[Search for an Optimal Formula for Calculation of the Corrected QT Interval in Children Based on Data of Clinical-Epidemiological Study].

The aim of the study was to compare different types of QT correction, establish age norms of QT duration, and assess associations between QT duration and heart rate (HR) in children. The sample comprised 0-18-year-old children (n=5909) selected from general population. The study examined several existing formulas of corrected QT (Bazett, Fridericia, Framingham, and Hodges) and modified Bazett formula developed for healthy children. The analysis demonstrated that neither formula enabled complete exclusion of the correlation between QT and RR intervals. Among existing formulas, Bazett formula provided maximum possible elimination of the HR influence on QT duration. Modified Bazett formula, developed by us, provided even less correlation of QT and RR intervals. Therefore, we recommend implementing modified Bazett formula to pediatric practice.

Glucagon test in insulinoma: Is it useful?

Diagnosis of endogenous hyperinsulinism caused by insulinoma is based on confirmation of hypoglycemia during the symptoms associated to elevated insulin levels. Patients with insulinoma may demonstrate an excessive insulin response and subsequent hypoglycemia after 1 mg of glucagon iv injection. Glucagon test was performed in 11 patients with insulinoma before therapy and in 4 after therapy. Our study suggests that the presence of plasma glucose levels less than 55 mg/dl and below baseline at time 120 min of glucagon test strongly reinforce the diagnosis of insulinoma.

[Effect of tests with dosed physical load on sinus node function and repolarization in children with hereditary long QT syndrome].

The study is devoted to assessment of effect of physical effort of sinus rhythm rate and the state of the process of repolarization in children with 1 and 2 molecular-genetic variants of the long QT syndrome (LQT). We have shown that LQT1 is characterized by inadequate increment of heart rate (HR) and substantial increase of QTc interval during exercise. In LQT2 compared with control reduction of HR increment also takes place while shortening of QTc interval is more pronounced. Delta QTc<0 is an important differential diagnostic criterion in patients with LQT1 and LQT2. Variatins in T wave morphology in LQT1 and LQT2 diminish at the background of physical exercise. The use of ß-blockers influences relationship between length of QT interval and HR in patients with LQT but does not eliminate distinction from a group of patients with analogous variant of the syndrome not taking these drugs.

[Diagnosis, sudden death risk stratification, and treatment of main long QT syndrome molecular-genetic variants].

Inherited long QT syndrome (LQTS) refers to the primary electrical diseases of the heart. It is characterized by QT prolongation on resting ECG and syncope due to life-threatening ventricular arrhythmias. This review focuses on diagnosis, differential diagnosis, risk stratification of sudden cardiac death, and treatment strategy of patients with most prevalent genetic fOrms of LQTS - LQT1, LQT2 and LQT3, which accounted for about 90% of all genetically confirmed cases. Recent advances in understanding of relationship between clinical, electrocardiographic features (on ECG, body surface mapping, stress test) and genetic variants of LQT presented. Characteristics of syncopal events and ECG features of LQTl, LQT2 and LQT3 in the majority of cases are helpful to make an appropriate choice for therapy, even before positive result of molecular genetic testing. Management has focused on the use of beta blockers as first-line treatment and exclusion of triggers of life-threatening arrhythmia which are specific for each molecular-genetic variant. Implantation of cardioverter defibrillator for secondary prevention of sudden death in the high-risk patients or patients with insufficient effect of antiarrhythmic therapy is required.

[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.

[The influence of a low- and high-frequency electromagnetic fields on seeds].

It was shown that the exposure of seeds in the rest phase to a low-frequency pulse electromagnetic field leads to substantial changes in seed physiology during germination. The changes at the physiological level in sprouting seeds depend not only on the frequency of the external EMF and its power characteristics but also on the kind of seeds. Low- and high-frequency electromagnetic fields are able to produce a biostimulation effect; however, the mechanisms of its appearance are different in their nature. The biochemical studies of seeds after EMF treatment in the modes resulting in expressed biological effects showed an increase in the activity of alpha-amylase, which testifies an increase in the gibberellin output and in the activity of the hydrolytic enzyme sour phosphatase. The response of seeds to EMF treatment demonstrates the possibility of electromagnetic control of growth processes.

[Physical model of the plant tissue response to exposure to the microwave electromagnetic field]. / Fizicheskaia model' otklika rastitel'noi tkani na vozdeistvie mikrovolnovogo élektromagnitnogo polia.

A hypothesis was suggested to explain the effect of biostimulation of seeds exposed to microwave electromagnetic field. It was shown that the assumption on the determining influence of the microwave field on the transport properties of the conducting system of a plant satisfactorily explains the phenomena observed in germinating seeds and growing plants. A physical model of the response of a plant cell to a microwave field is presented, which served as a basis for the method of calculating the maximum possible time of exposure of plant tissue.