Interpretation of the electrocardiography of the heart: ECG rate
Electrocardiography is a technique for recording and studying electric fields generated by the heart. Electrocardiography is a relatively inexpensive but valuable method of electrophysiological instrumental diagnostics in cardiology. A direct result of electrocardiography is an electrocardiogram (ECG).
We continue our series of articles on ECG. In this article we will consider, in the opinion of the editors, the most important topic - the norms of electrocardiography indicators. We will review standards for adults and children, and also try to understand the reason for the discrepancy in indicators. Article updated - stay tuned.
Indications of the heart are recorded in the electrocardiogram, expressed in the form of teeth and horizontally positioned segments and intervals. The teeth are on the isoelectric line, retracted up and down and resemble a curve.
Marked by the Latin letters P, T, S, Q, R, and recorded the line of the horizontal segment between the T and P teeth in the resting stage.
When decoding the ECG of the heart rate is carried out between TQ or TP. It determines the amplitude of oscillations of the length of teeth, intervals and width.
Electrocardiography (ECG) is a non-invasive test, which allows you to obtain valuable information about the condition of the heart.
The essence of this method consists in the registration of electrical potentials arising during the work of the heart and in their graphic display on the display or paper.
Indicators of the normal cardiogram
When interpreting the result, you must adhere to the sequence. First, pay attention to:
- heart muscle rhythm
- interval conductivity
- electric axis
- QRS complex analysis
- ST segments and T wave
Decoding ECG of the heart to determine the norm is reduced to the indications of the position of the teeth. Normal heart rate is measured by the duration of RR intervals (the distance between high teeth). They must be the same and not exceed the difference of 10%.
A fast rhythm indicates tachycardia, a slow rhythm indicates bradycardia. Norm - 60-80 pulsations per minute.
On the intervals of P-QRS-T, located between the teeth, you can judge the passage of the pulse in the heart departments. The interval rate is 120-200 ms or 3-5 squares.
The PQ interval will show the biopotential penetration 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 - width is 60-100 ms.
Interpretation of the ECG of the heart rate 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 speaks of ischemia, atherosclerosis or myocarditis and rheumatism, while a shortened one speaks of hypercalcemia.
When ECG decoding, the norm, the electrical axis of the heart reveals impaired conduction disturbance zones. 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 1 drop, the height of the S wave is less than the R-wave, this indicates deviations in the right ventricle. 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 the depth of the R wave.
The ST segment is measured from the end of the S wave to the start of the T-wave. Heart rate affects the duration of ST. Segment rate: tolerances from the contour line - 0.5 mm in depression, the rise in leads - up to 1 mm.
We read teeth
Normally, the P wave is positive in I and II leads, in VR it is negative. Width up to 120ms. Reflects the pattern of distribution of biopotential across the atria. Negative T in I and II are signs of ischemia, ventricular hypertrophy, heart attack.
The Q tooth - fixes excitement of the left half of a partition. Norm: 1/4 tine R at 0.3 s. An increase in the norms indicates a 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 the ventricular hypertrophy.
S-wave - shows the excitation of the septum and basal layers of the ventricles. Tooth height norm is designated 20 mm. Attention is drawn to the ST segment, which determines the state of the heart. Fluctuations in the position of a segment indicate myocardial ischemia.
The T wave is marked upward in leads I and II, in VR leads it is constantly negative. Acute high T is an indicator of hyperkalemia, flat and long - hypokalemia.
ECG transcript in children: normal
- The heart rate in children (HR) up to 3 years is 100 -110 pulsations
- From 3 to 5 years - 100 strokes, in adolescents - from 60 to 90
- Norm of a tooth P - not higher than 0, 1s
- The QRS complex is designated by indications from 0.6 - 0.1 with
- PQ intervals vary from 0.2 - 0.2, QT - up to 0.4 s
- Electric axis unchanged
- Sinus rhythm
The ECG indicators in deciphering the sinus rhythm rate expresses the dependence of the pulse rate on breathing. This means that the rhythm of the heart muscle is normal, and is 60 -80 beats per minute. In an interval of QRS has a P wave of the correct form.
Causes of different ECG indicators
The patient's ECG may sometimes differ. For accurate results, many factors are worth considering.
Often, the distortion of the results due to technical defects. This is possible if the resulting cardiogram is not properly glued. Confusion occurs because of Roman numerals, which are the same in the correct and inverted values.
Quite often, problems arise when cutting the graph, where the first P wave or the last T wave may not survive.
What matters is the preliminary preparation for the procedure (read how to prepare for an ECG).
The impact of working in the neighboring rooms of electrical appliances, affects the fluctuations of alternating current, which is reflected in the repetition of teeth.
The excitement of the patient or uncomfortable position during the session affects the instability of the zero line.
The possibility of inattentive placement of electrodes or their displacement is not excluded.
Measurements on the multichannel electrocardiograph are the most accurate.