[Normal values of temporal parameters of ECG in children according to results of clinico-epidemiological study ECG-screening of children and adolescents in Russian federation].

In order to obtain reliable information about time-domain ECG parameters in Russian children and to analyse their links with physiological changes the Project "ECG screening of children and adolescents of the Russian Federation" was carried out in 2003-2008. Time domain ECG parameters were studied in the representative sample of 5387 healthy individuals aged 0 to 18 years. In each age group, lower and upper limits of the norm for heart rate (HR), P wave, PQ and QRS intervals were defined as 2nd and 98th percentiles of their distribution. The equivalent limits of QT interval duration were defined as its 5th and 95th percentiles. Relationship between time domain parameters of pediatric ECG and HR was analyzed as well as relationship of these parameters with sex and age. The most important differences from prior pediatric studies completed 30 years ago were obtained for the heart rate limits. Among children aged 0 to 3, there was a tendency toward lowering of age-specific lower limits and elevation of age-specific upper limits. At ages older than 3 years, there was a tendency toward lowering of both the upper and the lower limits of HR. The newly obtained 2nd percentiles of the heart rate were lower than the known lower limits in nearly all ages. This indicates the necessity for revision of criteria of bradicardia in children. The present study showed that 5th and 95th percentiles of QTc interval (Bazett's formula) varied between 340 ms and 465 ms and were not significantly dependent on children's age and only for ages under 13 also on sex. Results of the study allowed to build age-specific ranges of norm for the time domain ECG parameters presented in a tabular form.

[Assesment of Parameters of QT Interval in Children and Adolescents.].

Aim. To determine limits of interval QT in children and adolescents aged 0-17 years and to detect possible ethnic differences of its changes. Material and Method. Twelve lead ECGs were recorded in 1531 subjects without overt cardiovascular pathology (47.2% females, 52.8 males, 57.3% of Slavic and 42.7% of Buryat i.e. mongoloid ethnicity). Results. Corrected QT interval (QTc) exceeded 440, 460 and 480 ms in 2.3, 1.05, and 0.26% of children. Prolongation of QTc was found in 0.46% and 0.11% of Slavic and Buryat children, respectively (p=ns). Starting from the age of 8 years girls had longer QTc than boys (454.1+/-15.2 and 438.3+/-8.4 ms, respectively, p<0.05). QTc less than 350 ms was registered in 12 children (0.78%). Eight of these children with mean QTc 329.1+/-32.3 ms had family history of syncope or sudden death. Variability of absolute QT values was 8+/-14.3 ms (maximally up to 40 ms). Conclusions. QT interval is prolonged when QTc duration exceeds 440 ms in children younger than 8 years and in male adolescents or 460 ms in girls aged 8 years or older and in children during first year of life. QT interval is shortened when QTc is less than 350 ms (1st degree of shortening). In children with QTc below 330 ms (2nd degree of shortening) short QT syndrome should be excluded. Normal variability of absolute QT value during sinus arrhythm on ECG at rest does not exceed 40 ms.