter Method
And how to learn to read an ECG, if it is not always clear which teeth and how are located? In such cases, continuous registration of the cardiogram with the help of a mobile device is prescribed. He constantly writes ECG data to a special tape .
This method of examination is necessary in cases where the classic ECG fails to identify pathologies. During Holter’s diagnosis, a detailed diary is always kept, where the patient records all his actions: sleep, walking, sensations during activity, all activity, rest, symptoms of the disease.
Typically, data is recorded within 24 hours. However, there are times when it is necessary to take readings up to three days.
ECG decryption schemes
When decoding a cardiogram, it is recommended to follow a certain sequence.
- Conductivity and heart rate are analyzed. To do this, assess the regularity of heart contractions, calculate the number of heart rates, and determine the conductive system.
- Axial turns are revealed: they determine the position of the electric axis in the frontal plane; around the transverse, longitudinal axis.
- The R wave is analyzed.
- QRS-T is being analyzed. At the same time, the state of the QRS, RS-T complex, T wave, and also the QT interval are evaluated.
- The conclusion is made.
According to the duration of the RR cycle, they speak of regularity and heart rate. When evaluating the work of the heart, not one RR interval is evaluated, but all. Normally, deviations within 10% of the norm are allowed. In other cases, an incorrect (pathological) rhythm is determined.
To establish the pathology, the QRS complex and a specific time section are taken. It counts how many times the segment is repeated. Then the same period of time is taken, but further on the cardiogram, it is again counted. If the number of QRS is the same in equal time sections, then this is the norm. With different amounts, a pathology is assumed, while focusing on the P waves. They should be positive and face the QRS complex. Throughout the graph, the P form should be the same. This option indicates a sinus rhythm of the heart.
At atrial rhythms, the P wave is negative. Behind it is the QRS segment. In some people, the P wave on the ECG may be absent, completely merging with QRS, which indicates the pathology of the atria and ventricles, which the impulse reaches at the same time.
The ventricular rhythm is shown on the electrocardiogram with a deformed and expanded QRS. Moreover, the connection between P and QRS is not visible. Between R teeth long distances.
Cardiac conduction
The ECG determines cardiac conduction. Atrial P determines the atrial impulse, normally this indicator should be 0.1 s. The P-QRS interval displays the total atrial conduction rate. The norm of this indicator should be in the range of 0.12 to 0.2 s.
The QRS segment shows ventricular conduction; a limit of 0.08 to 0.09 s is considered normal. With increasing intervals, there is a slowdown in cardiac conduction.
What the ECG shows, patients do not need to know. This should be understood by a specialist. Only a doctor can correctly decode a cardiogram and make the correct diagnosis, given the degree of deformation of each individual tooth, segment.
It is not always possible to independently read the result of the electrocardiogram due to a lack of experience and fuzzy teeth, segments, intervals, as well as paper features.