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

The Effect of Obesity on Repolarization and Other ECG Parameters

Background: Overweight and obesity are important risk factors in the development of cardiovascular diseases. New repolarization markers, such as the Tpeak-Tend interval and JTpeak intervals, have not yet been profoundly studied in obese patients. The study aims to analyze whether, in patients with obesity and overweight, repolarization markers, including the Tpeak-Tend interval, are prolonged and simultaneously check the frequency of other ECG pathologies in a 12-lead ECG in this group of patients. Methods: A study group consisted of 181 adults (90 females and 91 males) with overweight and first-class obesity. The participants completed a questionnaire, and the ECG was performed and analyzed. Results: When analyzing the classic markers, only QT dispersion was significantly higher in obese people. The Tpeak-Tend parameter (97.08 ms ± 23.38 vs. 89.74 ms ± 12.88, respectively), its dispersion, and JTpeak-JTend parameters were statistically significantly longer in the obese group than in the controls. There were also substantial differences in P-wave, QRS duration, and P-wave dispersion, which were the highest in obese people. Tpeak-Tend was positively correlated with body mass and waist circumference, while JTpeak was with BMI, hip circumference, and WHR. Tpeak/JT was positively correlated with WHR and BMI. In backward stepwise multiple regression analysis for JTpeak-WHR, type 2 diabetes and smoking had the highest statistical significance. Conclusions: Only selected repolarization markers are significantly prolonged in patients with class 1 obesity and, additionally, in this group, we identified more pathologies of P wave as well as prolonged QRS duration.

Association between lipoprotein(a) and premature atherosclerotic cardiovascular disease: a systematic review and meta-analysis

Aims

High lipoprotein(a) [Lp(a)] level has been demonstrated as an important risk factor for atherosclerotic cardiovascular diseases (ASCVD) amongst the older populations, whereas its effects in the younger population remain unclear. This study evaluated the associations between Lp(a) and the risk of premature ASCVD.

Method and results

PubMed and Embase were searched for related studies until 12 November 2023. Fifty-one studies including 100 540 participants were included. Mean age of patients ranged from 35.3 to 62.3 years. The proportion of male participants ranged from 0% to 100%. The mean follow-up was provided in five studies ranging from 1 year to 40 years. The definition of elevated Lp(a) varied among studies, such as >30 mg/dL, >50 mg/dL, the top tertiles, the top quartiles, the top quintiles, and so on. Higher Lp(a) was significantly associated with the composite ASCVD [odds ratio (OR): 2.15, 95% confidence interval (95% CI): 1.53-3.02, P < 0.001], especially for coronary artery disease (OR: 2.44, 95% CI: 2.06-2.90, P < 0.001) and peripheral arterial disease (OR: 2.56, 95% CI: 1.56-4.21, P < 0.001). This association remained significant in familial hypercholesterolaemia (FH) (OR: 3.11, 95% CI: 1.63-5.96, P < 0.001) and type 2 diabetes mellitus (T2DM) patients (OR: 2.23; 95% CI: 1.54-3.23, P < 0.001).Significant results were observed in South Asians (OR: 3.71, 95% CI: 2.31-5.96, P < 0.001), Caucasians (OR: 3.17, 95% CI: 2.22-4.52, P < 0.001), and patients with baseline low-density lipoprotein cholesterol (LDL-c) level ≥ 2.6 mmol/L.

Conclusion

Elevated Lp(a) predicts the risk of the composite or individual ASCVD in young, regardless of study design, gender, population characteristics (community or hospitalized), different premature definitions, and various Lp(a) measurement approaches. This association was important in South Asians, Caucasians, FH patients, T2DM patients, and patients with baseline LDL-c level ≥ 2.6 mmol/L.

Spatiotemporal repolarization dispersion before and after exercise in patients with long QT syndrome type 1 versus controls: probing into the arrhythmia substrate

Congenital long QT syndrome (LQTS) carries an increased risk for syncope and sudden death. QT prolongation promotes ventricular extrasystoles, which, in the presence of an arrhythmia substrate, might trigger ventricular tachycardia degenerating into fibrillation. Increased electrical heterogeneity (dispersion) is the suggested arrhythmia substrate in LQTS. In the most common subtype LQT1, physical exercise predisposes for arrhythmia and spatiotemporal dispersion was therefore studied in this context. Thirty-seven patients (57% on β-blockers) and 37 healthy controls (mean age, 31 vs. 35; range, 6-68 vs. 6-72 yr) performed an exercise test. Frank vectorcardiography was used to assess spatiotemporal dispersion as Tampl, Tarea, the ventricular gradient (VG), and the Tpeak-end interval from 10-s signal averages before and 7 ± 2 min after exercise; during exercise too much signal disturbance excluded analysis. Baseline and maximum heart rates as well as estimated exercise intensity were similar, but heart rate recovery was slower in patients. At baseline, QT and heart rate-corrected QT (QTcB) were significantly longer in patients (as expected), whereas dispersion parameters were numerically larger in controls. After exercise, QTpeakcB and Tpeak-endcB increased significantly more in patients (18 ± 23 vs. 7 ± 10 ms and 12 ± 17 vs. 2 ± 6 ms; P < 0.001 and P < 0.01). There was, however, no difference in the change in Tampl, Tarea, and VG between groups. In conclusion, although temporal dispersion of repolarization increased significantly more after exercise in patients with LQT1, there were no signs of exercise-induced increase in global dispersion of action potential duration and morphology. The arrhythmia substrate/mechanism in LQT1 warrants further study.NEW & NOTEWORTHY Physical activity increases the risk for life-threatening arrhythmias in LQTS type 1 (LQT1). The arrhythmia substrate is presumably altered electrical heterogeneity (a.k.a. dispersion). Spatiotemporal dispersion parameters were therefore compared before and after exercise in patients versus healthy controls using Frank vectorcardiography, a novelty. Physical exercise prolonged the time between the earliest and latest complete repolarization in patients versus controls, but did not increase parameters reflecting global dispersion of action potential duration and morphology, another novelty.

Cardiovascular magnetic resonance native T1 mapping in Anderson-Fabry disease: a systematic review and meta-analysis

BACKGROUND

T1 mapping is an established cardiovascular magnetic resonance (CMR) technique that can characterize myocardial tissue. We aimed to determine the weighted mean native T1 values of Anderson-Fabry disease (AFD) patients and the standardized mean differences (SMD) as compared to healthy control subjects.

METHODS

A comprehensive literature search of the PubMed, Scopus and Web of Science databases was conducted according to the PRISMA statement to retrieve original studies reporting myocardial native T1 values in AFD patients and healthy controls. A random effects model was used to calculate SMD, and meta-regression analysis was conducted to explore heterogeneity sources. Subgroup analysis was also performed according to scanner field strength and sequence type.

RESULTS

From a total of 151 items, 14 articles were included in the final analysis accounting for a total population of 982 subjects. Overall, the weighted mean native T1 values was 984 ± 47 ms in AFD patients and 1016 ± 26 ms in controls (P < 0.0001) with a pooled SMD of - 2.38. In AFD patients there was an inverse correlation between native T1 values and male gender (P = 0.002) and left ventricular hypertrophy (LVH) (P < 0.001). Subgroup analyses confirmed lower T1 values in AFD patients compared to controls with a pooled SMD of -  2.54,  -  2.28, -   2.46 for studies performed on 1.5T with modified Look-Locker inversion recovery (MOLLI), shortened MOLLI and saturation-recovery single-shot acquisition, respectively and of -  2.41 for studies conducted on 3T.

CONCLUSIONS

Our findings confirm a reduction of native T1 values in AFD patients compared to healthy controls and point out that the degree of T1 shortening in AFD is influenced by gender and LVH. Although T1 mapping is useful in proving cardiac involvement in AFD patients, there is need to standardize shreshold values according to imaging equipment and protocols.

OUP accepted manuscript

An abundance of literature describes physiological and pathological determinants of cardiac performance, building on the principles of excitation–contraction coupling. However, the mutual influencing of excitation–contraction and mechano-electrical feedback in the beating heart, here designated ‘electromechanical reciprocity’, remains poorly recognized clinically, despite the awareness that external and cardiac-internal mechanical stimuli can trigger electrical responses and arrhythmia. This review focuses on electromechanical reciprocity in the long-QT syndrome (LQTS), historically considered a purely electrical disease, but now appreciated as paradigmatic for the understanding of mechano-electrical contributions to arrhythmogenesis in this and other cardiac conditions. Electromechanical dispersion in LQTS is characterized by heterogeneously prolonged ventricular repolarization, besides altered contraction duration and relaxation. Mechanical alterations may deviate from what would be expected from global and regional repolarization abnormalities. Pathological repolarization prolongation outlasts mechanical systole in patients with LQTS, yielding a negative electromechanical window (EMW), which is most pronounced in symptomatic patients. The electromechanical window is a superior and independent arrhythmia-risk predictor compared with the heart rate-corrected QT. A negative EMW implies that the ventricle is deformed—by volume loading during the rapid filling phase—when repolarization is still ongoing. This creates a ‘sensitized’ electromechanical substrate, in which inadvertent electrical or mechanical stimuli such as local after-depolarizations, after-contractions, or dyssynchrony can trigger abnormal impulses. Increased sympathetic-nerve activity and pause-dependent potentiation further exaggerate electromechanical heterogeneities, promoting arrhythmogenesis. Unraveling electromechanical reciprocity advances the understanding of arrhythmia formation in various conditions. Real-time image integration of cardiac electrophysiology and mechanics offers new opportunities to address challenges in arrhythmia management.

QT interval and repolarization dispersion changes during the administration of hydroxychloroquine/chloroquine with/without azithromycin in early COVID 19 pandemic: A prospective observational study from two academic hospitals in Indonesia

BACKGROUND

Hydroxychloroquine/chloroquine (HCQ/CQ) treatment for COVID-19 was associated with QT interval prolongation and arrhythmia risks. This study aimed to investigate QTc interval and ventricular repolarization dispersion changes, as markers of arrhythmia risks, after HCQ/CQ administration with/without azithromycin (AZT) during COVID-19 pandemic.

METHODS

A prospective observational study was performed in two academic hospitals in Indonesia. Adult patients who received HCQ/CQ alone and HCQ/CQ + AZT concomitant treatments for COVID-19 infection were enrolled. Baseline and post HCQ/CQ treatment electrocardiograms were obtained. Baseline and post HCQ/CQ treatment QT interval by Bazett (B-QTc) and Fridericia (F-QTc) formulas and ventricular repolarization dispersion indices by Tpeak-Tend (Tp-e) interval and Tpeak-Tend/QT (Tp-e/QT) ratio were calculated and analyzed.

RESULTS

The study enrolled 55 (HCQ/CQ alone) and 77 subjects (HCQ/CQ + AZT concomitant). F-QTc interval significantly lengthened in subjects with HCQ/CQ + AZT (mean difference 11.89 ms [P = .028]). The incidences of severe B-QTc and F-QTc lengthening were 13.1% and 12.3%, B-QTc and F-QTc prolongation were 25.4% and 12.3%, and severe B-QTc and F-QTc prolongation were 6.2% and 3.2%. Tp-e interval lengthened significantly from baseline to posttreatment in HCQ/CQ alone and HCQ/CQ + AZT (mean difference 10.83 ms [P = .006] and 18.73 ms [P < .001], respectively). Tp-e/QT ratio increased significantly from baseline to posttreatment in HCQ/CQ + AZT concomitant (mean difference 0.035 [P < .001]). No fatal arrhytmia occurred.

CONCLUSIONS

During COVID-19 pandemic, HCQ/CQ + AZT concomitant treatment caused significant F-QTc lengthening, significantly increased Tp-e interval and increased Tp-e/QT ratio. HCQ/CQ alone only caused significant increase of Tp-e interval. Incidences of severe QTc lengthening and prolongation were low in both HCQ/CQ alone and HCQ/CQ + AZT concomitant.

Paediatric/young versus adult patients with long QT syndrome

Introduction

Long QT syndrome (LQTS) is a less prevalent cardiac ion channelopathy than Brugada syndrome in Asia. The present study compared the outcomes between paediatric/young and adult LQTS patients.

Methods

This was a population-based retrospective cohort study of consecutive patients diagnosed with LQTS attending public hospitals in Hong Kong. The primary outcome was spontaneous ventricular tachycardia/ventricular fibrillation (VT/VF).

Results

A total of 142 LQTS (mean onset age=27±23 years old) were included. Arrhythmias other than VT/VF (HR 4.67, 95% CI (1.53 to 14.3), p=0.007), initial VT/VF (HR=3.25 (95% CI 1.29 to 8.16), p=0.012) and Schwartz score (HR=1.90 (95% CI 1.11 to 3.26), p=0.020) were predictive of the primary outcome for the overall cohort, while arrhythmias other than VT/VF (HR=5.41 (95% CI 1.36 to 21.4), p=0.016) and Schwartz score (HR=4.67 (95% CI 1.48 to 14.7), p=0.009) were predictive for the adult subgroup (>25 years old; n=58). A random survival forest model identified initial VT/VF, Schwartz score, initial QTc interval, family history of LQTS, initially asymptomatic and arrhythmias other than VT/VF as the most important variables for risk prediction.

Conclusion

Clinical and ECG presentation varies between the paediatric/young and adult LQTS population. Machine learning models achieved more accurate VT/VF prediction.

The impact of hydroxychloroquine-azithromycin combination on Tpeak-to-end and Tpeak-to-end/QT ratio during a short treatment course

BACKGROUND

Since there was no proven treatment of coronavirus disease 2019 (COVID-19), hydroxychloroquine-azithromycin (HCQ-AZM) combination is being used in different countries as a treatment option. Many controversies exist related to the safety and effectiveness of this combination, and questions about how HCQ-AZM combination affects the ventricular repolarization are still unknown.

OBJECTIVE

The aim of the study was to show whether the hydroxychloroquine-azithromycin (HCQ-AZM) combination prolonged Tpeak-to-end (TpTe) duration and TpTe/QT interval ratio or not.

METHODS

One hundred and twenty-six consequent COVID-19(+) patients meeting the study criteria were enrolled in this study. Baseline ECGs were obtained immediately after hospitalization and before commencing the HCQ-AZM combination. On-treatment ECG was obtained 24-48 hr after the loading dose of HCQ/AZM. ECG parameters including PR interval, QRS duration, QT interval, QTc interval, TpTe duration, and TpTe/QT interval ratio were assessed. Demographic and laboratory findings were collected from an electronic recording system.

RESULTS

ECGs of 126 COVID-19(+) patients who received HCQ-AZM combination were assessed. Mean baseline QTc (by Fridericia formula), TpTe, and TpTe/QT ratio were 420.0 ± 26.5 ms, 82.43 ± 9.77 ms, and 0.22 ± 0.02, respectively. On-treatment QTc, TpTe and TpTe/QT ratio were 425.7 ± 27.18 ms, 85.17 ± 11.17 ms, and 0.22 ± 0.03, respectively. No statistically significant acute impacts of HCQ-AZM combination on TpTe duration and TpTe/QT interval ratio were observed compared with baseline values. No ventricular tachycardia/fibrillation and the significant conduction delays were seen during in-hospital follow-up.

CONCLUSION

HCQ-AZM combination increased TpTe duration. However, no significant impact on TpTe/QT interval ratio was observed.

The ECG Characteristics of Patients With Isolated Hypomagnesemia

Background

Electrocardiographic (ECG) characteristics of patients with isolated hypomagnesemia are not well defined. We aimed to investigate these ECG characteristics in order to define clearly the features of isolated hypomagnesemia.

Hypothesis

Lower serum magnesium could affect ECG parameters after excluding potential confounders.

Methods

This retrospective study was of patients with low serum magnesium <0.65 mmol/L compared with the same patients after restoration to normal serum magnesium. Patients with hypokalemia, hypocalcemia and other electrolyte disturbances were excluded. ECG parameters manually determined and analyzed were P wave dispersion, PR interval, QRS duration, ST-T changes, T wave amplitude, T peak-to-end interval (Tpe), corrected Tpe (Tpec), QT, corrected QT (QTc), QT peak corrected (QTpc) and Tpe dispersion, Tpe/QT ratio.

Results

Two-hundred-and-fourteen patients with isolated hypomagnesemia were identified with 50 of them (56.9 ± 13.6 years; 25 males) being eligible for final analysis from 270,997 patients presenting April 2011–October 2017. In the period of isolated hypomagnesemia, P wave duration was found prolonged (p ≤ 0.02); as was QTc (439 ± 27 vs. 433 ± 22, p = 0.01). Tpec (122 ± 24vs. 111 ± 22, p = 0.000) and Tpe/QT ratio (0.29 ± 0.05 vs. 0.27 ± 0.05, p = 0.000) were increased. QTpc decreased during hypomagnesemia (334 ± 28 vs. 342 ± 21, p = 0.02). However, no significant differences were found in PR interval, QRS duration (85 ± 12 ms vs. 86 ± 12 ms, p = 0.122) and ST-T segments between the patients and their own controls.

Conclusions

In patients with isolated hypomagnesemia, P wave duration, QTc, Tpec, and Tpe/QT ratio suggesting atrial depolarization and ventricular repolarization dispersion were significantly increased compared with normal magnesium levels in the same patients after restoration to normal levels.

Territory-Wide Chinese Cohort of Long QT Syndrome: Random Survival Forest and Cox Analyses

Introduction: Congenital long QT syndrome (LQTS) is a cardiac ion channelopathy that predisposes affected individuals to spontaneous ventricular tachycardia/fibrillation (VT/VF) and sudden cardiac death (SCD). The main aims of the study were to: (1) provide a description of the local epidemiology of LQTS, (2) identify significant risk factors of ventricular arrhythmias in this cohort, and (3) compare the performance of traditional Cox regression with that of random survival forests.

Methods: This was a territory-wide retrospective cohort study of patients diagnosed with congenital LQTS between 1997 and 2019. The primary outcome was spontaneous VT/VF.

Results: This study included 121 patients [median age of initial presentation: 20 (interquartile range: 8–44) years, 62% female] with a median follow-up of 88 (51–143) months. Genetic analysis identified novel mutations in KCNQ1, KCNH2, SCN5A, ANK2, CACNA1C, CAV3, and AKAP9. During follow-up, 23 patients developed VT/VF. Univariate Cox regression analysis revealed that age [hazard ratio (HR): 1.02 (1.01–1.04), P = 0.007; optimum cut-off: 19 years], presentation with syncope [HR: 3.86 (1.43–10.42), P = 0.008] or VT/VF [HR: 3.68 (1.62–8.37), P = 0.002] and the presence of PVCs [HR: 2.89 (1.22–6.83), P = 0.015] were significant predictors of spontaneous VT/VF. Only initial presentation with syncope remained significant after multivariate adjustment [HR: 3.58 (1.32–9.71), P = 0.011]. Random survival forest (RSF) model provided significant improvement in prediction performance over Cox regression (precision: 0.80 vs. 0.69; recall: 0.79 vs. 0.68; AUC: 0.77 vs. 0.68; c-statistic: 0.79 vs. 0.67). Decision rules were generated by RSF model to predict VT/VF post-diagnosis.

Conclusions: Effective risk stratification in congenital LQTS can be achieved by clinical history, electrocardiographic indices, and different investigation results, irrespective of underlying genetic defects. A machine learning approach using RSF can improve risk prediction over traditional Cox regression models.

Exercise-induced electrocardiographic changes after treadmill exercise testing in healthy children: A comprehensive study

Background:

Aims and Objectives:

Materials and Methods:

Results:

Conclusion:

Mechanisms of Premature Ventricular Complexes Caused by QT Prolongation

QT prolongation, due to lengthening of the action potential duration in the ventricles, is a major risk factor of lethal ventricular arrhythmias. A widely known consequence of QT prolongation is the genesis of early afterdepolarizations (EADs), which are associated with arrhythmias through the generation of premature ventricular complexes (PVCs). However, the vast majority of the EADs observed experimentally in isolated ventricular myocytes are phase-2 EADs, and whether phase-2 EADs are mechanistically linked to PVCs in cardiac tissue remains an unanswered question. In this study, we investigate the genesis of PVCs using computer simulations with eight different ventricular action potential models of various species. Based on our results, we classify PVCs as arising from two distinct mechanisms: repolarization gradient (RG)-induced PVCs and phase-2 EAD-induced PVCs. The RG-induced PVCs are promoted by increasing RG and L-type calcium current and are insensitive to gap junction coupling. EADs are not required for this PVC mechanism. In a paced beat, a single or multiple PVCs can occur depending on the properties of the RG. In contrast, phase-2 EAD-induced PVCs occur only when the RG is small and are suppressed by increasing RG and more sensitive to gap junction coupling. Unlike with RG-induced PVCs, in each paced beat, only a single EAD-induced PVC can occur no matter how many EADs in an action potential. In the wide parameter ranges we explore, RG-induced PVCs can be observed in all models, but the EAD-induced PVCs can only be observed in five of the eight models. The links between these two distinct PVC mechanisms and arrhythmogenesis in animal experiments and clinical settings are discussed.

Low rate of life-threatening events and limitations in predicting invasive and noninvasive markers of symptoms in a cohort of type 1 Brugada syndrome patients: Data and insights from the GenBra registry

BACKGROUND

Brugada syndrome (BrS) has diagnostic challenges and controversial risk assessment. We aimed to investigate invasive and noninvasive parameters in symptomatic and asymptomatic patients from a Brazilian cohort of type-1 BrS.

METHODS

Patients with spontaneous and drug-induced type-1 BrS were classified into two groups, asymptomatic (n = 116, 84.1%) and symptomatic (n = 22, 15.9%; 13 with arrhythmogenic syncope, 9 with aborted sudden cardiac death). Genetic testing, EPS parameters, and electrocardiogram (ECG) parameters were analyzed.

RESULTS

A total of 138 consecutive patients were eligible, 101 men (73.2%), mean 41.4 years, mostly probands (79%). Spontaneous pattern, observed in 77.5% of the patients, was associated with symptoms only if expressed in V1 and V2 standard position (not high precordial leads; p = .014). All symptomatic patients were probands. The presence of right ventricular outflow tract conduction delay (RVOTcd) signs, positive EPS, and SCN5A status was similar between symptomatic and asymptomatic subjects. During the mean 75-month follow-up, eight patients had appropriate therapies. All had spontaneous type-1 ECG pattern and 2/8 (25%) were asymptomatic, with positive EPS. The overall LAE incidence of 1.1% per year dropped to 0.27% in asymptomatic patients. RVOTcd occurred more frequently in SCN5A carriers (QRS-f 33.3% vs. 7.7%; p = .005, AVR sign 58.3% vs. 13.6%; p < .001; deep S in lead I 75% vs. 48.5%, p = .025%), as well as longer HV interval (66 vs. 49 ms; p < .001).

CONCLUSIONS

Spontaneous type-1 Brugada pattern in standard leads and proband status were more frequent in symptomatic subjects. RVOTcd, more common in SCN5A carriers, did not predict symptoms in BrS patients. EPS exhibited limited prognostic value for this low-risk population.

Association of QT dispersion with mortality and arrhythmic events-A meta-analysis of observational studies

BACKGROUND

The risk stratification of coronary heart disease (CHD) and/or heart failure (HF) patients with easily measured electrocardiographic markers is of clinical importance. The aim of this meta-analysis is to indicate whether increased QT dispersion (QTd) is associated with fatal and nonfatal outcomes in patients with CHD and/or HF.

METHODS

We systematically searched MEDLINE and Cochrane databases without restrictions until August 15, 2018 using the keyword "QT dispersion". Studies including data on the association between QTd and all-cause mortality, sudden cardiac death (SCD) or arrhythmic events in patients with HF and/or CHD were classified as eligible.

RESULTS

In the analysis including patients with CHD and/or HF, we found that QTd did not differ significantly in patients with SCD compared to no SCD patients while QTd was significantly greater in the group of all-cause mortality patients and in patients who experienced a sustained ventricular arrhythmia. Subgroup analysis showed that in myocardial infarction studies, QTd was significantly higher in patients with an arrhythmic event compared to arrhythmic event-free patients while a nonsignificant difference was found in QTd in patients who died from any cause compared to survivors. Similarly, in HF patients, the QTd was significantly greater in patients with an arrhythmic event while a nonsignificant difference was found regarding all-cause mortality and SCD outcomes.

CONCLUSIONS

QTd has a prognostic role for stratifying myocardial infarction or HF patients who are at higher risk of arrhythmic events. However, no prognostic role was found regarding all-cause mortality or SCD in this patient population.

Effects of nicorandil infusion on ECG parameters in patients with unstable angina pectoris and percutaneous coronary intervention

Background

Percutaneous coronary intervention (PCI) is effective in treating patients with acute coronary syndrome (ACS) but is associated with some serious complications. Nicorandil is an anti‐anginal agent acting to improve microvascular circulation and to increase coronary blood flow. The objective of this article is to evaluate the effects of intracoronary injection followed with continuous intravenous injection of nicorandil on ECG parameters in patients with unstable angina pectoris (UA) undergoing PCI.

Methods

A single‐center, self‐controlled clinical trial was conducted at the Second Hospital of Tianjin Medical University between January 2019 and April 2019. Sixty‐three consecutive patients with UA who received coronary angiography and selective PCI were enrolled. ECG was recorded and analyzed before and 24 hr after nicorandil infusion.

Results

Patients were divided into three groups: control group (n = 23, aged 63.43 ± 12.55 years), short‐term, and prolonged use with nicorandil group (n = 20 and 20, aged 66.45 ± 8.06 years and 65.80 ± 9.49 years, respectively). Clinical characteristics and ECG parameters were similar before PCI among three groups (p > .05). In nicorandil treatment groups, intervals of QTd and Tp‐e in patients post‐PCI were significantly shorter than that in control and pre‐PCI (p < .05).

Conclusions

Nicorandil infusion reduces QTd and Tp‐e interval in patients with UA. Further studies will be needed to determine whether these electrophysiological changes are associated with a reduction of ventricular arrhythmias and improved outcomes.

A novel prediction model for risk stratification in patients with a type 1 Brugada ECG pattern

BACKGROUND

Risk stratification in Brugada syndrome remains a controversial and unresolved clinical problem, especially in asymptomatic patients with a type 1 ECG pattern. The purpose of this study is to derive and validate a prediction model based on clinical and ECG parameters to effectively identify patients with a type 1 ECG pattern who are at high risk of major arrhythmic events (MAE) during follow-up.

METHODS

This study analysed data from 103 consecutive patients with Brugada Type 1 ECG pattern and no history of previous cardiac arrest. The prediction model was derived using logistic regression with MAE as the primary outcome, and patient demographic and electrocardiographic parameters as potential predictor variables. The model was externally validated in an independent cohort of 42 patients.

RESULTS

The final model (Brugada Risk Stratification [BRS] score) consisted of 4 independent predictors (1 point each) of MAE during follow-up (median 85.3 months): spontaneous type 1 pattern, QRS fragments in inferior leads≥3,S wave upslope duration ratio ≥ 0.8, and T peak - T end ≥ 100 ms. The BRS score (AUC = 0.95,95% CI 0.0.92-0.98) stratifies patients with a type 1 ECG pattern into low (BRS score ≤ 2) and high (BRS score ≥ 3) risk classes, with a class specific risk of MAE of 0-1.1% and 92.3-100% across the derivation and validation cohorts, respectively.

CONCLUSIONS

The BRS score is a simple bed-side tool with high predictive accuracy, for risk stratification of patients with a Brugada Type 1 ECG pattern. Prospective validation of the prediction model is necessary before this score can be implemented in clinical practice.

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.

T-Wave Indices and Atherosclerosis

Tpeak-Tend interval, the time difference between the peak and the end of the T-wave, reflects the degree of dispersion of repolarization. Its prolongation has been associated with higher risks of developing ventricular arrhythmias and sudden cardiac death in different pro-arrhythmic conditions such as Brugada and long QT syndromes. In this review, we will provide a comprehensive overview on how Tpeak-Tend is altered in different atherosclerotic conditions such as hypertension, stable coronary artery disease, acute coronary obstruction, and coronary slow flow as well as inflammatory diseases affecting the arterial tree. We will explore its relationship with arterial function and dysfunction, ventricular remodeling, and arrhythmic and mortality outcomes. The published literature shows that patients with coronary atherosclerosis, whether in the form of stable coronary artery disease, chronic total occlusion, slow flow, or acute coronary obstruction, have prolonged Tpeak-Tend intervals and Tpeak-Tend/QT ratios. These can be used to predict the occurrence of ventricular arrhythmias and sudden cardiac death. They also correlate with the extent and severity of arterial stenosis and structural remodeling of the ventricles as well as arterial function and dysfunction. Finally, they can be normalized following revascularization and may therefore be used as a surrogate measure of treatment success.

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.