Evaluation of Index of Cardio-Electrophysiological Balance (iCEB) as a New Biomarker for the Identification of Patients at Increased Arrhythmic Risk

Influence of cigarette smoking on the Index of Cardiac Electrophysiological Balance in apparently healthy Angolans

Background: Tobacco use accelerates atherosclerosis and is one of the predictors of death from ischemic heart disease, arrhythmias, heart failure, and sudden death. A new non-invasive parameter, the Index of Cardiac Electrophysiological Balance (iCEB) between depolarization and repolarization of the action potential, was considered a new biomarker for the identification of patients at increased arrhythmic risk. Objectives: We aimed to evaluate the iCEB in apparently healthy Angolans with habitual cigarette smoking compared to non-smokers. Subjects and methods: Data were obtained from the CardioBengo study, a cross-sectional community-based study in which a random sample of individuals aged between 15 and 84 years was selected. In total, 214 apparently healthy subjects, 102 smokers, and 112 non-smokers in the same age group were included in the final analysis. Results: The average age of the participants was 42.17 ± 13.04 years old and 26.6% of the sample was female. Smoking subjects had higher iCEB and corrected Index of Cardiac Electrophysiological Balance (iCEBc) values compared with non-smoking controls (4.39 vs. 4.25; p = 0.024, respectively), and (4.74 vs. 4.57; p = 0.030, respectively). Conclusions: In summary, iCEB and iCEBc were significantly higher in habitual smokers than in nonsmokers, which represents an increased risk of ventricular arrhythmogenesis in healthy habitual smokers. To the best of our knowledge, this is the first study performed in Africa to evaluate iCEB in smokers, making this type of study very important in low- and middle-income countries in the context of epidemiological transition.

Index of cardio-electrophysiological balance and Parkinson disease

Neurodegeneration of the autonomic nervous systems due to Parkinson disease (PD) may lead to increase in the QT duration. In recent years, a new parameter index of cardio-electrophysiological balance (ICEB) was found. ICEB is a significant parameter of medicine related dysrhythmia. The purpose of this research is to assess ICEB in PD. Twenty-eight PD cases and 26 controls participated in our investigation. First diagnosed PD patients were registered in the research. The symptom progression of PD was assessed Modified Hoehn and Yahr Scale. Analyzed ECG variables are QRS, PR, QT, corrected QT (QTc) interval, ICEB and corrected index of cardio-electrophysiological balance (ICEBc). All cases had sinus rhythm. ICEB was analyzed by the ratio of QT/QRS. ICEBc was analyzed by the ratio of QTc/QRS. Twenty-eight PD cases participated in this research. Among PD cases, 15 patients were female (53.5%). The mean age of PD patients are 59.03 ± 9.94 years. There was no important difference between groups with respect to the clinical variables. The Modified Hoehn and Yahr Scale was appreciably higher in the PD group than the Control group. The heart rate of the PD group was significantly lower than that of the control group. PR intervals and QRS duration were similar in both groups. QT and QTc duration were significantly longer in PD patients. Also, the ICEB and ICEBc variables were appreciably higher in PD cases. The findings of our investigation suggest that ICEB is related to PD. ICEB can help to evaluate arrhythmia risk in patients with PD.

The Potential Mechanisms behind Loperamide-Induced Cardiac Arrhythmias Associated with Human Abuse and Extreme Overdose

Loperamide has been a safe and effective treatment for diarrhea for many years. However, many cases of cardiotoxicity with intentional abuse of loperamide ingestion have recently been reported. We evaluated loperamide in in vitro and in vivo cardiac safety models to understand the mechanisms for this cardiotoxicity. Loperamide slowed conduction (QRS-duration) starting at 0.3 µM [~1200-fold (×) its human Free Therapeutic Plasma Concentration; FTPC] and reduced the QT-interval and caused cardiac arrhythmias starting at 3 µM (~12,000× FTPC) in an isolated rabbit ventricular-wedge model. Loperamide also slowed conduction and elicited Type II/III A-V block in anesthetized guinea pigs at overdose exposures of 879× and 3802× FTPC. In ion-channel studies, loperamide inhibited hERG (IKr), INa, and ICa currents with IC50 values of 0.390 µM, 0.526 µM, and 4.091 µM, respectively (i.e., >1560× FTPC). Additionally, in silico trials in human ventricular action potential models based on these IC50s confirmed that loperamide has large safety margins at therapeutic exposures (≤600× FTPC) and confirmed repolarization abnormalities in the case of extreme doses of loperamide. The studies confirmed the large safety margin for the therapeutic use of loperamide but revealed that at the extreme exposure levels observed in human overdose, loperamide can cause a combination of conduction slowing and alterations in repolarization time, resulting in cardiac proarrhythmia. Loperamide's inhibition of the INa channel and hERG-mediated IKr are the most likely basis for this cardiac electrophysiological toxicity at overdose exposures. The cardiac toxic effects of loperamide at the overdoses could be aggravated by co-medication with other drug(s) causing ion channel inhibition.

The relationship between premature ventricular complexes and index of cardiac-electrophysiological balance

OBJECTIVE

Premature ventricular complexes are common in healthy individuals' ambulatory monitoring. The index of cardiac-electrophysiological balance may predict malignant ventricular arrhythmias. This study investigated the relation between Premature ventricular complex burden and index of cardiac-electrophysiological balance in 24-h Holter monitoring.

METHODS

A total of 257 patients who were admitted to a cardiology outpatient clinic without structural heart disease and underwent 24-h Holter monitoring were included in the study. Demographic features, laboratory parameters, and electrocardiographic and echocardiographic values of all patients were obtained from the hospital database. Patients were categorized into the following four groups according to their premature ventricular complex burden: ≤5% premature ventricular complexes as group 1, >6 and ≤10% premature ventricular complexes as group 2, >11 and ≤20% premature ventricular complexes as group 3, and >20% premature ventricular complexes as group 4. QRS, QT, and T peak to end interval were measured by resting electrocardiography. QT interval was corrected using Bazett's formula. T peak to end interval/QT, T peak to end interval/corrected QT interval, index of cardiac-electrophysiological balance, and corrected index of cardio-electrophysiological balance ratios were calculated.

RESULTS

There was no significant difference between groups regarding cardiovascular risk factors. In group 4, beta-blocker usage was significantly higher, and the serum magnesium levels were significantly lower than in other groups. There was no difference in QT duration or index of cardiac-electrophysiological balance values; however, corrected index of cardio-electrophysiological balance was significantly lower in the highest premature ventricular complex group (5.1, 5.1, 4.8, 4.7, p=0.005). In multivariate backward logistic regression analyses, it was found that lower corrected index of cardio-electrophysiological balance, lower serum magnesium levels, lower serum creatinine levels, larger left atrium size, and higher T peak to end interval were associated with higher premature ventricular complexes.

CONCLUSION

Corrected index of cardio-electrophysiological balance is a novel and noninvasive marker that can predict premature ventricular complex burden in patients with structurally normal hearts.

Brugada Syndrome: From Molecular Mechanisms and Genetics to Risk Stratification

Brugada syndrome (BrS) is a rare hereditary arrhythmia disorder, with a distinctive ECG pattern, correlated with an increased risk of ventricular arrhythmias and sudden cardiac death (SCD) in young adults. BrS is a complex entity in terms of mechanisms, genetics, diagnosis, arrhythmia risk stratification, and management. The main electrophysiological mechanism of BrS requires further research, with prevailing theories centered on aberrant repolarization, depolarization, and current-load match. Computational modelling, pre-clinical, and clinical research show that BrS molecular anomalies result in excitation wavelength (k) modifications, which eventually increase the risk of arrhythmia. Although a mutation in the SCN5A (Sodium Voltage-Gated Channel Alpha Subunit 5) gene was first reported almost two decades ago, BrS is still currently regarded as a Mendelian condition inherited in an autosomal dominant manner with incomplete penetrance, despite the recent developments in the field of genetics and the latest hypothesis of additional inheritance pathways proposing a more complex mode of inheritance. In spite of the extensive use of the next-generation sequencing (NGS) technique with high coverage, genetics remains unexplained in a number of clinically confirmed cases. Except for the SCN5A which encodes the cardiac sodium channel NaV1.5, susceptibility genes remain mostly unidentified. The predominance of cardiac transcription factor loci suggests that transcriptional regulation is essential to the Brugada syndrome's pathogenesis. It appears that BrS is a multifactorial disease, which is influenced by several loci, each of which is affected by the environment. The primary challenge in individuals with a BrS type 1 ECG is to identify those who are at risk for sudden death, researchers propose the use of a multiparametric clinical and instrumental strategy for risk stratification. The aim of this review is to summarize the latest findings addressing the genetic architecture of BrS and to provide novel perspectives into its molecular underpinnings and novel models of risk stratification.

Is T-Wave Alternans a Repolarization Abnormality Marker in COVID-19? An Investigation on the Potentialities of Portable Electrocardiogram Device

Background

Cardiac arrhythmias are significantly associated with poor outcomes in coronavirus disease 2019 (COVID-19) patients. Microvolt T-wave alternans (TWA) can be automatically quantified and has been recognized as a representation of repolarization heterogeneity and linked to arrhythmogenesis in various cardiovascular diseases. This study aimed to explore the correlation between microvolt TWA and COVID-19 pathology.

Methods

Patients suspected of COVID-19 in Mohammad Hoesin General Hospital were consecutively evaluated using Alivecor^® Kardiamobile 6L™ portable electrocardiogram (ECG) device. Severe COVID-19 patients or those who are unable to cooperate in active ECG self-recording were excluded from the study. TWA was detected and its amplitude was quantified using the novel enhanced adaptive match filter (EAMF) method.

Results

A total of 175 patients, 114 COVID-19 patients (polymerase chain reaction (PCR)-positive group), and 61 non-COVID-19 patients (PCR-negative group) were enrolled in the study. PCR-positive group was subdivided according to the severity of COVID-19 pathology into mild and moderate severity subgroups. Baseline TWA levels were similar between both groups during admission (42.47 ± 26.52 µV vs. 44.72 ± 38.21 µV), but higher TWA levels were observed during discharge in the PCR-positive compared to the PCR-negative group (53.45 ± 34.42 µV vs. 25.15 ± 17.64 µV, P = 0.03). The correlation between PCR-positive result in COVID-19 and TWA value was significant, after adjustment of other confounding variables (R² = 0.081, P = 0.030). There was no significant difference in TWA levels between mild and moderate severity subgroups in patients with COVID-19, both during admission (44.29 ± 27.14 µV vs. 36.75 ± 24.46 µV, P = 0.34) and discharge (49.47 ± 33.62 µV vs. 61.09 ± 35.99 µV, P = 0.33).

Conclusions

Higher TWA values can be observed on follow-up ECG obtained during discharge in the PCR-positive COVID-19 patients.

Evaluation of Index of Cardiac Electrophysiological Balance in Patients With Myotonic Dystrophy Type 1

BACKGROUND

Myotonic dystrophy type 1(MD1), which is characterized by decreased muscle tone, progressive muscle weakness, and cardiac involvement, is an autosomal dominant and progressive congenital muscle disease. Cardiac involvement more often manifests as conduction abnormalities and arrhythmias (such as supraventricular or ventricular). Approximately one-third of MD1-related deaths occur due to cardiac causes. The index of cardiac-electrophysiological balance (ICEB) is a current parameter calculated as QT interval/QRS duration. The increase in this parameter has been associated with malignant ventricular arrhythmias. In this study, our aim was to compare the ICEB values ​​of MD1 patients and the normal population.

MATERIAL AND METHOD

A total of 62 patients were included in our study. They were divided into two groups - 32 MD patients and 30 controls. The demographic, clinical, laboratory, and electrocardiographic parameters of the two groups were compared.

RESULTS

The median age of the study population was 24 (20-36 IQR), and 36 (58%) of these patients were female. Body mass index was higher in the control group (p = 0.037). While in the MD1 group creatinine kinase was significantly higher (p <0.001), In the control group creatinine, aspartate aminotransferase, alanine aminotransferase, calcium, and lymphocyte levels were significantly higher (p=0.031, p= 0.003, p=0.001, p=0.002, p=0.031, respectively). ICEB [3.96 (3.65-4.46) vs 3.74 (3.49-3.85) p=0.015] and corrected ICEB (ICEBc) [4.48 (4.08-4.92) vs 4.20 (4.03-4.51) p = 0.048] were significantly higher in the MD1 group.

CONCLUSION

In our study, ICEB was found to be higher in MD1 patients than in the control group. Increased ICEB and ICEBc values ​​in MD1 patients may precipitate ventricular arrhythmias in the future. Close monitoring of these parameters can be helpful in predicting possible ventricular arrhythmias and in risk stratification.

The effect of coronary slow flow on ventricular repolarization parameters

INTRODUCTION

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.

MATERIALS AND METHODS

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.

RESULTS

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.

CONCLUSION

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.

Prognostic value of index of cardiac electrophysiological balance among US middle-aged adults

Background

Index of cardiac electrophysiological balance (iCEB) has been widely used in clinical practice but no studies investigated the association between iCEB and prognosis in the general population.

Objective

To assess the correlation between the iCEB and the prognosis in the general population.

Methods

This retrospective cohort study involved adults aged 40-65 years who participated in the Third National Health and Nutrition Examination Survey (NHANES-III) and whose electrocardiograms were in sinus rhythm. The corrected iCEB (iCEBc) was the ratio of corrected QT interval (QTc) to QRS duration, and outcomes were cardiac and all-cause mortality. Cox proportional hazards regression model was used to identify the associations of iCEBc with end point. The value of iCEBc for predicting adverse events was evaluated by reclassification and discrimination analyses.

Results

Among 5,010 participants (mean age 51.10 ± 7.67 years, 52.5% female), 3,454 (68.9%) were Non-Hispanic White. The mean iCEBc was 4.45 ± 0.56. A total of 2,147 deaths were recorded during a median follow-up of 319 months. The adjusted model shown iCEBc was an independent risk factor for all-cause death. The iCEBc was linearly correlated with all-cause mortality and the optimal cutoff value was 4.57 in males and 4.98 in females. In the resultant model, prolonged iCEBc remained independently associated with a higher rate of mortality (HR: 1.25; 95% CI: 1.11-1.42) and cardiac death (HR: 1.34; 95% CI: 1.04-1.71). Among the complete study population or the group with normal QTc interval, the performance of the predictive model after addition of iCEBc was not weaker than the model after the addition of prolonged QTc.

Conclusion

Elevated iCEBc (male ≥4.57 and female ≥4.98) is an independent risk factor for cardiac or all-cause death among the middle-age adults. The clinical application value of iCEBc is firmly based on basic physiological principles and its application deserves further attention.

The effect of empagliflozin on index of cardio-electrophysiological balance in patients with diabetes mellitus

BACKGROUND

Empagliflozin is a new antidiabetic drug with positive effects on glucose regulation and the prevention of cardiovascular diseases (CVD). The effect of empagliflozin on arrhythmias has not been adequately studied. The index of cardio-electrophysiological balance (iCEB) is a popular marker used to predict ventricular arrhythmias. Therefore, in our study, we aimed to examine the effect of empagliflozin on iCEB and iCEBc in patients with type 2 diabetes mellitus (T2DM) without heart failure (HF).

METHODS

A total of 70 patients were included in the study prospectively. Electrocardiographic and echocardiographic evaluations of all patients were reviewed at baseline and the end of the third month.

RESULTS

The median age of the patients was 57 (43-68 IQR), and 30 (42.9%) were male. Tp-e (100 [88-120] vs. 94 [82-105], p = .01), Tp-e/QT (0.27 [0.25-0.33] vs. 0.25 [0.23-0.30], p = .001) were significantly shorter after treatment. iCEB (4.24 [3.8-4.5] vs. 3.92 [3.79-4.42], p = .009) and iCEBc (4.78 [4.25-4.92] vs. 4.48 [4.0-4.71], p = .001) values decreased significantly after treatment compared to baseline.

CONCLUSIONS

Tp-e, Tp-e/QT, iCEB, and iCEBc values decreased within physiological limits in patients with T2DM without HF. This result may be associated with a reduced risk of potential ventricular arrhythmias.

Evaluation of index of cardiac-electrophysiological balance in patients with subarachnoid hemorrhage

Background

Various electrocardiographic (ECG) changes occur after subarachnoid hemorrhage (SAH). Prolonged QT and corrected QT (QTc) intervals are notable changes. QT, QTc, T peak-to-end T(p-e) intervals, and Tp-e/QTc ratio are used as ventricular arrhythmia indices. In recent publications, the cardiac electrophysiological balance index (ICEB), which provides more information than other ECG parameters (QT, QTc, etc.), is recommended in predicting the risk of ventricular arrhythmia. This study aims to assess ICEB in aneurysmal SAH patients.

Methods

The study included 50 patients diagnosed with aneurysmal SAH and 50 patients diagnosed with hypertension without end-organ damage as the control group. All patients’ Fisher scores and Glasgow Coma Scale (GCS) scores were recorded. Both groups were given 12-lead ECGs. QT, QTc, Tp-e intervals, QRS duration, ICEB (QT/QRS), ICEBc (QTc/QRS), and T(p-e)/QTc values were calculated and analyzed between groups.

Results

Compared to the control group; QT (426,64 ± 14,62 vs. 348,84 ± 12,24 ms, p < 0,001), QTc (456,24 ± 28,84 vs. 392,48 ± 14,36 ms, p < 0,001), Tp-e (84,32 ± 3,46 vs. 70,12 ± 3,12, p < 0,001), Tp-e/QTc (0,185 ± 0,08 vs. 0,178 ± 0,02, p < 0,001), ICEB (4,53 ± 0,78 vs. 3,74 ± 0,28, p < 0,001) and ICEBc (4,86 ± 0,86 vs. 4,21 ± 0,24, p < 0,001) were significantly higher in patients with aneurysmal SAH. QT, QTc and Tp-e interval, Tp-e/QTc ratio, ICEB (QT/QRS) and ICEBc (QTc/QRS) were positively correlated with the Fisher score and were negatively correlated with the GCS. According to linear regression analyses, the ICEBc (QTc/QRS) found to be independently associated with the Fisher score.

Conclusion

The values of the ICEB and ICEBc were significantly increased in patients with aneurysmal SAH. The severity of SAH was positively correlated with the ICEB and ICEBc. The ICEBc (QTc/QRS) independently associated with the Fisher score. This may that SAH suggest may predispose to malignant ventricular arrhythmias.

Electrocardiographic abnormalities in patients with COVID-19 pneumonia and raised interleukin-6

Background

Cardiac injury is associated with high mortality in patients with COVID-19 infection. Electrocardiographic changes can give clues to the underlying cardiovascular abnormalities. Raised inflammatory markers like raised interleukin-6 (IL-6) are associated with arrhythmia, heart failure, and coronary artery disease. However, past studies have not highlighted the electrocardiographic abnormalities in patients with COVID-19 infection with raised IL- 6 levels. This study compared the electrocardiogram (ECG) changes in COVID-19 patients with high and normal IL-6 levels.

Methods

A retrospective analysis of ECG of 306 patients with COVID-19 infection was done, out of which 250 patients had normal IL- 6 levels, whereas 56 patients had raised IL-6 levels. IL-6 levels were measured in all the patients. Detailed clinicodemographic profile of all the serial COVID-19 patients admitted with moderate to severe COVID-19 pneumonia was noted from the hospital record section. Electrocardiographic findings and biochemical parameters of all the patients were noted.

Results

Out of 56 patients with raised IL-6 levels, 41 (73.2%) patients had ECG abnormalities compared to 177 (70.8%) patients with normal IL-6 levels. This difference was not statistically significant. However, ECG abnormality such as sinus tachycardia was significantly more common in patients with raised IL-6 levels than those with normal levels. Among patients with raised IL-6 levels who were discharged, 5 (16.6%) had sinus tachycardia, 2 (6.6%) had ST/T wave changes as compared to 15 (57.6%), and 10 (38.4%) who had tachycardia and ST/T wave change respectably succumbed to death. This difference was statistically significant.

Conclusions

Sinus tachycardia followed by atrial fibrillation and right bundle branch block are common ECG changes in patients with COVID-19 infection with raised IL-6. The possible association of cardiac injury in patients with COVID-19 infection with coexisting raised IL-6 levels should be explored further.

Effects of dexmedetomidine on cardiac electrophysiology in patients undergoing general anesthesia during perioperative period: a randomized controlled trial

Background

Dexmedetomidine has controversial influence on cardiac electrophysiology. The aim of this study was to explore the effects of dexmedetomidine on perioperative cardiac electrophysiology in patients undergoing general anesthesia.

Methods

Eighty-one patients were randomly divided into four groups: groups D₁, D₂, D₃ receiving dexmedetomidine 1, 1, 0.5 μg/kg over 10 min and 1, 0.5, 0.5 μg/kg/h continuous infusion respectively, and control group (group C) receiving normal saline. Twelve-lead electrocardiograms were recorded at the time before dexmedetomidine/normal saline infusion (T₁), loading dose finish (T₂), surgery ending (T₆), 1 h (T₇) after entering PACU, 24 h (T₈), 48 h (T₉), 72 h (T₁₀) and 1 month (T₁₁) postoperatively. Cardiac circulation efficiency (CCE) were also recorded.

Results

Compared with group C, QTc were significantly increased at T₂ in groups D₁ and D₂ while decreased at T₇ and T₈ in group D₃ (P < 0.05), iCEB were decreased at T₈ (P < 0.05). Compared with group D₁, QTc at T₂, T₆, T₇, T₉ and T₁₀ and iCEB at T₈ were decreased, and CCE at T₂-T₄ were increased in group D₃ significantly (P < 0.05). Compared with group D₂, QTc at T₂ and iCEB at T₈ were decreased and CCE at T₂ and T₃ were increased in group D₃ significantly (P < 0.05).

Conclusions

Dexmedetomidine at a loading dose of 0.5 μg/kg and a maintenance dose of 0.5 μg/kg/h can maintain stability of cardiac electrophysiology during perioperative period and has no significant adverse effects on CCE.

Trial registration

ClinicalTrials.gov NCT04577430 (Date of registration: 06/10/2020).

Clinical Characteristics, Genetic Findings and Arrhythmic Outcomes of Patients with Catecholaminergic Polymorphic Ventricular Tachycardia from China: A Systematic Review

INTRODUCTION

Catecholaminergic polymorphic ventricular tachycardia (CPVT) is a rare inherited cardiac ion channelopathy. The present study aims to examine the clinical characteristics, genetic basis, and arrhythmic outcomes of CPVT patients from China to elucidate the difference between CPVT patients in Asia and Western countries.

METHODS

PubMed and Embase were systematically searched for case reports or series reporting on CPVT patients from China until 19 February 2022 using the keyword: "Catecholaminergic Polymorphic Ventricular Tachycardia" or "CPVT", with the location limited to: "China" or "Hong Kong" or "Macau" in Embase, with no language or publication-type restriction. Articles that did not state a definite diagnosis of CPVT and articles with duplicate cases found in larger cohorts were excluded. All the included publications in this review were critically appraised based on the Joanna Briggs Institute Critical Appraisal Checklist. Clinical characteristics, genetic findings, and the primary outcome of spontaneous ventricular tachycardia/ventricular fibrillation (VT/VF) were analyzed.

RESULTS

A total of 58 unique cases from 15 studies (median presentation age: 8 (5.0-11.8) years old) were included. All patients, except one, presented at or before 19 years of age. There were 56 patients (96.6%) who were initially symptomatic. Premature ventricular complexes (PVCs) were present in 44 out of 51 patients (86.3%) and VT in 52 out of 58 patients (89.7%). Genetic tests were performed on 54 patients (93.1%) with a yield of 87%. RyR2, CASQ2, TERCL, and SCN10A mutations were found in 35 (71.4%), 12 (24.5%), 1 (0.02%) patient, and 1 patient (0.02%), respectively. There were 54 patients who were treated with beta-blockers, 8 received flecainide, 5 received amiodarone, 2 received verapamil and 2 received propafenone. Sympathectomy (n = 10), implantable cardioverter-defibrillator implantation (n = 8) and ablation (n = 1) were performed. On follow-up, 13 patients developed VT/VF.

CONCLUSION

This was the first systematic review of CPVT patients from China. Most patients had symptoms on initial presentation, with syncope as the presenting complaint. RyR2 mutation accounts for more than half of the CPVT cases, followed by CASQ2, TERCL and SCN10A mutations.

Anesthesia induction regimens may affect QT interval in cardiac surgery patients: A randomized-controlled trial

Background: The aim of this study was to investigate the effects on QT interval of the propofol-ketamine combination and the midazolam-fentanyl combination in anesthesia induction for cardiac surgery.

Methods: Between September 2020 and June 2021, a total of 9 5 c ardiac s urgery p atients ( 80 m ales, 1 5 f emales; mean age: 57±9.1 years; range, 26 to 76 years) were included. The patients were divided into two groups as Group PK (propofol-ketamine, n=50) and Group MF (midazolam-fentanyl, n=45). The 12-lead electrocardiographic and hemodynamic measurements were performed at three time points: before anesthesia induction, after anesthesia induction, and after endotracheal intubation. The measurements were evaluated with conventional Bazett's formula and a new model called index of cardio-electrophysiological balance.

Results: The evaluated QTc values of 95 patients after anesthesia induction were significantly prolonged with the Bazett's formula and the index of cardio-electrophysiological balance in Group PK (p=0.034 and p=0.003, respectively). A statistically significant QTc prolongation was observed with the index of cardio-electrophysiological balance after laryngoscopy and endotracheal intubation in Group PK (p=0.042). Hemodynamic parameters were also higher in Group PK.

Conclusion: Our study shows that the propofol-ketamine combination prolongs the QTc value determined by the Bazett's formula and the index of cardio-electrophysiological balance model. Using both QTc measurement models, the midazolam-fentanyl combination has no prolongation effect on QTc interval in coronary surgery patients.

Evaluation of index of cardio-electrophysiological balance in patients with coronary slow flow

BACKGROUND

Coronary slow flow (CSF) is defined as the late progression of applied contrast through coronary arteries. The cardiac electrophysiological balance index (iCEB) reflects the balance between ventricular depolarisation and repolarisation and provides more information about ventricular arrhythmogenesis (VA) than other electrocardiography (ECG) parameters (QT, corrected QT [QTc], etc.).

AIM

We aimed to evaluate iCEB in patients with CSF.

METHODS

We divided the study population into two groups as CSF and control. The CSF group consisted of 100 patients (33 female, 67 male, mean age 52.2 ± 2.6), while the control group consisted of the same number of age and sex-matched patients (35 female, 65 male, mean age 51.7 ± 1.4). ECG parameters of the study population (QRS duration, QT, T wave peak-to-end (Tp-e) intervals, iCEB (QT/QRS), and iCEBc (heart rate QTc/QRS) rates were calculated and compared between CSF and control groups.

RESULTS

Intervals (QT and QTc intervals) and Tp-e/QTc ratio were greater in the CSF group compared with controls [422.1 ± 12.8 vs. 349.4 ± 14.3 bpm, respectively, p  <  .001; 457.0 ± 12.2 vs. 378.1 ± 12.3 bpm, respectively, p < .001, and 0.19 vs. 0.12, respectively, p  <  .001]. ICEB and iCEBc were significantly greater than controls [(4.9 ± 0.4 vs. 4.2 ± 0.4, respectively, p < .001), (5.7 ± 0.3 vs. 4.4 ± 0.3, respectively, p < .001)].

CONCLUSIONS

ICEB and iCEBc were significantly increased in patients with CSF. This may suggest that CSF may predispose to malign arrhythmias.

The relationship between white coat hypertension and the index of cardiac electrophysiological balance (ICEB)

Aim: The index of cardiac electrophysiological balance (ICEB) is a new marker that can show the potential for ventricular arrhythmia and indicate the balancebetween ventricular depolarization and repolarization. A tendency toward ventricular arrhythmia has been shown innon-dipper hypertension and prehypertensive patients in various studies. White coat hypertension (WCH) has been shown to be associated with target organ damage and the actual development of hypertension. In this study, we aimed to evaluate the effect of dipper and non-dipper patterns on the ICEB in patients diagnosed with WCH. Material and Method: A total of 108 patients were included in this study. Patients were divided into two groups as dipper and non-dipper patterns according to ABPM. QT/QRS (ICEB) and cQT/QRS (ICEBc) were recorded with computerized interpretation of the electrocardiogram. Results: While electrocardiographic parameters including heart rate, PR interval, QT interval, cQT interval, and ICEB were similar in both groups (p>.05), in the non-dipper group, QRS duration was lower (p=.017) and ICEBc was higher (p=.001). Conclusion: ICEBc may predict asusceptibility to ventricular arrhythmias in WCH patients. Therefore, non-dipper WCH patients with a high ICEBc should be followed for arrhythmia outcomes in addition to hypertensive outcomes.

Evaluation of Tp-e interval, Tp-e/QT ratio and index of cardiac-electrophysiological balance in patients with tinnitus

Background

Tinnitus is a common auditory symptom. Dysfunction in the autonomic nervous system (ANS) is an essential part of the etiopathogenesis of tinnitus. ANS regulates heart rate and heart rhythm and can lead to ventricular repolarization changes, which can cause malignant ventricular arrhythmias. T wave peak-to-end T(p-e) interval and T(p-e)/QT ratio are known ventricular arrhythmia indexes, and the index of cardiac-electrophysiological balance (iCEB) is a novel index that can be used to predict the risk of malignant ventricular arrhythmia. The goal of the study was to investigate these ventricular arrhythmia indexes in patients with tinnitus.

Methods

The study population consisted of 240 patients with tinnitus and 240 healthy subjects. A standard 12-channel surface electrocardiogram was applied to both groups. T(p-e) interval, QT interval and QRS duration were determined. Corrected QT (QTc) was determined via Bazett’s formula. To predict ventricular arrhythmia, iCEB (QT/QRS), T(p-e)/QT, corrected iCEB (QTc/QRS) and T(p-e)/QTc values were determined and compared between groups.

Results

Compared to the control group, QT (376.46 ± 36.54 vs 346.52 ± 24.51 ms), QTc (426.68 ± 24.68 vs 390.42 ± 24.04 ms), T(p-e) (75.86 ± 14.68 vs 62.42 ± 8.64 ms), T(p-e)/QT (0.201 ± 0.06 vs 0.180 ± 0.01) and T(p-e)/QTc (0.177 ± 0.06 vs 0.159 ± 0.02) were significantly higher in patients with tinnitus (p < 0.001 for all). QT/QRS (3.92 ± 0.68 vs 3.56 ± 0.32) and QTc/QRS (4.44 ± 1.03 vs 4.01 ± 0.64) were also significantly higher in patients with tinnitus (p = 0.018 and p = 0.008, respectively). In addition, significant positive correlations were found between T(p-e), T(p-e)/QTc ratio and disease duration (r = 0.792, p < 0.001; r = 0.500, p < 0.001, respectively).

Conclusion

As a result, patients with tinnitus may have an increased risk of malignant ventricular arrhythmia.

Effect of ranolazine on Tp-e interval, Tp-e/QTc, and P-wave dispersion in patients with stable coronary artery disease

INTRODUCTION

Ranolazine is an antianginal drug and also exhibits antiarrhythmic effect by affecting action potential time, refractory period, and repolarization reserve. We evaluated the effect of ranolazine therapy on myocardial repolarization parameters (Tp-e, QT, QTc intervals, Tp-e/QT, and Tp-e/QTc ratios), index of cardiac electrophysiological balance (iCEB) (QT/QRS, QTc/QRS) and P-wave dispersion (PWD) in patients with stable coronary artery disease (CAD).

METHODS

This study included 175 patients, aged between 35 and 90 years who were followed with stable CAD for at least 3 months. Ninety patients had been receiving ranolazine for at least 1 month, and 85 patients had never received ranolazine. All patients' basic demographic data, risk factors, medications, and echocardiographic parameters recorded. Myocardial repolarization parameters, P-wave times, and PWD were analyzed from 12 lead electrodes.

RESULTS

There was no variation between the groups in terms of basic demographic parameters and CAD risk factors. Tp-e interval (87.3 ± 14.4 vs. 90.8 ± 12.4 msn, P < .001), Tp-e/QT (0.22 ± 0.04 vs. 0.23 ± 0.03; P = .03), Tp-e/QTc (0.21 ± 0.04 vs. 0.22 ± 0.04 P = .001), and PWD (39.2 ± 13.7 vs. 43.5 ± 12.9 P = .028) were significantly lower in the ranolazine group. But iCEB was similar in both groups. In multivariate analysis after adjusted confounding factors such as age and BMI, Tp-e/QTc ratio, QTc, Pmax, and PWD were found significantly in ranolazine group again.

CONCLUSION

Tp-e/QTc ratio, QTc, Pmax, and PWD were significantly lower in stable CAD patients under ranolazine therapy. In stable CAD patients, the prognostic significance of ranolazine for arrhythmic events requires further evaluation of these parameters through long-term follow-up and large-scale prospective studies.

Evaluation of Index of Cardio-Electrophysiological Balance in Patients With Atrial Fibrillation on Antiarrhythmic-Drug Therapy

BACKGROUND

Index of cardio-electrophysiological balance (iCEB) has been described as a novel risk marker for predicting malignant ventricular arrhythmia. There remains limited evidence on the effects of amiodarone and propafenone used for sinus rhythm maintenance on iCEB in patients with atrial fibrillation (AF). The aim of this study was to evaluate iCEB in patients with AF on antiarrhythmic-drug therapy.

METHODS

A total of 108 patients with AF (68 patients using amiodarone and 40 patients using propafenone) and 50 healthy subjects were included in the study. All groups underwent a standard 12-lead surface electrocardiogram. QRS duration, QT, T wave peak-to-end (Tp-e) intervals, iCEB (QT/QRS) and iCEBc (heart rate-corrected QT (QTc)/QRS) rates were calculated from the electrocardiogram and compared between groups.

RESULTS

QT, Tp-e intervals and Tp-e/QT ratio were significantly longer in the amiodarone group than the propafenone and control groups (P < 0.001, for all). iCEB was similar in the amiodarone and control groups (4.4 ± 0.6 and 4.2 ± 0.4; P > 0.05), while iCEB values in the propafenone group were significantly lower than the amiodarone group and control groups (3.9 ± 0.5; P < 0.001). There was a significantly difference in iCEBc values among the amiodarone, control and propafenone groups (4.8 ± 0.6, 4.6 ± 0.4 and 4.3 ± 0.6; P < 0.001, respectively).

CONCLUSIONS

In this study, higher iCEBc parameters were observed in patients using amiodarone, while iCEBc values were lowest among patients with AF using propafenone. Further studies are needed to determine whether these electrophysiological changes are associated with ventricular arrhythmias for patients with AF on antiarrhythmic-drug therapy.

Favorable electrocardiographic changes after substantial weight loss in patients with morbid obesity : Results of a prospective study

BACKGROUND

Obese patients have an increased risk of arrhythmias and sudden death, even in the absence of structural heart disease and cardiac dysfunction. This study aimed to determine whether weight loss by bariatric surgery has an effect on arrhythmia-related electrocardiographic (ECG) variables in morbidly obese patients.

METHODS

In this prospective study, the data of 48 patients were analyzed. All ECG variables that have the potential to predict ventricular arrhythmia were evaluated before surgery, and were compared with the 1‑month and 6‑month follow-up results.

RESULTS

The mean body mass index was 45.74 ± 5.60 kg/m² before surgery. There was a statistically significant decline in body mass index in the first and sixth month after surgery (39.26 ± 5.00 kg/m² and 31.71 ± 4.49 kg/m², respectively; p < 0.001). Furthermore, notable reduction was found in terms of heart rate measurements-QTc‑d, JTc, JTc‑d, Tp‑e, TP-e/QT, TP-e/QTc-in the first month and sixth month compared with baseline (p < 0.001 for all comparisons). Several ECG variables, such as heart rate (r = 0.369, p = 0.001), QTc‑d (r = 0.449, p = 0.001), JTc‑d (r = 0.324, p = 0.002), Tp‑e (r = 0.592, p = 0.001), Tp-e/QTc (r = 0.543, p = 0.001), Tp-e/JTc (r = 0.515, p = 0.001), exhibited a positive and significant correlation with weigh loss. Moreover, a negative and weakly significant correlation was found between the index of cardiac electrophysiological balance (r = -0.239, p = 0.004) and body mass index.

CONCLUSION

Substantial weight loss following laparoscopic sleeve gastrectomy in obese patients is accompanied by a significant improvement in ventricular repolarization. Therefore, this effect may lead to a decrease in the incidence of lethal ventricular arrhythmia and sudden cardiac death.

Electrocardiographic markers of increased risk of sudden cardiac death in patients with COVID-19 pneumonia

Background

Little is known about the role of ECG markers of increased risk of sudden cardiac death during the acute period of coronavirus disease 2019 ( COVID‐19) pneumonia.

Objectives

To evaluate ECG markers of sudden cardiac death on admission, including the index of cardiac electrophysiological balance (iCEB) (QTc/QRS) and transmural dispersion of repolarization (TDR) (T from peak to end (Tp‐e) interval and Tp‐e/QTc), in patients with COVID‐19 pneumonia.

Patients and methods

This cross‐sectional study included 63 patients with newly diagnosed COVID‐19 pneumonia who presented to the outpatient clinic or admitted to the respiratory care unit between August 20 and September 15, 2020. Forty‐six persons matched for sex and age were selected from data collected before COVID‐19 pandemic.

Results

QRS and QTc showed a significant prolongation in patients with COVID‐19 pneumonia compared to the controls (87 vs. 78, p < .00, and 429 versus. 400, p < .00, respectively). After categorization of patients with COVID‐19 pneumonia into 3 groups according to the severity of pneumonia as mild‐moderate, severe, and critical groups, a decreased values of QRS were observed in the critical COVID‐19 pneumonia group compared to severe and mild‐moderate COVID‐19 pneumonia groups (p = .04) while increased values of QTc and iCEB(QTc/QRS) were noted in critical COVID‐19 pneumonia group compared to other 2 groups(p < .00).

Conclusions

Patients with COVID‐19 pneumonia showed significant changes in repolarization and conduction parameters compared to controls. Patients with mild to severe COVID‐19 pneumonia may be at low risk for torsades de pointes development.

Index of cardiac-electrophysiological balance and the effects of thrombolytic therapy on the electrocardiogram of patients with pulmonary embolism

OBJECTIVE

Different parameters on electrocardiograms (ECG) have been investigated to predict arrhythmia and mortality in patients with acute pulmonary embolism (APE). The acute effect of thrombolytic therapy (TT) on these parameters has not been investigated yet.

METHODS

We examined the data of 83 patients who were evaluated as high-risk APE and discharged from the hospital after TT. First, the high-risk APE patients' ECGs were compared with healthy control subjects (n = 55). After their admission and 24 hours later, the ECGs of patients with APE were compared. Heart rate, P-wave morphology, QRS duration, QT distance, Tp-e, and the index of cardiac electrophysiological balance (iCEB) were analyzed.

RESULTS

Although P maximum was not different between the groups' ECGs, heart rate, QT, QTc (corrected QT) interval, Tp-e intervals, Tp-e/QT ratio, and P wave dispersion were significantly higher in the APE group ( P values < 0.031). iCEB or iCEBc (corrected iCEB) values were lower in APE group ( P < 0.001). After TT, we determined a decrease in heart rate, Tp-e interval, and Tp-e/QT ratio ( P < 0.001). Although we detected a decrease in the QT and QTc interval and QT dispersion (QTd), QTd had no statistical significance (respectively P -value 0.013, 0.029, and 0.096). The iCEB and iCEBc levels were lower after TT ( P -value was 0.035 and 0.044 respectively).

CONCLUSION

The QT, QTc, Tp-e interval, Tp-e/QTc ratio, iCEB, and iCEBc values significantly decreased after TT. It may be thought that effective TT causes partial improvement in ventricular repolarization in an early period.

Electrocardiographic Characteristics of Breast Cancer Patients Treated with Chemotherapy

Introduction

Patients receiving chemotherapy for breast cancer may be at risk of developing cardiac dysfunction and electrophysiological abnormalities. The aim of this study is to evaluate alterations in electrocardiographic (ECG) parameters in breast cancer patients receiving chemotherapy.

Materials and Methods

This was a prospective single-center cohort study conducted in the Fourth Hospital of Hebei Medical University, China. Participants with breast cancer referred for chemotherapy from May 1, 2019, to October 1, 2019, were invited to participate in the study. Standard 12-lead ECG and echocardiography were performed at baseline or before chemotherapy (prechemotherapy) (T0), after 1 cycle (T1), after 3 cycles (T2), and at the end of chemotherapy (T3).

Results

A total of 64 patients with diagnosed breast cancer undergoing chemotherapy were included. Echocardiographic parameters showed no significant variation during the entire procedure (all P > 0.05). The incidence of abnormal ECG increased from 43.75% at baseline to 65.63% at the end of chemotherapy, of which only the prevalence of fragmented QRS (fQRS) was significantly increased after the drug regimen (26.56% to 53.13%). At the end of the treatment, heart rate, P-wave dispersion, corrected QT interval, T-peak to T-end, RR, SV1, RV5, Sokolow–Lyon index (SLI), and index of cardioelectrophysiological balance deteriorated markedly (all P < 0.05). The area under the curve for SLI and QT dispersion (QTd) derived by ECG was 0.710 and 0.606, respectively. The cutoff value with 2.12 of SLI by ECG had a sensitivity of 67.2% and specificity of 71.9% for differentiating patients after therapy from baselines. The cutoff value with 0.55 of QTd had a sensitivity of 60.9% and specificity of 60.9%.

Conclusions

The current study demonstrated that ECGs can be used to detect electrophysiological abnormalities in breast cancer patients receiving chemotherapy. ECG changes can reflect subclinical cardiac dysfunction before the echocardiographic abnormalities.

Decompressive Craniectomy Improves QTc Interval in Traumatic Brain Injury Patients

Background: Traumatic brain injury (TBI) is commonly associated with cardiac dysfunction, which may be reflected by abnormal electrocardiograms (ECG) and/or contractility. TBI-related cardiac disorders depend on the type of cerebral injury, the region of brain damage and the severity of the intracranial hypertension. Decompressive craniectomy (DC) is commonly used to reduce intra-cranial hypertension (ICH). Although DC decreases ICH rapidly, its effect on ECG has not been systematically studied. The aim of this study was to analyze the changes in ECG in patients undergoing DC. Methods: Adult patients without previously known cardiac diseases treated for isolated TBI with DC were studied. ECG variables, such as: spatial QRS-T angle (spQRS-T), corrected QT interval (QTc), QRS and T axes (QRS_ax and T_ax, respectively), STJ segment and the index of cardio-electrophysiological balance (iCEB) were analyzed before DC and at 12–24 h after DC. Changes in ECG were analyzed according to the occurrence of cardiac arrhythmias and 28-day mortality. Results: 48 patients (17 female and 31 male) aged 18–64 were studied. Intra-cranial pressure correlated with QTc before DC (p < 0.01, r = 0.49). DC reduced spQRS-T (p < 0.001) and QTc interval (p < 0.01), increased Tax (p < 0.01) and changed STJ in a majority of leads but did not affect QRS_ax and iCEB. The iCEB was relatively increased before DC in patients who eventually experienced cardiac arrhythmias after DC (p < 0.05). Higher post-DC iCEB was also noted in non-survivors (p < 0.05), although iCEB values were notably heart rate-dependent. Conclusions: ICP positively correlates with QTc interval in patients with isolated TBI, and DC for relief of ICH reduces QTc and spQRS-T. However, DC might also increase risk for life-threatening cardiac arrhythmias, especially in ICH patients with notably prolonged QTc before and increased iCEB after DC.

Evaluation of index of cardiac-electrophysiological balance as arrhythmia predictor in bonsai users

BACKGROUND

Synthetic cannabinoids are part of a group of drugs called new psychoactive substances. The increase in substance use among young adults is becoming a major problem in the world. In this study we aimed to investigate the effects of synthetic cannabinoid drugs such as bonsai to electrocardiographic (ECG) parameters, in patients who were admitted to emergency service with self-reported usage of bonsai.

METHODS

Seventy-two patients (68 males; mean age 33.8±11.8) with self-reported use of bonsai and 27 (22 males; mean age 37.1±8.7) age and sex-matched healthy control group enrolled the study. ECG parameters and rhythm holter were measurements calculated in both groups.

RESULTS

Groups were age and sex matched. Glucose, potassium, white blood cell count, heart rate end smoking status was significantly different in patients compared to control group. P wave max time, P wave min. time, P wave dispersion, QT max. time QT dispersion, QT corrected time and index of cardiac-electrophysiological balance measurements (iCEB) were significantly different in groups of patients. A multivariate logistic regression analysis was used to determine independent predictors of ≥30 Ventricular premature beat (VPB)/h using parameters found to be associated with ≥30 VPB/h in a univariate analysis (potassium, QT<inf>max</inf> time, QTc, QRS time, iCEB).In a multivariate analysis, independent predictors of ≥30 VPB/h were potassium (Odds ratio [OR]: 0.107, 95% CI: 0.024-0.481;P=0.004) and iCEB (OR: 4.474, 95% CI: 1.752-11.429;P=0.002). In generalize linear model β-coefficient value of interaction terms between K*iCEB has no important effect on ventricular premature beats.

CONCLUSIONS

If the results are confirmed in further studies, iCEB seems to be a simple, easily measurable and non-invasive marker to predict cannabinoid-induced ventricular arrhythmias.

Brugada syndrome: A comprehensive review of pathophysiological mechanisms and risk stratification strategies

Brugada syndrome (BrS) is an inherited ion channel channelopathy predisposing to ventricular arrhythmias and sudden cardiac death. Originally believed to be predominantly associated with mutations in SCN5A encoding for the cardiac sodium channel, mutations of 18 genes other than SCN5A have been implicated in the pathogenesis of BrS to date. Diagnosis is based on the presence of a spontaneous or drug-induced coved-type ST segment elevation. The predominant electrophysiological mechanism underlying BrS remains disputed, commonly revolving around the three main hypotheses based on abnormal repolarization, depolarization or current-load match. Evidence from computational modelling, pre-clinical and clinical studies illustrates that molecular abnormalities found in BrS lead to alterations in excitation wavelength (λ), which ultimately elevates arrhythmic risk. A major challenge for clinicians in managing this condition is the difficulty in predicting the subset of patients who will suffer from life-threatening ventricular arrhythmic events. Several repolarization risk markers have been used thus far, but these neglect the contributions of conduction abnormalities in the form of slowing and dispersion. Indices incorporating both repolarization and conduction based on the concept of λ have recently been proposed. These may have better predictive values than the existing markers. Current treatment options include pharmacological therapy to reduce the occurrence of arrhythmic events or to abort these episodes, and interventions such as implantable cardioverter-defibrillator insertion or radiofrequency ablation of abnormal arrhythmic substrate.

Effect of habitual cigarette smoking on the index of cardiac electrophysiological balance in apparently healthy individuals

BACKGROUND AND AIM

Chronic cigarette smoking has been suggested to portend risk for cardiac arrhythmia generation. Index of cardiac electrophysiological balance (iCEB) is a relatively new ECG parameter indicating balance between ventricular depolarization and repolarization, thereby providing more insight concerning ventricular arrhythmogenesis (VA) than other classical ECG parameters such as QT and corrected QT (QTc) intervals. The present study aimed to assess the status of iCEB in healthy habitual smokers.

METHODS

This retrospective study included a total of 80 apparently healthy subjects (45% female, mean age 39.4 ± 8.1 years) with smoking habit and 82 healthy non-smoking subjects (40% female, mean age 37.0 ± 8.6 years) were included between January-September 2019. Demographic, clinical and ECG characteristics were obtained from medical records. iCEB and corrected iCEB values were calculated by dividing respective QT and QTc intervals by QRS duration.

RESULTS

Mean PR, QRS and QT intervals were similar between the groups, whereas mean heart rate and QTc interval were greater in the smoker group compared with the non-smokers [(82.0 ± 8.9 bpm vs 77.8 ± 12.4 bpm, respectively, p = 0.016) and (427.05 ± 22.6 msec vs 399.9 ± 12.8 msec, respectively, p < 0.001)]. Subject with smoking habit had greater iCEBc than the controls (5.10 ± 0.49 vs 4.68 ± 0.39, respectively, p < 0.001). However, there was no significant difference in regard of iCEB between the groups (4.37 ± 0.46 vs 4.32 ± 0.42, respectively, p = 0.456).

CONCLUSION

iCEBc increases significantly in healthy smokers compared with non-smokers. This may suggest an increased predisposition to Torsades de Pointes-mediated VA in healthy smokers, or in chronic smokers with inherent QT-prolonging genetic variations or those on QT-prolonging drug therapy.

Missing Link between Molecular Aspects of Ventricular Arrhythmias and QRS Complex Morphology in Left Ventricular Hypertrophy

The aim of this opinion paper is to point out the knowledge gap between evidence on the molecular level and clinical diagnostic possibilities in left ventricular hypertrophy (LVH) regarding the prediction of ventricular arrhythmias and monitoring the effect of therapy. LVH is defined as an increase in left ventricular size and is associated with increased occurrence of ventricular arrhythmia. Hypertrophic rebuilding of myocardium comprises interrelated processes on molecular, subcellular, cellular, tissue, and organ levels affecting electrogenesis, creating a substrate for triggering and maintaining arrhythmias. The knowledge of these processes serves as a basis for developing targeted therapy to prevent and treat arrhythmias. In the clinical practice, the method for recording electrical phenomena of the heart is electrocardiography. The recognized clinical electrocardiogram (ECG) predictors of ventricular arrhythmias are related to alterations in electrical impulse propagation, such as QRS complex duration, QT interval, early repolarization, late potentials, and fragmented QRS, and they are not specific for LVH. However, the simulation studies have shown that the QRS complex patterns documented in patients with LVH are also conditioned remarkably by the alterations in impulse propagation. These QRS complex patterns in LVH could be potentially recognized for predicting ventricular arrhythmia and for monitoring the effect of therapy.

Restitution metrics in Brugada syndrome: a systematic review and meta-analysis

BACKGROUND

Brugada syndrome (BrS) is an ion channelopathy that predisposes affected subjects to ventricular tachycardia/fibrillation (VT/VF) and sudden cardiac death. Restitution analysis has been examined in BrS patients but not all studies have reported significant differences between BrS patients and controls. Therefore, we conducted a systematic review and meta-analysis to investigate the different restitution indices used in BrS.

METHODS

PubMed and Embase were searched until April 7, 2019, identifying 20 and 27 studies.

RESULTS

A total of ten studies involving 178 BrS (mean age 38 years old, 63% male) and 102 controls (mean age 31 years old, 42% male) were included in this systematic review. Pacing was carried out at the right ventricular outflow tract (RVOT)/right ventricular apex (RPA) (n = 4), RPA (n = 4), or right atrium (RA) (n = 1). Basic cycle lengths of 400 (n = 4), 500 (n = 2), 600 (n = 6) and 750 ms (n = 1) were used. Recording methods include electrograms (n = 4), monophasic action potentials (n = 5), and electrocardiograms (n = 1). Signals were obtained from the RVOT (n = 8), RVA (n = 3), RA (n = 1), or the body surface (n = 1). The maximum restitution slope for endocardial repolarization at the RVOT was 0.87 for BrS patients (n = 5; 95% confidence interval [CI] 0.68-1.07) compared with 0.74 in control subjects (n = 4; 95% CI 0.42-1.06), with a significant mean difference of 0.40 (n = 4; 95% CI 0.11-0.69; P = 0.007).

CONCLUSIONS

Steeper endocardial repolarization restitution slopes are found in BrS patients compared with controls at baseline. Restitution analysis can provide important information for risk stratification in BrS.

Effects of different concentrations of desflurane on the index of cardiac electrophysiological balance in gynecologic surgery patients

The objectives were to observe the effects of different concentrations of desflurane on QT, QTc, Tp-e, Tp-e/QT, and the index of cardiac electrophysiological balance (iCEB). Sixty patients were randomly divided into group D₁, group D₂, and group D₃ by using a random number table, 20 in each group. After entering the operating room, patients received 10 mL/kg hydroxyethyl starch, 0.1 mg/kg midazolam, 0.1 mg/kg vecuronium, 3 μg/kg fentanyl, and 0.3 mg/kg etomidate intravenously and then accepted intubation and mechanical ventilation. The desflurane evaporator was opened. The concentrations of desflurane in the D₁, D₂, and D₃ groups were maintained at 0.6, 1.3, and 2.0 minimum alveolar concentration (MAC), respectively. Twelve-lead ECGs were recorded at time before induction (T₁) and at 20 min after desflurane reached the required concentration (T₂). HR and MAP were recorded measure and the QT interval, QTc interval, Tp-e interval, Tp-e/QT ratio, and iCEB were calculated. Compared with before inhalation (T₁), the QTc interval was prolonged in the D₁, D₂, and D₃ groups after inhalation of different concentrations of desflurane for 20 min (T₂) (P < 0.05) and the Tp-e/QT ratio decreased in the D₁ and D₂ groups at T₂ (P < 0.05). Compared with the D₁ and D₂ groups, the Tp-e/QT ratio of the D₃ group increased at T₂ (P < 0.05). There was no significant difference in Tp-e interval and iCEB at any time (P > 0.05). The study suggested that inhalation of desflurane at a normal concentration cannot cause arrhythmogenic characteristics and affect the cardiac electrophysiological stability.

Electrocardiographic conduction and repolarization markers associated with sudden cardiac death: moving along the electrocardiography waveform

The QT interval along with its heart rate corrected form (QTc) are well-established ECG markers that have been found to be associated with malignant ventricular arrhythmogenesis. However, extensive preclinical and clinical investigations over the years have allowed for novel clinical ECG markers to be generated as predictors of arrhythmogenesis and sudden cardiac death. Repolarization markers include the older QTc, QT dispersion and newer Tpeak - Tend intervals, (Tpeak - Tend) / QT ratios, T-wave alternans (TWA), microvolt TWA and T-wave area dispersion. Meanwhile, conduction markers dissecting the QRS complex, such as QRS dispersion (QRSD) and fragmented QRS, were also found to correlate conduction velocity and unidirectional block with re-entrant substrates in various cardiac conditions. Both repolarization and conduction parameters can be combined into the excitation wavelength (λ). A surrogate marker for λ is the index of Cardiac Electrophysiological Balance (iCEB: QT / QRSd). Other markers based on conduction-repolarization are [QRSD x (Tpeak-Tend) / QRSd] and [QRSD x (Tpeak-Tend) / (QRSd x QT)]. Advancement in technology permitted sophisticated electrophysiological analyses such as principal component analysis and periodic repolarization dynamics to further improve risk stratification. This was closely followed by other novel indices including ventricular ectopic QRS interval, the f99 index and EntropyXQT, which integrates mathematical and physical calculations for determining the risk markers. Though proven to be effective in limited patient cohorts, more clinical studies across different cardiac pathologies are required to confirm their validity. As such, this review seeks to encapsulate the development of old and new ECG markers along with their associated utility and shortcomings in clinical practice.

Evaluation of index of cardiac-electrophysiological balance before and after hemodialysis in patients with end-stage renal disease

BACKGROUND

Ventricular arrhythmias and sudden cardiac deaths are the most common cause of mortality in patients with end-stage renal disease (ESRD). Index of cardiac-electrophysiological balance (iCEB) (QT/QRS) may predict malignant ventricular arrhythmias. In this study, we investigated whether iCEB value is increased in ESRD patients and whether it changes before and after hemodialysis.

METHODS

The study included 52 ESRD patients and 53 control subjects matched for age and comorbidities. Biochemical, electrocardiographic and echocardiographic values of all participants were recorded. QRS, QT, Tp-e were measured manually. QTC was calculated using Bazett's formula. Then, Tp-e/QT, Tp-e/QTc, QT/QRS, and QTc/QRS ratios were calculated. The changes in ECG parameters of the ESRD patients before and after HD were compared using paired t-test.

RESULTS

Mean age and male sex ratio was comparable in both groups (p = 0.448 and p = 0.777, respectively). Comorbidity incidences, and biochemical parameters except eGFR (p < 0.001), albumin (p < 0.001), HDL cholesterol (p = 0.03) and platelet counts (p < 0.001) were comparable in both groups. Compared to the control group, QT, QTc, Tp-e, Tp-e/QT, Tp-e/QTc, QT/QRS, and QTc/QRS ratios were higher in the ESRD group (p < 0.05 for each). While QT and QTc intervals did not change after HD in ESRD patients, Tp-e, Tp-e/QT, Tp-e/QTc, QT/QRS, and QTc/QRS parameters increased significantly.

CONCLUSION

In addition to ventricular repolarization dispersion indices in ESRD patients, iCEB elevation and increasing values after HD session indicate the increased risk of TdP-mediated ventricular arrhythmia after HD. Larger studies are needed to confirm our results.

Tpeak-Tend, Tpeak-Tend/QT ratio and Tpeak-Tend dispersion for risk stratification in Brugada Syndrome: A systematic review and meta-analysis

BACKGROUND

Brugada syndrome is an ion channelopathy that predisposes affected subjects to ventricular tachycardia/fibrillation (VT/VF), potentially leading to sudden cardiac death (SCD). Tpeak-Tend intervals, (Tpeak-Tend)/QT ratio and Tpeak-Tend dispersion have been proposed for risk stratification, but their predictive values in Brugada syndrome have been challenged recently.

METHODS

A systematic review and meta-analysis was conducted to examine their values in predicting arrhythmic and mortality outcomes in Brugada Syndrome. PubMed and Embase databases were searched until 1 May 2018, identifying 29 and 57 studies.

RESULTS

Nine studies involving 1740 subjects (mean age 45 years old, 80% male, mean follow-up duration was 68 ± 27 months) were included. The mean Tpeak-Tend interval was 98.9 ms (95% CI: 90.5-107.2 ms) for patients with adverse events (ventricular arrhythmias or SCD) compared to 87.7 ms (95% CI: 80.5-94.9 ms) for those without such events, with a mean difference of 11.9 ms (95% CI: 3.6-20.2 ms, P = 0.005; I 2 = 86%). Higher (Tpeak-Tend)/QT ratios (mean difference = 0.019, 95% CI: 0.003-0.036, P = 0.024; I 2 = 74%) and Tpeak-Tend dispersion (mean difference = 7.8 ms, 95% CI: 2.1-13.4 ms, P = 0.007; I 2 = 80%) were observed for the event-positive group.

CONCLUSION

Tpeak-Tend interval, (Tpeak-Tend)/QT ratio and Tpeak-Tend dispersion were higher in high-risk than low-risk Brugada subjects, and thus offer incremental value for risk stratification.

Higher Dispersion Measures of Conduction and Repolarization in Type 1 Compared to Non-type 1 Brugada Syndrome Patients: An Electrocardiographic Study From a Single Center

Background: Brugada syndrome (BrS) is a cardiac ion channelopathy that predisposes affected individuals to sudden cardiac death (SCD). Type 1 BrS is thought to take a more malignant clinical course than non-type 1 BrS. We hypothesized that the degrees of abnormal repolarization and conduction are greater in type 1 subjects and these differences can be detected by electrocardiography (ECG). Methods: Electrocardiographic data from spontaneous type 1 and non-type 1 BrS patients were analyzed. ECG parameters were measured from leads V1 to V3. Values were expressed as median [lower quartile-upper quartile] and compared using Kruskal-Wallis ANOVA. Results: Compared to non-type 1 BrS patients (n = 29), patients with spontaneous type 1 patterns (n = 22) showed similar (P > 0.05) heart rate (73 [64-77] vs. 68 [62-80] bpm), QRS duration (136 [124-161] vs. 127 [117-144] ms), uncorrected QT (418 [393-443] vs. 402 [386-424] ms) and corrected QT intervals (457 [414-474] vs. 430 [417-457] ms), JTpeak intervals (174 [144-183] vs. 174 [150-188] ms), Tpeak- Tend intervals (101 [93-120] vs. 99 [90-105] ms), Tpeak- Tend/QT ratios (0.25 [0.23-0.27] vs. 0.24 [0.22-0.27]), Tpeak- Tend/QRS (0.77 [0.62-0.87] vs. 0.77 [0.69-0.86]), Tpeak- Tend/(QRS × QT) (0.00074 [0.00034-0.00096] vs. 0.00073 [0.00048-0.00012] ms-1), index of Cardiac Electrophysiological Balance (iCEB, QT/QRS, marker of wavelength: 3.14 [2.56-3.35] vs. 3.21 [2.85-3.46]) and corrected iCEB (QTc/QRS: 3.25 [2.91-3.73] vs. 3.49 [2.99-3.78]). Higher QRS dispersion was seen in type 1 subjects (QRSd: 34 [24-66] vs. 24 [12-34] ms) but QT dispersion (QTd: 48 [39-71] vs. 43 [22-94] ms), QTc dispersion (QTcd: 52 [41-79] vs. 46 [23-104] ms), JTpeak dispersion (44 [23-62] vs. 45 [30-62] ms), Tpeak- Tend dispersion (28 [15-34] vs. 29 [22-53] ms) or Tpeak- Tend/QT dispersion (0.06 [0.03-0.08] vs. 0.08 [0.04-0.12]) did not differ between the two groups. Type 1 subjects showed higher (QRSd × Tpeak- Tend)/QRS (25 [19-44] vs. 19 [9-30] ms) but similar iCEB dispersion (0.83 [0.49-1.14] vs. 0.61 [0.34-0.92]) and iCEBc dispersion (0.93 [0.51-1.15] vs. 0.65 [0.39-0.96]). Conclusion: Higher levels of dispersion in conduction and repolarization are found in type 1 than non-type 1 BrS patients, potentially explaining the higher incidence of ventricular arrhythmias in the former group.

Prognostic value of electrocardiographic time intervals and QT rate dependence in hypertrophic cardiomyopathy

INTRODUCTION

Preventing sudden cardiac death (SCD) is one of the main goals in hypertrophic cardiomyopathy (HCM). Many variables have been proposed, however the European and American guidelines do not incorporate any ECG or Holter monitoring derived variables other than the presence of ventricular arrhythmia in their risk stratification models. In the present study we evaluated electrocardiographic parameters in risk stratification of HCM.

METHODS AND RESULTS

Novel electrocardiographic parameters including the index of cardio-electrophysiological balance (iCEB), individualized QT correction (QTi) and QT rate dependence were evaluated along with established risk factors. A composite endpoint of SCD was defined as out of hospital cardiac arrest, appropriate ICD shock and sustained ventricular tachycardia. Cox regression analysis was used to evaluate predictors of SCD. Out of the 466 HCM patients, 31 reached the composite endpoint during a follow up of 75 ± 86 months. In a multivariate model, nor iCEB, QTi or QT rate dependence were predictors of SCD. Only male gender (p < 0.01; OR 13.1; CI 1.74-98.83), negative T waves in the inferior leads (p = 0.04; OR 2.51; CI 1.03-6.13) and familial sudden death (p < 0.01; OR 3.03; CI 1.39-6.59) were significant predictors. On top of either the ESC risk score or the 3 traditional 'American risk factors', only male gender was a significant predictor of SCD.

CONCLUSION

No ECG or Holter monitoring parameters added in risk stratification for SCD in HCM. However, male gender and negative T waves in the inferior leads are promising novel markers to evaluate in larger cohorts.

Predictive Value of T peak - T end Indices for Adverse Outcomes in Acquired QT Prolongation: A Meta-Analysis

Background: Acquired QT interval prolongation has been linked with malignant ventricular arrhythmias, such as torsade de pointes, in turn predisposing to sudden cardiac death. Increased dispersion of repolarization has been identified as a pro-arrhythmic factor and can be observed as longer T_peak - T_end interval and higher T_peak - T_end/QT ratio on the electrocardiogram. However, the values of these repolarization indices for predicting adverse outcomes in this context have not been systematically evaluated. Method: PubMed, Embase and Cochrane Library databases were searched until 14th February 2018, identifying 232 studies. Results: Five studies on acquired QT prolongation met the inclusion criteria and 308 subjects with drug-induced LQTS patients (mean age: 66 ± 18 years old; 46% male) were included in this meta-analysis. T_peak - T_end intervals were longer [mean difference [MD]: 76 ms, standard error [SE]: 26 ms, P = 0.003; I² = 98%] and T_peak - T_end/QT ratios were higher (MD: 0.14, SE: 0.03, P = 0.000; I² = 29%) in patients with torsade de pointes compared to those without these events. Conclusion: T_peak - T_end interval and T_peak - T_end/QT ratio were higher in patients with acquired QT prolongation suffering from torsade de pointes compared to those who did not. These repolarization indices may provide additional predictive value for identifying high-risk individuals.

Evaluation of cardiac arrhythmic risks using a rabbit model of left ventricular systolic dysfunction

Patients with heart disease have a higher risk to develop cardiac arrhythmias, either spontaneously or drug-induced. In this study, we have used a rabbit model of myocardial infarction (MI) with severe left ventricular systolic dysfunction (LVSD) to study potential drug-induced cardiac risks with N-(piperidin-2-ylmethyl)-2,5-bis(2,2,2-trifluoroethoxy)benzamide (flecainide). Upon ligation of the left circumflex arteries, male New Zealand White rabbits developed a large MI and moderate or severe LVSD 7 weeks after surgery, in comparison to SHAM-operated animals. Subsequently, animals were exposed to escalating doses of flecainide (0.25-4 mg/kg) or solvent. Electrocardiograms (ECG) were recorded before surgery, 1 and 7 weeks after surgery and continuously during the drug protocol. The ECG biomarker iCEB (index of Cardio-Electrophysiological Balance = QT/QRS ratio) was calculated. During the ECG recording at week 1 and week 7 post MI, rabbits had no spontaneous cardiac arrhythmias. When rabbits were exposed to escalating doses of flecainide, 2 out of 5 rabbits with MI and moderate LVSD versus 0 out of 5 solvent-treated rabbits developed arrhythmias, such as ventricular tachycardia/ventricular fibrillation. These were preceded by a marked decrease of iCEB just before the onset (from 4.09 to 2.42 and from 5.56 to 2.25, respectively). Furthermore, 1 out of 5 MI rabbits with moderate LVSD and 1 out of 7 MI rabbits with severe LVSD developed total atrioventricular block after flecainide infusion and died. This rabbit model of MI and severe LVSD may be useful for preclinical evaluation of drug (similar mechanism as flecainide)-induced arrhythmic risks, which might be predicted by iCEB.

Quantitative approach for cardiac risk assessment and interpretation in tuberculosis drug development

Cardiotoxicity is among the top drug safety concerns, and is of specific interest in tuberculosis, where this is a known or potential adverse event of current and emerging treatment regimens. As there is a need for a tool, beyond the QT interval, to quantify cardiotoxicity early in drug development, an empirical decision tree based classifier was developed to predict the risk of Torsades de pointes (TdP). The cardiac risk algorithm was developed using pseudo-electrocardiogram (ECG) outputs derived from cardiac myocyte electromechanical model simulations of increasing concentrations of 96 reference compounds which represented a range of clinical TdP risk. The algorithm correctly classified 89% of reference compounds with moderate sensitivity and high specificity (71 and 96%, respectively) as well as 10 out of 12 external validation compounds and the anti-TB drugs moxifloxacin and bedaquiline. The cardiac risk algorithm is suitable to help inform early drug development decisions in TB and will evolve with the addition of emerging data.

Index of cardiac electrophysiological balance and transmural dispersion of the repolarization index relationships with pericardial fat volume and coronary calcification

AIM

To assess the possible relationship between coronary atherosclerosis markers, pericardial fat volume (PFV) and coronary artery calcification, with ECG markers of index of the cardiac electrophysiological balance (iCEB) and transmural dispersion of the repolarization in patients with suspected coronary artery disease.

METHODOLOGY

One hundred patients who underwent 64-slice multidetector computed tomography angiography were found to be eligible and were enrolled in the study.

RESULTS

Patients with high iCEB levels tended to have a higher PFV values compared with patients with low iCEB levels (median [interquartile range]) (152 [29-206] vs 96 [14-177]; p = 0.03). No significant differences in coronary artery calcification values were observed between iCEB and transmural dispersion of the repolarization groups.

CONCLUSION

A higher PFV value was observed in patients with high iCEB. Larger prospective studies are required to confirm the results.

Meta-analysis of Tpeak-Tend and Tpeak-Tend/QT ratio for risk stratification in congenital long QT syndrome

BACKGROUND AND OBJECTIVES

Congenital long QT syndrome (LQTS) predisposes affected individuals to ventricular tachycardia/fibrillation (VF/VF), potentially resulting in sudden cardiac death. The T_peak-T_end interval and the T_peak-T_end/QT ratio, electrocardiographic markers of dispersion of ventricular repolarization, were proposed for risk stratification but their predictive values in LQTS have been controversial. A systematic review and meta-analysis was conducted to examine the value of T_peak-T_end intervals and T_peak-T_end/QT ratios in predicting arrhythmic and mortality outcomes in congenital LQTS.

METHOD

PubMed and Embase databases were searched until 9th May 2017, identifying 199 studies.

RESULTS

Five studies on long QT syndrome were included in the final meta-analysis. T_peak-T_end intervals were longer (mean difference [MD]: 13ms, standard error [SE]: 4ms, P=0.002; I²=34%) in congenital LQTS patients with adverse events [syncope, ventricular arrhythmias or sudden cardiac death] compared to LQTS patients without such events. By contrast, T_peak-T_end/QT ratios were not significantly different between the two groups (MD: 0.02, SE: 0.02, P=0.26; I²=0%).

CONCLUSION

This meta-analysis showed that T_peak-T_end interval is significant higher in individuals who are at elevated risk of adverse events in congenital LQTS, offering incremental value for risk stratification.