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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]

Abstract Obesity is associated with dysfunctional electrocardiographic and cardiac autonomic parameters, which may lead to increased cardiovascular morbidity. Novel electrocardiographic repolarization markers such as Tpeak-Tend (Tpe) interval have not yet been deeply studied in obese patients. We aimed to investigate the association between ventricular repolarization parameters and heart rate variability (HRV) and how they are affected by changes occurring in the cardiac autonomic nervous system. Ninety subjects categorized by Southeast Asian BMI (kg/m2) standards - normal (18-22.9), overweight (23-24.9), and obese (> 24.9), underwent assessment of ventricular repolarization parameters and HRV. Linear correlation between different parameters was also conducted. Obese subjects exhibited longer QTc and Tpe intervals compared to normal-weight subjects (p-value

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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]

In dogs, myocardial injury (MI) is a poorly characterized clinical entity; therefore, this study aimed to provide a detailed description of dogs affected by this condition. Dogs diagnosed with MI according to the concentration of cardiac troponin I (cTnI) were retrospectively searched. Signalment, diagnostic, therapeutic, and outcome data were retrieved. Dogs were divided into six echocardiographic (dilated cardiomyopathy phenotype; hypertrophic cardiomyopathy phenotype; hypertrophic cardiomyopathy phenotype with systolic dysfunction; abnormal echogenicity only; endocarditis; and no echocardiographic abnormalities suggestive of MI), four electrocardiographic (abnormalities of impulse formation; abnormalities of impulse conduction; abnormalities of ventricular repolarization; and no electrocardiographic abnormalities suggestive of MI), and nine etiological (infective; inflammatory; neoplastic; metabolic; toxic; nutritional; immune-mediated; traumatic/mechanical; and unknown) categories. Statistical analysis was performed to compare cTnI values among different categories and analyze survival. One hundred two dogs were included. The median cTnI value was 3.71 ng/mL (0.2–180 ng/mL). Echocardiographic and electrocardiographic abnormalities were documented in 86 of 102 and 89 of 102 dogs, respectively. Among echocardiographic and electrocardiographic categories, the dilated cardiomyopathy phenotype (n = 52) and abnormalities of impulse formation (n = 67) were overrepresented, respectively. Among dogs in which a suspected etiological trigger was identified (68/102), the infective category was overrepresented (n = 20). Among dogs belonging to different echocardiographic, electrocardiographic, and etiological categories, cTnI did not differ significantly. The median survival time was 603 days; only eight of 102 dogs died due to MI. Dogs with MI often have an identifiable suspected trigger, show various echocardiographic and electrocardiographic abnormalities, and frequently survive to MI-related complications. [ABSTRACT FROM AUTHOR]

Background Ventricular repolarization time (ECG QT and JT intervals) is associated with malignant arrhythmia. Genome‐wide association studies have identified 230 independent loci for QT and JT; however, 50% of their heritability remains unexplained. Previous work supports a causal effect of lower serum calcium concentrations on longer ventricular repolarization time. We hypothesized calcium interactions with QT and JT variant associations could explain a proportion of the missing heritability. Methods and Results We performed genome‐wide calcium interaction analyses for QT and JT intervals. Participants were stratified by their calcium level relative to the study distribution (top or bottom 20%). We performed a 2‐stage analysis (genome‐wide discovery [N=62 532] and replication [N=59 861] of lead variants) and a single‐stage genome‐wide meta‐analysis (N=122 393, [European ancestry N=117 581, African ancestry N=4812]). We also calculated 2‐degrees of freedom joint main and interaction and 1‐degree of freedom interaction P values. In 2‐stage and single‐stage analyses, 50 and 98 independent loci, respectively, were associated with either QT or JT intervals (2‐degrees of freedom joint main and interaction P value

ABSTRACTThe aim of this study was to examine the acute effects of a non-caloric energy drink (C4E) compared to a traditional sugar-containing energy drink (MED) and non-caloric placebo (PLA) on exercise performance and cardiovascular safety. Thirty healthy, physically active males (25 ± 4 y) completed three experimental visits under semi-fasted conditions (5–10 h) and in randomized order, during which they consumed C4E, MED, or PLA matched for volume, appearance, taste, and mouthfeel. One hour after drink consumption, participants completed a maximal, graded exercise test (GXT) with measurement of pulmonary gases, an isometric leg extension fatigue test (ISOFTG), and had their cardiac electrical activity (ECG), leg blood flow (LBF), and blood pressure (BP) measured throughout the visit. Neither MED nor C4E had an ergogenic effect on maximal oxygen consumption, time to exhaustion, or peak power during the GXT (p > 0.05). Compared to PLA, MED reduced fat oxidation (respiratory exchange ratio (RER) +0.030 ± 0.01; p = 0.026) during the GXT and did not influence ISOFTG performance. Compared to PLA, C4E did not alter RER (p = 0.94) and improved impulse during the ISOFTG (+0.658 ± 0.25 V·s; p = 0.032). Relative to MED, C4E did not significantly improve gas exchange threshold (p = 0.05–0.07). Both MED and C4E increased systolic BP at rest (+7.1 ± 1.2 mmHg; p

AbstractThe 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.

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]

BackgroundThe 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.ObjectiveThe purpose of the current study was to determine the optimal leads, if any, to capture the maximal Tp-e interval in healthy young adults.MethodsIn 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.ResultsIn 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

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]

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]

Purpose: The purpose of this study is to evaluate ventricular repolarization before, at the first month, and sixth month after Sacubutril/Valsartan, an angiotensin receptor neprilysin inhibitor (ARNI) treatment in heart failure patients with reduced ejection fraction (HFrEF). Materials and Methods: We included 49 patients with HFrEF who switched to ARNI therapy. The 12-lead electrocardiography (ECG) was evaluated before ARNI therapy and also during the first and sixth months of the therapy. We evaluated demographic, clinical, and laboratory parameters, as well as medications and ECG data, including heart rate. Additionally, we examined QT, QTc, Tp-e, Tp-e calculated (Tp-ec), Tp-ec/QTc, Tpe/QT, and Tp-e/QTc. Results: After receiving ARNI treatment, ventricular repolarization indices were significantly reduced in the first and sixth months compared to before treatment. Specifically, the QTc values decreased from 457.6 ms to 443.8 ms, and the Tp-e/QT ratio decreased from 0.21±0.03 to 0.19±0.03. Additionally, the QTc values decreased from 457.6 ms to 444.9 ms, and the Tp-e/QT ratio decreased from 0.21±0.03 to 0.18±0.03. However, when the first and sixth months under ARNI treatment were compared, no significant difference was found (QTc: 443.8 ms vs. 444.9 ms, Tp-e/QT: 0.19±0.03 vs. 0.18±0.003). Conclusion: ARNI treatment in HFrEF positively affected QTc, Tp-e, and Tp-ec intervals and Tp-e/QT, Tp-e/QTc, and Tp-ec/QTc ratios, which are indicators of ventricular repolarization. Moreover, this effect started in the first month and continued in the sixth month. [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]

Abstract 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.

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]

OBJECTIVE: Obese people are at increased risk of arrhythmia and sudden death, even in the absence of heart dysfunction. Increased insulin resistance, neurohumoral and autonomic changes in obesity can cause atrial and ventricular repolarization abnormalities. This study aimed to investigate the effect on ventricular repolarization parameters and to show the increased risk of ventricular arrhythmia in obese children. PATIENTS AND METHODS: The data of 50 obese children aged 2-18 who applied to the Pediatric Endocrinology Outpatient Clinic were evaluated prospectively. In 12-lead ECGs, heart rate, Pmax, Pmin, P-wave dispersion (Pwdisp), QTmax, QTmin, QT dispersion (QTd), QTcmax, QTcmin, QTc interval dispersion (QTcd), Tpeak-Tend interval (Tp-e), Tp-e/QT, Tp-e/QTc were calculated electronically. RESULTS: Tp-e time (0.041 ± 0.004/0.049 ± 0.015/p=0.018) and Tp parameters were measured in obese children with and without insulin resistance. Tp-e/QT ratio was also found to be high (p=0.035). There is a negative correlation between BMI SDS values and QTcmax and QTcmin values in patients with insulin resistance (p=0.015). CONCLUSIONS: In our study, the Tp-e interval and Tp-e/QT ratios, which had been revealed in literature to be more sensitive in demonstrating ventricular arrhythmias, were found to be higher in obese individuals with insulin resistance than in those without insulin resistance. Obese individuals with or without insulin resistance should be carefully evaluated in terms of atrial and ventricular depolarization and repolarization parameters with 12-lead ECG during their outpatient controls, and annual 24-hour Holter control should be performed to detect arrhythmias. [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]

Aim: Bipolar disorder (BD) is one of the chronic psychiatric diseases. It has been reported that cardiovascular diseases are seen twice as often in patients with BD. Fragmented QRS (fQRS) has been found to be associated with myocardial scarring and is used as a marker of arrhythmia and mortality. Ventricular repolarization (VR) is often evaluated using QT interval and T wave measurement data. In our study, we aimed to evaluate fQRS, QTc interval, QT dispersion (QTd), Tp-e interval, Tp-e/QT ratio results and VR, together with blood biochemistry parameter results of cases with BD. Material and Method: Our research was conducted with 51 people diagnosed with bipolar disorder and 52 healthy people as the control group. fQRS, QTc interval, QT dispersion (QTd), Tp-e interval, Tp-e/QT ratio were measured using 12-lead electrocardiography (ECG). The results of the data obtained from ECG and blood biochemistry parameter levels were used to compare the healthy and patient groups. Results: Tp-e interval (p=0.018) and Tpe/QT ratio (p=0.036) were found to be statistically significantly higher and total cholesterol level (p=0.006) lower in patients with bipolar disorder compared to the control group. Conclusion: An increased Tpe/QT ratio, along with a prolonged Tp-e interval, may be a useful marker of ventricular arrhythmia risk in individuals with fQRS BD. [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]

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]

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: 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]

Tobacco cigarette smoking is associated with increased sudden death risk, perhaps through adverse effects on ventricular repolarization. The effect of electronic (e-)cigarettes on ventricular repolarization is unknown. The objective of the study was to test the hypothesis that tobacco cigarettes and e-cigarettes have similar adverse effects on electrocardiogram (ECG) indexes of ventricular repolarization and these effects are attributable to nicotine. ECG recordings were obtained in 37 chronic tobacco cigarette smokers, 43 chronic e-cigarette users, and 65 nonusers. Primary outcomes, Tpeak to Tend (Tp-e), Tp-e/QT ratio, and Tp-e/QTc ratio, were measured in tobacco cigarette smokers pre-/post-straw control and smoking one tobacco cigarette and in e-cigarette users and nonusers pre-/post-straw control and using an e-cigarette with and without nicotine (different days). Mean values of the primary outcomes were not different among the three groups at baseline. In chronic tobacco cigarette smokers, all primary outcomes, including the Tp-e (12.9 ± 5.0% vs. 1.5 ± 5%, P = 0.017), Tp-e/QT (14.9 ± 5.0% vs. 0.7 ± 5.1%, P = 0.004), and Tp-e/QTc (11.9 ± 5.0% vs. 2.1 ± 5.1%, P = 0.036), were significantly increased pre-/post-smoking one tobacco cigarette compared with pre-/post-straw control. In chronic e-cigarette users, the Tp-e/QT (6.3 ± 1.9%, P = 0.046) was increased only pre/post using an e-cigarette with nicotine but not pre/post the other exposures. The changes relative to the changes after straw control were greater after smoking the tobacco cigarette compared with using the e-cigarette with nicotine for Tp-e (11.4 ± 4.4% vs. 1.1 ± 2.5%, P < 0.05) and Tp-e/QTc (9.8 ± 4.4% vs. -1.6 ± 2.6%, P = 0.05) but not Tp-e/QT(14.2 ± 4.5% vs. 4.2 ± 2.6%, P = 0.061) . Heart rate increased similarly after the tobacco cigarette and e-cigarette with nicotine. Baseline ECG indexes of ventricular repolarization were not different among chronic tobacco cigarette smokers, electronic cigarette users and nonusers. An adverse effect of acute tobacco cigarette smoking on ECG indexes of ventricular repolarization was confirmed. In chronic e-cigarette users, an adverse effect of using an e-cigarette with nicotine, but not without nicotine, on ECG indexes of ventricular repolarization was also observed.NEW & NOTEWORTHY Abnormal ventricular repolarization, as indicated by prolonged Tpeak-end (Tp-e), is associated with increased sudden death risk. Baseline ECG indexes of repolarization, Tp-e, Tp-e/QT, and Tp-e/QTc, were not different among tobacco cigarette (TC) smokers, electronic cigarette (EC) users, and nonsmokers at baseline, but when TC smokers smoked one TC, all parameters were prolonged. Using an electronic cigarette with nicotine, but not without nicotine, increased the Tp-e/QT. Smoking induces changes in ECG indexes of ventricular repolarization associated with increased sudden death risk.

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 Aim Although Myocardial bridge (MB) is known as a benign condition, it has been demonstrated to be associated with cardiac arrhythmias and poor outcomes. Frontal QRS‐T angle (fQRSTa) is a novel indicator of repolarization and depolarization heterogeneity. Last studies indicated that associated with fQRSTa and adverse cardiac events. No study evaluated the relationship between fQRSTa and MB. In the present study, we aimed to investigate the relationship between MB and fQRSTa. Methods This study included 91 patients with normal coronary arteries and 89 patients with MB. Coronary angiography was performed in all patients due to ischemia findings on treadmill exercise test or myocardial scintigraphy.2‐lead surface electrocardiograms (ECGs) of all patients were evaluated. QT interval, fQRSTa, QTc interval were measured from surface ECGs. Results Baseline clinical, echocardiographic and laboratory parameters were similar between MB and control group. However, when compared to control group, patients with MB had importantly raised fQRSTa [27 (20–41) vs. 23 (12–37) p = 0.007]. In correlation analysis, fQRSTa was positively correlated with MB length (r = 0.411, p

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]

Ischemia due to microvascular dysfunction may be responsible for the heterogeneity of ventricular repolarization in coronary slow flow. To our knowledge, there is no study in which QT interval, Tp-Te interval, index of cardiac-electrophysiological balance (iCEB), and frontal QRS-T angle were evaluated together in patients with CSF. In this study, we examined for the first time the relationship between all these myocardial repolarization parameters and CSF. The study group included 178 patients (99 female, mean age: 50.6 ± 8.6 years) with isolated CSF without stenotic lesions and with angiographically proven normal coronary arteries. The control group included 120 patients (71 female, mean age: 49.3 ± 9.4 years) with normal coronary angiography. QRS duration, QT interval, QTc interval, Tp-Te interval, Tp-Te/QT, Tp- Te/QTc, iCEB score, and frontal QRS-T angle were calculated from 12‑lead ECGs. There was no significant difference in demographic parameters between the two groups. Compared with the control group, patients with CSF had significantly longer QTmax duration, QT dispersion, Tp-Te interval, and higher iCEB score, wider frontal QRS-T angle. In our study, we found that many of the ventricular repolarization parameters were adversely affected in patients with CSF. Impaired parameters may be associated with the risk of malignant ventricular arrhythmias. [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: 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.

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:The relevance of Tp-e, QT dispersion and the ratios between these two as predictive variables of ventricular arrhythmias, particularly ventricular prematurity depolarization and sudden cardiac death, were assessed in this study of patients who were identified with small heart syndrome.Method:The study included 94 female patients, as 47 small-heart and 47 normal-heart patients, by calculating their cardiothoracic ratios. We measured QTmax, QTmin, QRS, JT and Tp-e intervals, Tp-e/QTmax, Tp-e/QTcmax, Tp-e/JT and Tp-e/JTc rates and estimated QTcmax, QTcmin, cQTd and JTc intervals.Results:cQTd, Tp-e, Tp-e/QTcmax, and Tp-e/JTc values were significantly higher in the small heart patient group. QTcmin and QTcmin values were significantly lower.Conclusion:Tp-e and QT dispersion values are important markers in patients with small heart syndrome in terms of predicting ventricular repolarization and a possible ventricular arrhythmia.

Currently, there is a lack of research on the Tp-Te interval and Tp-e/QT ratio in obese adolescents who have metabolic syndrome. Our study aims to compare established ventricular repolarization parameters with these intervals and ratios in obese adolescents with or without metabolic syndrome, alongside a healthy control group, while exploring the association of these repolarization parameters with cardiovascular risk factors and echocardiographic variables. The study included 100 obese adolescents and 50 lean subjects, with the obese participants categorized into two subgroups. The Tp-Te interval was identified as the duration from the peak to the end of the T wave. The metabolic and non-metabolic syndrome obese groups exhibited significantly elevated QTc and TpTe values compared to the control group, with no statistically significant differences observed in minimum QT, maximum QT, QT dispersion, QTc dispersion, TpTe dispersion, and TpTe/QT ratio values among obese subjects with metabolic or non-metabolic syndrome and controls. Specifically, TpTe values were significantly elevated in the non-metabolic syndrome obese groups compared to controls, while minimum TpTe values were significantly elevated in the metabolic syndrome obese groups compared to controls, and the prolongation of the QTc interval was notably elevated in the obese groups than in controls. Obese adolescents demonstrated an elevated TpTe interval compared to healthy controls, without any significant differences observed in TpTe dispersion, and TpTe/QT ratio values between the two groups. Results of our study showed that a negative correlation between TpTe and HDL-cholesterol and a positive correlation between the TpTe/QT ratio and insulin sensitivity indices in adolescents with metabolic syndrome. [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: 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]

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]

Aim: Although Myocardial bridge (MB) is known as a benign condition, it has been demonstrated to be associated with cardiac arrhythmias and poor outcomes. Frontal QRS‐T angle (fQRSTa) is a novel indicator of repolarization and depolarization heterogeneity. Last studies indicated that associated with fQRSTa and adverse cardiac events. No study evaluated the relationship between fQRSTa and MB. In the present study, we aimed to investigate the relationship between MB and fQRSTa. Methods: This study included 91 patients with normal coronary arteries and 89 patients with MB. Coronary angiography was performed in all patients due to ischemia findings on treadmill exercise test or myocardial scintigraphy.2‐lead surface electrocardiograms (ECGs) of all patients were evaluated. QT interval, fQRSTa, QTc interval were measured from surface ECGs. Results: Baseline clinical, echocardiographic and laboratory parameters were similar between MB and control group. However, when compared to control group, patients with MB had importantly raised fQRSTa [27 (20–41) vs. 23 (12–37) p = 0.007]. In correlation analysis, fQRSTa was positively correlated with MB length (r = 0.411, p < 0.001). Linear regression analysis showed that MB length was the just considerable predictor of fQRSTa (β = 0.247, p = 0.041). Conclusions: The fQRSTa is a novel electrocardiographic marker that can be easily obtained from surface ECG. We have shown for the first time that MB length is a significant predictor of fQRSTa. [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: Patients with anterior ST elevation myocardial infarction (STEMI) are vulnerable to life-threatening ventricular arrhythmia and arrhythmic death. This study aimed to investigate the predictive value of Tpeak-to-Tend (TpTe) and TpTe/QT ratio in patients with anterior STEMI on admission for the occurrence of in-hospital life-threatening ventricular arrhythmias and arrhythmic death., Methods: This observational cross-sectional research was performed on patients with anterior STEMI who showed up within 12 hours of the beginning of symptoms and received the initial percutaneous coronary intervention (pPCI). The primary study endpoints included the assessment of sustained ventricular arrhythmias and all-cause/arrhythmic deaths throughout the hospitalization. Data collection involved clinical history, vital signs monitoring, ECG measurements, LVEF evaluation, and performance of pPCI procedures., Results: The studied patients had a mean age of 53 ± 11 years. Patients with arrhythmic events displayed a significant rise in QT dispersion, TpTe, TpTe/QT, and arrhythmic death rates (P < 0.05). A multivariate logistic regression examination revealed that HR (with an OR of 1.037 and a 95% CI of 1.004 to 1.071, P = 0.027), TpTe (with an OR of 1.025 and a 95% CI of 1.004 to 1.047, P = 0.022), and TpTe/QT (with an OR of 5.464 and a 95% CI of 2.027 to 14.726, P = 0.001) were found to be significant predictors of arrhythmic events or mortality., Conclusion: In patients with anterior STEMI, TpTe and TpTe/QT ratio are significant predictors of in-hospital VA and arrhythmic death. Higher TpTe and TpTe/QT values are linked to a higher risk of these occurrences., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Masson SAS. All rights reserved.)

Background: Ventricular repolarization time (ECG QT and JT intervals) is associated with malignant arrhythmia. Genome-wide association studies have identified 230 independent loci for QT and JT; however, 50% of their heritability remains unexplained. Previous work supports a causal effect of lower serum calcium concentrations on longer ventricular repolarization time. We hypothesized calcium interactions with QT and JT variant associations could explain a proportion of the missing heritability., Methods and Results: We performed genome-wide calcium interaction analyses for QT and JT intervals. Participants were stratified by their calcium level relative to the study distribution (top or bottom 20%). We performed a 2-stage analysis (genome-wide discovery [N=62 532] and replication [N=59 861] of lead variants) and a single-stage genome-wide meta-analysis (N=122 393, [European ancestry N=117 581, African ancestry N=4812]). We also calculated 2-degrees of freedom joint main and interaction and 1-degree of freedom interaction P values. In 2-stage and single-stage analyses, 50 and 98 independent loci, respectively, were associated with either QT or JT intervals (2-degrees of freedom joint main and interaction P value <5×10 -8 ). No lead variant had a significant interaction result after correcting for multiple testing and sensitivity analyses provided similar findings. Two loci in the single-stage meta-analysis were not reported previously ( SPPL2B and RFX6 )., Conclusions: We have found limited support for an interaction effect of serum calcium on QT and JT variant associations despite sample sizes with suitable power to detect relevant effects. Therefore, such effects are unlikely to explain a meaningful proportion of the heritability of QT and JT, and factors including rare variation and other environmental interactions need to be considered.

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

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.