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The waveform of ventricular action potential (AP) is a key determinant of the cardiac cycle, a marker of beating pathophysiology, and a target for anti‐arrhythmic drug design. The information contained in the waveform, though, is limited to the actual dynamics of the AP under consideration. By measuring quasi‐instantaneous current–voltage relationships during repolarization, I propose a three‐dimensional representation of the ventricular AP which includes potential dynamic responses that the beat can show when electrically perturbed. This representation is described in the case of a numerically reconstructed ventricular AP, but it can be, at least partially, derived in real cardiomyocytes. Simulation allows to disclose the potentialities and the limitations of the approach, that can be extended to any non‐cardiac AP. By reporting, at any AP time, the ion current available within the physiological membrane potential range at that time, the representation makes all together available: (1) refractory period, (2) thresholds for eliciting full or calcium‐driven APs, (3) threshold for all‐or‐none repolarization, (4) membrane resistance during repolarization, (5) the safety of membrane repolarization. It provides further evidence of a negative membrane resistance during the late phase of ventricular AP and a quantitative estimate of repolarization reserve (RR), key determinants of repolarization dynamics. [ABSTRACT FROM AUTHOR]

Cardiovascular disease is a major global burden and a leading cause of premature death among patients with severe mental illness. Over time, research and clinical practice have paid increased attention to the impact of psychiatric medications on cardiac repolarization. In a resource-limited setting, it is common for psychotropic medications to be initiated and maintained in an outpatient setting without baseline or follow up ECG. This study evaluated the determinants and predictors of QT abnormalities among patient taking psychotropic drugs. We conducted a cross-sectional study in a population of 150 psychiatric patients on psychotropics and 75 controls. We studied the effects of various psychotropic drugs on QT dispersion (QTd) and corrected QT interval (QTc) as well as correlation with the types and dosages of psychotropic drugs used. All the subjects had detailed clinical examination and resting electrocardiogram (ECG) at 25 mm/sec done. QTc was determined using Bazett formula and QTd was determined by subtracting shortest from longest QT in 12-lead ECG. The prevalence of prolonged QTc and QTd as well as the mean QTc and QTd were significantly higher in patients than the control group. The mean QTc was significantly higher in patient on typical antipsychotics compared to those on atypical antipsychotics. Age, heart rate and antipsychotic dose in chlorpromazine equivalent were predictors of QTc with the heart rate being the most powerful predictor among them. Psychotropic drugs use is associated with QTc and QTd prolongation with age, heart rate and antipsychotic dose as predictors of QTc. [ABSTRACT FROM AUTHOR]

Copyright of Pamukkale Medical Journal is the property of Pamukkale Journal of Medicine and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Obstructive sleep apnea (OSA) is associated with the progression of cardiovascular diseases, arrhythmias, and sudden cardiac death (SCD). However, the acute impacts of OSA and its consequences on heart function are not yet fully elucidated. We hypothesized that desaturation events acutely destabilize ventricular repolarization, and the presence of accompanying arousals magnifies this destabilization. Ventricular repolarization lability measures, comprising heart rate corrected QT (QTc), short-time-variability of QT (STVQT), and QT variability index (QTVI), were calculated before, during, and after 20,955 desaturations from lead II electrocardiography signals of 492 patients with suspected OSA (52% men). Variations in repolarization parameters were assessed during and after desaturations, both with and without accompanying arousals, and groupwise comparisons were performed based on desaturation duration and depth. Regression analyses were used to investigate the influence of confounding factors, comorbidities, and medications. The standard deviation (SD) of QT, mean QTc, SDQTc, and STVQT increased significantly (P < 0.01), whereas QTVI decreased (P < 0.01) during and after desaturations. The changes in SDQT, mean QTc, SDQTc, and QTVI were significantly amplified (P < 0.01) in the presence of accompanying arousals. Desaturation depth was an independent predictor of increased SDQTc (β = 0.405, P < 0.01), STVQT (β = 0.151, P < 0.01), and QTVI (β = 0.009, P < 0.01) during desaturation. Desaturations cause acute changes in ventricular repolarization, with deeper desaturations and accompanying arousals independently contributing to increased ventricular repolarization lability. This may partially explain the increased risk of arrhythmias and SCD in patients with OSA, especially when the OSA phenotype includes high hypoxic load and fragmented sleep. NEW & NOTEWORTHY Nocturnal desaturations are associated with increased ventricular repolarization lability. Deeper desaturations with accompanying arousals increase the magnitude of alterations, independent of confounding factors, comorbidities, and medications. Changes associated with desaturations can partially explain the increased risk of arrhythmias and sudden cardiac death in patients with OSA, especially in patients with high hypoxic load and fragmented sleep. This highlights the importance of detailed electrocardiogram analytics for patients with OSA. [ABSTRACT FROM AUTHOR]

Background: An example of a sodium-glucose cotransporter-2 (SGLT-2) inhibitor is Empagliflozin. It is a new medicine for treating type 2 diabetes mellitus (T2DM), but there is increasing interest in how empagliflozin affects the heart. This study aims to examine the impact of empagliflozin treatment on ventricular repolarization parameters in T2DM patients. Methods: T2DM patients were included in a prospective study. Measurements of ventricular repolarization parameters, including QT interval, corrected QT interval (QTc), QT dispersion (QTd), Tpeak-to-Tend interval (Tp-e), and Tpeak-to-Tend interval corrected for QTc (Tp-e/QTc), were obtained before initiating empagliflozin treatment and six months following treatment initiation. Statistical analysis was performed to assess changes in these parameters. Results: In this study, 95 patients were diagnosed with T2DM out of 177 patients. Among T2DM patients, 40 were male (42%) compared to 48% males in controls (p = 0.152). The average age of the T2DM patients was 60.2 ± 9.0 years, compared to 58.2 ± 9.2 years in the control group (p = 0.374). When comparing pre- and post-treatment measurements of parameters representing ventricular repolarization (QT 408.5 ± 22.9/378.8 ± 14.1,p < 0.001; QTc 427.0 ± 20.5/404.7 ± 13.8, p < 0.001; QTd 52.1 ± 1.2/47.8 ± 1.7, p < 0.001; Tp-e 82.3 ± 8.7/67.1 ± 5.1, p < 0.001; Tp-e/QTc 0.19 ± 0.01/0.17 ± 0.01, p < 0.001 (respectively)), statistically significant improvements were observed. A statistically significant dose-dependent decline in the magnitude of change in the QTc parameter (19.4/29.6, p = 0.038) was also observed. Conclusions: According to these results, empagliflozin may decrease the risk of potential ventricular arrhythmias. [ABSTRACT FROM AUTHOR]

The cold pressor test (CPT) elicits strong cardiovascular reactions via activation of the sympathetic nervous system (SNS), yielding subsequent increases in heart rate (HR) and blood pressure (BP). However, little is known on how exposure to the CPT affects cardiac ventricular repolarization. Twenty-eight healthy males underwent both a bilateral feet CPT and a warm water (WW) control condition on two separate days, one week apart. During pre-stress baseline and stress induction cardiovascular signals (ECG lead II, Finometer BP) were monitored continuously. Salivary cortisol and subjective stress ratings were assessed intermittently. Corrected QT (QTc) interval length and T-wave amplitude (TWA) were assessed for each heartbeat and subsequently aggregated individually over baseline and stress phases, respectively. CPT increases QTc interval length and elevates the TWA. Stress-induced changes in cardiac repolarization are only in part and weakly correlated with cardiovascular and cortisol stress-reactivity. Besides its already well-established effects on cardiovascular, endocrine, and subjective responses, CPT also impacts on cardiac repolarization by elongation of QTc interval length and elevation of TWA. CPT effects on cardiac repolarization share little variance with the other indices of stress reactivity, suggesting a potentially incremental value of this parameter for understanding psychobiological adaptation to acute CPT stress. [ABSTRACT FROM AUTHOR]

Sudden changes in pacing cycle length are frequently associated with repolarization abnormalities initiating cardiac arrhythmias, and physiologists have long been interested in measuring the likelihood of these events before their manifestation. A marker of repolarization stability has been found in the electrical restitution (ER), the response of the ventricular action potential duration to a pre- or post-mature stimulation, graphically represented by the so-called ER curve. According to the restitution hypothesis (ERH), the slope of this curve provides a quantitative discrimination between stable repolarization and proneness to arrhythmias. ER has been studied at the body surface, whole organ, and tissue level, and ERH has soon become a key reference point in theoretical, clinical, and pharmacological studies concerning arrhythmia development, and, despite criticisms, it is still widely adopted. The ionic mechanism of ER and cellular applications of ERH are covered in the present review. The main criticism on ERH concerns its dependence from the way ER is measured. Over the years, in fact, several different experimental protocols have been established to measure ER, which are also described in this article. In reviewing the state-of-the art on cardiac cellular ER, I have introduced a notation specifying protocols and graphical representations, with the aim of unifying a sometime confusing nomenclature, and providing a physiological tool, better defined in its scope and limitations, to meet the growing expectations of clinical and pharmacological research. [ABSTRACT FROM AUTHOR]

Whether sodium–glucose cotransporter-2 inhibitors (SGLT2is) reduce ventricular arrhythmias and sudden cardiac death is controversial. Ventricular repolarization heterogeneity is associated with ventricular arrhythmias; however, the effect of SGLT2is on ventricular repolarization in patients with heart failure with reduced ejection fraction (HFrEF) has not been fully investigated. We prospectively evaluated 31 HFrEF patients in sinus rhythm who were newly started on dapagliflozin 10 mg/day. Changes in QT interval, corrected QT interval (QTc), QT dispersion (QTD), corrected QTD (QTcD), T peak to T end (TpTe), TpTe/QT ratio, and TpTe/QTc ratio were evaluated at 1-year follow-up. QT interval, QTc interval, QTD, QTcD, TpTe, and TpTe/QTc ratio decreased significantly at 1-year follow-up (427.6 ± 52.6 ms vs. 415.4 ± 35.1 ms; p = 0.047, 437.1 ± 37.3 ms vs. 425.6 ± 22.7 ms; p = 0.019, 54.1 ± 11.8 ms vs. 47.6 ± 14.7 ms; p = 0.003, 56.0 ± 11.2 ms vs. 49.4 ± 12.3 ms; p = 0.004, 98.0 ± 15.6 ms vs. 85.5 ± 20.9 ms; p = 0.018, and 0.225 ± 0.035 vs. 0.202 ± 0.051; p = 0.044, respectively). TpTe/QT ratio did not change significantly (0.231 ± 0.040 vs. 0.208 ± 0.054; p = 0.052). QT interval, QTD, and TpTe were significantly reduced 1 year after dapagliflozin treatment in patients with HFrEF. The beneficial effect of dapagliflozin on the heterogeneity of ventricular repolarization may contribute to the suppression of ventricular arrhythmias. Registry informationhttps://center6.umin.ac.jp/cgi-open-bin/ctr/ctr%5fview.cgi?recptno=R000049428. Registry number: UMIN000044902. [ABSTRACT FROM AUTHOR]

Introduction: Coronavirus disease‐2019 (COVID‐19) has cardiac manifestations. Data about electrocardiogram (ECG) changes after COVID‐19 recovery is limited in hemodialysis patients. We aimed to investigate the changes in ventricular repolarization parameters after COVID‐19 recovery in hemodialysis patients. Methods: Fifty‐five hemodialysis patients who recovered from COVID‐19 infection were included. QT interval, Tp‐e interval, corrected QT (QTc), QTc dispersion, and Tp‐e dispersion values were determined on the patients' ECGs, taken before COVID‐19 and at least 1 month after recovery. The patients' data before COVID‐19 infection and after recovery were compared. Results: It was found that longest QTc (QTcmax) and QTc dispersion values after recovery were prolonged compared with pre‐infection period (427 ± 28 ms vs. 455 ± 26 ms, p = 0.000 and 39 ± 16 ms vs. 65 ± 20 ms, p = 0.000). Conclusion: In our hemodialysis patients, ventricular repolarization parameters increased after COVİD‐19 recovery. In hemodialysis patients, already predisposed to arrhythmic deaths, arrhythmia risk after COVİD‐19 recovery may become more pronounced. [ABSTRACT FROM AUTHOR]

Background: Roxadustat is a novel oral medication used to treat anemia in CKD patients. Several studies have shown that Roxadustat can alleviate anemia in CKD patients by increasing hemoglobin levels and regulating iron metabolism. We aimed to evaluate the effect of Roxadustat on ventricular repolarization in PD patients. This study may provide a new integrated approach to the assessment and treatment of CKD. Methods: The present prospective cohort study enrolled 65 CKD patients who were treated with Roxadustat and 31 CKD patients who received conventional therapy between January 2021 and June 2022. All patients were examined for ECG in the absence of clinical symptoms and compared the ECG indicators. Demographic and clinical data of all patients were collected. All data used SPSS 18.0 for statistical analyses. Results: The T peak-to-end (Tpe) of PD patients in the Roxadustat group was remarkably slower than that of patients in the conventional group. Additionally, the Tpe/QT ratio in the conventional group was significantly elevated than that in the Roxadustat group. The results of logistic regression analysis showed that Tpe (95%CI 1.191 ~ 2.141, P = 0.002) and Roxadustat treatment (95%CI 1.357 ~ 42.121, P = 0.021) were the risk factors of PD patients with high Tp-e/QT ratio. Conclusion: In summary, we found that Roxadustat could improve ventricular repolarization in peritoneal dialysis patients, which indicated a potential cardiovascular protective effect of Roxadustat. This study might provide a new integrated approach to the assessment and treatment of CKD. [ABSTRACT FROM AUTHOR]

The index of the cardio-electrophysiological balance may be used to assess ventricular arrhythmogenesis. The index of cardio-electrophysiologic al balance has been associated with malignant ventricular arrhythmias. Ventricular arrhythmias caused by drugs have been connected to a new risk measure called the index of cardio-electrophysiological balance the interval from the beginning of the QRS complex to the end of the T wave (QT) interval divided by the deflections in an electrocardiogram (EKG) tracing that represent the ventricular activity of the heart (QRS) duration), which was recently tested in an animal model. The cardiac wavelength index of cardio-electrophysiological balance was considered to equal the effective refractory period multiplied by the conduction velocity. An increase or decrease in the index of cardio-electrophysiological balance could suggest an increased risk of ventricular tachycardia/fibrillation induced by torsades de pointes or non-torsades de pointes. The index of cardio-electrophysio logical balance is one of the most often used methods for measuring the cardiac waveform. Because it is noninvasive and simple to measure, index of cardio-electrophysiological balance may be used to predict ventricular arrhythmia risk. [ABSTRACT FROM AUTHOR]

Copyright of Kafkas Journal of Medical Sciences / Kafkas Tıp Bilimleri Dergisi is the property of Kafkas Journal of Medical Sciences, Kafkas Tip Bilimleri Dergisi and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Background: Cardiac complications due to anthracycline treatment may become evident several years after chemotherapy and are recognized as a serious cause of morbidity and mortality in cancer patients or childhood cancer survivors. Objectives: We analyzed ventricular repolarization parameters in electrocardiography for pediatric acute lymphoblastic leukemia patients during chemotherapy and in long-term follow-up. To establish the reference values of ventricular repolarization parameters in children, we retrospectively summarized the Tpe interval, QT interval, QTc interval, and Tpe/QT ratio in healthy Japanese children. Methods: Electrocardiography data recorded from students in 1st and 7th grades were randomly selected from a database maintained by the school-based screening system in the Oita city cohort, Japan. Subsequently, chronological data of the Tpe/QT ratio in 17 pediatric patients with acute lymphoblastic leukemia were analyzed over time. Results: The mean ± standard deviation of the Tpe interval in 1st and 7th graders was 70 ± 7 and 78 ± 17 ms, respectively, while the mean ± standard deviation of the Tpe/QT ratio was 0.21 ± 0.02 and 0.22 ± 0.02 ms, respectively. During the intensive phase of treatment, the Tpe/QT ratios of 3 high-risk patients among the 17 patients with acute lymphoblastic leukemia exceeded the upper limit. Conclusion: The Tpe/QT ratio has a potential clinical application in predicting the risk of long-term ventricular arrhythmia of cancer patients or childhood cancer survivors from childhood to adulthood. [ABSTRACT FROM AUTHOR]

Objectives: Atrial and ventricular arrhythmias can be observed in children after transcatheter atrial septal defect (ASD) closure. This study investigated ventricular repolarization parameters, which are considered to indicate an increased risk of arrhythmias in patients with transcatheter ASD closure. Materials and Methods: The study included 225 patients aged 0-18 years who underwent transcatheter ASD closure at a tertiary medical school university hospital between 2005 and 2020. Heart rate, Pmax, Pmin, Pdispersion, QTmax, QTmin, QTdispersion, QTcmax, QTcmin, QTcdispersion, Tp-e interval, Tp-e/QT, and Tp-e/QTc values were calculated electronically in 12-lead electrocardiographies (ECGs) taken before the procedure and at 24 h, 1, 6, and 12 months after the procedure. Results: Of the 225 patients who underwent transcatheter closure, 144 (64%) were female and 81 (36%) were male. The mean age at angiography was 9.2±4.1 years, and the mean weight was 29.6±14.3 kg. Statistically significant differences were observed in the Tp-e interval and Tp-e/QTc values measured before transcatheter closure compared with those measured after closure (p=0.028; p=0.032), while no significant differences were found between the two groups in terms of other ECG parameters. A negative correlation was found between P and QT dispersion measured before transcatheter closure and after closure (r=-0.408; p=0.041). Conclusion: Changes in ventricular repolarization parameters were observed in children after transcatheter ASD closure. QT dispersion, Tp-e interval, and Tp-e/QTc ratios, which are sensitive indicators of ventricular arrhythmias, were significant in the post-closure group. Therefore, careful evaluation of these parameters, which are markers for predicting ventricular arrhythmias before and after ASD closure, will serve as a warning for potentially fatal arrhythmias of vital importance in the long term. Each patient undergoing transcatheter ASD closure should be monitored with a 12-lead ECG for atrial and ventricular depolarization and repolarization parameters, and annual 24-hour Holter ECG monitoring should be performed to detect arrhythmias. [ABSTRACT FROM AUTHOR]

Background and Objectives: Smokeless tobacco (ST) use has recently become an alternative to cigarettes, and it has been concluded that ST is at least as harmful as cigarettes. ST use is thought to play a role in the pathogenesis of arrhythmia by affecting ventricular repolarization. In this study, we aimed to examine the relationships of Maras powder (MP), one of the ST varieties, with epicardial fat thickness and new ventricular repolarization parameters, which have not previously been described. Materials and Methods: A total of 289 male individuals were included in this study between April 2022 and December 2022. Three groups, 97 MP users, 97 smokers, and 95 healthy (non-tobacco), were compared according to electrocardiographic and echocardiographic data. Electrocardiograms (ECG) were evaluated with a magnifying glass by two expert cardiologists at a speed of 50 m/s. Epicardial fat thickness (EFT) was measured by echocardiography in the parasternal short- and long-axis images. A model was created with variables that could affect epicardial fat thickness. Results: There were no differences between the groups regarding body mass index (p = 0.672) and age (p = 0.306). The low-density lipoprotein value was higher in the MP user group (p = 0.003). The QT interval was similar between groups. Tp-e (p = 0.022), cTp-e (p = 0.013), Tp-e/QT (p =0.005), and Tp-e/cQT (p = 0.012) were higher in the MP user group. While the Tp-e/QT ratio did not affect EFT, MP predicted the epicardial fat thickness (p < 0.001, B = 0.522, 95%CI 0.272–0.773). Conclusions: Maras powder may play a role in ventricular arrhythmia by affecting EFT and causing an increase in the Tp-e interval. [ABSTRACT FROM AUTHOR]

Electronic cigarettes are often used for smoking cessation as a harm reduction strategy, but studies comparing risks of electronic cigarettes (ECs) and tobacco cigarettes (TCs) are scarce. Ventricular repolarization in people who smoke TCs is abnormal. Baseline repolarization was compared among nonusers (people who do not use TCs or ECs) and people who use ECs or TCs. The acute effects of ECs and TCs on metrics of ventricular repolarization were then compared in people who chronically smoke. A total of 110 participants (59 female), including 35 people (21 females) in the TC cohort, 34 people (17 females) in the EC cohort, and 41 people (21 females) in the nonuser cohort, were included. None of the primary outcomes, Tpeak-end (Tp-e), Tp-e/QT, and Tp-e/QTc, were different among the three cohorts at supine baseline, even when adjusted for sex. When compared with the control exposure standing after acutely using the EC but not the TC, significantly prolonged all three primary indices of ventricular repolarization in people who smoke TCs. The major new finding in this study is that in people who smoke TCs, using an EC compared with a TC significantly prolongs ventricular repolarization. Furthermore, in our subgroup analysis by sex, this adverse effect on repolarization is found only in male, not female, smokers. In summary, chronic TC smoking is the most prevalent, modifiable risk factor for cardiovascular death, including sudden cardiac death. If used for smoking cessation, ECs should only be used in the short term since they too carry their own risks; this risk appears to be greatest in males compared with females who smoke. NEW & NOTEWORTHY The major new finding in this study is that in people who smoke tobacco cigarettes, using an electronic cigarette but not a tobacco cigarette acutely and significantly prolongs several metrics of ventricular repolarization, including Tpeak-Tend, Tpeak-Tend/QT, and Tpeak-Tend/QTc. Furthermore, in our subgroup analysis by sex, this adverse effect on repolarization is found only in male, not female, smokers. [ABSTRACT FROM AUTHOR]

Background and Objectives: This study aimed to examine the ventricular repolarization (VR) disturbances of patients operated on for acute spontaneous Achilles tendon ruptures (ATRs), by comparing them with a healthy individual control group. Materials and Methods: Between June 2014 and July 2020, a total of 29 patients (28 males, 1 female; mean age: 40 ± 9.78 years; range, 21–66 years) who presented to the emergency department within the first three weeks of injury, and were diagnosed with acute spontaneous ATRs and treated with an open Krackow suture technique, were retrospectively analyzed. Fifty-two healthy individuals (47 males, 5 females; mean age: 39 ± 11.45 years; range, 21–66 years) were recruited as a control group from the cardiology outpatient clinic. Clinical data (demographic features and laboratory parameters (serum glucose, creatinine, hemoglobin, white blood cell count, and lipid profile)) and electrocardiograms (ECGs) were collected from medical records. ECGs were evaluated for heart rate and VR parameters of QRS width, QTc interval, cQTd interval, Tp-e interval, and Tp-e/QT ratio. The clinical data and these ECG parameters were compared between groups. Results: There was no statistically significant difference between groups, regarding clinical data (all p < 0.05). Among ECG parameters, heart rate, QRS width, QTc interval, and cQTd interval were similar between groups (all p < 0.05). There were two important statistically significant findings of this research: The mean Tp-e interval was longer (ATR group: 72.4 ± 24.7, control group: 58.8 ± 14.5, p: 0.01), and the Tp-e/QT ratio was higher (ATR group: 0.2 ± 0.1, control group: 0.16 ± 0.4, p: 0.027) in the ATR group. Conclusions: According to the ventricular repolarization disturbances found in this study, patients with ATR may be at a higher risk of ventricular arrhythmia than healthy people. As a result, ATR patients should be assessed for ventricular arrhythmia risk by an expert cardiologist. [ABSTRACT FROM AUTHOR]

Objectives: T wave's peak and end interval (Tp-e), Tp-e/QT ratio and Tp-e/QTc ratio are novel markers of ventricular repolarization and are associated with ventricular arrhythmias. Increased ventricular arrhythmia incidence is reported in patients with acromegaly. The purpose of this study is to evaluate ventricular repolarization using the Tp-e interval, Tp-e/QT ratio, and Tp-e/QTc ratio in patients with acromegaly. Methods: Thirty-five patients with acromegaly were included in the study. The control group was consisted of forty-one subjects without acromegaly that having similar age, sex ratio and comorbidities. The Tp-e interval, Tp-e/QT ratio, Tp-e/QTc ratio, and other ventricular repolarization parameters of all patients were evaluated using electrocardiography. Results: Tp-e interval, Tp-e/QT ratio and Tp-e/QTc ratio were significantly prolonged in patients with acromegaly compared to the control group. Furthermore, Tp-e interval, Tp-e/QT ratio, and Tp-e/QTc ratio showed a significant correlation with plasma GH levels and LVMI values. Conclusions: Our study revealed that Tp-e interval, Tp-e/QT ratio, and Tp-e/QTc ratio are prolonged in patients with acromegaly. We believe that the Tp-e interval, Tp-e/QT ratio, and Tpe/QTc ratio can be used in the evaluation of increased cardiovascular risk in patients with acromegaly. [ABSTRACT FROM AUTHOR]

Late sodium current (INa,late) is an important inward current contributing to the plateau phase of the action potential (AP) in the mammalian heart. Although INa,late is considered as a possible target for antiarrhythmic agents, several aspects of this current remained hidden. In this work, the profile of INa,late, together with the respective conductance changes (GNa,late), were studied and compared in rabbit, canine, and guinea pig ventricular myocytes using the action potential voltage clamp (APVC) technique. In canine and rabbit myocytes, the density of INa,late was relatively stable during the plateau and decreased only along terminal repolarization of the AP, while GNa,late decreased monotonically. In contrast, INa,late increased monotonically, while GNa,late remained largely unchanged during the AP in guinea pig. The estimated slow inactivation of Na+ channels was much slower in guinea pig than in canine or rabbit myocytes. The characteristics of canine INa,late and GNa,late were not altered by using command APs recorded from rabbit or guinea pig myocytes, indicating that the different shapes of the current profiles are related to genuine interspecies differences in the gating of INa,late. Both INa,late and GNa,late decreased in canine myocytes when the intracellular Ca2+ concentration was reduced either by the extracellular application of 1 µM nisoldipine or by the intracellular application of BAPTA. Finally, a comparison of the INa,late and GNa,late profiles induced by the toxin of Anemonia sulcata (ATX-II) in canine and guinea pig myocytes revealed profound differences between the two species: in dog, the ATX-II induced INa,late and GNa,late showed kinetics similar to those observed with the native current, while in guinea pig, the ATX-II induced GNa,late increased during the AP. Our results show that there are notable interspecies differences in the gating kinetics of INa,late that cannot be explained by differences in AP morphology. These differences must be considered when interpreting the INa,late results obtained in guinea pig. [ABSTRACT FROM AUTHOR]

Aims To evaluate the relationship between spatial heterogeneity of electrocardiographic repolarization and spatial heterogeneity of atrial depolarization with arrhythmic substrate represented by left ventricular fibrosis. Methods and results We assessed the associations of T- and P-wave morphology parameters analysed from the standard 12-lead electrocardiograms with left ventricular fibrosis in 378 victims of unexpected sudden cardiac death (SCD) who underwent medico-legal autopsy. Based on autopsy findings, the SCD victims were categorized into four different groups according to different stages of severity of left ventricular fibrosis (substantial fibrosis, moderate patchy fibrosis, scattered mild fibrosis, no fibrosis). T-wave and P-wave area dispersion (TWAd: 0.0841 ± 0.496, 0.170 ± 0.492, 0.302 ± 404, 0.296 ± 0.476, P = 0.008; PWAd: 0.574 ± 0.384, 0.561 ± 0.367, 0.654 ± 0.281, 0.717 ± 0.257, P = 0.011, respectively; low values abnormal), non-dipolar components of T-wave and P-wave morphology (T_NonDipolarABS: 0.0496 ± 0.0377, 0.0571 ± 0.0487, 0.0432 ± 0.0476, 0.0380 ± 0.0377, P = 0.027; P_NonDipolarABS: 0.0132 ± 0.0164, 0.0130 ± 0.0135, 0.0092 ± 0.0117, 0.0069 ± 0.00472, P = 0.005, respectively, high values abnormal), T-wave morphology dispersion (TMD: 45.9 ± 28.3, 40.5 ± 25.8, 35.5 ± 24.9, 33.0 ± 24.6, P = 0.030, respectively, high values abnormal), and P-wave heterogeneity (PWH: 20.0 ± 9.44, 19.7 ± 8.87, 17.9 ± 9.78, 15.4 ± 4.60, P = 0.019, respectively, high values abnormal) differed significantly between the groups with different stages of left ventricular fibrosis. After adjustment with heart weight, T_NonDipolarABS [standardized β (sβ) = 0.131, P = 0.014], PWAd (sβ = −0.161, P = 0.003), P_NonDipolarABS (sβ = 0.174, P = 0.001), and PWH (sβ = 0.128, P = 0.015) retained independent association, and TWAd (sβ = −0.091, P = 0.074) and TMD (sβ = 0.097, P = 0.063) tended to retain their association with the degree of myocardial fibrosis. Conclusion Our findings suggest that abnormal values of T- and P-wave morphology are associated with arrhythmic substrate represented by ventricular fibrosis partly explaining the mechanism behind their prognostic significance. [ABSTRACT FROM AUTHOR]

Background: Sleep is fragmented by brief arousals, and excessive arousal burden has been linked to increased cardiovascular (CV) risk, but mechanisms are poorly understood.Research Question: Do arousals trigger cardiac ventricular repolarization lability that may predispose people to long-term cardiovascular mortality?Study Design and Methods: This study analyzed 407,541 arousals in the overnight polysomnograms of 2,558 older men in the Osteoporotic Fractures in Men sleep study. QT and RR intervals were measured beat-to-beat starting 15 s prior to arousal onset until 15 s past onset. Ventricular repolarization lability was quantified by using the QT variability index (QTVi).Results: During 10.1 ± 2.5 years of follow-up, 1,000 men died of any cause, including 348 CV deaths. During arousals, QT and RR variability increased on average by 5 and 55 ms, respectively, resulting in a paradoxical transient decrease in QTVi from 0.07 ± 1.68 to -1.00 ± 1.68. Multivariable Cox proportional hazards analysis adjusted for age, BMI, cardiovascular and respiratory risk factors, sleep-disordered breathing and arousal, diabetes, and Parkinson disease indicated that excessive QTVi during arousal was independently associated with all-cause and CV mortality (all-cause hazard ratio, 1.20 [95% CI, 1.04-1.38; P = .012]; CV hazard ratio, 1.29 [95% CI, 1.01 -1.65; P = .043]).Interpretation: Arousals affect ventricular repolarization. A disproportionate increase in QT variability during arousal is associated with an increased all-cause and CV mortality and may reflect ventricular repolarization maladaptation to the arousal stimulus. Whether arousal-related QTVi can be used for more tailored risk stratification warrants further study, including evaluating whether arousal suppression attenuates ventricular repolarization lability and reduces subsequent mortality.Clinical Trial Registration: ClinicalTrials.gov; No.: NCT00070681; URL: www.Clinicaltrials: gov. [ABSTRACT FROM AUTHOR]

Copyright of Online Turkish Journal of Health Sciences (OTJHS) / Online Türk Sağlık Bilimleri Dergisi is the property of Oguz KARABAY and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Objective: T-wave alternans (TWA) manifests as beat-to-beat fluctuations of T-wave morphology on the electrocardiogram (ECG), with physiological bases not fully understood. Using a biophysical model of the ECG, we demonstrate and give explicit relations that TWA depends on the i) spatial covariance between myocytes' repolarization time and alternans; and ii) global alternans (common to every myocyte). Methods: We quantified the spatial covariance and global alternans by means of two new metrics, $\mathcal {R}$ index and $\bar{\delta }$ , respectively. They were validated on both synthetic and real signals. Computerized simulations were generated using a biophysical model linking the action potentials with the surface ECG. Then, the metrics were computed in STAFF-III dataset, containing ECGs from patients who underwent coronary angioplasty with prolonged balloon inflations, and the time courses of the metrics were analyzed together with TWA measured on the surface ECG. Results: The metrics properly estimated the spatial covariance and global alternans in the synthetic data. In the STAFF-III dataset, the $\mathcal {R}$ index progressively increased from baseline to the fourth minute of inflation (median $\Delta \mathcal {R}=0.81$ ms; p $< $ 0.05), whereas $\bar{\delta }$ was mostly unaltered during the intervention ($\bar{\delta }=0$ ms). Conclusion: We reported, for the first time, that TWA is significantly driven by the myocyte's spatial covariance between their repolarization times and alternans, and not by global alternans, when TWA is generated by regional ischemia. Significance: The metrics may reveal new complementary insights into the mechanisms underlying TWA. [ABSTRACT FROM AUTHOR]

Approximately 30% to 70% of patients with cirrhosis have QT interval prolongation. In patients without cirrhosis, QT prolongation is associated with an increased risk of ventricular arrhythmias, such as torsade de pointes (TdP). In cirrhotic patients, there is likely a significant association between the corrected QT (QTc) interval and the severity of liver disease, and possibly with increased mortality. We present a stepwise overview of the pathophysiology and management of acquired long QT syndrome in cirrhosis. The QT interval is mainly determined by ventricular repolarization. To compare the QT interval in time it should be corrected for heart rate (QTc), preferably by the Fridericia method. A QTc interval >450 ms in males and >470 ms in females is considered prolonged. The pathophysiological mechanism remains incompletely understood, but may include metabolic, autonomic or hormonal imbalances, cirrhotic heart failure and/or genetic predisposition. Additional external risk factors for QTc prolongation include medication (IKr blockade and altered cytochrome P450 activity), bradycardia, electrolyte abnormalities, underlying cardiomyopathy and acute illness. In patients with cirrhosis, multiple hits and cardiac-hepatic interactions are often required to sufficiently erode the repolarization reserve before long QT syndrome and TdP can occur. While some risk factors are unavoidable, overall risk can be mitigated by electrocardiogram monitoring and avoiding drug interactions and electrolyte and acidbase disturbances. In cirrhotic patients with prolonged QTc interval, a joint effort by cardiologists and hepatologists may be useful and significantly improve the clinical course and outcome. [ABSTRACT FROM AUTHOR]

Objective: The clinical significance of QT interval adaptation to heart rate changes has been poorly investigated in atrial fibrillation (AF), since QT delineation in the presence of f-waves is challenging. The objective of the present study is to investigate new techniques for QT adaptation estimation in permanent AF. Methods: A multilead strategy based on periodic component analysis, to emphasize T-wave periodicity, is proposed for QT delineation. QT adaptation is modeled by a linear, time-invariant filter, which describes the dependence between the current QT interval and the preceding RR intervals, followed by a memoryless, nonlinear, function. The QT adaptation time lag is determined from the estimated impulse response. Results: Using simulated ECGs in permanent AF, the transformed lead was found to offer more accurate QT delineation and time lag estimation than did the original ECG leads for a wide range of f-wave amplitudes. In a population with chronic heart failure and permanent AF, the time lag estimated from the transformed lead was found to have the strongest, statistically significant association with sudden cardiac death (SCD) (hazard ratio = 3.49). Conclusions: Periodic component analysis provides more accurate QT delineation and improves time lag estimation in AF. A prolonged QT adaptation time lag is associated with a high risk for SCD. Significance: SCD risk markers originally developed for sinus rhythm can also be used in AF, provided that T-wave periodicity is emphasized. The time lag is a potentially useful biomarker for identifying patients at risk for SCD, guiding clinicians in adopting effective therapeutic decisions. [ABSTRACT FROM AUTHOR]

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The article is focused on the evaluation of the electrical activity of the heart in rats during ventricular repolarization after a single bout of forced treadmill running until exhaustion. Electrophysiological properties of the myocardium were studied by conventional ECG and body surface potential mapping. Cardiac potentials were registered in zoletil-anesthetized rats 3–5 days before (baseline) and 5, 10, 20 and 30 min after exhaustive treadmill running. Compared with baseline, an increase in the duration of the QTII, JTII and Tpeak–TendII intervals, an earlier onset and a later completion, as well as an increase in the duration of ventricular repolarization on body surface equipotential maps (BSPMs) were revealed in rats 5 min after exhaustive exercise. Ten min following treadmill running to exhaustion, the temporal parameters of the heart electrical activity returned to pre-exercise values. Changes in the amplitude characteristics of both ECGII (ST segment depression, a decrease in the T-wave amplitude) and BSPMs (a decrease in the maximum amplitudes of positive and negative extrema during ventricular repolarization) were showed after 5–10 min and persisted up to 20–30 min after running to exhaustion. A positive correlation was found between changes in the maximum amplitude of negative extremum of BSPMs and changes in the amplitude of the TII-wave in the analyzed time periods after exhausting exercise. It is assumed that the observed changes in the electrical properties of the heart in rats during ventricular repolarization after forced treadmill running were due to ischemic myocardial damage induced by exhaustive physical exercise. [ABSTRACT FROM AUTHOR]

Background: The Tpeak‐end(Tp‐e) has not been compared in all 12 ECG leads in healthy adults to determine if the Tp‐e varies across leads. If there is variation, it remains uncertain, which lead(s) are preferred for recording in order to capture the maximal Tp‐e value. Objective: The purpose of the current study was to determine the optimal leads, if any, to capture the maximal Tp‐e interval in healthy young adults. Methods: In 88 healthy adults (ages 21–38 years), including derivation (n = 21), validation (n = 20), and smoker/vaper (n = 47) cohorts, the Tp‐e was measured using commercial computer software (LabChart Pro 8 with ECG module, ADInstruments) in all 12 leads at rest and following a provocative maneuver, abrupt standing. Tp‐e was compared to determine which lead(s) most frequently captured the maximal Tp‐e interval. Results: In the rest and abrupt standing positions, the Tp‐e was not uniform among the 12 leads; the maximal Tp‐e was most frequently captured in the precordial leads. At rest, grouping leads V2–V4 resulted in detection of the maximum Tp‐e in 85.7% of participants (CI 70.7, 99.9%) versus all other leads (p <.001). Upon abrupt standing, grouping leads V2‐V6 together, resulted in detection of the maximum Tp‐e 85.0% of participants (CI 69.4, 99.9% versus all other leads; p <.001). These findings were confirmed in the validation cohort, and extended to the smoking/vaping cohort. Conclusion: If only a subset of ECG leads will be recorded or analyzed for the Tp‐e interval, selection of the precordial leads is preferred since these leads are most likely to capture the maximal Tp‐e value. [ABSTRACT FROM AUTHOR]

Background: Obesity, a rapidly increasing global health problem in all age groups, is accepted as the basis for many chronic diseases through insulin resistance mechanism. This study aimed to examine whether insulin resistance and other comorbidities of obesity have an effect on the cardiac conduction system. Methods: The study included 50 obese and 47 healthy individuals aged 6-18 years. ECGs of all cases were taken; ECG waves and intervals were measured manually. Results: Of the obese group, 19 were boys (38%) and 31 were girls (62%), 27 were children (54%) and 23 were adolescents (46%), their ages were 11.3 ± 3.5 years. These particular characteristics were similar compared to the control group. However, in the obese group, the ECG parameters QTc (p = 0.001), QTd (p < 0.001), QTdc (p < 0.001), JTc (p < 0.001), Tp-e (p < 0.001), Tp-e/QT (p < 0.001), Tp-e/QTc (p < 0.001), Tp-e/JT (p < 0.001), and Tp-e/JTc (p < 0.001) were significantly longer. Twenty-five obese subjects (50%) had insulin resistance, when ECG parameters are compared to those without it, only JTc was significantly longer (332.3 ± 16.5 vs 321.7 ± 17.7 ms, p = 0.033). JTc duration mostly affected JT (p < 0.001) and QTc (p < 0.001). The 327 ms cut-off value of JTc indicated insulin resistance in the obese patients (p = 0.044) (sensitivity 60%, specificity 60%). Conclusion: Insulin resistance and other comorbidities of obesity may cause ventricular repolarization abnormalities at an early age. JTc, an ECG parameter, can be a guide in assessing ventricular repolarization abnormality and the risk of arrhythmia in these patients. [ABSTRACT FROM AUTHOR]

The global prevalence of vitamin D deficiency is more than 20%, and the main causes include insufficient intake, reduced absorption, abnormal metabolism, or resistance to its effects. The levels of serum vitamin D appear to influence cardiovascular risk, and the mechanism involved is linked to the transient outward current and the ultrarapid delayed rectifier K+ current densities, activated through the nuclear vitamin D receptor and Akt pathway. A significant number of studies have correlated vitamin D deficiency with an increased risk of developing cardiac arrhythmias and sudden cardiac death. For this reason, the purpose of this review is to analyze the relation between vitamin D deficiency and the pathogenesis of cardiac arrhythmias. Atrial fibrillation, increased QT interval, and QT dispersion were the most common findings associated with vitamin D deficiency. Due to the heterogeneity among existing studies, further research is necessary to confirm the existing data and to analyze its relationship with other types of arrhythmias. [ABSTRACT FROM AUTHOR]

Cardiac electrophysiological studies demonstrate that restricting the feeding of mice to the light cycle (time restricted feeding or TRF) causes a pronounced change in heart rate and ventricular repolarization as measured by the RR- and QT-interval, respectively. TRF slows heart rate and shifts the peak (acrophase) of the day/night rhythms in the RR- and QT-intervals from the light to the dark cycle. This study tested the hypothesis that these changes in cardiac electrophysiology are driven by the cardiomyocyte circadian clock mechanism. We determined the impact that TRF had on RR- and QT-intervals in control mice or mice that had the cardiomyocyte circadian clock mechanism disrupted by inducing the deletion of Bmal1 in adult cardiomyocytes (iCSΔBmal1−/− mice). In control and iCSΔBmal1−/− mice, TRF increased the RR-intervals measured during the dark cycle and shifted the acrophase of the day/night rhythm in the RR-interval from the light to the dark cycle. Compared to control mice, TRF caused a larger prolongation of the QT-interval measured from iCSΔBmal1−/− mice during the dark cycle. The larger QT-interval prolongation in the iCSΔBmal1−/− mice caused an increased mean and amplitude in the day/night rhythm of the QT-interval. There was not a difference in the TRF-induced shift in the day/night rhythm of the QT-interval measured from control or iCSΔBmal1−/− mice. We conclude that the cardiomyocyte circadian clock does not drive the changes in heart rate or ventricular repolarization with TRF. However, TRF unmasks an important role for the cardiomyocyte circadian clock to prevent excessive QT-interval prolongation, especially at slow heart rates. [ABSTRACT FROM AUTHOR]

Introduction: His‐bundle pacing (HBP) and left‐bundle‐area pacing (LBAP) are conduction system pacing (CSP) modalities increasingly used as alternatives to conventional biventricular pacing (BiVP). While effects of CSP on ventricular depolarization have been reported, effects on ventricular repolarization have not. Methods: QRS duration (QRSd) and validated ECG parameters of ventricular repolarization associated with arrhythmic risk (T‐peak‐to‐T‐endTransmural, T‐peak‐to‐T‐endTotal, T‐peak dispersion, QTc, QTc dispersion) were analyzed post‐implant in 107 patients: 60 with CSP (HBP: n = 35, LBAP: n = 25) and 47 with BiVP. T‐wave memory resolution and QTc shortening were analyzed on ECGs obtained ≥25 days post‐implant. Twenty blinded measurements were obtained by both authors to assess Interobserver variability. Results: Although QRSd was shorter with HBP versus LBAP (119 ± 7 ms vs. 132 ± 9 ms, p =.02), there were no significant differences in any repolarization parameters between these methods of CSP. However, when comparing CSP (HBP + LBAP) to BiVP, both QRSd (125 ± 5 ms vs. 147 ± 7 ms, p <.0001) and repolarization parameters (T‐peak‐to‐T‐endTransmural: 83 ± 5 ms vs. 107 ± 8 ms; T‐peak‐to‐T‐endTotal: 110 ± 7 ms vs. 137 ± 10 ms; QTc: 470 ± 12 ms vs. 506 ± 12 ms; all p ≤.0001) were significantly shorter with CSP. Improved T‐peak‐to‐T‐end values were unrelated to pre‐implant QRSd or LV function. Interobserver variability was 4.6 ± 1.9 ms. Frontal QRS‐T angle narrowing (132° to 104°, p =.001) and QTc shortening (483 ± 13 ms to 464 ± 12 ms, p =.008) were seen only with CSP. Conclusions: In addition to improved depolarization, CSP reduced repolarization heterogeneity and provided greater T‐wave memory resolution as compared to BiVP. Both modalities of CSP (HBP + LBAP) resulted in comparably reduced repolarization heterogeneity regardless of baseline QRSd and LV function. These observations may confer lower arrhythmogenic risk and warrant further study. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Practical Electrocardiology is the property of Journal of Practical Electrocardiology Editorial Board and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Background: Arrhythmias can be seen as a sign of cardiac autonomic neuropathy in type 1 diabetes mellitus. We aimed to evaluate pulmonary artery pressure, ventricular depolarization and repolarization variability in children with type 1 diabetes mellitus. Methods: We investigated 78 children with type 1 diabetes mellitus (mean age 11.6 ± 3.6 years) and 68 age-gender matched healthy children as control group. All type 1 diabetes mellitus patients were divided into three subgroups according to glycated hemoglobin (HbA1c) levels and the duration of disease. Electrocardiogram and transthoracic echocardiograms were performed on both groups. Results: In patients with type 1 diabetes mellitus, there was an elongation in P, Pd, PR, QTc, QTd, QTcd, JT, JTc, JTd, Tp-Te and Tp-Te/QT, Tp-Te/QTc, Tp-Te/JT, Tp-Te/JTc ratios were higher (P < 0.05). In patients with type 1 diabetes mellitus, pulmonary artery pressure was higher than control group (P = 0.001). Prolongation of QTc, thickness of left ventricle end-diastolic diameter and left ventricle posterior wall diameter were higher in the HbA1c ≥9% subgroup. When adjusted for age there was no significant correlation between left ventricle parameters and HbA1c. Conclusions: Atrial conduction delay and impairment of ventricular repolarization were significantly high and there was a predisposition for the development of pulmonary artery hypertension in children with type 1 diabetes mellitus. Poor glycemic control was not a risk factor for propensity of left ventricle hypertrophy and left ventricle dysfunction. [ABSTRACT FROM AUTHOR]

Copyright of Bagcilar Medical Bulletin / Bağcılar Tıp Bülteni is the property of Galenos Yayinevi Tic. LTD. STI and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Herz is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

OBJECTIVES: Low levels of vitamin D are known to increase cardiovascular mortality due to different risks. We aimed to examine whether low vitamin D levels in children and adolescents cause ventricular repolarization changes. METHODS: Sixtyseven healthy cases aged between 3.5 and 17 years were included. According to levels of vitamin D, cases were grouped as sufficient (n=44), insufficient (n=13) and deficiency (n=10). Ventricular repolarization parameters were measured manually. RESULTS: Levels of vitamin D were different for cases with insufficiency and deficiency compared to sufficiency ones (102±54.9 vs 24.4±7 ng/ml, p<0.001 and 102±54.9 vs 16.6±8.3 ng/ml, respectively, p<0.001). In the insufficient group the following parameters were different from sufficient group: QTmean (357.8±25.3 vs 332±29.9 ms, p=0.012), JTc (310.8±20.2 vs 331.6±21 ms, p=0.005) and Tpe/QT (0.2±0.02 vs 0.22±0.02, p=0.02). It was found that the level of serum vitamin D correlated with JTc (r=-0.37, p=0.002), Tp-e (r=-0.29, p=0.015) and Tp-e/QT (r=-0.24, p=0.047). In the linear regression analysis, it was found that dropping level of vitamin D below normal was an independent risk factor for prolonged duration of JTc (p=0.015). CONCLUSIONS: Decline in vitamin D levels causes ventricular repolarization anomaly. As the decrease in vitamin D levels deepens, repolarization times become longer. These results could indicate that decrease in vitamin D levels can increase sensitivity to ventricular arrhythmias. [ABSTRACT FROM AUTHOR]

Background: Tp-e interval, Tp-e/QT ratio and Tp-e/QTc ratio are electrocardiographic markers and indices of ventricular arrhythmogenic events. We aimed to investigate ventricular repolarization in normal weight, overweight, obese and morbidly obese individuals by using ECG parameters including the above markers. Methods: A total of 310 obese patients with various cardiac complaints, who were admitted to our outpatient clinic between May 2020 and January 2021, were prospectively included in the study. Using the World Health Organization (WHO) body mass index (BMI) classification, patients were divided into four groups: normal weight (18.5–24.9 kg/m2, n = 48), overweight (25–29.9 kg/m2, n = 98), obese (30–39.9 kg/m2, n = 119), and morbidly obese (>40 kg/m2, n = 45). Results: The morbidly obese and normal groups were younger in age than the other two groups. The Tp-e interval values for Groups I–IV were 72.1 ± 6.9, 73.1 ± 6.2, 75.7 ± 7.3 and 81.1 ± 6.9, respectively, and significantly different (P <.001). We found that age, BMI, systolic blood pressure (BP) and diastolic BP were independent predictors of a prolonged Tp-e interval. Conclusions: The principal finding of our study was the gradual increase in Tp-e interval, Tp-e/QT ratio and Tp-e/QTc ratio starting from the overweight stage and these parameters gradually increase in obese and morbidly obese patients. Additionally, systolic and diastolic blood pressure predicted Tp-e interval, Tp-e/QT ratio and Tp-e/QTc ratio. [ABSTRACT FROM AUTHOR]

The frontal plane QRS-T [f(QRS-T)] angle is an easy marker of myocardial repolarization and was associated with adverse cardiovascular outcomes like prehypertension (PHT). This study was aimed to investigate to evaluate the f(QRS-T) angle in patients with PHT. We measured f(QRS-T) angle of 70 subjects with PHT, 109 patients with hypertension (HT), and 102 normotensive healthy volunteers. The f(QRS-T) angle was calculated from 12-lead electrocardiography. The f(QRS-T) angle was significantly higher in the HT and PHT groups as compared to the control group, but there was no significant difference in the f(QRS-T) angle between the HT and PHT groups. The f(QRS-T) angle was significantly and positively correlated with age, systolic blood pressure (BP) in 24 hours, average BP in 24 hours, pulse pressure in 24 hours, hemoglobin, QT dispersion, TpE distance while was negatively correlated with left ventricular ejection fraction. In multivariable analysis, we showed that systolic BP, average BP in 24 hours, pulse pressure in 24 hours, hemoglobin, QT dispersion, Tpe distance were independent predictors of higher f(QRS-T) angle. The f(QRS-T) angle, a noninvasive measurement analyzing the dysfunction in cardiac conduction system, was increased in subjects with PHT as compared to normotensives, and the subjects with PHT had f(QRS-T) angle as higher as patients with HT did. Our findings are supportive for the hypothesis that disturbances in ventricular repolarization is present in an early stage of essential hypertension. [ABSTRACT FROM AUTHOR]

Background/Aim: Diabetes Mellitus (DM), considered the equivalent of coronary artery disease, is one cause of ventricular repolarization (VR) dispersion. Retinopathy is one of the vascular consequences of diabetes. The association between myocardial repolarization dispersion and diabetic retinopathy is not fully elucidated. We aimed to evaluate ventricular repolarization using Tp-e interval and corrected (c) Tpe/QT ratio in DM patients with and without retinopathy. Methods: A total of 124 diabetic subjects were included in this retrospective cohort study. All medical data were obtained from the electronic database of our university hospital. The subjects were divided into the no diabetic retinopathy (NDR) group (n=45), and the diabetic retinopathy (DR) group (n=79), which were compared in terms of demographic features, clinic and laboratory findings, and electrocardiographic findings such as QT, QTc, Tp-e, Tp-e/QT, Tp-e/QTc. Results: The groups were similar in terms of demographic features (P>0.05). Both Tp-e interval and Tpe/QTc were significantly prolonged in the DR group compared to the NDR group. There were significant correlations between Tp-e, Tp-e/QTc, DM duration, and age. In multivariate logistic regression analysis, Tp-e (OR=6.01, %95 CI=4.17-7.52, P=0.012), Tp-e/QTc (OR=1.215, 95% CI=0.874-1.612, P=0.029), and DM duration (OR=1.422, 95% CI= 1.146-1.712, P<0.001) were independent predictors of DR. Conclusion: We showed that DM patients with retinopathy may also have an increased risk for sudden cardiac death due to ventricular arrhythmogenesis. [ABSTRACT FROM AUTHOR]

Objective: Exercise‐induced repolarization changes have not been systematically evaluated in children and young adults with congenital heart disease (CHD). We carried out this study to assess the QTc responses during exercise in children and young adults (≤ 21 years) with CHD with comparison to those with structurally normal hearts. Methods: Baseline QRS duration, calculated baseline QTc, QTc at 4 min of recovery and delta QTc was measured in 360 exercise stress tests which were performed in 360 subjects (137 stress tests in patients with CHD [CHD group] and 223 stress tests in patients with structurally normal hearts). The effects of presence of CHD and potential confounders on primary outcome measure, change in QTc (delta QTc), and secondary outcome measures (QTc at baseline and QTc at 4 min of recovery) were determined using multiple linear regression analyses. Results: The baseline QTc and the QTc at 4 min of recovery in the CHD group was longer than patients with structurally normal hearts (respective p values =.00 and.001). No significant difference was noted in delta QTc between the CHD and structurally normal heart groups. Conclusions: While patients with CHD had a longer QRS duration and QTc interval at baseline than those with structurally normal hearts, these differences did not persist or augment with exercise. [ABSTRACT FROM AUTHOR]

Background: Electromechanical coupling may play a significant role in the association between abnormal myocardial mechanics and heterogeneity of repolarization. This study sought to assess the potential relationship between the left atrial volume index (LAVI), which is an important marker of cardiac diastolic function, and ventricular repolarization variables, such as the QT interval, Tpeak-to-Tend (Tpe) interval and Tpe/QT ratio, in an apparently healthy Chinese population. Methods: This was a community-based cross-sectional study conducted in Shenyang, China. A total of 414 healthy subjects aged 35– 91 years, including 186 men (44.9%), were enrolled. In addition to performing clinical and laboratory measurements, all subjects underwent comprehensive echocardiography and standard 12-lead electrocardiography. Echocardiographic and electrocardiographic results were analysed separately and in a blinded fashion. Correlation and regression analyses were applied to determine associations. Results: Subjects were divided into four groups according to quartile of LAVI levels (< 16.0, 16.0– 18.9, 19.0– 22.5 and > 22.5 mL/m2). Ventricular repolarization variables, such as QT interval and QTc interval, gradually increased with the progression from low to high LAVI levels (P< 0.05). LAVI was positively and significantly correlated with the QT interval, the QTc interval, and the Tpe interval (P< 0.01). After adjusting for age and other possible confounders, LAVI showed significant and independent associations with the QT interval and the QTc interval (P< 0.001; P=0.003). Conclusion: Echocardiographic LAVI is linearly associated with ventricular repolarization variables even in healthy people. [ABSTRACT FROM AUTHOR]

Savolitinib (AZD6094, HMPL‐504, volitinib) is an oral, bioavailable, selective MET‐tyrosine kinase inhibitor. This randomized, double‐blind, 3‐way, crossover phase 1 study of savolitinib versus moxifloxacin (positive control) and placebo‐evaluated effects on the QT interval after a single savolitinib dose. Healthy non‐Japanese men were randomized to 1 of 6 treatment sequences, receiving single doses of savolitinib 600 mg, moxifloxacin 400 mg, and placebo. The primary end point was time‐matched, placebo‐adjusted change from baseline in the QT interval corrected for the time between corresponding points on 2 consecutive R waves on electrocardiogram (RR) by the Fridericia formula (ΔΔQTcF). Secondary end points included 12‐lead electrocardiogram (ECG) variables, pharmacokinetics, and safety. All 3 treatment periods were completed by 44 of 45 participants (98%). Baseline demographics were balanced across treatment groups. After a single savolitinib 600‐mg dose, the highest least‐squares mean ΔΔQTcF of 12 milliseconds was observed 5 hours postdose. Upper limits of the 2‐sided 90% confidence interval for ΔΔQTcF exceeded 10 milliseconds (the prespecified International Council for Harmonisation limit) 3‐6 hours postsavolitinib but otherwise remained less than the threshold. Savolitinib showed no additional effect on PR, QRS, QT, or RR intervals. A positive ΔΔQTcF signal from the moxifloxacin group confirmed study validity. Savolitinib was well tolerated, with a low incidence of adverse events. In this thorough QT/QTc study, QTcF prolongation was observed with a single savolitinib 600‐mg dose. ECG monitoring will be implemented in ongoing and future studies of savolitinib to assess the clinical relevance of the observed QT changes from this study. [ABSTRACT FROM AUTHOR]

Copyright of Cumhuriyet Medical Journal is the property of Cumhuriyet Medical Journal and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Background/Aim: Hypertension (HT) may modulate left ventricular (LV) geometry. Electrocardiographic Tp-Te, QT and QTc interval, and Tp-Te/QTc ratio are among the parameters of ventricular repolarization (VR) that may predict ventricular arrhytmogenic potential and possess prognostic significance. It is well known that left ventricular hypertrophy is associated with increase in the parameters of VR; however, little is known about the association of these parameters with other forms of LV geometry in HT. Our aim was to assess this association. Methods: A total of 162 newly diagnosed essential HT patients were enrolled and divided into those with concentric LV remodeling (n=79) and those with normal LV geometry (n=83). Healthy normotensive subjects (n=76) comprised the control group. Data were gathered retrospectively from electrocardiographic, echocardiographic, and demographic records. Results: QT interval, P-wave duration, and QRS duration were similar among the 3 groups (P>0.05). Tp-Te, QTc and Tp-Te/QTc were greater in the HT group compared with the controls (P<0.001). In a pairwise comparison between 2 HT subgroups, these parameters were similar (P>0.05). There was no correlation between Tp-Te interval, LV mass and LV mass index among the study population. Conclusion: Tp-Te may be useful in prognostic stratification of HT. Regardless of the LV geometry, HT patients have prolonged Tp-Te and QTc intervals, and increased Tp-Te/QTc ratio compared to the healthy subjects. Our findings may suggest possible utilization of Tp-Te as HT-related end-organ damage in the future. [ABSTRACT FROM AUTHOR]

Under the hypothesis that sympathetic control of ventricular repolarization may change once the second ventilatory threshold (VT2) has been reached, a novel methodology for non‐invasive VT2 estimation based on the analysis of the T wave from the electrocardiogram (ECG) is proposed, and potential underlying physiological mechanisms are suggested. 25 volunteers (33.4 ± 5.2 years) underwent an incremental power cycle ergometer test (25 W/minute). During the test, respiratory gas exchange and multi‐lead ECG were acquired. The former was employed to determine VT2, used here as a reference, whereas the latter was used to compute the temporal profiles of an index of ventricular repolarization instability (dT) and its low‐frequency (LF) oscillations (LFdT). The sudden increases observed in dT and LFdT profiles above an established heart rate threshold were employed to derive VT2 estimates, referred to as VT2dT and VT2LFdT, respectively. Estimation errors of −4.7 ± 25.2 W were obtained when considering VT2dT. Errors were lower than the one‐minute power increment of 25 W in 68% of the subjects and lower than 50 W in 89.5% of them. When using VT2LFdT, estimation error was of 15.3 ± 32.4 W. Most of the subjects shared common characteristic dT and LFdT profiles, which could be reflecting changes in the autonomic control of ventricular repolarization before and after reaching VT2. The analysis of ventricular repolarization dynamics during exercise allows non‐invasive ECG‐based estimation of VT2, possibly in relation to changes in the autonomic control of ventricular electrical activity when VT2 is reached. [ABSTRACT FROM AUTHOR]

Head-down tilt (HDT) bed rest elicits changes in cardiac circadian rhythms, generating possible adverse health outcomes such as increased arrhythmic risk. Our aim was to study the impact of HDT duration on the circadian rhythms of heart beat (RR) and ventricular repolarization (QTend) duration intervals from 24-h Holter ECG recordings acquired in 63 subjects during six different HDT bed rest campaigns of different duration (two 5-day, two 21-day, and two 60-day). Circadian rhythms of RR and QTend intervals series were evaluated by Cosinor analysis, resulting in a value of midline (MESOR), oscillation amplitude (OA) and acrophase (φ). In addition, the QTc (with Bazett correction) was computed, and day-time, night-time, maximum and minimum RR, QTend and QTc intervals were calculated. Statistical analysis was conducted, comparing: (1) the effects at 5 (HDT5), 21 (HDT21) and 58 (HDT58) days of HDT with baseline (PRE); (2) trends in recovery period at post-HDT epochs (R) in 5-day, 21-day, and 60-day HDT separately vs. PRE; (3) differences at R + 0 due to bed rest duration; (4) changes between the last HDT acquisition and the respective R + 0 in 5-day, 21-day, and 60-day HDT. During HDT, major changes were observed at HDT5, with increased RR and QTend intervals' MESOR, mostly related to day-time lengthening and increased minima, while the QTc shortened. Afterward, a progressive trend toward baseline values was observed with HDT progression. Additionally, the φ anticipated, and the OA was reduced during HDT, decreasing system's ability to react to incoming stimuli. Consequently, the restoration of the orthostatic position elicited the shortening of RR and QTend intervals together with QTc prolongation, notwithstanding the period spent in HDT. However, the magnitude of post-HDT changes, as well as the difference between the last HDT day and R + 0, showed a trend to increase with increasing HDT duration, and 5/7 days were not sufficient for recovering after 60-day HDT. Additionally, the φ postponed and the OA significantly increased at R + 0 compared to PRE after 5-day and 60-day HDT, possibly increasing the arrhythmic risk. These results provide evidence that continuous monitoring of astronauts' circadian rhythms, and further investigations on possible measures for counteracting the observed modifications, will be key for future missions including long periods of weightlessness and gravity transitions, for preserving astronauts' health and mission success. [ABSTRACT FROM AUTHOR]

Adequate adaptation of ventricular repolarization (VR) duration to changes in heart rate (HR) is important for cardiac electromechanical function and electrical stability. We studied the QT and QTpeak adaptation in response to abrupt start and stop of atrial and ventricular pacing on two occasions with an interval of at least 1 mo in 25 study subjects with permanent pacemakers. Frank vectorcardiography was used for data collection. Atrial or ventricular pacing was performed for 8 min aiming at a cycle length (CL) of 500 ms. We measured the immediate response (IR), the time constant (τ) of the exponential phase, and T90 End, the time to reach 90% change of QT and QTpeak from baseline to steady state during and after pacing. During atrial pacing, the CL decreased on average 45% from mean (SD) 944 (120) to 518 (46) ms and QT decreased on average 18% from 388 (20) to 318 (17) ms. For QT, T90 End was 103 (24) s and 126 (15) s after start versus stop of atrial pacing; a difference of 24 (27) s (P = 0.006). The response pattern was similar for τ but IR did not differ significantly between pacing start and stop. The response pattern was similar for QTpeak and also for QT and QTpeak following ventricular pacing start and stop. The coefficients of variation for repeated measures were 7%-21% for T90 End and τ. In conclusion, the adaptation of VR duration was significantly more rapid following increasing than decreasing HR and intraindividually a relatively reproducible process. NEW & NOTEWORTHY We studied the duration of ventricular repolarization (VR) adaptation and its hysteresis, following increasing and decreasing heart rate by abrupt start and stop of 8-min atrial or ventricular pacing in study subjects with permanent pacemakers and repeated the protocol with ≥1 mo interval, a novel approach. VR adaptation was significantly longer following decreasing than increasing heart rate corroborating previous observations. Furthermore, VR adaptation was intraindividually a reproducible and, hence, robust phenomenon, a novel finding. [ABSTRACT FROM AUTHOR]