JT Interval Research Articles

Association of vitamin D deficiency with ventricular repolarization abnormalities.

Vitamin D is involved in cardiac contractility and myocardial calcium hemostasis, and vitamin D deficiencies are known to cause various cardiovascular disorders and have been linked with sudden cardiac death. The aim of the study was to evaluate repolarization distribution, represented by QT interval, corrected QT interval (QTc), QT dispersion, Tpeak‑to‑Tend (Tp‑e) interval, Tp‑e/QTc ratio, JT interval, JT dispersion, and Tp‑e/JTpeak ratio in children with vitamin D deficiency. Moreover, we aimed to determine the relationship between ventricular repolarization anomalies and vitamin D deficiency. The study included 50 adolescent patients with vitamin D deficiency (vitamin D <20 ng/ml), 50 adolescent patients with vitamin D insufficiency, and 50 age‑matched controls (vitamin D level >30 ng/ml). QTc duration, QT dispersion, JTpeak duration, JT dispersion, Tp‑e, Tp‑e/JTpeak ratio, and Tp‑e/QTc ratio were recorded on electrocardiogram. Patients with vitamin D deficiency or insufficiency had longer Tp‑e interval (P <0.001), while Tp‑e/QTc and Tp‑e/JTpeak ratios were found to be increased in the same group of patients (P = 0.005 and P <0.001, respectively). QT dispersion and JT dispersion were higher in the deficient group when compared with the other groups (P = 0.045 and P = 0.02, respectively). The present study, conducted in a pediatric population, is the first in the current literature to assess the relationship between ventricular repolarization anomalies and vitamin D deficiency.

Interactions between Earth’s local magnetic field and cardiovascular system parameters of women, performing sedentary work, during their workweek

The aim of this research was to identify the interactions between Earth's local time varying magnetic field and cardiovascular system parameters in women, performing sedentary work, during their workweek. The tasks of research: 1. To examine the relationship between the Earth's local magnetic field and the electrocardiographic parameters of women performing sedentary work, during the workweek. 2. To examine the relationship between the Earth's local magnetic field and arterial blood pressure of women performing sedentary work, during the work week. The methods used: electrocardiographic monitoring and arterial blood pressure measurement. The Earth's magnetic field data was obtained using a magnetometer located in the town of Baisogala. Every female was assessed four times: before and after work on Monday, before and after work on Friday of the same week. Participants of the research: the research group consisted of 21 females who perform sedentary work (average age ± SD – 50.1±9.5 years). Conclusions of the research: 1. The most significant correlations between local GMF and ECG and arterial blood pressure parameters were found with the low frequency field, the most often in SDelta [0-3.5] Hz and STheta [3.5-7] Hz bands. 2. The correlations between ECG parameters (RR, JT and QRS intervals ant ST amplitude) during the workweek changed from negative to positive, which appears to be associated with fatigue influence on person sensitivity to local GMF. 3. Systolic and diastolic arterial blood pressure changed in different ways. The correlations between local GMF and diastolic arterial blood pressure were especially pronounced. 4. All ECG and arterial blood pressure parameters showed great variability in correlation with local GMF. It can be associated with changing human sensitivity to GMF due to increasing fatigue.

Effects of Calcium, Magnesium, and Potassium Concentrations on Ventricular Repolarization in Unselected Individuals

BackgroundSubclinical changes on the electrocardiogram are risk factors for cardiovascular mortality. Recognition and knowledge of electrolyte associations in cardiac electrophysiology are based on only in vitro models and observations in patients with severe medical conditions. ObjectivesThis study sought to investigate associations between serum electrolyte concentrations and changes in cardiac electrophysiology in the general population. MethodsSummary results collected from 153,014 individuals (54.4% women; mean age 55.1 ± 12.1 years) from 33 studies (of 5 ancestries) were meta-analyzed. Linear regression analyses examining associations between electrolyte concentrations (mmol/l of calcium, potassium, sodium, and magnesium), and electrocardiographic intervals (RR, QT, QRS, JT, and PR intervals) were performed. The study adjusted for potential confounders and also stratified by ancestry, sex, and use of antihypertensive drugs. ResultsLower calcium was associated with longer QT intervals (−11.5 ms; 99.75% confidence interval [CI]: −13.7 to −9.3) and JT duration, with sex-specific effects. In contrast, higher magnesium was associated with longer QT intervals (7.2 ms; 99.75% CI: 1.3 to 13.1) and JT. Lower potassium was associated with longer QT intervals (−2.8 ms; 99.75% CI: −3.5 to −2.0), JT, QRS, and PR durations, but all potassium associations were driven by use of antihypertensive drugs. No physiologically relevant associations were observed for sodium or RR intervals. ConclusionsThe study identified physiologically relevant associations between electrolytes and electrocardiographic intervals in a large-scale analysis combining cohorts from different settings. The results provide insights for further cardiac electrophysiology research and could potentially influence clinical practice, especially the association between calcium and QT duration, by which calcium levels at the bottom 2% of the population distribution led to clinically relevant QT prolongation by >5 ms.

Assessment of QT interval in ventricular paced rhythm: Derivation of a novel formula

ObjectiveThe objective of the study was to determine the optimal formula to estimate QT interval adjusting for QRS prolongation during right ventricular (RV) pacing. MethodsThis observational study included individuals (n = 43) with a newly implanted permanent ventricular pacemaker, who had a narrow QRS complex before pacemaker insertion. QT interval with RV pacing was related to QT interval before pacemaker implantation. The validation cohort (n = 442) had permanent RV pacing in DDD mode. ResultsA new QTc formula was derived utilizing the constants from the relationship between the spline heart rate QT correction (QTcRBK) before and after pacing; specifically, QTcRBKPACED = QTcRBK × 0.86. The JT interval from paced complexes was highly heart rate (HR) dependent and was not accurate for QT assessment. Previous, QTc formula for paced complexes were not highly correlated with QT before pacing unless a robust HR correction is added. Formulae subtracting a fixed amount from QTcPACED markedly overestimated QTc before pacing. ConclusionWe proposed a new, simple formula for QT estimation in RV pacing. JT interval in paced complexes is highly HR dependent and is not accurate for QT assessment. The new spline approach for HR correction for the QT, once incorporated into some previously proposed formulae, blunts HR dependency and improves prediction of QT before pacing. QTcRBKPACED*0.86 and QTcRBKPACED – (QRS*0.5) demonstrated the best balance of relatively strong correlation to QTc before pacing and accurate QTc prolongation identification. Abnormal QT for QTcRBKPACED*0.86 as defined by the 97.5th and 99th percentile are 469 and 479 ms respectively.

Ventricular repolarization changes in children with breath holding spells

ObjectiveBreath holding spells is a non-epileptic paroxysmal disease which is frequently seen in childhood. In this study, we aimed to investigate electrocardiographic atrial conduction and ventricular repolarization changes in children with breath holding spells. Materials and methodsWe reviewed the electrocardiograms of 58 patients with breath holding spells who admitted to SBU Okmeydanı SUAM Pediatric Cardiology Clinic between November 2018 and February 2019. QT, QTc (calculated with Bazett formula), T peak-end (Tp-e), QT dispersion (QTd), QTc dispersion (QTcd), Tp-e/QT ratio, Tp-e/QTc ratio, JT interval, JTc (calculated with Bazett formula), Tp-e/JT ratio, Tp-e/JTc ratio and P dispersion (Pd) were measured and compared with the control group of 44 healthy children. ResultsIn the control and the case groups, mean QTd was 19.86 ms and 38.57 ms, QTcd was 28.34 ms and 58.03 ms, Tp-e/QT ratio was 0.16 and 0.26, Tp-e/QTc ratio was 0.11 and 0.17, JT interval was 204.09 ms and 224.52 ms, JTc value was 290.00 ms and 333.72 ms, Tp-e/JT ratio was 0.23 and 0.35, Tp-e/JTc ratio was 0.16 and 0.24, Pd was 29.32 ms and 40.53 ms respectively. Differences between two groups were statistically significant (p < 0,001). ConclusionQTd, QTcd, Tp-e, Tp-e/QT ratio, Tp-e/QTc ratio, JT, JTc, Tp-e/JT, Tp-e/JTc ratio and Pd were increased significantly compared to healthy children. Based on the results, ventricular repolarization and atrial conduction were affected in patients with breath holding spells. These patients may be under the risk of developing rhythm disorders.

The alteration of heart rate variability in Percutaneous Coronary Intervention

The risk of sudden death and cardiac arrhythmia increases in morbidly obese patients. We aimed to evaluate the marker of arrhythmias such as Tp-e/QT, Tp-e/QTc, Tp-e/JT and Tp-e/JTc ratios in extreme obesity.The study included 41 extremely obese patients and 41 control subjects. QTmax, QTmin, QRS, JT and Tp-e intervals were measured od 12‑lead electrocardiographies. In addition, Tp-e/QT, Tp-e/QTc, Tp-e/JT and Tp-e/JTc rates and QTc, cQTd and JTc intervals were calculated.Tp-e interval (79.2 ± 9.7 ms (milisecond) vs. 68.6 ± 8.1, p < 0.001), QTc interval (395.9 ± 18.8 vs. 377.9 ± 19.3 ms, p < 0.001), JTc interval (317.1 ± 27.0 vs. 297.4 ± 23.2 ms, p = 0.001), Tp-e/QT ratio (0.22 ± 0.03vs. 0.19 ± 0.02, p < 0.001), Tp-e/QTc ratio (0.20 ± 0.26vs. 0.18 ± 0.02, p = 0.001), Tp-e/JT ratio (0.29 ± 0.04 vs. 0.25 ± 0.03, p < 0.001), TPe/JTc ratio (0.25 ± 0.04 vs. 0.23 ± 0.03, p = 0.018), QTd (32.8 ± 10 vs.15 ± 6.4 ms, p < 0.001) and cQTd (70.0 ± 30.1 vs. 31.3 ± 22.4 ms, p < 0.001) were significantly higher in obese patients.Compared to healthy subjects potential ECG repolarization predictors were significantly increased in extremely obese patients.

Determination of the QT Interval in Left Bundle Branch Block: Development of a Novel Formula

BackgroundDetermination of the prolonged QT interval in left bundle branch block (LBBB), which should be of special concern to identify individuals at high risk of potentially fatal cardiac arrhythmia risk, has been problematic. MethodsElectrocardiograms (ECGs) (n = 17) in intermittent LBBB were used to develop a new formula for the calculation of QTc in LBBB. This formula and 5 others were compared in a population with LBBB (n = 2610). The QT was corrected for heart rate (HR) using the Bazett formula (QTcBZT) and the spline QT formula (QTcRBK), which is relatively independent of HR. The JT interval was significantly related to HR. ResultsThe new approach (QTcLBBBNEW = 0.945*QTcRBKLBBB − 26) in LBBB showed the highest correlation with intrinsic QTc (without LBBB) and had minimal HR dependency. Previous formulae to determine the QT interval in LBBB showed significant HR dependency except for one proposed by Rautaharju et al. Inclusion of an HR correction factor in existing formulae blunted HR dependency but not if the QT interval was adjusted by the QTcBZT. In men and women, use of the QTcBZT markedly increases the proportion of individuals with prolonged QTc, which was more evident with increasing HR. The 99th and 97.5th percentiles for QTcLBBBNEW for men and women identified abnormal QT prolongation in LBBB. ConclusionsA new formula that modifies the QT and JT intervals in LBBB predicts the QT interval in the absence of LBBB. Abnormal QT intervals in the 99th and 97.5th percentiles can identify patients with LBBB who have QT interval prolongation.

Ajwa Nanopreparation Prevents Doxorubicin-Associated Cardiac Dysfunction: Effect on Cardiac Ischemia and Antioxidant Capacity.

Background: This study evaluated the cardioprotective effect of Ajwa nano-preparation against doxorubicin-associated cardiotoxicity. Methods: Twenty-four male Wistar rats (200-250 g) were divided into 3 groups. One group was given the nanopreparation containing both Ajwa fruit and pit in a dose of 1.4 g/kg orally 1 hour before doxorubicin infusion (Dates-DOX group). Another group was given the vehicle for 1 hour before doxorubicin infusion (DOX group). The third group received the vehicle but no DOX infusion (time control). Cardiac hemodynamics, blood pressure, cardiac contractility, and conductivity were recorded before and after 45 minutes of infusion of doxorubicin (15 mg/kg, slow intravenous over 45 minutes). Blood samples were collected before and after doxorubicin infusion. Heart tissue samples were collected and snap frozen until assay of reduced glutathione. Results: Rats pre-administered Ajwa nanopreparation were protected from doxorubicin-associated systolic and diastolic dysfunction based on the significant elevation in the rate of rise in left ventricular pressure (dp/dtmax) and (dp/dtmin) compared with the DOX group. In addition, it prevented the doxorubicin-associated ischemia based on the significant shortening in QT interval, JT interval, and Tpeak-Tend interval versus the DOX group. There was no effect on atrial conductivity (PR interval and P duration). Ajwa pretreatment increased the antioxidant capacity of cardiac tissue, as evidenced by increasing the cardiac content of reduced glutathione compared with the untreated doxorubicin group. Conclusion: Ajwa nanopreparation protects from doxorubicin-associated cardiotoxicity through alleviating cardiac ischemia and increasing cardiac antioxidant capacity.

The Influence of Age and Gender on Human Organism as a Complex System During Peloidotherapy Procedure

Introduction: Electrocardiogram (ECG) represents cardiac function in all fractal levels of complexity: regulatory system was evaluated by RR interval and heart supplying system was evaluated by the changes of JT interval. The type and intensity of body’s reactions to mud therapy depend mainly on the intensity of the procedure and the responsiveness of the organism that also is influenced by age and gender. Aim: of this research was to evaluate changes of dynamic concatenations of durational ECG parameters during peloidotherapy procedure in groups of people of various age and sex. Material and Methods: The 12-lead standard ECG was registered synchronously using computerized ECG analysis system “Kaunas-Load” 1 min before and during peloidotherapy (39-40oC) procedure (mud bath). Three segments were assessed from ECG: 1 min before the procedure (1), 1-10 min of the procedure (2) and 11-20 minutes of procedure (3). Concatenations of ECG parameters were assessed and calculated: RR/ JT, JT/dQRS, RR/dQRS. 48 patients (age mean 59.5 ±11.48) were divided into groups by gender (26 female and 22 male) and age (I gr. (N=24) age ≤59 y.), II gr. (N=24) age&gt; 59 y.). Results: A comparison by gender and age showed that dynamical concatenations of RR/JT, JT/QRS, RR/dQRS of male patients were significantly (p&lt;0.05) higher then those of female during all stages of the procedure. The complexity of reactions on organism level (RR/JT) during procedure was decreasing only in I age group. The complexity of organism reactions on sub systemic level (JT/dQRS) was decreasing in all groups at the start of the procedure (p&lt;0.05) (stage 2), but was increasing in next half of the procedure (stage 3) (p&lt;0.05). JT/dQRS values of female group and older people (II gr.) at the end of the procedure returned to their initial levels (p&gt;0.05). More pronounced decrease of JT/dQRS concatenations in male and younger (I gr.) patience groups at the first stages of the procedure was observed, so these values don’t reach their initial state till the end of the procedure (p&lt;0.05). Conclusions: 1) pronounced dynamics of organism’s processes were observed during peloidotherapy treatment; 2) the most pronounced influence of age and gender on changes of organism complexity reactions was observed on regulatory levels (RR/dQRS); 3) sudden reorganization of organism’s state was observed in all studied concatenations during the initial phase of peloidotherapy.

Mobilization of Cardiovascular Function at Onset of Dosed Aerobic and All-Out Anaerobic Workouts

The objective of this study was to compare the peculiarities in the mobilization of cardiovascular function at the onsetof an exercise test in dependence on age and the type of adaptation to physical loads. The study’s participants were boysof 11, 12, 13 and 14 years old and adults, i. e. 17 voluntary students who were not engaged in sports training and well-trained athletes (all participants were members of various national teams), i. e. 23 athletes in the endurance group, 19 —in the sprint group and 21 — in the combative sports group (box, judo and wrestling). The subjects underwent:1) Roufier’s test (30 squats per 45 seconds); 2) a 30-second duration maximal vertical jump test. A computerizedelectrocardiogram (ECG) system “Kaunas-Load” was employed for the 12-lead ECG recording and analysis during theperformance of workloads. A computerized program allowed to measure the ratio of JT and RR intervals (JT / RR) andthe velocity of adaptation of cardiovascular system to exercise, i.e. the index of velocity of adaptation (V Ad ), by calculationthe difference between the relative changes of JT and RR intervals as a difference: V Ad . = (Jt i / JT 0 ) 100% – (Rr i / RR 0 ) 100%. The results obtained during the study allowed to conclude that faster adaptation at the onset of the exerciseis rather characteristic for younger persons but the type of the exercise performed during the long term training processplays a significant role in the developing and improving the velocity of adaptation of cardiovascular system. A fasteradaptation at the onset of the exercise is a more characteristic feature for the trained athletes in sprint events andcombative sports than the representatives of the endurance group or non-athletes. One of the effects of long termadaptation to exercise is a smaller mobilization of cardiovascular system at the onset of the dosed aerobic and all-outanaerobic exercise and the endurance exercise has the most influence on it.Keywords: cardiovascular system, adaptation, exercise test.

Impact of Training in Sports Games and Cyclic Sports Events on Cardiovascular System, Motor and Sensomotor Abilities of 11—14 Year-Old Boys

Individual development depends not only on inherent qualities but also on the effective influence of the environment. The aim of this study was to compare the effect of variable intensity as partially regulated physical loads which are appropriate for sports games performances and cyclic nature as strictly regulated physical loads which is appropriate for cyclic sports events on the dynamics of muscular, cardiovascular and central nervous system (CNS). The contingent of this study was 70 boys of 11—14 years of age: cyclic sports events (track and field athletes) and sports games athletes (basketball, volleyball, football players) were tested for four years. The following methods were used: Tapping test, Roufier exercise test, vertical jump test, 30 s maximal jumping test, measurements of ABP, electrocardiography, dynamometry, measurements of the body mass components. Sports games athletes were superior over cyclic sports events athletes taking into account CNS mobility, anaerobic efficiency and anaerobic work capacity. Evaluating boys’ motor abilities (performing vertical jump and 30 s maximal jumping test), it was observed that these indices were improving with age in both sports games athletes and cyclic sports events athletes groups, but they did not vary statistically significantly among each other. Evaluating the indices of muscle power by dynamometry measurements, it was determined that cyclic sports events had greater influence on muscle power. These results show that 11—14 year-old boys are still developing and are not mature. Long-time research of body components revealed that body fat decreased with age and active body mass and total body liquid mass increased with age, but in case of sports games athletes and cyclic sports events athletes, they did not vary. Sports games athletes were characterized as having lower HR values than cyclic sports events athletes, though during all investigation statistically significant differences were observed in 13 year-old group. Statistically significant differences were found evaluating JT interval data. The development rate of muscular, cardiovascular system and performance abilities of CNS increase under the influence of variable intensity of physical load which is appropriate for sports games in contrast to cyclic sports events, which is an essential external factor at the age of 11—13. Decisive influence of endogenous factors on growth and development of boys significantly increases at the age of 13—14 years due to the changes of cardiovascular system, and CNS indices accelerate.Keywords: cardiovascular system, central nervous system, cyclic sports, sports games.

Influence of Short-Term Fasting on the Changes in Women’s Cardiovascular Functional Parameters

Research background and hypothesis. Recently, cardiovascular diseases (CVD) have been the major cause of mortality as a result of poor diet, emotional stress and insuffi cient physical activity. Improvement of dietary habits based on reduction of body weight by short-term or long-term fasting has been observed. While analyzing the effect of fasting, its psychological rather than physiological features are usually emphasized.Research aim was to assess the impact of daily fasting on the changes in women’s cardiovascular functional parameters during physical load. Research methods. Thirty six women performed exercise test on bicycle ergometer (the load increased each minute by 25 W) before and after 24 hours of fasting. After the 1 st exercise test the subjects used only non-energetic liquid. Evaluation of electrocardiogram (ECG) data was performed applying computerized ECG analysis system “Kaunas–Load“(Institute of Cardiology, LUHS). We analyzed systolic blood pressure (S), heart rate (HR) and JT interval at rest and throughout the load.Research results. After 24 hours of fasting, HR of women at rest and during the fi rst 3 minutes of the load signifi cantly decreased (p &lt; 0.05). Duration of the JT interval decreased during both exercise tests. Longer JT interval was obtained at rest and during the fi rst 2 minutes of the load after 24 hours of fasting (p &lt; 0.05). S at rest and throughout the load was signifi cantly lower after fasting (p &lt; 0.05). Discusion and conclusions. Functional state evaluation of untrained women after 24 hours of fasting during bicycle ergometery test demonstrated dynamical changes of many cardiovascular function variables: lower HR, increased the JT interval, and decreased S.Keywords: cardiovascular system, short-term fasting, bicycle ergometer test.

Dynamical Peculiarities of Concatenational Changes in Functional Cardiovascular Parameters

Research background and hypothesis. Traditional time series analysis techniques, which are also used for the analysis of cardiovascular signals, do not reveal the relationship between the changes in the indices recorded associated with the multiscale and chaotic structure of the tested object, which allows establishing short-and long-term structural and functional changes.Research aim was to reveal the dynamical peculiarities of interactions of cardiovascular system indices while evaluating the functional state of track-and-field athletes and Greco-Roman wrestlers.Research methods. Twenty two subjects participated in the study, their average age of 23.5 ± 1.7 years. During the study standard 12 lead electrocardiograms (ECG) were recorded. The following ECG parameters were used in the study: duration of RR interval taken from the II standard lead, duration of QRS complex, duration of JT interval and amplitude of ST segment taken from the V standard lead.Research results. Significant differences were found between inter-parametric connections of ST segment amplitude and JT interval duration at the pre and post-training testing. Observed changes at different hierarchical levels of the body systems revealed inadequate cardiac metabolic processes, leading to changes in the metabolic rate of the myocardium and reflected in the dynamics of all investigated interactions.Discussion and conclusions. It has been found that peculiarities of the interactions of ECG indices interactions show the exposure of the functional changes in the body at the onset of the workload. The alterations of the functional state of the body and the signs of fatigue, after athletes performed two high intensity training sessions per day, can be assessed using the approach of the evaluation of interactions between functional variables. Therefore the evaluation of the interactions of physiological signals by using time series analysis methods is suitable for the observation of these processes and the functional state of the body.Keywords: electrocardiogram, time series, functional state.

Peculiarities of Cardiovascular Reactions of Elite Greco‑Roman Wrestlers to Repetitive Dosed Exercise Test

Research background and hypothesis. The synergy of central and peripheral changes while performing easy exercises in repetitive manner should show central or peripheral changes which start increasing and become a trigger for functional mobilization.Research aim. The aim of this study was to determine the mobilization peculiarities of central and peripheral cardiovascular function in Greco-Roman wrestlers cohort while performing a dosed exercise test in repetitive manner.Research methods. Greco-Roman wrestlers, sprinters, endurance runners and non-athletes underwent three Roufier tests (30 squats per 45s) with 2 minutes of recovery between them. The changes in the heart rate (HR) and JT interval taken from 12-lead ECG and O 2 desaturation (StO 2 ) registered by near-infrared spectroscopy were analyzed.Research results. HR increased and JT interval decreased more and more in both non-athlete cohorts while there were no significant changes in all three athlete cohorts, i. e. we did not find any summing effects of the repetition of workloads. The tendency of increase in StO 2 at the second minute after the dosed workload was greater and greater with each consequent repetition of the testing workload in all cohorts.Discussion and conclusions. We have proved our hypothesis that peripheral changes during repetitive exercising start increasing earlier than the central ones. The dynamics of central and peripheral cardiovascular indices in non-athlete cohorts while repeating a dosed aerobic exercise test every two minutes demonstrates the cumulative effect of physical exertion whereas in elite Greco-Roman wrestlers as well as in other individuals adapted to physical loads functional indices reiterated.Keywords: electrocardiogram, dosed exercise test, oxygen saturation.

Peculiarities of Central and Peripheral Changes at Onset of Dosed and Maximal Exercise Tests

Research background and hypothesis. Since varying types of physical workloads activate different physiological system activity at different degree, during dosed and maximal exercises the total effects can highlight the properties of central and peripheral mechanisms and reveal significant synergies between the central and peripheral cardiovascular processes. Research aim was to determine the peculiarities of central and peripheral indices of cardiovascular system while performing dosed and maximal exercise tests. Research methods. Two groups took part in the study – sportsmen-sprinters (16) and sportsmen – endurance group (11). The participants of the study performed Roufier exercise and 30 s maximal jump test with maximal efforts. The 12-leads ECG was registered continuously and the changes of heart rate (HR), JT interval and ratio JT/RR were analysed. Near-infrared spectroscopy was employed for continuous registration of the changes in oxygen saturation (StO 2 ) and arterial blood flow.Research results. The results obtained during the study showed increasingly changing ECG indices while performing exercise load in both athlete groups but there was no statistically significant difference between groups while performing maximal exercise, thus oxygen saturation and arterial blood flow was statistically significantly faster and decreased more in sprint athlete group. Discussion and conclusion. Dosed and maximal exercise test indicated the peculiarities of cardiovascular function of athletes, although more differences between individual peculiarities of athletes can be revealed while performing a dosed exercise test and still more differences – while the maximal exercise tests are performed and during the recovery after exercising.Keywords: dosed and maximal exercise test, cardiovascular system, endurance, sprint.

Cardiovascular Adjustments during Graded Exercise Stress

Research background and hypothesis. Cardiac function provides an adequate blood supply to all organs thus changes in the performance and functional state of cardiac muscles during exercising are very important.Research aim. The aim of the study was to find out the peculiarities in adjustment of cardiovascular system in dependence on the type of adaptation to physical loads during graded stress.Research methods. The study participants, 17 non-athletes, 23 endurance, 19 sprint and 21 combat sport athletes, underwent a bicycle ergometry of incremental increase in provocative workload (graded stress). A 12-lead ECG was reordered and a computerized program allowed to measure ECG parameter, the ratio of JT/RR intervals and the velocity of adaptation of cardiovascular system to exercising (V Ad ), by calculating the difference between the relative changes of JT interval and RR interval as a difference: V Ad . = (JTi/JT0) 100% – (RRi/RR0) 100%.Research results. No significant functional ischemia was found in endurance cohort during the graded stress while it was expressed in non-athletes’ cohort and slightly smaller in sprint and combat cohorts. Maximal values of other ECG or ABP parameters registered during graded stress did not reveal significant differences between cohorts.Discussion and conclusions. Functional ischemia is an important factor limiting muscular and cardiac performance during the graded exercise stress. The exercise type plays a significant role in developing the velocity of adaptation of cardiovascular system at onset of exercising. Faster adaptation at onset of exercise is more characteristic of sprint and combat sports than representatives of endurance or non-athletes.Keywords: cardiovascular system, adaptation, functional ischemia.

Is sofosbuvir/ledipasvir safe for the hearts of children with hepatitis C virus?

BackgroundSymptomatic bradycardia has been reported in adults treated for chronic hepatitis C using sofosbuvir based regimens. AimWe studied the cardiac safety of sofosbuvir/ledipasvir in Egyptian children, treated for chronic hepatitis C. MethodsThe study included 40 hepatitis C virus infected children and adolescents 12–17 years old, using the combination of sofosbuvir (400 mg)/ledipasvir (90 mg) in a single oral tablet (Harvoni) taken daily for 12 weeks. All subjects underwent a baseline standard 12-lead surface Electrocardiography that was repeated at 4 and 12 weeks of therapy. Electrocardiography parameters (Heart Rate, RR interval, PR interval, QRS, QT interval, corrected QT interval, QT dispersion, JT interval, corrected JT interval, JT dispersion, Tpeak-Tend interval) were compared at the 3 different time points during antiviral therapy. ResultsNo symptoms related to the cardiovascular system were reported during treatment. There were no cases of symptomatic bradycardia/syncope. Heart rate was noted to be significantly lower and RR and QT intervals were significantly longer in the baseline electrocardiography. Heart rate was significantly lower and RR interval was significantly longer in patients with higher viral load. ConclusionNo adverse cardiovascular events were observed in this group of HCV infected children and adolescents treated with sofosbuvir/ledipasvir. None of the patients developed bradyarrhythmias during treatment.

Correction to: ExomeChip-Wide Analysis of 95 626 Individuals Identifies 10 Novel Loci Associated With QT and JT Intervals.

Correction to: ExomeChip-Wide Analysis of 95 626 Individuals Identifies 10 Novel Loci Associated With QT and JT Intervals.

Impact of cardiac rehabilitation on ventricular repolarization indexes in patients with rheumatid arthritis

ObjectiveAbnormalities in ventricular repolarization (VR) parameters have been associated with sudden cardiac death (SCD) in patients with rheumatoid arthritis (RA). The benefits of cardiac rehabilitation (CR) in patients with RA are well recognized. We aimed to assess its impact on VR indexes in patients with RA. MethodsThis study included 45 patients with RA (36 female, age 58 ± 5.5 years) and 50 age- and sex-matched otherwise healthy controls. Baseline electrocardiogram (ECG) recordings were used to compare VR parameters such as maximum and minimum QT intervals, and corrected, and dispersion (QTmax, QTmin, cQTmax, cQTmin, QTd, cQTd, respectively), JT and cJT intervals, Tp-e and cTp-e intervals, and Tp-e/QT and Tp-e/cQT ratios in patients with RA and healthy individuals. The effects of 6-week CR in patients with RA were also evaluated by comparing pre- and post-CR ECGs, exercise tolerance test (MET and VO2max) and RA characteristics (C-reactive protein (CRP), Disease Activity Score 28 (DAS28) and Health Assessment Questionnaire(HAQ)). ResultsIn comparison with the healthy individuals, the patients with RA had significantly higher cQTmax and QTmin intervals, QTd, cQTd, Tp-e and cTp-e intervals, and Tp-e/QT and Tp-e/cQT ratios. At the end of CR, all VR indexes (p < 005), except QTd, were significantly decreased as did the results for CRP, DAS28, and HAQ (all p < 0.05), and MET and VO2max (p < 0.05 for both) were significantly increased in patients with RA. ConclusionsCR may provide an improvement in the majority of VR indexes which are related with ventricular arrhythmia and SCD in patients with RA. Changes in ETT parameters and RA characteristics may contribute to improvement of several VR indexes such as cQTd, cJT and Tp-e intervals at the end of CR.

Association of low-moderate urine arsenic and QT interval: Cross-sectional and longitudinal evidence from the Strong Heart Study

Epidemiologic studies suggest that chronic exposure to arsenic is related to cardiovascular disease (CVD), but the pathophysiological link remains uncertain. We evaluated the association of chronic low-moderate arsenic exposure and arsenic metabolism with baseline difference and annual change in ECG measures (QT interval, JT interval, PR interval, QRS duration, and QT dispersion) using linear mixed models in the Strong Heart Study main cohort (N = 1174, median age 55 years) and family study (N = 1695 diabetes-free, median age 36 years). At baseline, arsenic exposure was measured as the sum of inorganic and methylated species in urine (ΣAs) and arsenic metabolism was measured as the relative percentage of arsenic species. Median ΣAs and Bazett heart rate-corrected QT interval (QTc) were 8.6 μg/g creatinine and 424 ms in the main cohort and 4.3 μg/g and 414 ms in the family study, respectively. In the main cohort, a comparison of the highest to lowest ΣAs quartile (>14.4 vs. <5.2 μg/g creatinine) was associated with a 5.3 (95% CI: 1.2, 9.5) ms higher mean baseline QTc interval but no difference in annual change in QTc interval. In the family study, a comparison of the highest to lowest quartile (>7.1 vs. <2.9 μg/g creatinine) was associated with a 3.2 (95% CI: 0.6, 5.7) ms higher baseline QTc interval and a 0.6 (95% CI: 0.04, 1.2) ms larger annual increase in QTc interval. Associations with JTc interval were similar but stronger in magnitude compared to QTc interval. Arsenic exposure was largely not associated with PR interval, QRS duration or QT dispersion. Similar to arsenic exposure, a pattern of lower %MMA and higher %DMA was associated with longer baseline QTc interval in both cohorts and with a larger annual change in QTc interval in the family study. Chronic low-moderate arsenic exposure and arsenic metabolism were associated with prolonged ventricular repolarization.