ECG features in children

ECG in children is important for the diagnosis of heart damage. The technique of ECG removal, the system of leads and the theoretical basis of the method are common for all age groups. However, the interpretation of ECG results in children is more difficult due to the age differences of individual ECG parameters.

[1], [2], [3], [4], [5], [6], [7], [8], [9]

Teeth and intervals of ECG in children

Zubets P reflects the spread of excitation in the myocardium of the atria. The first half of the tooth to its apex corresponds to the excitation of the right atrium, the second - to the left. The duration of the P wave in healthy children does not exceed 0.1 s. In the III standard lead, the tooth may be negative, biphasic or smoothed.

The P-Q or P-R interval includes a tooth P and an isoelectric line from P to a Q or R wave. The interval varies with the heart rate and its normal values are estimated from the tables.

Interval P-Q and QRS complex in children (duration in seconds in the II lead), according to Yu. M. Belozerov

Age, years	R-Q			QRS
	10	50	90	10	50	90
1	0.08	0.10	0.13	0.053	0.065	0.077
2	0.08	0.11	0.14	0.053	0.065	0.077
3	0.08	0.11	0.14	0.053	0.064	0.077
4	0.08	0.12	0.14	0.063	0.072	0.082
5	0.09	0.12	0.14	0.063	0.070	0.083
6th	0.09	0.12	0,15	0.053	0.068	0.079
7th	0.10	0.12	0,15	0.062	0.067	0.081
8	0.10	0.13	0.16	0.053	0.067	0.081
9	0.10	0.13	0.17	0.053	0.073	0.085
10	0.11	0.14	0.17	0.053	0.072	0.086
Eleven	0.11	0.14	0.16	0.053	0.073	0.085
12	0.11	0.14	0.16	0.053	0.073	0.086
13	0.11	0.14	0.16	0.044	0.068	0.087
14	0.11	0.14	0.16	0.044	0.068	0.087
15	0.12	0.14	0.16	0.044	0.068	0.087

In newborns, the value of the interval is 0.08-0.14 s, in infants - 0.08-0.16 s, in the older - from 0.10 to 0.18 s. The tooth of Q is the most unstable element of the ECG of children. Quite often, and in healthy children, there is a deep Q tooth in the III lead. The tooth R always points upwards. Newborns are characterized by fluctuations in the height of the tooth within the same lead - an electrical alternative. Sine S - unstable negative. At an early age, it is often deep in the 1st standard lead. The QRS and T wave, reflecting the spread of excitation in the ventricular myocardium (depolarization) and the extinction of this excitation (repolarization), have a total duration in children not exceeding 0.35-0.40 s and closely related to the heart rate.

All this period is considered to be the electric systole of the heart, more precisely, of its ventricles. MK Oskolkova identifies and recommends separately calculating the phase of excitation - the interval from the origin of the Q wave to the start of the T wave - and the phase of excitation termination - from the beginning of the T wave to its termination.

In the thoracic leads, the ratios of the teeth R and S vary significantly with age. They, as well as changes in the electrical axis of the heart, are due to the decreasing anatomical and, correspondingly, electrophysiological predominance of the right ventricle in the newborn and the young child. However, if the anatomical predominance disappears already in the first weeks of life, the electrical predominance over the ratios in the main leads and the shifts in the electric axis of the heart disappears. The first 6 months, according to the data of thoracic leads, the reorganization of the ratios of ventricular activity can last up to 5-6 years. Perhaps this is due to the turn of the heart and changes in the degree of attachment of the right ventricle to the chest wall in the first years of life. The zone of equal amplitude of the R and S teeth in the thoracic leads is called the transition zone. In newborns, she falls on V5, which characterizes the dominant predominance of the right ventricle. At the age of 1 month, the transition zone shifts to leads V3-4. At the age of 1 year, the transition zone is in the V2-V3 region. This is already a period when the dominance of the right ventricle ceased, but there is no dominance of the left ventricle. Sometimes such relationships can persist in children up to 5-6 years. But more often by the age of 6 the transition zone shifts to the V2 lead and all the abdominal leads except V1 are dominated by the R wave. At the same time, the teeth R are deepened, which confirms the prevalence of left ventricular potentials.

Changes in the teeth and intervals of the ECG

Pathological character may have a change in the direction of the P wave, ie, its transition to the negative in the leads I, II, V or the transition to the positive in the lead aVR.

An increase in the height of the tooth P with a pointed apex indicates a hypertrophy of the right atrium, and its expansion in combination with cleavage - on hypertrophy of the left atrium. Lengthening of the P-Q interval indicates a violation of atrioventricular conduction, i.e., blockade, and its shortening is an important sign of Wolff-Parkinson-White syndrome (WFW) or its variants. These syndromes characterize the congenital anomalies of the conduction system underlying the occurrence of rhythm disturbances in children.

Elongation of the ventricular complex QRS occurs with blockage of the legs of the atrioventricular bundle, ventricular extrasystoles, ventricular paroxysmal tachycardia, ventricular hypertrophy.

Hypertrophy may be accompanied by an increase in the voltage of the teeth of the complex.

The decrease in the voltage of the complex can be of myocardial origin and be caused by myocardial dystrophy or inflammatory changes in the myocardium, as well as a violation of the conductivity of electrical potentials due to the large thickness of the subcutaneous fatty layer of the child, the occurrence of inflammatory edema of the pericardium or hydropericardium.

Thickening, chipping and splitting of the teeth of the ventricular complex are often found in children and can have diagnostic significance only if they are observed not in one but in two or three leads and are located close to the apex of teeth with a sufficiently high amplitude. In such cases, one can speak of disturbances in the distribution of excitation in the myocardium of the ventricles.

The presence of a Q wave in the right thoracic leads, often in combination with a high R wave, indicates right ventricular hypertrophy.

Very important in electrocardiographic diagnosis is given to changes in the Q wave. The combination of a deep, often widened Q wave with a decreased R wave and successive changes in the S-T interval and a T wave is a symptomatic complex of focal myocardial damage. The interval S-T first rises above the isoelectric line, is later dropped, and the T-tooth becomes negative. By localization of this symptom complex in different leads, we can roughly judge the location of the lesion. 

• The posterior wall of the left ventricle is the leads II, III and aVF, while the extension of the R wave in the lead V1-2.
• Front wall - leads V3-4.
• Heart partition - leads V1-2.
• Anterobranial area - leads V1-4.
• Side wall - leads I, aVR, V5-6.
• Anterolateral wall - leads I, aVR, V3-6.
• The bottom wall is lead II, III, aVF.

The amplitude of the R wave in various leads is determined mainly by the position of the electric axis of the heart, but more often it is maximal in the lead II. If the amplitude of the tooth R in the lead V5 is greater than in the lead V6, then we can assume the presence of changes in the position of the heart. Changes in the magnitude of the R wave in standard leads, where they can be equal to the R teeth or even higher, occur in some healthy children with a pronounced asthenic constitution, having a so-called hanging heart with an electric axis sharply deflected to the right. A similar picture is observed in patients with high blood pressure in the small circle of blood circulation, which can be a consequence of chronic lung diseases or congenital heart defects with a small circulation. Changes in the position of the segment of the ST (above or below the isoelectric line), as well as the T wave (its expansion, inversion or biphasic, decrease or increase) are usually considered together and indicate a violation of the repolarization phase. The reasons for the occurrence of these violations are many. In childhood, the most frequent are non-cardiac causes, in particular, disturbances in the balance of electrolytes. The picture of the end part of the ventricular complex often diagnoses and controls the state of hypo- and hyperkalemia, hypo- and hypercalcemia in children. Changes in this part can characterize hypoxia of the myocardium, inflammation of the heart muscle and inflammation of the pericardium. Secondary disturbances of this part of the ECG are accompanied by ventricular hypertrophy, blockage of the atrioventricular bundle, ventricular extrasystoles and paroxysmal tachycardia.

[10], [11], [12], [13], [14], [15]

Changes in the electrocardiogram detected by mass examinations of children and adolescents

Electrocardiographic studies used in the complex of mass preventive examinations allow to reveal with high frequency various features and ECG syndromes that do not have an obvious link to diseases of the cardiovascular system, i.e. In unconditionally or practically healthy children and adolescents. This, on the one hand, characterizes electrocardiography as a method of very high sensitivity, catching a wide range of functional and metabolic changes in the state of the child's body. On the other hand, there is a certainty that among the electrophysiological findings revealed during such examinations there may be phenomena of different clinical significance. Taking into account the complexity of the processes of purely age-related development and differentiation of heart structures, participation in these processes in parallel with both growth and accumulation processes and resorptive-destructive processes, it can be considered that some ECG changes in practically healthy children can reflect exactly the contradictions and rearrangements of normal growth and development of the heart. It can not be excluded that some of the signs or symptoms detected are a reflection of early and subclinical current pathological processes in the myocardium - dystrophic, dysplastic, inflammatory or immune. There can be revealed and residual changes of heart after the transferred diseases of membranes of heart and vessels. The attitude of the doctor to such minimal signs or signs-precursors of diseases should be very careful.

The accumulated experience allows us to divide the relatively frequent and minimal ECG changes into two groups.

1. ECG-syndromes, which can be referred to variants of the age norm or transient phenomena of the age-evolutionary plan:
   • moderately pronounced sinus tachycardia and bradycardia;
   • middle right atrial rhythm;
   • migration of the rhythm driver at the atrium between the sinus node and the atrial and automatism environments (in children 14-15 years old);
   • respiratory alternation of ECG teeth;
   • "Failure" of the R wave in V3 lead;
   • crest syndrome - delayed excitation of the right supraventricular scallop - extension of the S-wave in the leads V1 and (or) V2.
2. ECG syndromes occupying an intermediate position between normal and pathological, or borderline syndromes, which require mandatory additional in-depth examination of the child, his observation and follow-up of the evolution of ECG changes:
   • sinus tachycardia with a heart rate of more than 100 beats / min;
   • sinus bradycardia at a heart rate of less than 55 beats per minute;
   • middle right atrial rhythm and migration of the rhythm driver between the sinus node and the mid-atrial centers of automatism in children 16-18 years old;
   • lower atrial rhythm;
   • supraventricular extrasystole;
   • sinoauric blockade of the 2nd degree, atrioventricular block of the 1st degree, incomplete blockages of the anterolateral or posterior-lower branches of the left foot of the atrioventricular bundle;
   • the phenomenon of a shortened P-Q interval;
   • syndrome of premature repolarization of the ventricles.

[16], [17], [18], [19]

QRS ECG complex in children of various ages

The analysis of the ventricular complex is important for characterizing the electrical activity of the myocardium. It is described by the duration of the electric systole, the value of the systolic index (the ratio of the time of the electric systole and the total duration of the RR cycle), by the ratio of the excitation time and the time of cessation of excitation. The change in the duration of electric systole indicates a violation of the functional state of the myocardium.

The electrical axis of the heart is determined by the degree of one-sided predominance of the electrical activity of the ventricles and the position of the heart in the thoracic cavity. It is measured by the ratio of the teeth R and S in two standard leads - I and III and by the deposition of these quantities on the corresponding coordinates of the triangle of B. Einthoven. In newborns there is a sharp deviation of the electric axis of the heart to the right, reaching the values of the angle a on the average from + 135 ° to + 150 °. This deviation persists for a relatively short time and decreases to 90-75 ° in the interval from 3 months to 1 year, and in older children it can be about 35 ° on the average. The age-related position of the electric axis can change significantly if blockades or hypertrophy of one of the ventricles of the heart occur.

The electric axis of the vector T forms an adjacent angle with the electrical axis of the heart (QRS), which is the maximum angle in newborns. Here its value reaches 75-85 °. In the future, the magnitude of this angle is significantly reduced.

ECG monitoring in children

In the last 1-2 decades, the method of continuous recording and automatic analysis of electrocardiography data is becoming increasingly widespread.

For this purpose, portable instrument-recorders have been created with the possibility of continuous or intermittent ECG recording. The device does not prevent a child, even 3-4 years of age, from carrying out all the necessary for him mode of household and game activity. The most interesting and informative is the recording of the electrocardiogram in the hours of night sleep. Holter monitoring is used:

• to detect cardiac rhythm disturbances in groups of patients at high risk of their occurrence ( congenital heart diseases, cardiomyopathies, primary pulmonary hypertension, etc.);
• to confirm the arrhythmogenic nature of regular or recurrent abnormalities of the child's well-being ( pain in the heart, fits of weakness, dizziness or fainting );
• to assess the frequency, structure, and cyclicity of heart rhythm disturbances already detected in children;
• to assess the effectiveness of ongoing treatment activities.

The use of Holter ECG monitoring in practically healthy children allowed to get completely new ideas about the frequency of heart rhythm disturbances, the influence of night sleep on various rhythm and ECG parameters, on the existence of pauses of the heart rhythm lasting from 1 to 1.4 s in 100% of healthy children in hours sleep. There was a need to create additional criteria for assessing the normal and abnormal heart rhythm.

[20], [21], [22], [23], [24], [25], [26], [27]