Decoding of electrocardiography of the heart: ECG norm
Electrocardiography - a technique for recording and studying the electric fields generated during the work of the heart. Electrocardiography is a relatively inexpensive but valuable method of electrophysiological instrumental diagnostics in cardiology. The direct result of electrocardiography is to obtain an electrocardiogram (ECG).
We continue our series of articles about ECG. In this article, we consider, according to the editors, the most important topic - the norms of indicators of electrocardiography. We will consider the standards for adults and children, and also try to understand the reason for the discrepancy between the indicators. Article updated - stay tuned.
Indications of the heart are recorded in an electrocardiogram, expressed as teeth and horizontally located segments and intervals. The teeth are on the isoelectric line, are drawn up and down and resemble a curve.
They are marked with Latin letters P, T, S, Q, R, and are written with a line of the horizontal segment between the T and P teeth at the resting stage.
When decoding the ECG of the heart, the norm is drawn between TQ or TP. It determines the amplitude of fluctuations in the duration of the teeth, intervals and widths.
Electrocardiography (ECG) - is a non-invasive test, the conduct of which allows you to obtain valuable information about the state of the heart.
The essence of this method is to register the electrical potentials that arise during the work of the heart and in their graphical display on a display or paper.
When interpreting the result, it is necessary to adhere to the sequence. First pay attention to:
- heart rhythm
- interval conductivity
- electric axis
- QRS complex analysis
- ST segments and T wave
Decryption of the ECG of the heart to determine the norm is reduced to indications of the position of the teeth. Normal heart rate is measured by the duration of the RR intervals (the distance between the high teeth). They should be the same and not exceed a difference of 10%.
Rapid rhythm indicates tachycardia, slower - bradycardia. The norm is 60-80 pulsations per minute.
By the intervals of P-QRS-T located between the teeth, it is possible to judge the passage of the pulse through the heart. The interval norm is 120-200 ms or 3-5 squares.
The PQ interval will show the penetration of the biopotential to the ventricles through the ventricular node directly to the atrium.
The QRS complex will give an idea of the excitation of the ventricles. To do this, measure the width of the complex from the Q wave to the S-wave. Norm - the width is 60 -100 ms.
Deciphering the ECG of the heart is the norm - this is the severity of the Q wave, not exceeding the value in duration - 0, 04 and 3 mm in depth.
The QT interval informs about the duration of ventricular contraction. Norm - 390 -450ms. A longer interval indicates ischemia, atherosclerosis or myocarditis and rheumatism, and a shorter one indicates hypercalcemia.
When decoding the ECG, the norm of the electrical axis of the heart reveals zones of impulse conduction disturbance. Values are calculated automatically.
To do this, follow the height of the teeth. Norm: the S wave should not be higher than the R wave. If there is a deviation to the right, in the 1 lead the height of the S wave is less than the R wave, this indicates abnormalities in the work of the right ventricle. A similar deviation to the left, the S wave is higher than the R wave, determines left ventricular hypertrophy. The QRS complex shows the passage of biopotential through the septum and myocardium. Norm: the absence of a Q wave or not more than such values as 20-40ms in width and 1/3 of the depth of the R wave.
The ST segment is measured from the end of the S wave to the beginning of the T wave. Heart rate affects the duration of ST. Segment norm: permissible deviations from the isoline - 0.5 mm in depression, rise in leads - up to 1 mm.
We read the teeth
Normally, the P wave is positive in I and II leads, in VR it is negative. Width up to 120ms. Reflects the picture of the distribution of biopotential in the atria. Negative T in I and II are signs of ischemia, ventricular hypertrophy, heart attack.
Q wave - fixes excitation of the left half of the septum. Norm: 1/4 R wave at 0.3 s. An increase in norms indicates necrotic pathology of the myocardium.
R wave - reflects the activity of the walls of the ventricles of the heart. Normally recorded in all leads. If there is another picture, one can judge about ventricular hypertrophy.
S wave - shows the excitation of partitions and basal layers of the ventricles. The tooth height norm is indicated by 20 mm. Attention is drawn to the ST segment, which determines the state of the heart. Oscillation of the position of the segment indicates myocardial ischemia.
The T wave is marked upward in leads I and II, in VR leads it is constantly negative. Acute high T - an indicator of hyperkalemia, flat and long - hypokalemia.
ECG decoding in children: normal
- The frequency of heart beats in children (heart rate) up to 3 years is 100 -110 pulsations
- From 3 to 5 years - 100 strokes, in adolescents - from 60 to 90
- The norm of the P wave is not higher than 0.1 s
- The QRS complex is indicated by readings from 0.6 - 0.1 s
- PQ intervals vary from 0.2 - 0.2, QT - up to 0.4 s
- Electric axis unchanged
- Sinus rhythm
ECG indicators for decoding the norm of the sinus rhythm expresses the dependence of the frequency of pulse beats on breathing. This means that the rhythm of the heart muscle is normal, and is 60-80 beats per minute. The QRS interval has a P wave of regular shape.
Causes of different ECG indicators
ECG readings in a patient can sometimes differ. To obtain accurate results, it is worth considering many factors.
Often the distortion of the results due to technical defects. This is possible with incorrect gluing of the resulting cardiogram. The confusion is due to Roman numerals, which are the same in the correct and inverted meanings.
Quite often, problems arise when cutting a graph where the first P wave or last T may not be saved
Preliminary preparation for the procedure is important (read how to prepare for the ECG).
The impact of electrical appliances working in neighboring rooms affects the oscillations of the alternating current, which is reflected by the repetition of the teeth.
Excitement of the patient or an uncomfortable position during the session affects the instability of the zero line.
The possibility of an inattentive arrangement of the electrodes or their displacement is not excluded.
Measurements on a multi-channel electrocardiograph are the most accurate.