ECG criteria
- Heart rate by age (approximate values for a calm child at rest, not asleep and without fever): neonates and infants approx. 100–160 bpm, preschoolers approx. 80–120 bpm, school-aged children and adolescents approx. 60–110 bpm; exact limits differ between age tables, see the "What the ECG looks like" section
- QRS axis (electrical axis of the heart): deviated to the right in neonates (approximately +90…+160°), with right deviation gradually decreasing with age; normal ranges across age groups overlap significantly, and a moderate right axis deviation in a child may remain normal longer than in an adult
- R/S ratio in V1: in neonates and infants, R in V1 typically dominates (transitional neonatal right ventricular dominance); with age, R in V1 gradually decreases while R in V6 increases, with S in V6 usually decreasing whereas S in V1 may become deeper
- T wave in right precordial leads (V1–V3): often positive in the first days of life, then inverts in V1 during the first week; a negative T wave in V2–V3 ("juvenile T-wave pattern") is typical for childhood and may persist into adolescence, especially in girls; isolated T-wave inversion in V1 often remains a normal variant in adults as well
- PQ (PR) interval: age-dependent, shorter in neonates and infants, gradually increasing with age; in adolescents, normal values approach adult values (upper limit is approximately 0.20 s), therefore a fixed uniform range for all ages is not used—values are assessed using age- and heart rate-dependent tables
- QTc: generally evaluated using Bazett's formula with manual verification of measurements and age-specific reference values; at high heart rates, Bazett's formula may overestimate QTc, so in case of doubt, Fredericia's formula and a repeat ECG are additionally used
- Q wave: a small Q wave in III, aVF, V5–V6 can be a normal variant in children; a pathological Q wave (deep, wide, in atypical leads) is diagnosed with caution, taking age criteria into account
What it looks like on ECG
A child's ECG goes through several age stages, and the tracing must always be interpreted considering the age at the time of recording. The given values are approximate for a calm, awake child; heart rate and some parameters are affected by sleep, temperature, agitation, and the specific reference table used by the physician.
| Age | Heart rate, bpm (approximate) | QRS Axis | R/S in V1 | T in V1–V3 |
|---|---|---|---|---|
| Neonate (first days) | 100–160 | marked right axis deviation | R dominates | often positive in the first days, then inverting in V1 by the end of the 1st week |
| Infant (1–12 mos) | 100–160 | right / intermediate | R is tall, but decreasing | negative in V1, usually negative in V2–V3 |
| Preschooler (1–6 yrs) | 80–120 | closer to normal, a residual mild right deviation is possible | R/S decreases, R in V6 increases | more frequently negative in V1–V3 |
| School-aged (7–12 yrs) | 70–110 | normal | adult pattern is forming | often negative in V1, may remain negative in V2–V3 ("juvenile T wave") |
| Adolescent | 60–100 | same as in adults | same as in adults | frequently negative in V1 (normal variant), usually positive in V2–V3, but inversion is possible, especially in girls |
In neonates, the intrauterine dominance of the right ventricular electrical mass persists, which is why R is tall in V1 and the QRS axis is deviated to the right—this is a physiological age-related phenomenon, not hypertrophy. After birth, pulmonary vascular resistance rapidly decreases, and over the subsequent months and years, postnatal regression of the right ventricle occurs with relative left ventricular predominance: R in V1 decreases, R in V6 increases, S in V6 usually decreases, and S in V1 may become deeper; the axis shifts to the left. A separate note is the T wave in right precordial leads: in the first days of life, it is often positive, then inverts in V1 during the first week, while a negative T wave in V2–V3 may persist through childhood and in some cases into adolescence as a juvenile pattern. In adults, isolated T-wave inversion in V1 is also frequently a normal variant, particularly in women, whereas widespread or deep T-wave inversion in V2–V3 and beyond after puberty requires clinical evaluation considering sex, symptoms, family history, wave morphology, and ECG dynamics. The absolute duration of the PR and QRS intervals in young children is usually shorter than in adults due to smaller atrial and ventricular volumes, but in adolescents, these intervals approach adult values; the QT interval depends primarily on heart rate, so it is evaluated only after correction (QTc) using age- and sex-specific references rather than simply being called "short in children."
Mechanism
In the fetus, the right ventricle works against the systemic vascular resistance of the greater circulation via the ductus arteriosus, which is why its electrical mass predominates in the neonatal period—this is reflected on the ECG as right axis deviation and a dominant R wave in the right precordial leads. After birth, pulmonary vascular resistance drops, the workload on the right ventricle decreases, and as the child grows, the relative mass of the left ventricle gradually increases due to the systemic load. This electrical remodeling does not happen abruptly, but over months and years, which is why normal ECG limits are divided into age groups. The juvenile negative T wave in right precordial leads is associated with repolarization features of the growing right ventricle and the myocardium as a whole; it gradually disappears as the heart matures, although inversion in V1 may remain normal in adults as well.
Normal Variants
- Right axis deviation in neonates and infants, with a gradual decrease in degree with age
- Tall R in V1 in infants with a relatively deep S in V1, which deepens even further over time with right ventricular regression; the R/S ratio is assessed using age tables rather than adult criteria for right ventricular hypertrophy
- Positive T wave in right precordial leads in the first days of life, T-wave inversion in V1 by the end of the first week, negative T wave in V2–V3 (juvenile type) in childhood, sometimes persisting into adolescence, especially in girls
- Higher heart rate and shorter absolute PR and QRS intervals compared to adult norms (QT is evaluated only after heart rate correction)
- Sinus arrhythmia (respiratory) is a frequent normal variant in children and adolescents
Pathological changes requiring attention
- True right or left ventricular hypertrophy (differentiated from age norms based on the severity of changes and clinical presentation)
- Prolonged or shortened QTc outside age-related reference values
- Pathological Q wave that does not fit into age-related normal variants
- Signs of pre-excitation (WPW syndrome), bundle branch blocks, AV blocks
- Supraventricular tachycardia—an important pathological arrhythmia in children that requires differentiation from sinus tachycardia
- Channelopathies (long QT syndrome, Brugada syndrome, catecholaminergic polymorphic ventricular tachycardia) manifesting in childhood
Clinical significance and management
The primary task of a physician when evaluating a pediatric ECG is to compare findings with age-related normative tables rather than adult norms. A positive T wave in right precordial leads in a neonate during the first days of life, a tall R wave in V1, or a negative T wave in V2–V3 in a preschool-aged child is not a cause for concern on its own; the same pattern in an adolescent requires clarification considering sex and clinical presentation. When pathology is suspected (symptomatic tachycardia, syncope, family history of sudden death, marked QTc prolongation, signs of hypertrophy with clinical symptoms), the child is referred to a pediatric cardiologist for echocardiography and, if necessary, Holter monitoring. Assessment of QTc, the electrical axis, and voltage criteria for hypertrophy in children is always performed using pediatric reference tables rather than adult criteria (for example, the Sokolov–Lyon index and Romhilt–Estes criteria are developed for adults and are not valid in children without adaptation).
Common interpretation errors
- Applying adult norms for heart rate, QRS axis, and intervals to a child without considering age
- Interpretation of juvenile negative T wave in V2–V3 as ischemia or right ventricular pathology
- Overdiagnosis of right ventricular hypertrophy in newborns and infants based on a tall R wave in V1
- Using adult voltage criteria for ventricular hypertrophy (Sokolow-Lyon index, Cornell product) without pediatric adaptation
- Diagnosing prolonged QT using Bazett's formula without manual verification of the measurement, especially at high heart rates
- Ignoring sinus arrhythmia as pathology, although it is a frequent variant of normal in children
1. Which QRS axis (electrical axis of the heart) position is typical for a healthy newborn?
In newborns, the intrauterine predominance of the electrical mass of the right ventricle persists, so the QRS axis is normally deviated to the right.
2. A negative T wave in leads V1–V3 in a healthy 5-year-old child is:
Juvenile negative T wave in the right precordial leads is a frequent and expected variant of normal in preschool and school-aged children.
3. Why cannot voltage criteria for ventricular hypertrophy (e.g., Sokolow-Lyon index) developed for adults be directly applied to children?
Children have physiologically different waveform amplitude ratios and QRS axes, which is why pediatric reference tables rather than adult criteria are needed to assess hypertrophy.
Frequently asked questions
Up to what age is a negative T wave in V1–V3 considered normal in children?
T-wave inversion in V1 often remains normal even in adulthood. The juvenile pattern in V2–V3 typically occurs in childhood and may persist into adolescence, especially in girls; there is no single age cutoff. After puberty, widespread or deep inversion in V2–V3 is evaluated taking into account sex, symptoms, family history, waveform morphology, and ECG dynamics.
Is a rightward deviation of the QRS axis dangerous in a newborn?
No, this is an expected transitional neonatal pattern associated with the intrauterine predominance of the right heart chambers and the gradual decrease in pulmonary vascular resistance after birth. It is considered pathological if the axis remains markedly deviated to the right at an older age or is accompanied by other signs of right heart overload.
How to distinguish the physiological right ventricular predominance in an infant from true right ventricular hypertrophy?
A tall R wave in V1 in a newborn without clinical and echocardiographic signs of right heart overload is a variant of normal. True right ventricular hypertrophy is suspected when prominent ECG changes are combined with clinical signs of congenital heart disease or pulmonary hypertension, and is confirmed by echocardiography.
How does heart rate in children differ from the adult norm?
Heart rate in children is on average higher than in adults and gradually decreases with age: roughly from 100–160 bpm in newborns and infants to 60–100 bpm in adolescents, with considerable variation among reference tables and dependence on the child's condition. Therefore, sinus tachycardia and bradycardia in a child are evaluated using age-specific threshold values rather than the adult scale.
Should Bazett's formula for QTc be used in children in the same way as in adults?
Bazett's formula is also used in children, but at high heart rates it can overestimate QTc, so the QT measurement is verified manually, and upper-limit reference values are taken from pediatric tables. In case of a questionable result, Fridericia's formula and a repeat ECG are additionally used, and if symptoms (syncope, family history) are present, the child is referred to a pediatric cardiologist.
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Related terms
More in the section "Children, Athletes, Pregnant Women"
Sources
- Goldberger A.L. «Clinical Electrocardiography: A Simplified Approach»
- Surawicz B., Knilans T. «Chou's Electrocardiography in Clinical Practice»
- Orlov, V.N. «Electrocardiography Guide»
- AHA/ACCF/HRS recommendations for the standardization and interpretation of the electrocardiogram, 2009
Educational material for medical students and physicians. Does not replace clinical guidelines and physical examination; the ECG must always be interpreted in conjunction with the clinical picture.