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PEDIATRICS
Kamola Nigman kizi YAKUBOVA
Akida Valievna MURATKHODZHAEVA
Department of Faculty Pediatrics,
Tashkent Pediatric Medical Institute, Uzbekistan
MAIN FUNCTIONAL INDICATORS OF HEART CONDUCTIVITY DISORDERS IN
CHILDREN
For citation: K.Ni. Yakubova, A.V. Muratkhodzhaeva MAIN FUNCTIONAL INDICATORS OF
HEART CONDUCTIVITY DISORDERS IN CHILDREN Journal of Biomedicine and Practice.
2021, vol. 6, issue 3, pp. 319-326
http://dx.doi.org/10.26739/2181-9300-2021-3-48
ANNOTATION
This work provides information on the most reliable anamnestic and clinical and instrumental
data on cardiac conduction disorders in children. Heart rhythm and conduction disturbances occupy
one of the leading places in the structure of cardiovascular pathology in children. Atrioventricular
block is a slowdown or cessation of impulses from the atria to the ventricles. Disturbances in the
rhythm and conduction of the heart of any degree alter the quality of life. The disease affects the
physical condition of the child. To prevent complications, timely diagnosis and treatment is required.
Key words:
cardiac arrhythmias, atrioventricular block, syncope, children, bradyarrhythmia,
electrocardiography, echocardiography, sick sinus syndrome.
Камола Нигман кизи ЯКУБОВА
Акида Валиевна МУРАТХОДЖАЕВА
Кафедра Факультетский педиатрии,
Ташкентский Педиатрический Медицинский институт, Узбекистан
ОСНОВНЫЕ ФУНУЦИОНАЛЬНЫЕ ПОКАЗАТЕЛИ НАРУШЕНИЙ
ПРОВОДИМОСТИ СЕРДЦА У ДЕТЕЙ
АННОТАЦИЯ
В данной работе приведена информация наиболее достоверными анамнестическими и
клинико-инструментальными данными нарушений проводимости сердца у детей. Нарушения
ритма и проводимости сердца занимают одно из ведущих мест в структуре сердечно-
сосудистой патологии у детей. Атриовентрикулярная блокада представляет собой замедление
или прекращение проведения импульсов со стороны предсердий на желудочки. Нарушения
ритма и проводимости сердца любого степени изменяют качество жизни. Заболевание влияет
на физическое состояние ребенка. Для предотвращения осложнений необходима
своевременная диагностика и лечение.
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Ключевые слова:
нарушения ритма сердца, атриовентрикулярная блокада, синкопе,
дети, брадиаритмия, электрокардиография, эхокардиография, синдром слабости синусового
узла.
Камола Нигман кизи ЯКУБОВА
Акида Валиевна МУРАТХОДЖАЕВА
Факультет педиатрия кафедраси,
Тошкент Педиатрия Тиббиёт институти, Ўзбекистон
БОЛАЛАРДА ЮРАК ЎТКАЗУВЧАНЛИГИ БУЗИЛИШИНИНГ АСОСИЙ
ФУНКЦИОНАЛ КЎРСАТКИЧЛАРИ
АННОТАЦИЯ
Ушбу мақолада болаларда юрак ўтказувчанлиги бузилишига оид ишончли анамнестик,
клиник ва инструментал маьлумотлар берилган. Юрак ритми ва ўтказувчанлигининг
бузилиши болаларда учрайдиган юрак қон-томир тизими касалликлари таркибида етакчи
ўринлардан бирини эгаллайди. Атриовентрикуляр блокада бу бўлмачадан қоринчаларга
узатилаётган импулсларни ўтказилишини секинлашиши ёки тўхташини англатади. Ҳар
қандай даражадаги юрак ритми ва ўтказувчанлигини бузилиши ҳаёт сифатини ўзгартиради.
Касаллик боланинг жисмоний холатига таьсир қилади. Касаллик асоратларини олдини олиш
учун ўз вақтида ташхис қўйиш ва даволаш талаб этилади.
Калит сўзлар:
юрак ритмини бузилиши, атриовентрикуляр блокада, синкопе, болалар,
брадиаритмия, электрокардиография, эхокардиография, синус тугуниниг холсизланиши
синдроми.
Introduction.
Diseases of the cardiovascular system are among the most common pathologies
at the present time. In children with these diseases, one of the first places is occupied by functional
disorders, the main of which is a violation of the heart rhythm. Heart rhythm disturbances are changes
in the basic electrophysiological properties of the heart, such as automatism, excitability and
conduction, leading to a violation of the coordinated contraction of the whole heart or its parts and
manifested by a change in the frequency and regularity of the heart rhythm [3, 7].
Violation of cardiac conduction is a pathological condition characterized by changes in the
frequency, regularity of the heart rhythm, with disturbances in the connection and sequence between
the activation of the atria and ventricles, proceeding benignly or with pronounced changes in
hemodynamics. [6, 11]. Depending on the degree of damage to the atrioventricular junction,
incomplete and complete atrioventricular blockages are distinguished. Incomplete, in turn, are
represented by blockages of the I and II degrees, and the atrioventricular block of the III degree is
called complete. All variants of atrioventricular block can be transient and persistent, congenital and
acquired. Slowing down of impulse conduction can occur in the atria, atrioventricular node, His –
Purkinje system [1, 21].
Heart rhythm and conduction disorders in children are currently one of the most socially
significant problems. So, according to statistics, asystole in patients with bradyarrhythmias is the
cause of unexpected circulatory arrest in 15-20% of cases, and in patients with acquired high-grade
autoventricular block, it is one of the main causes of death [13, 14].
Atrioventricular block I degree can occur in healthy children from 0.6 to 8% of cases. In
children with normal sinus rhythm, a transient increase in PQ occurs in younger children in 5% of
cases and in 15% in older children, mainly at night. A higher incidence of 1st degree atrioventricular
blockade was observed in trained athletes - 8.7%. The frequency of detection of I degree
atrioventricular blockade in children during Holter monitoring is much higher - up to 10–22%. The
incidence of II degree atrioventricular block is 0.003% in the population. A fairly high prevalence of
II degree atrioventricular blockade of the Mobitz I type (2.4%) is observed in trained athletes
undergoing a routine ECG. The average incidence of congenital complete atrioventricular blockade
is 1 case per 22,000 newborns and ranges from 1 in 15,000-25,000. The incidence of atrioventricular
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blockades after surgical correction of congenital heart defects ranges from 1 to 17%, which depends
on the anatomy of the defect and the type of performed cardiac surgery [2, 21, 27].
A change in atrioventricular conduction can be associated with both a dysregulation of its
activity by the autonomic nervous system and with organic and / or structural changes in the cardiac
conduction system. The appearance of atrioventricular blockade of the 1st degree against the
background of bradycardia may be associated with an increase in the tone of the parasympathetic
division of the autonomic nervous system. The cause of the development of atrioventricular blockade
of the 1st degree can be inflammatory diseases of the myocardium of various etiologies, infiltrative
and degenerative diseases. Grade I atrioventricular block can also occur after surgical or endovascular
correction of congenital heart defects or as a result of catheterization of the right heart [1, 17, 21].
Atrioventricular block II degree is often observed in pathological vagotonia, toxic heart
lesions associated with digitalis drugs, β-blockers and calcium channel blockers, as well as in
autoimmune lesions of the conducting system with the subsequent development of cardiosclerosis
and degenerative diseases of the cardiac conduction system. Atrioventricular block II degree is
observed in children after heart surgery. Atrioventricular block of both I and II degrees can be a
consequence of an anomaly in the development of the cardiac conduction system in congenital heart
defects [10, 23].
Complete atrioventricular block can be congenital, acquired, or hereditary. The most common
causes of acquired grade III atrioventricular block are cardiac surgery and viral infection. Children
with complete atrioventricular block, regardless of the genesis of the block, are threatened by the
development of syncope and, consequently, by the development of sudden cardiac death due to life-
threatening brady- and tachyarrhythmias, leading to the development of inadequate cardiac output
and cerebrovascular accident [9, 12, 13, 14].
Congenital isolated atrioventricular block is directly related to neonatal lupus - a symptom
complex diagnosed in newborns, whose mothers often suffer from autoimmune rheumatic diseases),
and manifested by two main symptoms - lesions of the skin and heart. In about half of all described
cases, neonatal lupus is presented in the form of an isolated skin disease, and in the other half of
observations - in the form of isolated atrioventricular blockade. In 10% of cases, there is a
combination of these syndromes. Rarely, neonatal lupus is accompanied by other manifestations,
more often of a transient nature [8, 15]. With neonatal lupus, in most cases, therapy is not required:
symptoms subside within a few months as maternal antibodies are eliminated from the newborn's
blood; the exception is congenital atrioventricular block [19, 25].
In the event of a congenital complete AV block in the first child, the likelihood of this disease
in the fetus during repeated pregnancy reaches 15%. Another cause of congenital complete AV block
is various disorders of embryonic development of the heart caused by chromosomal aberrations
(Down, Patau and Shereshevsky-Turner syndromes) or exposure to teratogenic factors (for example,
infection). It is characterized by a combination of complete AV block with congenital heart defects,
most often - with defects of the inter-ventricular septum (MPP) and interventricular septum (IVS),
tetralogy of Fallot and transposition of the main arteries [8, 25].
Genetic mutations can also cause complete congenital AV block. Mutations in the genes of
sodium (SCN5A) and calcium (CaCNAIB) channels, accompanied by a decrease in their functional
activity, which leads to impaired AV conduction, have been described. The prevalence of congenital
complete AV block due to genetic mutations in the general population is unknown. Many researchers
believe that the majority of “idiopathic” cases of this disease, accounting for up to 30%, according to
some data, are due to currently unknown genetic mutations [8, 15, 19].
Mutations in the genes of transcription factors are characteristic of conduction disorders
associated with organic heart damage. In most cases, the cause of the disease remains unknown,
which suggests the discovery of new genetic mutations in the future [15].
The most characteristic is the autosomal dominant type of inheritance. The degree of gene
penetrance in different generations may differ. This determines the differences in the age of onset of
clinical manifestations, the rate of progression and, accordingly, the prognosis of the disease [19, 26].
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The presence of "sporadic" cases, in which there are no obvious manifestations of a hereditary
disease, served as the basis for the assumption, in addition to genetic mutations, also autoimmune
mechanisms of the development of this disease [8, 15].
Conduction disturbances at various levels of localization and severity are often found in
congenital structural heart diseases. They can be caused both by a primary disorder in the
development of the cardiac conduction system, and be the result of morphological and hemodynamic
changes accompanying the congenital defect. Transcription factors are genes expressed in the early
stages of embryogenesis, the protein products of which determine the direction of further cell
proliferation and differentiation. Mutations in these genes can disrupt the formation of entire organs
and its individual components [8, 15, 19].
The spectrum of clinical manifestations of atrioventricular block is wide and ranges from
complete absence of symptoms to the development of heart failure, syncope and sudden death.
Among the most common complaints: decreased exercise tolerance (shortness of breath on exertion),
dizziness, loss of consciousness (syncope) [13, 16].
Grade I atrioventricular block can occur in healthy children. It has been proven that the 1st
degree AV block does not lead to a significant increase in the heart chambers. Grade I atrioventricular
block is asymptomatic, but children with grade I atrioventricular block who have a PQ (R) interval
of 240 msec or more need to be monitored to monitor the possible progression of the degree of
blockade. The clinical picture of the disease in children with atrioventricular block II – III degree
depends on the size of the rhythm pauses, the initial heart rate or the activity of the heterotopic rhythm.
With sudden pauses in the rhythm, there is a high risk of developing syncope. The onset of symptoms
of heart failure depends on the ability to provide adequate metabolic needs for the minute volume of
blood circulation, the value of which depends on the heart rate and stroke volume of the left ventricle
[4, 5].
In older children, despite a decrease in heart rate, the minute volume of blood circulation is
supported by an increase in stroke volume, which is based on an increase in the end diastolic size of
the left ventricle with bradycardia. Thus, the onset of symptoms of heart failure will depend either on
the level of baseline bradycardia and / or the lack of an adequate increase in heart rate during exercise,
as well as on the contractile function of the left ventricle. Attacks of loss of consciousness (Morgagni
– Adams – Stokes syndrome) are the most pronounced clinical manifestations of atrioventricular
block II – III degree. The cause of loss of consciousness is long periods of ventricular asystole, periods
of absence of effective ventricular contractions resulting from the transition of II degree
atrioventricular blockade to complete atrioventricular block, when a new ectopic ventricular
pacemaker located below the blockade level has not yet begun to function. Ventricular asystole can
also develop with a sharp suppression of the automatism of the ectopic centers of the II and III orders
with blockade of the III degree [10, 22].
The degree of conduction disturbances determines the severity of the course and the prognosis
of patients. The most characteristic is transient or permanent complete atrioventricular block with
periods of prolonged asystole and syncope, which is the most common cause of death in patients. A
progressive course of generalized lesion of the vascular system has been described, which begins with
a distal bundle branch block, then spreading to the atrioventricular and sinus nodes, which leads to
the development of complete atrioventricular block and the appearance of sick sinus syndrome [18,
20, 24, 25].
It has now been proven that in children, atrioventricular blockages can persist for a long time,
progress, having a negative effect on hemodynamics, leading to a delay in the pace of physical,
psychomotor and intellectual development of the child, and significantly reduce the quality of life
indicators [10, 23].
Materials and methods.
In total, we examined 43 children hospitalized in the cardio-
rheumatology department of the Children's Clinical City Hospital No. 4 for cardiac arrhythmias for
the period 2019 - 2020. The age of the examined children varied from 1 to 17 years and averaged 7.1
± 0.7 years.
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The complex of the examination included the analysis of anamnestic data (gynecological and
obstetric history: the course of pregnancy and childbirth, assessment of the state at birth according to
the Apgar scale), clinical and laboratory examination, electrocardiography, echocardiography, Holter
monitoring.
Results and discussion:
Analysis of biomedical factors showed that the disease is gender-
related and is more common in boys. In the age aspect, in children of early and preschool ages, the
number prevailed than in other age periods (tab. 1).
Table 1
Assessment of biomedical factors of atrioventricular blockade in children
Indicators
Children with
Atrioventricular block
n = 43
Boys
29 (67,4%)
Girls
14 (32,6%)
Up to 3 years
14 (32,6%)
3-6 years old
19 (44,2%)
7-10 years old
2 (4,7%)
10-14 years old
4 (9,3%)
14-18 years old
4 (9,3%)
Closely related marriage
4 (9,3%)
Heredity
5 (11,6%)
Heredity and environment act as etiological factors and play a role in the pathogenesis of any
human disease, but their share in each disease is different, and the greater the share of one factor, the
less the contribution of the other. So, among all children examined, one of the predisposing factors
for the development of the disease was hereditary burden of cardiovascular pathology. Closely related
marriage was registered in 4 (9.3%) patients with AV block (Figure 1).
Figure 1. Biomedical factors in children with atrioventricular blockades
In terms of the frequency of occurrence of atrioventricular blockade, degree I blockade
prevailed (74.4%). Grade III atrioventricular block was registered in only one patient (Table 2).
67,4%
32,6%
9%
11,6%
0,0%
50,0%
100,0%
Boys
Girls
Closely related marriage
Heredity
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Table 2
The incidence of atrioventricular blockade of varying degrees in children
№
Degrees of atrioventricular block
Number of children
1
AV blockade of the 1st sepena
32 (74,4%)
2
2nd degree AV block
10 (23,3%)
3
AV block III degree
1 (2,3%)
In 32 (74.4%) children with atrioventricular block, anemia of varying degrees was observed.
As can be seen from the table, mild anemia 28 (65.1%) prevailed in frequency of occurrence.
Moderate anemia was detected in 4 (9.3%) children with atrioventricular block (Table 3).
Table 3
Background diseases in children with atrioventricular block
Diseases
Children with AV block
п=43
Mild anemia
28 (65,1%)
Moderate anemia
4 (9,3%)
Severe anemia
-
Conduction disorders (sinoatrial, atrioventricular block, right and left bundle branch block)
were observed quite often - in 76.7% of cases. Violation of conduction was manifested primarily by
incomplete AV block of 1 degree, which was characterized by rather slow dynamics. Grade 2 AV
block was characterized by more pronounced changes. AV block of the 3rd degree was registered in
one case. Significantly more often (up to 67.4%), the bundle branch blockade was noted. AV-
blockade of II-III degree, blockade of the left or (less often) right branch of the His bundle indicate
the presence of a severe pathological process with a very unfavorable prognosis.
Conduction disturbances also manifested themselves in blockade of the branches of the
atrioventricular bundle, more often the anterior-superior branch, which is accompanied by a sharp
deviation of the electrical axis of the heart to the left, or in atrioventricular blockade of the I – II
degree. Children were characterized by changes in the repolarization phase in the form of depression
of the ST segment, flattening or inversion of T waves in the left leads.
In almost all children (91%), along with impaired repolarization processes, there was an
increase in the electrical systole of the ventricles (QT interval) from the required norm. Prolongation
of the QT interval can be considered as an indicator of a decrease in the functional or contractile
ability of the myocardium.
To confirm the diagnostic value of the lengthening of the electric systole of the ventricles,
these children underwent an echocardiographic study, which confirmed a decrease in myocardial
contractility.
Conclusion.
When assessing the anamnesis of patients with cardiac arrhythmias, it was found
that cardiac conduction abnormalities are detected more often in boys, early and preschool age. In
children with atrioventricular block, the most characteristic functional changes are changes in the
repolarization phase in the form of depression of the ST segment, flattening or inversion of T waves
in the left leads. There is also a lengthening of the electrical systole of the ventricles (QT interval)
from the norm. Prolongation of the QT interval with dystrophic changes in the myocardium can be
considered as an indicator of a decrease in the functional or contractile ability of the myocardium.
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