[QT Interval in Patients With COVID-19].

Since the first case recorded in the end of 2019, the virus SARS-CоV-2 and the related lung disease COVID-19 have spread over the world and became a threat for public health. The drugs used for treatment of this disease (azithromycin and hydroxychloroquine) can prolong the QT interval on the electrocardiogram to increase the risk of pirouette tachycardia and sudden cardiac death. This article presents a review of potential risks related with the drug treatment of COVID-19 and provides recommendations for management of patients during the pandemic.

[Andersen-Tawil syndrome. Efficacy of class IC drugs].

A case of a rare disease - Andersen-Tawil the syndrome (ATS) is presented. Diagnosis of ATS, 7-th molecular-genetic variant of long QT syndrome was made basing on the characteristic clinical picture (periodic stress induced syncopal states), data of ECG and its Holter monitoring (pronounced QT prolongation, bouts of polymorphic bidirectional ventricular tachycardia), typical dysmorphic features (low-set ears, small mandible, brachydactyly, fifth-digit clinodactyly). However mutation of the KCNJ2 gene typical for this variant was not detected. Problems of pathogenesis, diagnostics, and treatment of the disease are discussed with special stress on class IC antiarrhythmic drugs.

[Sudden death of two sisters in a family with combined progressive impairment of cardiac conduction system].

Sudden cardiac death (SCD) of two sisters from a family with combined progressive impairment of cardiac conduction system (CCS) is described. These two sisters (hetero-ovular twins) died suddenly in a kindergarten at the background of physical and emotional effort in the age of 4.8 and 5 years. Resuscitation and electrical defibrillation conducted in one of them after 20 min of heart arrest were not effective. Autopsy gave no clear-cut data relative to pathology of the heart and other organs. Analysis of preserved ECGs showed that in the age of 8 months both sisters had sharp leftward/upward deviation of electric axis of the heart (-41 in one sister and -43 in another). In 2 years these deviations became even more pronounced reaching -63. This was combined with small q-waves and tall R waves in leads I and aVL what corresponded to signs of block of the anterior branch of bundle of His and could be a manifestation of hereditary disease with progressive CCS involvement first of all of the Lev-Lenegre disease.

[Changes of QT interval during graded exercise test in healthy adolescents aged 11-15 years].

Aim of the study was determination of physiological limits of QT-intervals and its derivative values in healthy children and adolescents during graded exercise tests. We examined 100 healthy boys and girls aged 11-15 years (mean age 13.4+/-2.1 years) and performed electrocardiography at rest and standard veloergometry (VEM) in all of them. We analyzed corrected intervals according to Bazett (QTc=QT/RR) and Fredericia (FQTc/3RR) formulas. Hysteresis QTc was calculated as difference between QTc durations during recovery and exercise at same heart rate (HR) Baseline HR before VEM exceeded rhythm on resting electrocardiogram by 5-15 bpm (84+/-8 vs 70+/-6, respectively, p<0.05) Increase of HR at exercise (mean 172+/-11 bpm) was similar in both sexes. QT interval decreased by 7-10% (18-31 ms) per each 25 w (p<0.05). Values obtained at determination of FQTc we found values 26-52 ms lower than those calculated by the Bazett formula in the process of whole test. Determination of FQTc compared with calculation by Bazett formula revealed more pronounced (10% from baseline level) shortening of FQT at peak exercise. QT calculated by the Bazett formula at 100 w did not differ from baseline level with tendency to higher level. Corrected QT according to the most often used Bazett formula was maximal at the first stage of exercise (25 w) and did not exceed 450 ms in boys and 460ms in girls. Maximal QTc lengthening in the process of test did not exceed 50 ms in any of the examined persons. Hysteresis of QTc interval was equal to 21+/-6 (15-25) ms. The conclusion was made that algorithm of assessment of QT interval changes during exercise test should include initial values of QTc calculated according to the Bazett formula, maximal QTc value, level of exercise at which it was registered, maximal increase of QTc during exercise, and QTc interval hysteresis.

[Holter monitoring in healthy children during first days of life].

Aim of the study was to determine dynamics of main parameters of heart rhythm in children during first days of life. Material and methods. We examined 30 healthy newborns (14 boys and 16 girls) aged 1-4 days (2,6+/-1,3 days). Criteria of inclusion were healthy mother, normal course of pregnancy and delivery, gestational age at birth 38-40 weeks, body mass at birth 3200-3600 g; Algar score 8/9, no cardiovascular abnormalities at physical examination, informed consent of parents. On days 1-2 and 4 of life we carried out 12 lead ECG at rest and 24-hour Holter monitoring with assessment of heart rate (HR), arrhythmias, dynamics of QT-interval, HR variability (HRV) using methods "Time Domain" and "deceleration (DC)/acceleration capacity (AC)". Results. Average 24-hour HR was 138+/-17 beats/min, maximal pauses of sinus rhythm - 990 ms. Supraventricular extrasystoles (<10/24 hours) were registered in 35%, ventricular extrasystoles (<5/24 hours) in 15% of children. Values of HRV were as follows: N 442 (408-72) ms; SDNN 52 (43-75) ms; SDNNi 36 (35-61) ms; SDNNi24 (22-37) ms; SSD 14 (10-20) ms; NN50% 0,98(0-2,4)%. Analysis of D/ showed the following values: D = +3.43 +/- 0.54 (2.16-4.14),=-3.65+/-0.65 (from - 2.13 to - 4.38). Analysis of interval QT values: average 24-hour QT (QTo) - 293+/-10 (278-308) ms, maximal - 342+/-38 (328-360) ms; mean 24-hour QT 442+/-14 (428-470) ms; QT 204+/-11 (191-220) ms; QT - 308+/-17(284-337) ms, sl Q/RR 0.37 (0.304-0.505); intercept QT/RR 126 (92.0-151.0), correlation coefficient () QT/RR 0.65 (0.56-0.84). On day 4 compared with day 1 there were significantly higher values of correlation (r) QT/RR and lower values of sl QT/RR. Conclusions. During first days of life children can have supraventricular and ventricular extrasystoles (not more than 10 per 24 hours). First 24 hours of life are characterized by most pronounced signs of myocardial instability according to data of assessment of QT dynamics. HRV parameters of healthy newborns are characterized by high level of sympathetic activity, symmetry of deceleration capacity/acceleration capacity parameters.

[Physiological significance and normative parameters of rate adaptation of QT-interval during holter monitoring in healthy persons of young age].

Aim of the investigation consisted in to study parameters of " QT-dynamics " in healthy children and adolescents. We examined 26 children aged 7 - 17 years (mean 11,6 +/- 7 years) - 7 girls (9,3 +/- 2,3 years) and 19 boys (12,5 +/- 3,6 years). Holter monitoring with manual and automatic estimation of QT and QTc intervals. Dynamics of magnitude of QT interval was determined with the use of equation of linear regression Y = aX+b, where aX - coefficient of linear regression QT/RR (slope QT/RR), b - shear coefficient (intercept QT/RR). Values of QT interval at automatic analysis were 368,8 +/- 18,04 (340 - 410) ms for absolute QT and 424 +/- 14,99 (390 - 450) ms - for QTc, 289,4 +/- 14,6 (260 - 320). Mean values of " QT dynamics " were for slope QT/RR: 0,18 +/- 0,03 (0,13 - 0,24) for 24 hours, 0,16 +/- 0,03 (0,10 - 0,22) for daytime period, and 0,11 +/- 0,13 (0,05 - 0,18) for night time period; for intercept: QT/RR - 230,4 +/- 20,7 (192 - 282) for 24 hours, 299 +/- 25,5 (258 - 364) for day time period, and 242,7 +/- 21,8 (204 - 295) for night time period. Coefficient of correlation of intervals QT and RR (r QT/RR) was 0,79 +/- 0,05 (0,69 - 0,89) for 24 hours; 0,68 +/- 0,07 (0,52 - 0,82) for day time period, and 0,52 +/- 0,13 (0,19 - 0,74) for night time period. All values of " QT-dynamics " significantly differed from each other during various periods of day (p < 0,05). Negative relation was noted between 24 hour slope and intercept QT/RR (r= -0,88, p < 0,05), diurnal (r= -0,87, p < 0,05) and nocturnal slope and intercept QT/RR (r= -0,72, p < 0,05), positive relation was noted between 24 hour values of slope QT/RR and QT (r=0,49, p < 0,05), and intercept QT/RR with absolute QT (r=0,41, p < 0,05). Significantly higher values (p < 0,01) of slope QT/RR were in girls. Thus, increase of slope QT/RR is noted during augmentation of tone of sympathetic part of vegetative nervous system, lowering - when vagal influences are also enhanced. Intercept QT/RR appears to be combination parameter, increase of which reflects both lengthening of absolute mean value of QT interval and reciprocal nocturnal lowering of the slope parameter. It is necessary to assesses clinical and diagnostic significance of changes of novel parameters of " QT-dynamics " on the basis of normative sexual-aging values and physiological mechanisms, determining their variability.

[Heart rate turbulence in patients with ventricular tachy arrhythmias of noncoronary genesis].

AIM: To assess parameters of heart rate turbulence in patients with ventricular extrasystoles (VES). MATERIAL AND METHODS: Patients with VES during Holter ECG monitoring (n=65, age 1-17 years, 32 girls, 33 boys) including 3 with long QT syndrome, 4 with catecholaminergic ventricular tachycardia, 1 with arrhythmogenic right ventricular dysplasia, 4 with dilated cardiomyopathy, 2 with Brugada syndrome, 3 with Duchenne myopathy, and 48 with idiopathic VES. Parameters HRT onset and slope were calculated for 1678 VES. During follow-up (6+/-4.9 years) deaths, sudden deaths, and such complications as syncope, cardiac dilatation, heart failure were registered in 26 patients. RESULTS: HRT slope exceeded 2.5 ms/RR in all patients. HRT onset was >0 in patients with catecholaminergic ventricular tachycardia, dilated cardiomyopathy, and Duchenne myopathy. The following complications occurred in 7 of 8 patients (87.5%) with HRT onset >0: syncope, sudden deaths (2 patients with dilated cardiomyopathy), dilatation of cardiac chambers, tolerance to antiarrhythmic therapy. Patients with long QT syndrome and arrhythmogenic right ventricular dysplasia (including 2 who afterwards died suddenly) had normal HRT onset. The sensitivity and specificity of HRT onset measurement for unfavorable prognosis of VES was 27 and 97%, respectively. No relationship was found between HRT slope and onset (r=-0.057). CONCLUSION: Pathological HRT (mainly represented by changes of HRT onset) are characteristic for organic myocardial diseases. Therefore detection of abnormal HRT dictates necessity of exclusion of organic cardiac pathology.