Predictive value of electrocardiographic QT interval and T-wave morphology parameters for all-cause and cardiovascular mortality in a general population sample

Retracted: T-peak to T-end Interval Predicts Appropriate Shocks in Patients with Heart Failure Undergoing Implantable Cardioverter Defibrillator Implantation for Primary Prophylaxis

BACKGROUND

T-wave peak to T-wave end interval (Tp-e) correlates with dispersion of ventricular repolarization. The purpose of this study was to assess the ability of Tp-e to predict appropriate implantable cardioverter defibrillator (ICD) shocks and all-cause mortality in patients who underwent ICD implantation for primary prophylaxis.

METHODS

Two hundred twenty-eight patients with left ventricular ejection fraction ≤35% and an ICD implanted were followed-up prospectively. Patients divided into two subgroups according to presence of appropriate ICD shocks (Group 1: 112 patients with ICD shocks, Group 2: 116 patients without shocks). End points were appropriate ICD therapy due to ventricular tachycardia (VT)/ventricular fibrillation (VF), death, and a combined end point of VT/VF or death.

RESULTS

During a mean follow-up of 22.3 ± 7.7 months, appropriate ICD shocks were observed in 112 of 228 patients (49.1%). The mean duration of the Tp-e Group 1 was significantly longer than Group 2 (115.3 ± 22.2 vs 104.7 ± 20.2 ms, P < 0.001). Ischemic etiology and Tp-e duration were found to be independent predictors of ICD therapy. When the patients were divided into two groups based on Tp-e interval, there was no significant difference regarding the mortality between groups (21.2% vs 21.8%, P: 0.186). However, appropriate ICD shocks due to VT/VF (37.5% vs 58.8%, P < 0.001) and combined end point (39.4% vs 64.5%, P: 0.002) were significantly higher in patients with longer Tp-e group.

CONCLUSIONS

Tp-e interval independently predicts appropriate ICD shocks in patients with systolic dysfunction and ICDs implanted for primary prevention.

Predicting 1-, 3-, 5-, and 8-year all-cause mortality in a community-dwelling older adult cohort: relevance for predictive, preventive, and personalized medicine

BACKGROUND

Population aging is a global public health issue involving increased prevalence of age-related diseases, and concomitant burden on medical resources and the economy. Ninety-two diseases have been identified as age-related, accounting for 51.3% of the global adult disease burden. The economic cost per capita for older people over 60 years is 10 times that of the younger population. From the aspects of predictive, preventive, and personalized medicine (PPPM), developing a risk-prediction model can help identify individuals at high risk for all-cause mortality and provide an opportunity for targeted prevention through personalized intervention at an early stage. However, there is still a lack of predictive models to help community-dwelling older adults do well in healthcare.

OBJECTIVES

This study aims to develop an accurate 1-, 3-, 5-, and 8-year all-cause mortality risk-prediction model by using clinical multidimensional variables, and investigate risk factors for 1-, 3-, 5-, and 8-year all-cause mortality in community-dwelling older adults to guide primary prevention.

METHODS

This is a two-center cohort study. Inclusion criteria: (1) community-dwelling adult, (2) resided in the districts of Chaonan or Haojiang for more than 6 months in the past 12 months, and (3) completed a health examination. Exclusion criteria: (1) age less than 60 years, (2) more than 30 incomplete variables, (3) no signed informed consent. The primary outcome of the study was all-cause mortality obtained from face-to-face interviews, telephone interviews, and the medical death database from 2012 to 2021. Finally, we enrolled 5085 community-dwelling adults, 60 years and older, who underwent routine health screening in the Chaonan and Haojiang districts, southern China, from 2012 to 2021. Of them, 3091 participants from Chaonan were recruited as the primary training and internal validation study cohort, while 1994 participants from Haojiang were recruited as the external validation cohort. A total of 95 clinical multidimensional variables, including demographics, lifestyle behaviors, symptoms, medical history, family history, physical examination, laboratory tests, and electrocardiogram (ECG) data were collected to identify candidate risk factors and characteristics. Risk factors were identified using least absolute shrinkage and selection operator (LASSO) models and multivariable Cox proportional hazards regression analysis. A nomogram predictive model for 1-, 3-, 5- and 8-year all-cause mortality was constructed. The accuracy and calibration of the nomogram prediction model were assessed using the concordance index (C-index), integrated Brier score (IBS), receiver operating characteristic (ROC), and calibration curves. The clinical validity of the model was assessed using decision curve analysis (DCA).

RESULTS

Nine independent risk factors for 1-, 3-, 5-, and 8-year all-cause mortality were identified, including increased age, male, alcohol status, higher daily liquor consumption, history of cancer, elevated fasting glucose, lower hemoglobin, higher heart rate, and the occurrence of heart block. The acquisition of risk factor criteria is low cost, easily obtained, convenient for clinical application, and provides new insights and targets for the development of personalized prevention and interventions for high-risk individuals. The areas under the curve (AUC) of the nomogram model were 0.767, 0.776, and 0.806, and the C-indexes were 0.765, 0.775, and 0.797, in the training, internal validation, and external validation sets, respectively. The IBS was less than 0.25, which indicates good calibration. Calibration and decision curves showed that the predicted probabilities were in good agreement with the actual probabilities and had good clinical predictive value for PPPM.

CONCLUSION

The personalized risk prediction model can identify individuals at high risk of all-cause mortality, help offer primary care to prevent all-cause mortality, and provide personalized medical treatment for these high-risk individuals from the PPPM perspective. Strict control of daily liquor consumption, lowering fasting glucose, raising hemoglobin, controlling heart rate, and treatment of heart block could be beneficial for improving survival in elderly populations.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s13167-023-00342-4.

The Heart–Brain Interplay in Multiple Sclerosis from Pathophysiology to Clinical Practice: A Narrative Review

Multiple sclerosis (MS) is a chronic neurological disorder characterized by inflammation in the central nervous system (CNS) that leads to neurodegeneration. The clinical course is highly variable, but its prevalence is rising worldwide, partly thanks to novel disease-modifying therapies. Additionally, the lifespan of people with MS is increasing, and for this reason, it is fundamental to have a multidisciplinary approach to MS. MS may be associated with cardiovascular diseases (CVD), but there is scarce attention on this issue. In particular, CNS is essential in regulating the autonomic system and heart activity. Moreover, cardiovascular risk factors show a higher prevalence in MS patients. On the other hand, conditions like Takotsubo syndrome are rare complications of MS. The parallelism between MS and myocarditis is also interesting. Finally, cardiac toxicity represents a not infrequent adverse reaction to MS drugs. This narrative review aims to provide an overview of cardiovascular complications in MS and their management to prompt further clinical and pre-clinical research on this topic.

Improving explainability of deep neural network-based electrocardiogram interpretation using variational auto-encoders. EUROPEAN HEART JOURNAL. DIGITAL HEALTH 2022;3:390-404. [PMID: 36712164 PMCID: PMC9707974 DOI: 10.1093/ehjdh/ztac038]

Aims

Deep neural networks (DNNs) perform excellently in interpreting electrocardiograms (ECGs), both for conventional ECG interpretation and for novel applications such as detection of reduced ejection fraction (EF). Despite these promising developments, implementation is hampered by the lack of trustworthy techniques to explain the algorithms to clinicians. Especially, currently employed heatmap-based methods have shown to be inaccurate.

Methods and results

We present a novel pipeline consisting of a variational auto-encoder (VAE) to learn the underlying factors of variation of the median beat ECG morphology (the FactorECG), which are subsequently used in common and interpretable prediction models. As the ECG factors can be made explainable by generating and visualizing ECGs on both the model and individual level, the pipeline provides improved explainability over heatmap-based methods. By training on a database with 1.1 million ECGs, the VAE can compress the ECG into 21 generative ECG factors, most of which are associated with physiologically valid underlying processes. Performance of the explainable pipeline was similar to 'black box' DNNs in conventional ECG interpretation [area under the receiver operating curve (AUROC) 0.94 vs. 0.96], detection of reduced EF (AUROC 0.90 vs. 0.91), and prediction of 1-year mortality (AUROC 0.76 vs. 0.75). Contrary to the 'black box' DNNs, our pipeline provided explainability on which morphological ECG changes were important for prediction. Results were confirmed in a population-based external validation dataset.

Conclusions

Future studies on DNNs for ECGs should employ pipelines that are explainable to facilitate clinical implementation by gaining confidence in artificial intelligence and making it possible to identify biased models.

Deep neural networks reveal novel sex-specific electrocardiographic features relevant for mortality risk

Aims

Incorporation of sex in study design can lead to discoveries in medical research. Deep neural networks (DNNs) accurately predict sex based on the electrocardiogram (ECG) and we hypothesized that misclassification of sex is an important predictor for mortality. Therefore, we first developed and validated a DNN that classified sex based on the ECG and investigated the outcome. Second, we studied ECG drivers of DNN-classified sex and mortality.

Methods and results

A DNN was trained to classify sex based on 131 673 normal ECGs. The algorithm was validated on internal (68 500 ECGs) and external data sets (3303 and 4457 ECGs). The survival of sex (mis)classified groups was investigated using time-to-event analysis and sex-stratified mediation analysis of ECG features. The DNN successfully distinguished female from male ECGs {internal validation: area under the curve (AUC) 0.96 [95% confidence interval (CI): 0.96, 0.97]; external validations: AUC 0.89 (95% CI: 0.88, 0.90), 0.94 (95% CI: 0.93, 0.94)}. Sex-misclassified individuals (11%) had a 1.4 times higher mortality risk compared with correctly classified peers. The ventricular rate was the strongest mediating ECG variable (41%, 95% CI: 31%, 56%) in males, while the maximum amplitude of the ST segment was strongest in females (18%, 95% CI: 11%, 39%). Short QRS duration was associated with higher mortality risk.

Conclusion

Deep neural networks accurately classify sex based on ECGs. While the proportion of ECG-based sex misclassifications is low, it is an interesting biomarker. Investigation of the causal pathway between misclassification and mortality uncovered new ECG features that might be associated with mortality. Increased emphasis on sex as a biological variable in artificial intelligence is warranted.

Spectrum of clinical applications of interlead ECG heterogeneity assessment: From myocardial ischemia detection to sudden cardiac death risk stratification

Heterogeneity in depolarization and repolarization among regions of cardiac cells has long been recognized as a major factor in cardiac arrhythmogenesis. This fundamental principle has motivated development of noninvasive techniques for quantification of heterogeneity using the surface electrocardiogram (ECG). The initial approaches focused on interval analysis such as interlead QT dispersion and T_peak -T_end difference. However, because of inherent difficulties in measuring the termination point of the T wave and commonly encountered irregularities in the apex of the T wave, additional techniques have been pursued. The newer methods incorporate assessment of the entire morphology of the T wave and in some cases of the R wave as well. This goal has been accomplished using a number of promising vectorial approaches with the resting 12-lead ECG. An important limitation of vectorcardiographic analyses is that they require exquisite stability of the recordings and are not inherently suitable for use in exercise tolerance testing (ETT) and/or ambulatory ECG monitoring for provocative stress testing or evaluation of the influence of daily activities on cardiac electrical instability. The objectives of the present review are to describe a technique that has been under clinical evaluation for nearly a decade, termed "interlead ECG heterogeneity." Preclinical testing data will be briefly reviewed. We will discuss the main clinical findings with regard to sudden cardiac death risk stratification, heart failure evaluation, and myocardial ischemia detection using standard recording platforms including resting 12-lead ECG, ambulatory ECG monitoring, ETT, and pharmacologic stress testing in conjunction with single-photon emission computed tomography myocardial perfusion imaging.

Electrocardiographic parameters and prognosis of renal light chain amyloidosis

Background

Cardiac involvement frequently occurs in patients with renal light chain (AL) amyloidosis, which predisposes these patients to heart failure, arrhythmia, or infarction with poor prognosis.

Hypothesis

Twelve‐lead electrocardiogram (ECG) parameters may be associated with prognosis in renal AL amyloidosis.

Methods

A retrospective single‐center cohort study was performed. Biopsy‐proven renal AL amyloidosis patients from January 2014 to December 2018 at the First Affiliated Hospital of Xi'an Jiaotong University were enrolled. The baseline demographic information, laboratory tests, 12‐lead ECG parameters at the time of diagnosis were obtained from medical records. The endpoint was defined as the time to all‐cause death from baseline for all deceased patients and time to censor date (June 2019) for all other patients. Univariate and multivariate Cox proportional hazard models were conducted to identify the relationship between ECG parameters and all‐cause mortality.

Results

A total of 69 patients with a mean age of 61.5 ± 11.4 years were enrolled in this study. The median PR interval and QTc interval were 160 (140, 186) and 417 ± 42 ms. The mean follow‐up duration was 15.9 ± 13.8 months. Multivariate Cox regression analysis showed that regardless of adjustment for age, gender and serum creatinine, PR interval (HR 1.022, 95% CI: 1.007‐1.038, P = .005), and QTc interval (HR 1.012, 95% CI: 1.004‐1.021, P = .004) were independently associated with all‐cause mortality.

Conclusions

PR interval and QTc interval were independently associated with all‐cause mortality in renal AL amyloidosis patients. ECG parameters may provide prognostic potential of renal AL amyloidosis patients and promote the management of patients with renal AL amyloidosis.

Electrocardiographic T-wave morphology and risk of mortality

BACKGROUND

Electrocardiographic T-wave morphology is used in drug safety studies as an adjunct to the QT_c interval, but few measurements of T-wave morphology can be interpreted in clinical practice. Morphology combination score (MCS) is a combination of T-wave flatness/peakedness, asymmetry, and notching, enabling easy visual assessment of T-wave morphology. We aimed to test the association between T-wave morphology, quantified by MCS, and mortality.

METHODS

We included electrocardiograms recorded in 2001-2011 from 342,294 primary care patients. Using Cox regression, we evaluated the association between MCS, cardiovascular death, and all-cause mortality, adjusting for heart rate, QT_c, QT-prolonging drugs, diabetes, ischemic heart disease, hypertension, and congestive heart failure.

RESULTS

270,039 individuals (44% men, median age 55 [inter-quartile range: 42-67 years]) were included and followed for a median of 9.3 years, during which time 13,489 (5.0%) died from cardiovascular causes and 50,481 (18.7%) from any cause. High values of MCS (i.e. asymmetric, flattened, and/or notched T waves) were associated with an adjusted mortality Hazard Ratio of 1.75 (95% CI 1.62-1.89) and 1.61 (1.43-1.92) for women and men, respectively. Low values of MCS (i.e. peaked and symmetric T waves) were associated with a Hazard Ratio of 1.18 (1.08-1.28) and 1.71 (1.48-1.98) for women and men, respectively.

CONCLUSIONS

In a large primary care population, we found that T-wave asymmetry, flatness, and notching provided prognostic information on mortality independent of heart rate, QTc, and baseline comorbidities.

Normal ranges and potential modifiers of T-wave morphology parameters among healthy individuals: A meta-analysis

BACKGROUND

T-wave morphology parameters, such as total cosine R-to-T (TCRT), T-wave loop dispersion (TWLD), T-wave morphology dispersion (TMD), and T-wave residuum (TWR), were suggested to be robust markers for adverse cardiovascular outcomes. Yet, the normal range of these parameters is unknown. This study aimed to evaluate the weighted normal values of T-wave morphology parameters of healthy individuals and study the effect of potential modifiers.

METHODS

A systematic search of studies published in PubMed was conducted. Only those reporting on control groups of healthy individuals were included. Weighted means were calculated for TCRT, TWLD, TMD, and TWR. Linear regression analysis was conducted for age, percentage of males, heart rate, and QTc.

RESULTS

The weighted TCRT was 0.40 ± 0.05, significantly higher than the various cutoffs previously suggested to identify high risk. There was some overlap between the results of weighted normal TMD (19.42 ± 6.77°), TWLD (38.51 ± 0.31), and relative TWR (0.118 ± 0.056%) and reports on the same parameters from patients with cardiovascular disease. Women were also characterized by higher TWLD, TMD, and relative TWR. TCRT was negatively correlated with age and heart rate, and positively correlated with QTc duration, although all associations were weak (R²  < 0.9).

CONCLUSIONS

T-wave morphology parameters reported in the medical literature span a broad range of values in healthy individuals. Seemingly abnormal values of TWLD, TMD, and relative TWR were often reported in healthy adults. The variability between studies may stem from methodological issues. Therefore, standardizing the methodology for measuring T-wave morphology is imperative.

Effect of four classes of antihypertensive drugs on cardiac repolarization heterogeneity: A double-blind rotational study

Background

T-wave area dispersion (TW-Ad) is a novel electrocardiographic (ECG) repolarization marker associated with sudden cardiac death. However, limited data is available on the clinical correlates of TW-Ad. In addition, there are no previous studies on cardiovascular drug effects on TW-Ad. In this study, we examined the relation between TW-Ad and left ventricular mass. We also studied the effects of four commonly used antihypertensive drugs on TW-Ad.

Methods

A total of 242 moderately hypertensive males (age, 51±6 years; office systolic/diastolic blood pressure during placebo, 153±14/100±8 mmHg), participating in the GENRES study, were included. Left ventricular mass index was determined by transthoracic echocardiography. Antihypertensive four-week monotherapies (a diuretic, a beta-blocker, a calcium channel blocker, and an angiotensin receptor antagonist) were administered in a randomized rotational fashion. Four-week placebo periods preceded all monotherapies. The average value of measurements (over 1700 ECGs in total) from all available placebo periods served as a reference to which measurements during each drug period were compared.

Results

Lower, i.e. risk-associated TW-Ad values correlated with a higher left ventricular mass index (r = −0.14, p = 0.03). Bisoprolol, a beta-blocker, elicited a positive change in TW-Ad (p = 1.9×10⁻⁵), but the three other drugs had no significant effect on TW-Ad.

Conclusions

Our results show that TW-Ad is correlated with left ventricular mass and can be modified favorably by the use of bisoprolol, although demonstration of any effects on clinical endpoints requires long-term prospective studies. Altogether, our results suggest that TW-Ad is an ECG repolarization measure of left ventricular arrhythmogenic substrate.

Predictive value of Tpeak-Tend interval for ventricular arrhythmia and mortality in heart failure patients with an implantable cardioverter-defibrillator: A cohort study

BACKGROUND

Tpeak-Tend interval (TpTe), a measurement of transmural dispersion of repolarization (TDR), has been shown to predict ventricular tachyarrhythmia in cardiac resynchronization therapy with defibrillator (CRT-D) patients. However, the ability of TpTe to predict ventricular tachyarrhythmia and mortality for heart failure patients with a cardioverter-defibrillator (ICD) is not clear. The purpose of this study was to assess the predictive ability of TpTe in heart failure patients with ICD.

METHODS AND RESULTS

We enrolled 318 heart failure patients treated after ICD. Patients were divided into 3 groups according to their post-implantation TpTe values and were evaluated every 6 months. The primary endpoint was appropriate ICD therapy. The secondary endpoint was all-cause mortality. During long-term follow-up, the TpTe > 110 ms group (n = 111) experienced more VT/VF episodes (45%) and all-cause mortality (25.2%) than the TpTe 90-110 ms group (n = 109) (26.4%, 14.5%) and TpTe < 90 ms group (n = 98) (11.3%, 11.3%) (overall P < .05, respectively). In Cox regression, longer post-implantation TpTe was associated with an increased number of VT/VF episodes [HR: 1.017; 95% CI: 1.008-1.026; P < .001], all-cause mortality [HR: 1.015; 95% CI: 1.004-1.027; P = .010] and the combined endpoint [HR: 1.018; 95%CI: 1.010-1.026; P < .001].

CONCLUSIONS

Post-implantation TpTe was an independent predictor of both ventricular arrhythmias and all-cause mortality in heart failure patients with an implanted ICD.

Associations of Electrocardiographic Parameters with Left Ventricular Longitudinal Strain and Prognosis in Cardiac Light Chain Amyloidosis

A 12-lead ECG is a simple and less costly measure to assess cardiac amyloidosis and may reflect the infiltrative nature of cardiac amyloidosis and have prognostic value for predicting overall survival in patients with cardiac AL amyloidosis. Therefore, we investigated the associations of surface ECG parameters with left ventricular (LV) global longitudinal strain (GLS) and prognosis in patients with cardiac AL amyloidosis. We performed a multi-center, retrospective analysis of 102 biopsy-proven cardiac AL amyloidosis patients. Baseline studies included 12-lead surface ECG and echocardiography, with two-dimensional strain analysis performed within one month of diagnosis. From the Kaplan-Meier survival analysis, patients with prolonged QTc (≥483 msec) had significantly poorer survival. ECG scores were assigned according to presence of prolonged QTc (≥483 msec) and abnormal QRS axis, and the study participants were divided into three groups according to ECG score. Mean absolute value of LV GLS and regional LV longitudinal strain (LS) differed significantly among the three groups and decreased in a stepwise manner as ECG score increased. Log NT-proBNP increased in a stepwise manner as ECG score increased. Prolonged QTc (≥483 msec) and abnormal QRS axis showed significant incremental values in addition to the revised Mayo stage. The presence of prolonged QTc (≥483 msec) and abnormal QRS axis showed significant incremental values for overall mortality rates. In addition, ECG scores consisting of presence of prolonged QTc (≥483 msec), and abnormal QRS axis showed good association with longitudinal LV dysfunction and NT-proBNP. ECG finding may provide prognostic additional information regarding prognosis of AL amyloidosis with cardiac involvement.

Ambient and controlled exposures to particulate air pollution and acute changes in heart rate variability and repolarization

Previous studies have reported increased risks of myocardial infarction in association with elevated ambient particulate matter (PM) in the previous hour(s). However, whether PM can trigger mechanisms that act on this time scale is still unclear. We hypothesized that increases in PM are associated with rapid changes in measures of heart rate variability and repolarization. We used data from panel studies in Augsburg, Germany, and Rochester, New York, USA, and two controlled human exposure studies in Rochester. Data included ECG recordings from all four studies, controlled exposures to (concentrated) ultrafine particles (UFP; particles with an aerodynamic diameter <100 nm) and ambient concentrations of UFP and fine PM (PM_2.5, aerodynamic diameter <2.5 μm). Factor analysis identified three representative ECG parameters: standard deviation of NN-intervals (SDNN), root mean square of successive differences (RMSSD), and T-wave complexity. Associations between air pollutants and ECG parameters in the concurrent and previous six hours were estimated using additive mixed models adjusting for long- and short-term time trends, meteorology, and study visit number. We found decreases in SDNN in relation to increased exposures to UFP in the previous five hours in both of the panel studies (e.g. Augsburg study, lag 3 hours: −2.26%, 95% confidence interval [CI]: −3.98% to −0.53%; Rochester panel study, lag 1 hour: −2.69%; 95% CI: −5.13% to −0.26%) and one of the two controlled human exposure studies (1-hour lag: −13.22%; 95% CI: −24.11% to −2.33%). Similarly, we observed consistent decreases in SDNN and RMSSD in association with elevated PM_2.5 concentrations in the preceding six hours in both panel studies. We did not find consistent associations between particle metrics and T-wave complexity. This study provided consistent evidence that recent exposures to UFP and PM_2.5 can induce acute pathophysiological responses.

Comparison of automated interval measurements by widely used algorithms in digital electrocardiographs

BACKGROUND

Automated measurements of electrocardiographic (ECG) intervals by current-generation digital electrocardiographs are critical to computer-based ECG diagnostic statements, to serial comparison of ECGs, and to epidemiological studies of ECG findings in populations. A previous study demonstrated generally small but often significant systematic differences among 4 algorithms widely used for automated ECG in the United States and that measurement differences could be related to the degree of abnormality of the underlying tracing. Since that publication, some algorithms have been adjusted, whereas other large manufacturers of automated ECGs have asked to participate in an extension of this comparison.

METHODS

Seven widely used automated algorithms for computer-based interpretation participated in this blinded study of 800 digitized ECGs provided by the Cardiac Safety Research Consortium. All tracings were different from the study of 4 algorithms reported in 2014, and the selected population was heavily weighted toward groups with known effects on the QT interval: included were 200 normal subjects, 200 normal subjects receiving moxifloxacin as part of an active control arm of thorough QT studies, 200 subjects with genetically proved long QT syndrome type 1 (LQT1), and 200 subjects with genetically proved long QT syndrome Type 2 (LQT2).

RESULTS

For the entire population of 800 subjects, pairwise differences between algorithms for each mean interval value were clinically small, even where statistically significant, ranging from 0.2 to 3.6milliseconds for the PR interval, 0.1 to 8.1milliseconds for QRS duration, and 0.1 to 9.3milliseconds for QT interval. The mean value of all paired differences among algorithms was higher in the long QT groups than in normals for both QRS duration and QT intervals. Differences in mean QRS duration ranged from 0.2 to 13.3milliseconds in the LQT1 subjects and from 0.2 to 11.0milliseconds in the LQT2 subjects. Differences in measured QT duration (not corrected for heart rate) ranged from 0.2 to 10.5milliseconds in the LQT1 subjects and from 0.9 to 12.8milliseconds in the LQT2 subjects.

CONCLUSIONS

Among current-generation computer-based electrocardiographs, clinically small but statistically significant differences exist between ECG interval measurements by individual algorithms. Measurement differences between algorithms for QRS duration and for QT interval are larger in long QT interval subjects than in normal subjects. Comparisons of population study norms should be aware of small systematic differences in interval measurements due to different algorithm methodologies, within-individual interval measurement comparisons should use comparable methods, and further attempts to harmonize interval measurement methodologies are warranted.

Total cosine R-to-T for predicting ventricular arrhythmic and mortality outcomes: A systematic review and meta-analysis

BACKGROUND

The total cosine R-to-T (TCRT), a vectorcardiographic marker reflecting the spatial difference between the depolarization and repolarization wavefronts, has been used to predict ventricular tachycardia/fibrillation (VT/VF) and sudden cardiac death (SCD) in different clinical settings. However, its prognostic value has been controversial.

OBJECTIVE

This systematic review and meta-analysis evaluated the significance of TRCT in predicting arrhythmic and/or mortality endpoints.

METHODS

PubMed and Embase databases were searched through December 31, 2016.

RESULTS

Of the 890 studies identified initially, 13 observational studies were included in our meta-analysis. A total of 11,528 patients, mean age 47 years old, 72% male, were followed for 43 ± 6 months. Data from five studies demonstrated lower TCRT values in myocardial infarction patients with adverse events (syncope, ventricular arrhythmias, or sudden cardiac death) compared to those without these events (mean difference = -0.36 ± 0.05, p < .001; I2  = 48%). By contrast, only two studies analyzed outcomes in heart failure, and pooled meta-analysis did not demonstrate significant difference in TCRT between event-positive and event-negative patients (mean difference = -0.01 ± 0.10, p > .05; I2  = 80%).

CONCLUSION

TCRT is lower in MI patients at high risk of adverse events when compared to those free from such events. It can provide additional risk stratification beyond the use of clinical parameters and traditional electrocardiogram markers. Its value in other diseases such as heart failure requires further studies.

Arterial Stiffness Is Associated With QTc Interval Prolongation in Patients With Heart Failure

BACKGROUND

A prolonged corrected QT (QTc) interval is a known risk factor for adverse cardiac events. Understanding the determinants and physiologic correlates of QTc is necessary for selecting proper strategies to reduce the risk of adverse events in high-risk patients. We sought to evaluate the role of arterial stiffness in heart failure as a determinant of QTc prolongation.

METHOD

This was an observational study that recruited ambulatory heart failure patients (New York Heart Association Classes I-II) from an outpatient heart failure clinic. In the supine resting position, consented patients underwent noninvasive 12-lead electrocardiograph (ECG) and hemodynamic monitoring using BioZ Dx impedance cardiography. ECGs were evaluated by a reviewer blinded to clinical data, and QTc interval was automatically computed. Patients with pacing or bundle branch block (BBB) were analyzed separately. Strengths of associations were evaluated using Pearson's r coefficients and multivariate linear regression.

RESULTS

The final sample ( N = 44) was 62 ± 13 years of age and 64% male with ejection fraction of 34% ± 12%. At univariate level, QTc interval moderately ( r > .50) correlated with cardiac output, left cardiac work index, systemic vascular resistance, and total arterial compliance in patients with intrinsically narrow QRS complexes. At the multivariate level, increasing systemic vascular resistance and decreasing total arterial compliance remained independent predictors of widening QTc interval in this group ( R² = .54). No significant correlations were seen in patients with pacing or BBB.

CONCLUSIONS

In the absence of conduction abnormalities, magnitude of arterial stiffness, an indirect measure of endothelial dysfunction, is associated with QTc interval prolongation.

Ventricular repolarization alterations in women with angina pectoris and suspected coronary microvascular dysfunction

OBJECTIVES

CMD could be the explanation of angina pectoris with no obstructive CAD and may cause ventricular repolarization changes. We compared T-wave morphology and QTc interval in women with angina pectoris with a control group as well as the associations with CMD.

METHODS

Women with angina pectoris and no obstructive coronary artery disease (n=138) and age-matched controls were compared in regard to QTc interval and morphology combination score (MCS) based on T-wave asymmetry, flatness and presence of T-wave notch. CMD was assessed as a coronary flow velocity reserve (CFVR) by transthoracic echocardiography.

RESULTS

Women with angina pectoris had significantly longer QTc intervals (429±20ms) and increased MCS (IQR) (0.73 [0.64-0.80]) compared with the controls (419±20ms) and (0.63 [(0.53-0.73]), respectively (both p<0.001). CFVR was associated with longer QTc interval (p=0.02), but the association was attenuated after multivariable adjustment (p=0.08).

CONCLUSION

This study suggests that women with angina pectoris have alterations in T-wave morphology as well as longer QTc interval compared with a reference population. CMD might be an explanation.

The impact of multiple sclerosis onset symptom on cardiac repolarization

INTRODUCTION

Multiple sclerosis is associated with prolonged cardiac repolarization but the underlying physiology has remained unknown. In this study, we compared cardiac repolarization during the relapsing-remitting multiple sclerosis (RRMS) disease course in patients with motor and sensory onset symptom.

METHODS

Twenty-five RRMS patients with motor and 33 RRMS patients with sensory onset symptom having 12-lead electrocardiogram (ECG) recorded at the time of the first demyelinating event (ECG1) as well as at the later disease course (ECG2) were identified from the patient records. The average time interval between ECG1 and ECG2 was 8.6 ± 5.9 y. Heart rate-corrected QT intervals reflecting cardiac repolarization were calculated by Bazett (QTcBaz), Fridericia (QTcFri), and Karjalainen (QTcKar) formulas.

RESULTS

Heart rate-corrected QT intervals as well as heart rate were similar in patients with motor and sensory onset symptom in ECG1. However, QTcBaz (p = .002), QTcFri (p = .019), and QTcKar (p = .026) were longer and heart rate was higher (p = .035) in patients with motor than sensory onset symptom in ECG2. Correspondingly, QTcBaz (p = .002), QTcFri (p = .033), and QTcKar (p = .043) prolonged and heart rate tended to increase (p = .060) during the disease course only in the patients with motor onset symptom.

CONCLUSIONS

Cardiac repolarization prolonged and heart rate increased during the disease course in RRMS patients with motor but not with sensory onset symptom. This suggests different traits in RRMS according to its initial manifestation and also association of motor onset symptom with more unfavorable cardiovascular prognostic determinants.

Tracking interlead heterogeneity of R- and T-wave morphology to disclose latent risk for sudden cardiac death

Sudden cardiac death (SCD) due primarily to ventricular fibrillation claims 1.5 million lives worldwide each year. In 45%-50% of cases, it is the first manifestation of underlying heart disease. Traditional risk factors including smoking, hypertension, age, sex, as well as depressed left ventricular ejection fraction lack sufficient sensitivity and specificity to forewarn of impending life-threatening arrhythmias. There has been a decades-long search for electrocardiographic (ECG) markers of SCD risk. Several interval-based indices such as QT dispersion and T_peak-T_end interval held initial promise but ultimately yielded mixed results. Recently, the focus has been on interlead heterogeneity of R- and T-wave morphology. The new approaches have involved advanced analytical tools including vectorcardiographic techniques and second central moment analysis of QRS-aligned templates to quantify heterogeneity of depolarization and repolarization waveforms. The results of current studies appear to be robust and worthy of further exploration. This review examines the electrophysiological underpinnings of heterogeneity-based risk assessment and provides an update of clinical techniques. We also discuss future directions whereby tracking heterogeneity may help to disclose latent risk for SCD not only in ECG recordings made at rest but also during ambulatory ECG monitoring and exercise tolerance testing.

Cardiac Autonomic Regulation and Repolarization During Acute Experimental Hypoglycemia in Type 2 Diabetes

Hypoglycemia is associated with increased cardiovascular mortality in trials of intensive therapy in type 2 diabetes mellitus (T2DM). We previously observed an increase in arrhythmias during spontaneous prolonged hypoglycemia in patients with T2DM. We examined changes in cardiac autonomic function and repolarization during sustained experimental hypoglycemia. Twelve adults with T2DM and 11 age- and BMI-matched control participants without diabetes underwent paired hyperinsulinemic clamps separated by 4 weeks. Glucose was maintained at euglycemia (6.0 mmol/L) or hypoglycemia (2.5 mmol/L) for 1 h. Heart rate, blood pressure, and heart rate variability were assessed every 30 min and corrected QT intervals and T-wave morphology every 60 min. Heart rate initially increased in participants with T2DM but then fell toward baseline despite maintained hypoglycemia at 1 h accompanied by reactivation of vagal tone. In control participants, vagal tone remained depressed during sustained hypoglycemia. Participants with T2DM exhibited greater heterogeneity of repolarization during hypoglycemia as demonstrated by T-wave symmetry and principal component analysis ratio compared with control participants. Epinephrine levels during hypoglycemia were similar between groups. Cardiac autonomic regulation during hypoglycemia appears to be time dependent. Individuals with T2DM demonstrate greater repolarization abnormalities for a given hypoglycemic stimulus despite comparable sympathoadrenal responses. These mechanisms could contribute to arrhythmias during clinical hypoglycemic episodes.

Analysis of ECG Measures of Cardiac Repolarization in Relation to Arrhythmic Events in an Implantable Cardioverter Defibrillator Population

BACKGROUND

ECG-derived measures of cardiac repolarization may have utility in risk prediction of future ventricular arrhythmia, and a range of different measures have been proposed. We compared time-based, vectorcardiographic, and singular value decomposition (SVD) derived measures of repolarization to determine which was most predictive of appropriate therapy in an ICD population.

METHODS

We examined the independent prognostic value of a range of repolarization measures derived from 60 second 12-lead ECG recordings in 150 patients receiving new ICD implants in relation to the occurrence of appropriate therapy during follow-up.

RESULTS

Over an average follow-up of 2.15 ± 0.87 years, male gender, presence of premature ventricular complex (PVC), relative T wave residuum (TWR-rel, measures regional repolarization heterogeneity), and TCRT (the total cosine R-to-T, describes the global angle between repolarization and depolarization wavefronts) were the only independent predictors of appropriate therapy. With every 0.01% increase in TWR-rel, there was 2% increased risk of appropriate therapy (HR = 1.02, 95% CI 1.006-1.034, P < 0.001). With every 1° decrease in TCRT, there was an increase in arrhythmic risk of 0.9% (HR 1.009, 95% CI 1.003-1.015, P = 0.003).

CONCLUSIONS

The use of advanced analytic ECG techniques to derive measures of repolarization abnormality might shave utility in risk stratification in an ICD population.

A review of beat-to-beat vectorcardiographic (VCG) parameters for analyzing repolarization variability in ECG signals

Elevated ventricular repolarization lability is believed to be linked to the risk of ventricular tachycardia/ventricular fibrillation. However, ventricular repolarization is a complex electrical phenomenon, and abnormalities in ventricular repolarization are not completely understood. To evaluate repolarization lability, vectorcardiography (VCG) is an alternative approach where the electrocardiographic (ECG) signal can be considered as possessing both magnitude and direction. Recent research has shown that VCG is advantageous over ECG signal analysis for identification of repolarization abnormality. One of the key reasons is that the VCG approach does not rely on exact identification of the T-wave offset, which improves the reproducibility of the VCG technique. However, beat-to-beat variability in VCG is an emerging area for the investigation of repolarization abnormality though not yet fully realized. Therefore, the purpose of this review is to explore the techniques, findings, and efficacy of beat-to-beat VCG parameters for analyzing repolarization lability, which may have potential utility for further study.

The cardiac safety of aripiprazole treatment in patients at high risk for torsade: a systematic review with a meta-analytic approach

RATIONALE

Certain antipsychotics increase the risk of heart rate-corrected QT (QTc) prolongation and consequently Torsades de Pointes (TdP) and sudden cardiac death (SCD). Drug-induced Brugada syndrome (BrS) is also associated with SCD. Most SCDs occur in patients with additional cardiac risk factors.

OBJECTIVES

Aripiprazole's cardiac safety has not been assessed in patients at high risk for torsade, where QTc prolongation risk is highly increased.

METHODS

MEDLINE, Embase, and The Cochrane Library were searched for preclinical, clinical, and epidemiological studies. Eligible studies were reviewed and cardiac safety data were extracted. Continuous and dichotomous QTc data were used in the meta-analysis.

RESULTS

Preclinical studies suggested that aripiprazole has limited affinity for the delayed rectifier potassium current. TdP was reported in two case reports and SCD was reported in one case report and one case series. No clinical studies assessing aripiprazole's cardiac safety in patients at high risk for torsade were found. No thorough QT (TQT) study with aripiprazole was found. The meta-analysis revealed that the mean ΔQTc interval was decreased with aripiprazole and QTc prolongation risk was lower compared with placebo and active controls. Epidemiological studies linked aripiprazole to weak/moderate torsadogenicity. No studies were found associating aripiprazole with BrS suggesting low affinity for the fast sodium current.

CONCLUSIONS

Aripiprazole is a low-risk antipsychotic regarding cardiac safety in healthy patients. However, baseline and steady state electrocardiogram is recommended in patients at high risk for torsade due to marked QTc prolongation, absence of a TQT study, and lack of data in this group.

Cardiac QTc interval characteristics before and after hematopoietic stem cell transplantation: an analysis of 995 consecutive patients at a single center

Hematopoietic stem cell transplantation (HSCT) treats disorders affecting patients of all ages. We studied the rate-corrected cardiac QT interval (QTc) in 995 consecutive children and adults undergoing HSCT at the University of Minnesota. We sought to (1) describe QTc before and after HSCT; (2) describe the change in QTc after HSCT; (3) identify factors affecting QTc and its change; and (4) scrutinize an 'at risk' sub-cohort with a long QTc before HSCT. Pre HSCT: 952 (96%) patients had an evaluable electrocardiography (ECG); median QTc was 426 ms and depended upon disease necessitating transplant. Post HSCT: 506 (51%) patients had an evaluable ECG; median QTc was 441 ms. Intrapatient QTc change: 490 (49%) evaluable patients showed median QTc change (pre to post HSCT) of +16 ms (P<0.0001). At risk group: 68 patients were 'at risk' (long pre-HSCT QTc). In some, 'at-risk' status trended toward predictive of post-transplant nonrelapse mortality. QTc interval prolongation is evident in a large, diverse cohort undergoing HSCT at our institution. Prospective studies of this patient population may be warranted, particularly for 'at-risk' patients who demonstrate significant QTc prolongation both pre and post HSCT.

Heart rate-corrected QT interval is an independent predictor of all-cause and cardiovascular mortality in individuals with type 2 diabetes: the Diabetes Heart Study

OBJECTIVE

Heart rate-corrected QT (QTc) interval is associated with mortality in the general population, but this association is less clear in individuals with type 2 diabetes. We assessed the association of QTc interval with all-cause and cardiovascular disease (CVD) mortality in the Diabetes Heart Study.

RESEARCH DESIGN AND METHODS

We studied 1,020 participants with type 2 diabetes (83% European Americans; 55% women; mean age 61.4 years) who were free of atrial fibrillation, major ventricular conduction defects, and antiarrhythmic therapy at baseline. QT duration was automatically calculated from a standard 12-lead electrocardiogram (ECG). Following American Heart Association/American College of Cardiology Foundation recommendations, a linear scale was used to correct the QT for heart rate. Using Cox regression, risk was estimated per 1-SD increase in QTc interval as well as prolonged QTc interval (>450 ms) vs. normal QTc interval for mortality.

RESULTS

At baseline, the mean (SD) QTc duration was 414.9 ms (18.1), and 3.0% of participants had prolonged QTc. After a median follow-up time of 8.5 years (maximum follow-up time 13.9 years), 204 participants were deceased. In adjusted multivariate models, a 1-SD increase in QTc interval was associated with an 18% higher risk for all-cause mortality (hazard ratio 1.18 [95% CI 1.03-1.36]) and 29% increased risk for CVD mortality (1.29 [1.05-1.59]). Similar results were obtained when QTc interval was used as a categorical variable (prolonged vs. normal) (all-cause mortality 1.73 [0.95-3.15]; CVD mortality 2.86 [1.35-6.08]).

CONCLUSIONS

Heart rate QTc interval is an independent predictor of all-cause and CVD mortality in this population with type 2 diabetes, suggesting that additional prognostic information may be available from this simple ECG measure.

Predictive value of electrocardiographic T-wave morphology parameters and T-wave peak to T-wave end interval for sudden cardiac death in the general population

BACKGROUND

Previous population studies have found an association between electrocardiographic T-wave morphology parameters and cardiovascular mortality, but their relationship to sudden cardiac death (SCD) is not clear. To our knowledge, there are no follow-up studies assessing the association between electrocardiographic T-wave peak to T-wave end interval (TPE) and SCD. We assessed the predictive value of electrocardiographic T-wave morphology parameters and TPE for SCD in an adult general population sample.

METHODS AND RESULTS

A total of 4 T-wave morphology parameters (principal component analysis ratio, T-wave morphology dispersion, total cosine R-to-T, T-wave residuum) as well as TPE were measured from digital standard 12-lead ECGs in 5618 adults (46% men; mean age 50.9±12.5 years) participating in the Finnish population-based Health 2000 Study. After a mean follow-up time of 7.7±1.4 years, 72 SCDs had occurred. In univariable analyses, all T-wave morphology parameters were associated with an increased SCD risk. In multivariable Cox models, T-wave morphology dispersion and total cosine R-to-T remained as predictors of SCD, with T-wave morphology dispersion showing the highest SCD risk (hazard ratio of 1.4 [95% confidence interval 1.1-1.7, P=0.001] per 1 SD increase in the loge T-wave morphology dispersion). In contrast, TPE was not associated with SCD in univariable or multivariable analyses.

CONCLUSIONS

Electrocardiographic T-wave morphology parameters describing the 3-dimensional shape of the T-wave stratify SCD risk in the general population, but we did not find an association between TPE and SCD.

Usefulness of biventricular volume as a predictor of mortality in patients with diabetes mellitus (from the Diabetes Heart Study)

Patients with type 2 diabetes mellitus are at increased risk for cardiovascular disease (CVD) and mortality. Beyond traditional CVD risk factors, novel measures reflecting additional aspects of disease pathophysiology, such as biventricular volume (BiVV), may be useful for risk stratification. The aim of this study was to examine the relationship between BiVV and risk for mortality in European Americans with type 2 diabetes mellitus from the Diabetes Heart Study (DHS). BiVV was calculated from 771 noncontrast computed tomographic scans performed to image coronary artery calcified plaque. Relationships between BiVV and traditional CVD risk factors were examined. Cox proportional-hazards regression was performed to determine risk for mortality (all-cause and CVD mortality) associated with increasing BiVV. Area under the curve analysis was used to assess BiVV utility in risk prediction models. During 8.4 ± 2.4 years of follow-up, 23% of the patients died. In unadjusted analyses, BiVV was significantly associated with increasing body mass index, height, coronary artery calcified plaque, history of hypertension, and previous myocardial infarction (p <0.0001 to 0.012). BiVV was significantly associated with all-cause (hazard ratio 2.45, 95% confidence interval 1.06 to 5.67, p = 0.036) and CVD (hazard ratio 4.36, 95% confidence interval 1.36 to 14.03, p = 0.014) mortality in models adjusted for other known CVD risk factors. Area under the curve increased from 0.76 to 0.78 (p = 0.04) and from 0.74 to 0.77 (p = 0.02) for all-cause and CVD mortality with the inclusion of BiVV. In conclusion, in the absence of echocardiography or other noninvasive imaging modalities to assess ventricular volumes, or when such methods are contraindicated, BiVV from computed tomography may be considered a tool for the stratification of high-risk patients, such as those with type 2 diabetes mellitus.

Beat-to-beat vectorcardiographic analysis of ventricular depolarization and repolarization in myocardial infarction

Objectives

Increased beat-to-beat variability in the QT interval has been associated with heart disease and mortality. The purpose of this study was to investigate the beat-to-beat spatial and temporal variations of ventricular depolarization and repolarization in vectorcardiogram (VCG) for characterising myocardial infarction (MI) patients.

Methods

Standard 12-lead ECGs of 84 MI patients (22 f, 63±12 yrs; 62 m, 56±10 yrs) and 69 healthy subjects (17 f, 42±18 yrs; 52 m, 40±13 yrs) were investigated. To extract the beat-to-beat QT intervals, a template-matching algorithm and the singular value decomposition method have been applied to synthesise the ECG data to VCG. Spatial and temporal variations in the QRS complex and T-wave loops were studied by investigating several descriptors (point-to-point distance variability, mean loop length, T-wave morphology dispersion, percentage of loop area, total cosine R-to-T).

Results

Point-to-point distance variability of QRS and T-loops (0.13±0.04 vs. 0.10±0.04, p< 0.0001 and 0.16±0.07 vs. 0.13±0.06, p< 0.05) were significantly larger in the MI group than in the control group. The average T-wave morphology dispersion was significantly higher in the MI group than in the control group (62°±8° vs. 38°±16°, p< 0.0001). Further, its beat-to-beat variability appeared significantly lower in the MI group than in the control group (12°±5° vs. 15°±6°, p< 0.005). Moreover, the average percentage of the T-loop area was found significantly lower in the MI group than the controls (46±17 vs. 55±15, p< 0.001). Finally, the average and beat-to-beat variability of total cosine R-to-T were not found statistically significant between both groups.

Conclusions

Beat-to-beat assessment of VCG parameters may have diagnostic attributes that might help in identifying MI patients.

Effects of bilastine on T-wave morphology and the QTc interval: a randomized, double-blind, placebo-controlled, thorough QTc study

BACKGROUND AND OBJECTIVES

The International Conference of Harmonisation (ICH) E14 guideline for thorough QT studies requires assessing the propensity of new non-antiarrhythmic drugs to affect cardiac repolarization. The present study investigates whether a composite ECG measure of T-wave morphology (Morphology Combination Score [MCS]) can be used together with the heart rate corrected QT interval (QTc) in a fully ICH E14-compliant thorough QT study to exclude clinically relevant repolarization effects of bilastine, a novel antihistamine.

METHODS

Thirty participants in this crossover study were randomly assigned to receive placebo, moxifloxacin 400 mg, bilastine at therapeutic and supratherapeutic doses (20 and 100 mg) and bilastine 20 mg co-administered with ketoconazole 400 mg. Resting ECGs recorded at 12 nominal time points before and after treatments were used to determine Fridericia corrected QTc (QTcF) and MCS from the T-wave characteristics: asymmetry, flatness and notching.

RESULTS

There were no effects of bilastine monotherapy (20 and 100 mg) on MCS or QTcF at those study times where the bilastine plasma concentrations were highest. MCS changes for bilastine monotherapy did not exceed the normal intrasubject variance of T-wave shapes for triplicate ECG recordings. Maximum QTcF prolongation for bilastine monotherapy was 5 ms or less: 3.8 ms (90% CI 0.3, 7.3 ms) for bilastine 20 mg and 5.0 ms (90% CI 2.0, 8.0 ms) for bilastine 100 mg. There were no indications of bilastine inducing larger repolarization effects on T-wave morphology as compared with the QTcF interval, as evidenced by the similarity of z-score equivalents for placebo-corrected changes in MCS and QTcF values.

CONCLUSION

This study shows that bilastine, at therapeutic and supratherapeutic dosages, does not induce any effects on T-wave morphology or QTcF. These results confirm the absence of an effect for bilastine on cardiac repolarization.

Association between Tp-e/QT ratio and prognosis in patients undergoing primary percutaneous coronary intervention for ST-segment elevation myocardial infarction

BACKGROUND

Both the Tpeak-Tend interval (Tp-e) and the Tp-e/QT ratio have been linked to increased risk for arrhythmia. Patient Tp-e/QT ratios were investigated prior to primary percutaneous coronary intervention (pPCI) in patients with ST-segment elevation myocardial infarction (STEMI).

HYPOTHESIS

Tp-e/QT ratio maybe associated with the prognosis in patients with ST-segment elevation.

METHODS

A total of 338 patients (N = 338) with STEMI treated by pPCI were included. The Tp-e and Tp-e/QT ratio were determined using electrocardiograms in the subjects exhibiting ST-segment elevation.

RESULTS

The Tp-e/QT ratio was correlated with both short- and long-term outcomes. Analysis of the receiver operating characteristic curve demonstrated that the optimal cutoff value for outcome prediction was a Tp-e/QT ratio of 0.29. Of the 388 patients enrolled, 115 (34.0%) exhibited a Tp-e/QT ratio ≥ 0.29. Patients with a Tp-e/QT ratio ≥ 0.29 showed elevated rates of both in-hospital death (21.9% vs 2.3%; P < 0.001) and main adverse cardiac events (MACE) (48.1% vs 15.3%; P < 0.005). After discharge, Tp-e/QT ratios ≥ 0.29 remained an independent predictor of all-cause death (35.5% vs 5.2%, P < 0.001) and cardiac death (32.3% vs 2.6%, P < 0.001).

CONCLUSIONS

The Tp-e/QT ratio may serve as a prognostic predictor of adverse outcomes after successful pPCI treatment in STEMI patients.

Relationships between the T-peak to T-end interval, ventricular tachyarrhythmia, and death in left ventricular systolic dysfunction

AIMS

The interval between the T-wave's peak and end (Tpe), an electrocardiographic (ECG) index of ventricular repolarization, has been proposed as an indicator of arrhythmic risk. We aimed to clarify the clinical usefulness of Tpe for risk stratification.

METHODS AND RESULTS

We evaluated 327 patients with left ventricular ejection fraction (LVEF) ≤ 35% (75% male, LVEF 23 ± 7%). All patients had an implanted implantable cardioverter-defibrillator (ICD). Clinical data and ECGs were analysed at baseline. Prospective follow-up for the endpoints of appropriate ICD therapy and mortality was conducted via periodic device interrogation, chart review, and the Social Security Death Index. During device clinic follow-up of 17 ± 12 months, 59 (18%) patients had appropriate ICD therapy, and during mortality follow-up of 30 ± 13 months, 67 (21%) patients died. A longer Tpe(c) predicted appropriate ICD therapy, death, and the combination of appropriate ICD therapy or death (P< 0.01 for each endpoint). On multivariable analysis correcting for other univariable predictors, Tpe(c) remained predictive of ICD therapy [hazard ratio (HR) per 10 ms increase: 1.16, P= 0.02], all-cause mortality (HR per 10 ms: 1.14, P= 0.03), and the composite endpoint of ICD therapy or death (HR per 10 ms: 1.16, P< 0.01).

CONCLUSIONS

In patients with left ventricular systolic dysfunction and an implanted ICD, Tpe(c) independently predicts both ventricular tachyarrhythmia and overall mortality.

First-degree atrioventricular block is associated with heart failure and death in persons with stable coronary artery disease: data from the Heart and Soul Study

AIMS

First-degree atrioventricular block (AVB) has traditionally been considered a benign electrocardiographic finding in healthy individuals. However, the clinical significance of first-degree AVB has not been evaluated in patients with stable coronary heart disease. We investigated whether first-degree AVB is associated with heart failure (HF) and mortality in a prospective cohort study of outpatients with stable coronary artery disease (CAD).

METHODS AND RESULTS

We measured the P-R interval in 938 patients with stable CAD and classified them into those with (P-R interval ≥ 220 ms) and without (P-R interval <220 ms) first-degree AVB. Hazard ratios (HRs) and 95% confidence intervals were calculated for HF hospitalization and all-cause mortality. During 5 years of follow-up, there were 123 hospitalizations for HF and 285 deaths. Compared with patients who had normal atrioventricular conduction, those with first-degree AVB were at increased risk for HF hospitalization (age-adjusted HR 2.33: 95% CI 1.49-3.65; P= 0.0002), mortality [age-adjusted HR 1.58; 95% CI (1.13-2.20); P = 0.008], cardiovascular (CV) mortality [age-adjusted HR 2.33; 95% CI (1.28-4.22); P= 0.005], and the combined endpoint of HF hospitalization or CV mortality (age-adjusted HR 2.43: 95% CI 1.64-3.61; P ≤ 0.0001). These associations persisted after multivariable adjustment for heart rate, medication use, ischaemic burden, and QRS duration. Adjustment for left ventricular systolic and diastolic function partially attenuated the effect, but first-degree AVB remained associated with the combined endpoint of HF or CV death (HR 1.61, CI 1.02-2.54; P= 0.04).

CONCLUSION

In a large cohort of patients with stable coronary artery disease, first-degree AVB is associated with HF and death.

Common genetic variants, QT interval, and sudden cardiac death in a Finnish population-based study

BACKGROUND

Although sudden cardiac death (SCD) is heritable, its genetic underpinnings are poorly characterized. The QT interval appears to have a graded relationship to SCD, and 35% to 45% of its variation is heritable. We examined the relationship among recently reported common genetic variants, QT interval, and SCD.

METHODS AND RESULTS

We genotyped 15 common (minor allele frequency >1%) candidate single nucleotide polymorphisms (SNPs), based on association with the QT interval in prior studies, in individuals in 2 cohort studies (Health 2000, n = 6597; Mini-Finland, n = 801). After exclusions, we identified 116 incident SCDs from the remaining sample (n = 6808). We constructed a QT genotype score (QT(score)) using the allele copy number and previously reported effect estimates for each SNP. Cox proportional hazards models adjusting for age, sex, and geographical area were used for time to SCD analyses. The QT(score) was a continuous independent predictor of the heart rate-corrected QT interval (P<10(-107)). Comparing the top with the bottom quintile of QT(score), there was a 15.6-ms higher group mean QT interval (P<10(-84)). A 10-ms increase in the observed QT interval was associated with an increased risk of SCD (hazard ratio, 1.19; 95% confidence interval, 1.07 to 1.32; P = 0.002). There was no linear relationship between QT(score) and SCD risk; although in post hoc secondary analysis there was increased risk in the top compared with the middle QT(score) quintile (hazard ratio, 1.92; 95% confidence interval, 1.05 to 3.58; P = 0.04).

CONCLUSIONS

Our study strongly replicates the relationship between common genetic variants and the QT interval and confirms the relationship between the QT interval and SCD but does not show evidence for a linear relationship between QT(score) and SCD risk.

T-wave morphology abnormalities in benign, potent, and arrhythmogenic I(kr) inhibition

BACKGROUND

There is a consensus on the limited value of the QTc interval prolongation as a surrogate marker of drug cardiotoxicity and as a risk stratifier in inherited long QT syndrome (LQTS) patients.

OBJECTIVE

We investigated the interest of repolarization morphology in the acquired and the inherited LQTS.

METHODS

We analyzed 2 retrospective electrocardiographic (ECG) datasets from healthy on/off moxifloxacin and from genotyped KCNH2 patients. We measured QT, RR, and T-peak to T-end intervals, early repolarization duration (ERD) and late repolarization duration, T-roundness, T-amplitude, left (αL) and right slopes of T-waves. We designed multivariate logistic models to predict the presence of the KCNH2 mutation or moxifloxacin while adjusting for the level of QTc prolongation and the level of heart rate in LQT2 patients. Independent learning and validation sets were used. A list of 4,874 ECGs from 411 healthy individuals, 293 from 143 LQT2 carriers and 150 noncarrier family members were analyzed.

RESULTS

In the moxifloxacin model, ERD was associated with the presence of the drug (odds ratio = 1.15 per ms increase, confidence interval 1.04 to 1.26, P = .0001) after adjustment for QTc. The model for the LQT2 revealed that left slope was associated with the presence of the KCNH2 mutation (odds ratio = 0.38 per 1.5 μV/ms decrease, confidence interval 0.23 to 0.64, P = .0002). Only T-roundness complemented QTc in the model investigating cardiac events in LQT2.

CONCLUSIONS

These observations demonstrate that the phenotypic expression of KCNH2 mutations and the effect of IKr-inhibitory drug on the surface electrocardiogram are specific. Future research should investigate whether this phenomenon is linked to different level/form of loss functions of Ikr channels, and whether they could result in different arrhythmogenic mechanisms.

Dynamic QT/RR relationship in post-myocardial infarction patients with and without cardiac arrest

OBJECTIVES

Changes in QT interval dynamicity may be associated with susceptibility to ventricular fibrillation (VF) after myocardial infarction (MI). We tested the hypothesis that dynamic QT/RR relationship might differ between post-MI patients with and without a history of VF. We also evaluated the influence of negative T-waves on the assessment of QT/RR relationship.

DESIGN

We reviewed Holter recordings from 37 post-MI patients resuscitated from VF not associated with new MI (VF group) and 30 patients after MI without known sustained ventricular arrhythmias (control group). With an automated computerized program, we measured QT interval dynamicity as the mean QT/RR slope and as the maximal QT/RR slope determined at stable heart rates.

RESULTS

The mean QT/RR slope was 0.20 ± 0.08 in control group and 0.15 ± 0.09 in VF group (p=0.01) whereas corresponding maximal QT/RR slope values were 0.42 ± 0.20 and 0.33 ± 0.18 (p=0.01), respectively. Thirteen control patients (43%) and 22 VF patients (59%) showed only negative or both positive and negative T-waves (p=0.45). Mean QT/RR slope values were similar irrespective of T-wave polarity whereas maximal QT/RR slopes were steeper in cases with both positive and negative T-waves. Cases showing T-waves of both positive and negative polarity exhibited greatest intersubject variability of both QT/RR slope values.

CONCLUSIONS

Lower mean QT/RR slope may be associated with a risk of VF after MI. A detailed assessment and definition of differing T-wave polarities is essential in evaluating the QT/RR relation in post-MI patients.

QT interval prolongation and the risks of stroke and coronary heart disease in a general Japanese population: the Hisayama study

Uncertainty remains regarding the value of heart-rate-corrected QT interval (QTc) prolongation on electrocardiogram for predicting cardiovascular disease (CVD), particularly among Asian populations. The objective of the present analysis was to analyze the association of QTc prolongation with the development of CVD in a general Japanese population. During the follow-up period, 303 CVD events were observed. Among men, the age-adjusted incidence rates of CVD rose with prolonged QTc levels: 10.9, 12.1, 14.1 and 37.8 per 1000 person-years for subgroups defined by QTc levels of <400, 400-419, 420-439 and > or =440 ms, respectively (P=0.0007 for trend). The risk of CVD in the highest group was 3.09-fold (95% confidence interval, 1.82-5.25) higher than that in the lowest group even after controlling for other confounding factors: age, hypertension, heart rate, electrocardiogram abnormalities, diabetes, impaired glucose tolerance, impaired fasting glycemia, body mass index, total and high-density lipoprotein cholesterols, alcohol intake, smoking habit and regular exercise. Similar associations were observed for the outcomes of stroke and coronary heart disease. Among women, in contrast, no clear associations were found between QTc levels and the risk of CVD events. In conclusion, prolonged QTc levels were associated with the development of CVD among general Japanese men. Measurement of QTc intervals is likely to provide additional information for the detection of individuals at high risk of future CVD events.

Relationship of common candidate gene variants to electrocardiographic T-wave peak to T-wave end interval and T-wave morphology parameters

BACKGROUND

Single-nucleotide polymorphisms (SNPs) in genes encoding cardiac ion channels and nitric oxide synthase-1 adaptor protein (NOS1AP) are associated with electrocardiographic (ECG) QT-interval duration, but the association of these SNPs with new, prognostically important ECG measures of ventricular repolarization is unknown.

OBJECTIVE

The purpose of this study was to examine the relationship of SNPs to ECG T-wave peak to T-wave end (TPE) interval and T-wave morphology parameters.

METHODS

We studied 5,890 adults attending the Health 2000 Study, a Finnish epidemiologic survey. TPE interval and four T-wave morphology parameters were measured from digital 12-lead ECGs and related to the seven SNPs showing a phenotypic effect on QT-interval duration in the Health 2000 Study population.

RESULTS

In multivariable analyses, the KCNH2 K897T minor allele was associated with a 1.2-ms TPE-interval shortening (P = .00005) and the KCNH2 intronic rs3807375 minor allele was associated with a 0.8-ms TPE-interval prolongation (P = .001), whereas the KCNE1 D85N variant had no TPE-interval effect (P = .20). NOS1AP minor alleles (rs2880058, rs4657139, rs10918594, rs10494366) were associated with a shorter TPE interval (effects from 0.5 to 0.8 ms, P from .032 to .002), which resulted from their stronger effects on QT(peak) than QT(end) interval. None of the SNPs showed a consistent association with T-wave morphology parameters.

CONCLUSION

KCNH2 K897T and rs3807375 as well as the four studied NOS1AP variants have modest effects on ECG TPE interval but are not related to T-wave morphology measures. The previously observed prognostic value of T-wave morphology parameters likely is not based on these SNPs.

Thorough QT Studies: Questions and Quandaries

The International Conference on Harmonisation E14 Guidance was successful in largely standardizing the conduct of the so-called thorough QT/QTc studies (TQTS). Nevertheless, there is still a spectrum of frequently encountered problems with details of design, conduct and interpretation of TQTS. Several of these challenges are reviewed here, starting with explaining that the TQTS goal is only to identify drugs for which the proarrhythmic risk might be considered excluded for the purposes of regulatory benefit-risk assessment. Suggestions are made on how to categorize and quantify or exclude proarrhythmic risk if the TQTS is positive. There is a conceptual need for TQTS, and this is discussed, together with reasons why restricted clinical registries cannot prove the absence of proarrhythmic liability of any drug. Appropriate drug doses investigated in TQTS should be derived from the maximum clinically tolerable dose rather than from the known or expected therapeutic dose. With the help of concentration-QTc modelling, the standard therapeutic dose can be omitted from TQTS, especially if the study is expected to be negative. Conditions for single-dose TQTS acceptability are reviewed. The role of the so-called positive control is assessed, contrasting the role of a same-class comparator for the investigated drug. A single 400 mg dose of moxifloxacin is advocated as the present 'gold standard' assay sensitivity test. The necessity of careful placebo control is explained and the frequency of ECG assessments is considered. The central tendency and outlier analyses are discussed, together with the correct approaches to baseline adjustment. The review concludes that the design and interpretation of TQTS must not be approached with mechanistic stereotypes, and highlights the importance of relating the QTc changes to drug plasma levels.