TpeakTend interval in long QT syndrome

Cardiac Repolarization in Health and Disease

Abnormal cardiac repolarization is at the basis of life-threatening arrhythmias in various congenital and acquired cardiac diseases. Dysfunction of ion channels involved in repolarization at the cellular level are often the underlying cause of the repolarization abnormality. The expression pattern of the gene encoding the affected ion channel dictates its impact on the shape of the T-wave and duration of the QT interval, thereby setting the stage for both the occurrence of the trigger and the substrate for maintenance of the arrhythmia. Here we discuss how research into the genetic and electrophysiological basis of repolarization has provided us with insights into cardiac repolarization in health and disease and how this in turn may provide the basis for future improved patient-specific management.

Ventricular Repolarization Dispersion is a Potential Risk for the Development of Life-Threatening Arrhythmia in Children with Hypertrophic Cardiomyopathy

The risk stratification and early interventions are necessary in patients with hypertrophic cardiomyopathy (HCM), as life-threatening arrhythmia (LTA) is a leading cause of death. This study aimed to explore whether an interval between the peak of the T wave to the end terminal of the T wave (Tp-e), which represents ventricular repolarization dispersion, could predict the risk for LTA in children with HCM. We analyzed electrocardiography at the first and last visits in children (aged < 15 years) with HCM, and compared Tp-e interval and the ratio of Tp-e interval to QT interval (Tp-e/QT) between children with and without LTA. We studied 25 children with HCM. During the follow-up of 85 (38-146) months, there were 7 children with LTA. The 5-year sudden cardiac death (SCD) risk was 1.4 (1.1-2.5) %, which suggested that our cohort consisted of patients at a lower risk for SCD. Age was significantly older in children with LTA compared to those without it (12.5 vs.1.0 years, P = 0.037), although sex, the presence of family history and symptoms at diagnosis, the maximum left ventricular wall thickness Z-score did not differ between the groups. At the last electrocardiography before LTA, corrected Tp-e interval and Tp-e/QT ratio were significantly greater in patients with LTA compared to those in patients without LTA (corrected Tp-e: 103 vs. 78 ms, P = 0.020; Tp-e/QT: 0.28 vs. 0.22, P = 0.046). Corrected Tp-e and Tp-e/QT ratio cutoff values of 91 ms and 0.28 yielded as the predictors for LTA with sensitivity of 85% and 72%, specificity of 71% and 89%, respectively. Prolonged absolute and corrected Tp-e intervals and an increase in the Tp-e/QT ratio can be useful predictors for LTA in children with HCM. We offer temporal assessments of ventricular repolarization dispersion to stratify the risk for the development of LTA/SCD among children with HCM.

Tp-Te Interval and Tp-Te/QT Ratio Are Valuable Tools in Predicting Poor Outcome in Sepsis Patients

Objective

About 50% of patients with sepsis have different degrees of myocardial inhibition, known as sepsis-induced myocardial dysfunction (SMD), which increases the mortality rate of sepsis. Tp-Te interval and Tp-Te/QT ratio reflect ventricular transmural dispersion repolarization (TDR), and have good predictive value for death in patients with heart disease. This study aimed to investigate the prognostic value of Tp-Te and Tp-Te/QT in patients with sepsis.

Methods

The current study included a total of 625 participants: 201 patients with sepsis, 213 patients with heart failure, and 211 healthy participants. According to the severity and outcome, the patients with sepsis were divided into the sepsis group and the septic shock group, and the death group and the survival group to explore the differences of indicators among subgroups of sepsis. The ROC curve was used to analyze the predictive value of the indicators for deaths of patients with sepsis and calculate the cutoff point. Then, we investigated the incidence of arrhythmia in patients with sepsis with different TDR. The correlation between Tp-Te/QT and the commonly used predictive indicators in ICU was also discussed.

Results

(1) Tp-Te and Tp-Te/QT in patients with sepsis and heart failure (HF) were significantly higher than the control group (p < 0.01). (2) Compared with patients with sepsis, the increase of Tp-Te and Tp-Te/QT is more prominent in patients with HF. Especially, the increase of the Tp-Te/QT was statistically significant (p < 0.001). (3) compared with patients with sepsis (no shock), the Tp-Te, Tp-Te/QT, and SOFA were increased in patients with septic shock (p < 0.05). (4) In the death group, Tp-Te /QT, SOFA, and Apache-II were higher; LVEF was lower than the survival group (p < 0.05). (5) ROC curves showed that Tp-Te/QT, SOFA, and LVEF have predictive values for death (p < 0.05; AUC = 0.808, 0.716, 0.412). The cutoff point of Tp-Te/QT was 0.32. (6) The incidence of arrhythmia is different in patients with sepsis with different TDR. (7) There is a significant correlation between Tp-Te/QT and SOFA (p < 0.001, r = 0.79).

Conclusion

TDR in patients with sepsis is significantly increased, which was between healthy population and patients with HF. Tp-Te and Tp-Te/QT are effective indicators to reflect the severity and poor outcome of patients with sepsis.

Diagnostic Value of the TpTe Interval in Children with Ventricular Arrhythmias

BACKGROUND

The changes in the period of ventricular repolarization, i.e., QT interval, QTp (Q-Tpeak) and TpTe interval (Tpeak-Tend), make it possible to assess the electrical instability of the heart muscle, which may lead to the development of life-threatening ventricular arrhythmia. The aim of the study was to determine and evaluate the use of differences in T-wave morphology and durations of repolarization period parameters (QT, TpTe) in resting ECGs for children with ventricular arrhythmias.

METHODS

The retrospective analysis was made of the disease histories of 80 examined children with resting ECGs, which were admitted to the Children's Cardiology Department. The study group consisted of 46 children aged 4 to 18 with ventricular arrhythmias and the control group consisted of 34 healthy children between 4 and 18 years of age, with no arrhythmias.

RESULTS

The duration of the TpTe interval was significantly (p < 0.001) longer in the group of children with ventricular arrhythmia with abnormal T-wave (bactrian/bifid, humid/biphasic) compared to the TpTe interval in children with ventricular arrhythmia with the normal repolarization period. The duration of the TpTe (p < 0.001), QTcB (p < 0.001) and QTcF (p < 0.001) intervals were significantly longer in the group of children with ventricular arrhythmias and with abnormal T-wave compared to the values of the TpTe, QTcB, and QTcF intervals of the control group with normal morphology of the repolarization period. Only the duration of the TpTe interval was significantly (p = 0.020) longer in the group of children with ventricular arrhythmia without clinical symptoms.

CONCLUSIONS

Children with benign ventricular arrhythmias recorded on a standard ECG with prolonged TpTe and QT intervals and abnormal T-wave morphology require systematic and frequent cardiac check up with long term ECG recordings due to the possibility of future more severe ventricular arrhythmias. Further follow-up studies in even larger groups of patients are necessary to confirm the values of these repolarization parameters in clinical practice.

Evaluation of electrocardiographic repolarization parameters after administration of trimethoprim-sulfadiazine, detomidine, or their combination in horses

OBJECTIVE

To determine whether administration of trimethoprim-sulfadiazine (TMS), detomidine (DET), or TMS plus DET would be associated with changes in ECG repolarization parameters in horses.

ANIMALS

9 healthy adult horses.

PROCEDURES

Each horse received 4 treatments in a blinded, randomized, crossover study design as follows: TMS, 16 to 24 mg/kg, IV; DET, 0.015 to 0.02 mg/kg, IV; TMS plus DET; and saline (0.9% NaCl) solution. Surface ECG traces were obtained over 24 hours, and repolarization parameters were measured at predefined time points after each treatment and compared with a 2-way ANOVA for repeated measures.

RESULTS

Heart rate-corrected QT intervals (QTc) were significantly increased after administration of DET (mean ± SD difference in QTc, 36.57 ± 23.07 milliseconds; increase of 7%) and TMS plus DET (44.96 ± 29.16 milliseconds; increase of 9%), compared with baseline (before treatment) values and values after administration of saline solution. Saline solution and TMS alone did not affect QTc.

CONCLUSIONS AND CLINICAL RELEVANCE

Administration of DET or TMS plus DET was associated with a significant and possibly clinically relevant prolongation of QTc, with prolongation of 7% to 9%, a range that is considered as a risk factor for the development of cardiac arrhythmias in people. Results were unexpected because DET is considered to be a safe sedative for horses.

Tp-e and (Tp-e)/QT ratio as a non-invasive risk factors for malignant ventricular arrhythmia in patients with idiopathic ventricular premature complexes

Background

To evaluate the role of Tp‐e and (Tp‐e)/QT ratio in differentiating benign ventricular premature complex (VPC) and malignant polymorphic ventricular tachycardia (PVT).

Methods

From January 2017 to December 2017, patients with documented polymorphic ventricular tachycardia (PVT) or ventricular fibrillation (VF) were consecutive included and classified as PVT/VF group. Sixty age‐ and sex‐matched healthy individuals were recruited as comparative control and subdivided into non‐VPC and VPC group. Clinical characteristics and Tp‐e and Tp‐e/QT ratio between the three groups were compared.

Results

Tp‐e and (Tp‐e)/QT ratio were significantly higher in patients of PVT/VF group compared with the other two groups (P < .001). Episodes of syncope were more frequent in patients with PVT/VF (P < .05). The sensitivity and specificity of a Tp‐e interval ≥86 ms for malignant arrhythmias triggered by VPCs were 88% and 66%, respectively, while the sensitivity and specificity of the Tp‐e/QT ratio ≥0.24 were 82% and 70%, respectively. Five patients complained recurrence of syncope in the PVT/VF group and 1 patient died with mean follow‐up of 18 months.

Conclusion

Tp‐e interval and the Tp‐Te/QT ratio is significantly increased in patients with PVT/VF and may be used as a novel non‐invasive marker of differentiating malignant and benign VPC.

Noninvasive assessment of left-ventricular diastolic electromechanical coupling in hypertensive heart disease

BACKGROUND

There is a need to stratify patients who may develop heart failure because of the current "heart failure pandemic". We hypothesized that noninvasive assessment of diastolic electromechanical coupling by electrocardiography and Doppler echocardiography may be clinically useful for risk stratification of hypertensive patients who may develop heart failure.

METHODS

We measured the time from the peak to end of the T wave (TpTe) as an electrophysiological parameter, and peak early diastolic mitral flow (E) and lateral annular (e') velocities as mechanical parameters in 109 patients with hypertension. Relationships between these parameters and their association with the prognosis were evaluated.

RESULTS

The e' was inversely correlated with TpTe (p < 0.001) and QTc (p < 0.014), whereas E/e' was positively correlated with TpTe (p < 0.001) and QTc (p < 0.001). The TpTe predicted patients with E/e' > 12. There were 24 cardiovascular events during follow-up (57 ± 20 months), and Kaplan-Meier analysis showed that outcome was worse (p = 0.003) in patients with higher E/e' than lower E/e'; however, there was no difference between patients with longer TpTe (≧72 ms) and shorter TpTe (< 72 ms).

CONCLUSION

The correlation of TpTe with e' and E/e' in hypertensive patients suggests that these parameters reflect diastolic ventricular electromechanical coupling. The E/e' predicted outcome, and an elevated E/e' should be suspected when TpTe is prolonged (> 72 ms). Noninvasive evaluation of diastolic electromechanical coupling is clinically useful in patients with hypertension for predicting their outcome.

Tpeak-Tend/QT interval predicts ST-segment resolution and major adverse cardiac events in acute ST-segment elevation myocardial infarction patients undergoing percutaneous coronary intervention

Elevated ST-segment and increased Tpeak-Tend interval (Tp-e) were prognostic predictors in major adverse cardiac events (MACEs) in ST-segment elevation myocardial infarction (STEMI). The electrophysiologic relationship between them during percutaneous coronary intervention (PCI) needs to elucidate.Patients with STEMI admitted to hospital were prospectively evaluated. ST-segment resolution (STR) (defined as ≥50% reduction as the complete-STR [CSTR] group, <50% as incomplete-STR [ISTR] group), Tp-e interval, and ratio of Tp-e to QT interval (Tp-e/QT) were measured, calculated and analyzed with MACEs.Tp-ec interval (corrected Tp-e interval, P < .001) and Tp-e/QT ratio (P < .001) were significantly increased by myocardial infarction and partly recovered post-PCI. Patients with ISTR showed more increased Tp-ec interval (P < .001) and Tp-e/QT ratio (P < .001) than those in CSTR groups post-PCI. In multivariate analysis and receiver operating characteristic curves analysis, Tp-e/QT was an independent and strongest predictor for STR. STR and electrocardiogram parameters with a cutoff value for predicting STR showed prognostic value for MACE in STEMI in Kaplan-Meier survival analysis.Both STR and change of Tp-e parameters were not only predictors of arrhythmia, but also prognostic factors of MACE in patients with STEMI after PCI.

Tpeak-Tend dispersion as a predictor for malignant arrhythmia events in patients with vasospastic angina

BACKGROUND

Tpeak-Tend interval (Tp-e interval) in electrocardiogram (ECG) has been reported to predict malignant arrhythmia events (MAE) in ST-segment elevation myocardial infarction and ion channelopathy. Tp-e interval and other ECG parameters as predictors for MAE was evaluated in patients with vasospastic angina (VA).

METHODS AND RESULTS

Sixty-two patients with VA (Non-MAE group) and 20 patients with VA complicated by MAE (MAE group) were enrolled in our Division of Cardiology between January 2010 and December 2015. Continuous variables were analyzed by t-test and categorical variables by Chi-square analysis. Patients with MAE showed greater QTc (corrected QT interval) dispersion (P=0.005), Tp-ec (corrected Tp-e) interval (P=0.001), Tp-ec dispersion (P<0.001) and Tp-e/QT ratio (P<0.001) than those in non-MAE groups when ST-segment elevated. After elevated ST-segment returned, there were no significant differences in these ECG parameters between two groups (All P>0.05). At univariate binary logistic regression analysis QTc dispersion (odds ratio(OR)=1.133; P=0.013), Tp-ec (OR=1.058; P=0.003), Tp-e/QT (OR=1.403; P=0.001), and Tp-ec dispersion (OR=1.497; P=0.004) were significantly associated with MAE. At multivariable logistic regression analysis, Tp-ec dispersion remained a predictor of MAE. Receiver operating characteristic (ROC) curve analysis showed that only AUC (Area under curve) of Tp-ec dispersion had significant difference with those in QTc dispersion (P<0.001), Tp-ec (P=0.003), and Tp-e/QT ratio (P=0.012), respectively.

CONCLUSIONS

QTc dispersion, Tp-ec, Tp-e/QT and Tp-ec dispersion were significantly increased in VA patients with MAE than those without MAE when coronary spasm was onset. Prolonged Tp-ec dispersion was the best discriminators and a strong independent predictor of MAE in VA patients.

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

BACKGROUND AND OBJECTIVES

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

METHOD

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

RESULTS

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

CONCLUSION

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

Age- and sex-based reference ranges for non-invasive ventricular repolarisation parameters

BACKGROUND

Some electrocardiographic parameters are able to assess indirectly ventricular repolarisation homogeneity. It is consequently essential to discriminate between normal and abnormal values in clinical decision-making. Considering there is still not a consensus about normal cut-off values, the aim of this study was to document reference intervals in all age groups of a healthy population, providing for age- and sex-percentile tables, which can be used easily and quickly in clinical practice.

METHODS

We evaluated repolarisation markers in 606 sex-matched participants aged 1 day-94 years. Each subject underwent a 12-lead electrocardiogram at rest, and the following parameters were measured: QT, corrected QT, QTpeak, Tpeak-Tend, Tpeak-Tend dispersion, Tpeak-Tend/QT and QTpeak/QT ratio.

RESULTS

A relationship was demonstrated between age and QTpeak, Tpeak-Tend, QT and QTc. In children, QTpeak, Tpeak-Tend and QT intervals increased linearly with age. In adolescents, all the three parameters remained stable. In adults, QTpeak and QT showed a further significant increase. On the contrary, Tpeak-Tend interval was longer in adults aged between 20 and 64 years than in participants aged 65 years or over, but the difference was not statistically significant. Male vs female participants showed longer Tpeak-Tend intervals; this sex difference was not statistically significant at birth and during childhood, whereas it was in adolescents and in adults.

CONCLUSIONS

Repolarisation parameters showed age- and sex-based variations, which are important to know to differentiate normal from pathological values.

Glucose ingestion causes cardiac repolarization disturbances in type 1 long QT syndrome patients and healthy subjects

BACKGROUND

Both hypoglycemia and severe hyperglycemia constitute known risk factors for cardiac repolarization changes potentially leading to malignant arrhythmias. Patients with loss of function mutations in KCNQ1 are characterized by long QT syndrome (LQTS) and may be at increased risk for glucose-induced repolarization disturbances.

OBJECTIVE

The purpose of this study was to test the hypothesis that KCNQ1 LQTS patients are at particular risk for cardiac repolarization changes during the relative hyperglycemia that occurs after an oral glucose load.

METHODS

Fourteen KCNQ1 LQTS patients and 28 control participants matched for gender, body mass index, and age underwent a 3-hour oral 75-g glucose tolerance test with ECGs obtained at 7 time points. Fridericia corrected QT interval (QTcF), Bazett corrected QT interval (QTcB), and the Morphology Combination Score (MCS) were calculated.

RESULTS

QTc and MCS increased in both groups. MCS remained elevated until 150 minutes after glucose ingestion, and the maximal change from baseline was larger among KCNQ1 LQTS patients compared with control subjects (0.28 ± 0.27 vs 0.15 ± 0.13; P <.05).

CONCLUSION

Relative hyperglycemia induced by ingestion of 75-g glucose caused cardiac repolarization disturbances that were more severe in KCNQ1 LQTS patients compared with control subjects.

T-wave morphology can distinguish healthy controls from LQTS patients

Long QT syndrome (LQTS) is an inherited disorder associated with prolongation of the QT/QTc interval on the surface electrocardiogram (ECG) and a markedly increased risk of sudden cardiac death due to cardiac arrhythmias. Up to 25% of genotype-positive LQTS patients have QT/QTc intervals in the normal range. These patients are, however, still at increased risk of life-threatening events compared to their genotype-negative siblings. Previous studies have shown that analysis of T-wave morphology may enhance discrimination between control and LQTS patients. In this study we tested the hypothesis that automated analysis of T-wave morphology from Holter ECG recordings could distinguish between control and LQTS patients with QTc values in the range 400-450 ms. Holter ECGs were obtained from the Telemetric and Holter ECG Warehouse (THEW) database. Frequency binned averaged ECG waveforms were obtained and extracted T-waves were fitted with a combination of 3 sigmoid functions (upslope, downslope and switch) or two 9th order polynomial functions (upslope and downslope). Neural network classifiers, based on parameters obtained from the sigmoid or polynomial fits to the 1 Hz and 1.3 Hz ECG waveforms, were able to achieve up to 92% discrimination between control and LQTS patients and 88% discrimination between LQTS1 and LQTS2 patients. When we analysed a subgroup of subjects with normal QT intervals (400-450 ms, 67 controls and 61 LQTS), T-wave morphology based parameters enabled 90% discrimination between control and LQTS patients, compared to only 71% when the groups were classified based on QTc alone. In summary, our Holter ECG analysis algorithms demonstrate the feasibility of using automated analysis of T-wave morphology to distinguish LQTS patients, even those with normal QTc, from healthy controls.

Transgenic rabbit models to investigate the cardiac ion channel disease long QT syndrome

Long QT syndrome (LQTS) is a rare inherited channelopathy caused mainly by different mutations in genes encoding for cardiac K(+) or Na(+) channels, but can also be caused by commonly used ion-channel-blocking and QT-prolonging drugs, thus affecting a much larger population. To develop novel diagnostic and therapeutic strategies to improve the clinical management of these patients, a thorough understanding of the pathophysiological mechanisms of arrhythmogenesis and potential pharmacological targets is needed. Drug-induced and genetic animal models of various species have been generated and have been instrumental for identifying pro-arrhythmic triggers and important characteristics of the arrhythmogenic substrate in LQTS. However, due to species differences in features of cardiac electrical function, these different models do not entirely recapitulate all aspects of the human disease. In this review, we summarize advantages and shortcomings of different drug-induced and genetically mediated LQTS animal models - focusing on mouse and rabbit models since these represent the most commonly used small animal models for LQTS that can be subjected to genetic manipulation. In particular, we highlight the different aspects of arrhythmogenic mechanisms, pro-arrhythmic triggering factors, anti-arrhythmic agents, and electro-mechanical dysfunction investigated in transgenic LQTS rabbit models and their translational application for the clinical management of LQTS patients in detail. Transgenic LQTS rabbits have been instrumental to increase our understanding of the role of spatial and temporal dispersion of repolarization to provide an arrhythmogenic substrate, genotype-differences in the mechanisms for early afterdepolarization formation and arrhythmia maintenance, mechanisms of hormonal modification of arrhythmogenesis and regional heterogeneities in electro-mechanical dysfunction in LQTS.

Electro-mechanical dysfunction in long QT syndrome: Role for arrhythmogenic risk prediction and modulation by sex and sex hormones

Long QT syndrome (LQTS) is a congenital arrhythmogenic channelopathy characterized by impaired cardiac repolarization. Increasing evidence supports the notion that LQTS is not purely an "electrical" disease but rather an "electro-mechanical" disease with regionally heterogeneously impaired electrical and mechanical cardiac function. In the first part, this article reviews current knowledge on electro-mechanical (dys)function in LQTS, clinical consequences of the observed electro-mechanical dysfunction, and potential underlying mechanisms. Since several novel imaging techniques - Strain Echocardiography (SE) and Magnetic Resonance Tissue Phase Mapping (TPM) - are applied in clinical and experimental settings to assess the (regional) mechanical function, advantages of these non-invasive techniques and their feasibility in the clinical routine are particularly highlighted. The second part provides novel insights into sex differences and sex hormone effects on electro-mechanical cardiac function in a transgenic LQT2 rabbit model. Here we demonstrate that female LQT2 rabbits exhibit a prolonged time to diastolic peak - as marker for contraction duration and early relaxation - compared to males. Chronic estradiol-treatment enhances these differences in time to diastolic peak even more and additionally increases the risk for ventricular arrhythmia. Importantly, time to diastolic peak is particularly prolonged in rabbits exhibiting ventricular arrhythmia - regardless of hormone treatment - contrasting with a lack of differences in QT duration between symptomatic and asymptomatic LQT2 rabbits. This indicates the potential added value of the assessment of mechanical dysfunction in future risk stratification of LQTS patients.

Effects of droperidol and ondansetron on dispersion of ventricular repolarization: A randomized double-blind clinical study in anesthetized adult patients

BACKGROUND AND OBJECTIVE

Droperidol and ondansetron prolong QT interval, a circumstance that has raised some concerns regarding the possibility of inducing torsades de pointes (TdP). However drug-induced spatial dispersion of ventricular repolarization has been shown to be the principal arrhythmogenic substrate for TdP. The aim of this study is to explore the effects of droperidol and ondansetron on the dispersion of repolarization, measured using the T peak-to-end interval (Tp-e) and Tp-e/QT and Tp-e/RR(1/2) ratios in surgical anesthetized patients.

METHODS

A randomized, double-blind study carried out on sixty-three adult patients without cardiac disease or factors favoring QT prolongation and undergoing non-cardiac surgery were randomly assigned to the droperidol or ondansetron group. Under propofol anesthesia, a 12-lead EKG was obtained, and 1.25mg droperidol or 4mg ondansetron was injected. Five minutes later, a new 12-lead EKG was recorded. EKG analyses were independently performed by two cardiologists blinded to the state of the traces or group allocation. QT, RR and Tp-e intervals were measured by averaging five successive beats in leadII (QT) or V5 (Tp-e). The mean value for each measurement was calculated for statistical analysis.

RESULTS

Thirty-two patients (19 women) received droperidol, and 31 (22 women) ondansetron. Droperidol and ondansetron prolonged the QTcF interval (Fridericia formula) by 6.8 and 7.2ms (mean values) respectively, but neither droperidol nor ondansetron increased the Tp-e interval or Tp-e/QT and Tp-e/RR(1/2) ratios.

CONCLUSION

At antiemetic doses, neither ondansetron (4mg) nor droperidol (1.25mg) increases the dispersion of ventricular repolarization in healthy adult patients anesthetized with propofol.

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.

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

BACKGROUND

Recently a new risk marker for drug-induced arrhythmias called index of cardio-electrophysiological balance (iCEB), measured as QT interval divided by QRS duration, was evaluated in an animal model. It was hypothesized that iCEB is equivalent to the cardiac wavelength λ (λ = effective refractory period (ERP) x conduction velocity) and that an increased or decreased value of iCEB would potentially predict an increased susceptibility to TdP or non-TdP mediated VT/VF, respectively.

METHODS

First, the correlation between QT interval and ERP was evaluated by invasively measuring ERP during a ventricular stimulation protocol in humans (N = 40). Then the effect of administration of sotalol and flecainide on iCEB was measured in 40 patients with supraventricular tachycardias. Finally iCEB was assessed in carriers of a long QT syndrome (LQTS, N = 70) or Brugada syndrome (BrS, N = 57) mutation and compared them with genotype negative family members (N = 65).

RESULTS

The correlation between QT interval and ERP was established (Pearson R(2) = 0.25) which suggests that iCEB≈ERPxCV≈QT/QRS. Sotalol administration increased iCEB (+ 0.23; P = 0.01), while it decreased with the administration of flecainide (-0.21, P = 0.03). In the LQTS group iCEB was increased (5.22 ± 0.93, P < 0.0001) compared to genotype negative family members (4.24 ± 0.5), while it was decreased in the BrS group (3.52 ± 0.43, P < 0.0001).

CONCLUSIONS

Our data suggest that iCEB (QT/QRS) is a simple but effective ECG surrogate of cardiac wavelength. iCEB is increased in situations that predispose to TdP and is decreased in situations that predispose to non-TdP mediated VT/VF. Therefore, iCEB might serve as a noninvasive and readily measurable marker to detect increased arrhythmic risk.

Electrocardiographic Predictors of Cardiovascular Mortality

Cardiovascular diseases are the main causes of mortality. Sudden cardiac death may also appear in athletes, due to underlying congenital or inherited cardiac abnormalities. The electrocardiogram is used in clinical practice and clinical trials, as a valid, reliable, accessible, inexpensive method. The aim of the present paper was to review electrocardiographic (ECG) signs associated with cardiovascular mortality and the mechanisms underlying those associations, providing a brief description of the main studies in this area, and consider their implication for clinical practice in the general population and athletes. The main ECG parameters associated with cardiovascular mortality in the present paper are the P wave (duration, interatrial block, and deep terminal negativity of the P wave in V1), prolonged QT and Tpeak-Tend intervals, QRS duration and fragmentation, bundle branch block, ST segment depression and elevation, T waves (inverted, T wave axes), spatial angles between QRS and T vectors, premature ventricular contractions, and ECG hypertrophy criteria.

QT dynamics during treatment with sertindole

OBJECTIVES

Sertindole is a nonsedating atypical antipsychotic drug with low propensity to cause extrapyramidal side effects but it has been associated with a 20 ms QTc prolongation and increased risk of cardiac events. It is uncertain whether this drug-induced increase in cardiac risk might also be revealed by dynamic measures of the QT interval such as the ratio of QT variability to heart rate variability (variability ratio [VR]). The aim of this study was to investigate the effect of sertindole on QT dynamics.

METHODS

QTc and the VR were assessed in an observational study using 24-hour Holter monitoring at baseline and after 3 weeks of treatment with sertindole 16 mg. The VR was calculated by dividing the standard deviation of QT intervals with the standard deviation of heart rates. Outcome measures were compared using paired t-test.

RESULTS

A total of 18 patients participated in the study, two were excluded from further analysis due to low amplitude of the T-wave. When patients were shifted to sertindole, the VR increased from 0.192 (SD 0.045) to 0.223 (SD 0.061), p = 0.02. The QTcF interval increased from 388 (SD 16) to 403 ms (SD 14), p = 0.002. There was no difference in heart rate 78 bpm (SD 8) versus 80 bpm (SD 10), p = 0.3 or heart rate variability (SDNN) 127 (SD 40) versus 115 ms (SD 45), p = 0.4.

CONCLUSION

Sertindole was associated with 19 ms QTc prolongation and an increased ratio of QT variability to heart rate variability. Both measures may contribute to the increased cardiovascular mortality found with sertindole.

KCNQ1 long QT syndrome patients have hyperinsulinemia and symptomatic hypoglycemia

Patients with loss-of-function mutations in KCNQ1 have KCNQ1 long QT syndrome (LQTS). KCNQ1 encodes a voltage-gated K(+) channel located in both cardiomyocytes and pancreatic β-cells. Inhibition of KCNQ1 in β-cells increases insulin secretion. Therefore KCNQ1 LQTS patients may exhibit increased insulin secretion. Fourteen patients, from six families, diagnosed with KCNQ1 LQTS were individually matched to two randomly chosen BMI-, age-, and sex-matched control participants and underwent an oral glucose tolerance test (OGTT), a hypoglycemia questionnaire, and continuous glucose monitoring. KCNQ1 mutation carriers showed increased insulin release (area under the curve 45.6 ± 6.3 vs. 26.0 ± 2.8 min ⋅ nmol/L insulin) and β-cell glucose sensitivity and had lower levels of plasma glucose and serum potassium upon oral glucose stimulation and increased hypoglycemic symptoms. Prolonged OGTT in four available patients and matched control subjects revealed hypoglycemia in carriers after 210 min (range 1.4-3.6 vs. 4.1-5.3 mmol/L glucose), and 24-h glucose profiles showed that the patients spent 77 ± 18 min per 24 h in hypoglycemic states (<3.9 mmol/L glucose) with 36 ± 10 min (<2.8 mmol/L glucose) vs. 0 min (<3.9 mmol/L glucose) for the control participants. The phenotype of patients with KCNQ1 LQTS, caused by mutations in KCNQ1, includes, besides long QT, hyperinsulinemia, clinically relevant symptomatic reactive hypoglycemia, and low potassium after an oral glucose challenge, suggesting that KCNQ1 mutations may explain some cases of "essential" reactive hypoglycemia.

Mutations in Danish patients with long QT syndrome and the identification of a large founder family with p.F29L in KCNH2

Background

Long QT syndrome (LQTS) is a cardiac ion channelopathy which presents clinically with palpitations, syncope or sudden death. More than 700 LQTS-causing mutations have been identified in 13 genes, all of which encode proteins involved in the execution of the cardiac action potential. The most frequently affected genes, covering > 90% of cases, are KCNQ1, KCNH2 and SCN5A.

Methods

We describe 64 different mutations in 70 unrelated Danish families using a routine five-gene screen, comprising KCNQ1, KCNH2 and SCN5A as well as KCNE1 and KCNE2.

Results

Twenty-two mutations were found in KCNQ1, 28 in KCNH2, 9 in SCN5A, 3 in KCNE1 and 2 in KCNE2. Twenty-six of these have only been described in the Danish population and 18 are novel. One double heterozygote (1.4% of families) was found. A founder mutation, p.F29L in KCNH2, was identified in 5 “unrelated” families. Disease association, in 31.2% of cases, was based on the type of mutation identified (nonsense, insertion/deletion, frameshift or splice-site). Functional data was available for 22.7% of the missense mutations. None of the mutations were found in 364 Danish alleles and only three, all functionally characterised, were recorded in the Exome Variation Server, albeit at a frequency of < 1:1000.

Conclusion

The genetic etiology of LQTS in Denmark is similar to that found in other populations. A large founder family with p.F29L in KCNH2 was identified. In 48.4% of the mutations disease causation was based on mutation type or functional analysis.

Short-term repeatability of electrocardiographic Tpeak-Tend and QT intervals

BACKGROUND

The electrocardiographic (ECG) Tpeak-Tend interval (TpTe) is associated with arrhythmias and sudden cardiac death. TpTe offers a supplementary measure for the QT interval (QT), yet its repeatability has not been established.

PURPOSE

Evaluate short-term repeatability of TpTe and QT.

METHODS

Four ECGs were obtained on sixty participants. The sources of variation, intra-class correlation coefficient (ICC) - an index of reproducibility - and minimal detectable change (MDC) were estimated for TpTe and QT. The impact of repeated measurements on repeatability was estimated for a hypothetical clinical trial designed to detect drug-induced prolongation of TpTe and QT.

RESULTS

We used heart rate-adjusted QT [(QT)a] but TpTe in the study group was rate-invariant. The ICC [95% confidence interval (CI)] was 0.77 (0.69, 0.85) for TpTe, 0.75 (0.65, 0.85) for QT and 0.60 (0.47, 0.73) for (QT)a. The MDC (ms) was 21, 32 and 26 for TpTe, QT and (QT)a respectively.

CONCLUSION

TpTe has excellent repeatability supporting its use as a supplement to QT in observational and clinical studies.

The detection of T-wave variation linked to arrhythmic risk: an industry perspective

Although the scientific literature contains ample descriptions of peculiar patterns of repolarization linked to arrhythmic risk, the objective quantification and classification of these patterns continues to be a challenge that impacts their widespread adoption in clinical practice. To advance the science, computerized algorithms spawned in the academic environment have been essential in order to find, extract and measure these patterns. However, outside the strict control of a core lab, these algorithms are exposed to poor quality signals and need to be effective in the presence of different forms of noise that can either obscure or mimic the T-wave variation (TWV) of interest. To provide a practical solution that can be verified and validated for the market, important tradeoffs need to be made that are based on an intimate understanding of the end-user as well as the key characteristics of either the signal or the noise that can be used by the signal processing engineer to best differentiate them. To illustrate this, two contemporary medical devices used for quantifying T-wave variation are presented, including the modified moving average (MMA) for the detection of T-wave Alternans (TWA) and the quantification of T-wave shape as inputs to the Morphology Combination Score (MCS) for the trending of drug-induced repolarization abnormalities.

The phenotype characteristics of type 13 long QT syndrome with mutation in KCNJ5 (Kir3.4-G387R)

BACKGROUND

Long QT syndrome type 13 (LQT13) is caused by loss-of-function mutation in the KCNJ5-encoded cardiac G-protein-coupled inward rectifier potassium channel subtype 4 protein. The electrocardiographic (ECG) features of LQT13 are not described yet.

OBJECTIVE

To describe for the first time in detail the phenotype-genotype relationship of the ECG and clinical features in patients with LQT13.

METHODS

The 12-lead ECGs, 24-hour Holter recordings, and clinical information from KCNJ5-G387R mutation carriers of a fourth-generation Han Chinese family with LQT13 and a group of healthy Chinese individuals were analyzed.

RESULTS

Compared with the analysis of the healthy group (n = 8), age- and sex-matched pair analysis revealed that the mutation carriers (n = 8) had ventricular repolarization abnormality results in the prolongation of corrected QT and QTpeak intervals (P < .01); greater combined measure of repolarization morphology (T-wave morphology combination score) based on asymmetry, flatness, and notch (P < .01); and reduced low frequency/high frequency ratio of heart rate variability (P < .01) as a reflection of cardiac autonomic imbalance. Mean heart rate, time domain parameters of heart rate variability, time interval from T-wave peak to T-wave end, and T-wave amplitude were similar.

CONCLUSIONS

This study demonstrates for the first time the ECG features of patients with LQT13. Our data suggest that QTpeak intervals and T-wave morphology combination score may be the better parameters than the corrected QT interval to predict the phenotype-genotype relationship in patients with LQT13.

Normal standards for computer-ECG programs for prognostically and diagnostically important ECG variables derived from a large ethnically diverse female cohort: the Women's Health Initiative (WHI)

BACKGROUND

Substantial new information has emerged recently about the prognostic value for a variety of new ECG variables. The objective of the present study was to establish reference standards for these novel risk predictors in a large, ethnically diverse cohort of healthy women from the Women's Health Initiative (WHI) study.

METHODS AND RESULTS

The study population consisted of 36,299 healthy women. Racial differences in rate-adjusted QT end (QT(ea)) and QT peak (QT(pa)) intervals as linear functions of RR were small, leading to the conclusion that 450 and 390 ms are applicable as thresholds for prolonged and shortened QT(ea) and similarly, 365 and 295 ms for prolonged and shortened QT(pa), respectively. As a threshold for increased dispersion of global repolarization (T(peak)T(end) interval), 110 ms was established for white and Hispanic women and 120 ms for African-American and Asian women. ST elevation and depression values for the monitoring leads of each person with limb electrodes at Mason-Likar positions and chest leads at level of V1 and V2 were first computed from standard leads using lead transformation coefficients derived from 892 body surface maps, and subsequently normal standards were determined for the monitoring leads, including vessel-specific bipolar left anterior descending, left circumflex artery and right coronary artery leads. The results support the choice 150 μV as a tentative threshold for abnormal ST-onset elevation for all monitoring leads. Body mass index (BMI) had a profound effect on Cornell voltage and Sokolow-Lyon voltage in all racial groups and their utility for left ventricular hypertrophy classification remains open.

CONCLUSIONS

Common thresholds for all racial groups are applicable for QT(ea), and QT(pa) intervals and ST elevation. Race-specific normal standards are required for many other ECG parameters.

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.

Heritability of Tpeak-Tend interval and T-wave amplitude: a twin study

BACKGROUND

Tpeak-Tend interval (TpTe) and T-wave amplitude (Tamp) carry diagnostic and prognostic information regarding cardiac morbidity and mortality. Heart rate and QT interval are known to be heritable traits. The heritability of T-wave morphology parameters such as TpTe and Tamp is unknown. TpTe and Tamp were evaluated in a large sample of twins.

METHODS AND RESULTS

Twins from the GEMINAKAR study (611 pairs, 246 monozygotic, 365 dizygotic; mean age, 38±11 years; 49% men) who had an ECG performed during 1997 to 2000 were included. Tamp was measured in leads V1 and V5. Duration variables (RR interval, QTpeak and QTend interval) were measured and averaged over 3 consecutive beats in lead V5. TpTe was calculated as the QTend- and QTpeak-interval difference. Heritability was assessed using structural equation models adjusting for age, sex, and body mass index. All models were reducible to a model of additive genetics and unique environment. All variables had considerable genetic components. Adjusted heritability estimates were as follows: TpTe, 46%; Tamp lead V1, 34%; Tamp lead V5, 47%; RR interval, 55%; QT interval, 67%; and Bazett-corrected QT interval, 42%.

CONCLUSIONS

RR interval, QT interval, Tamp, and TpTe interval are heritable ECG parameters.

The relation between QT interval and T-wave variables in hypertensive patients

BACKGROUND

The standard 12-lead ECG (electrocardiogram) continues to be the most frequently recorded noninvasive test in medicine. A prolonged ECG QT interval and Tpeak-Tend (Tpe) interval are predictors of ventricular arrhythmia and sudden cardiac death.

AIM

The aim of this study is to analyze the relation between QT interval and T-wave variables in hypertensive patients, with and without left ventricular hypertrophy (LVH).

MATERIALS AND METHODS

Fifty-nine consecutive patients with grade 2 essential hypertension were included in the study. They underwent standard 12-lead ECG, and QT intervals: QTmax (the maximal duration of the QT interval in the 12 ECG leads), QTc (heart rate corrected QTmax), QTm (mean QT interval), QTII (the QT interval in lead DII), QTcII (heart rate corrected QTII), and QTd (QT dispersion); and T-wave variables: T0e (T wave duration), T0em (mean T0e), Tpe, Tpem (mean Tpem), Ta (T wave amplitude), and Tam (mean Ta) were manually assessed. LVH was diagnosed using both echocardiography and the ECG criteria.

RESULTS

QTc was prolonged in 41 patients (69%). Multiple regression analysis revealed a significant association between QT intervals and T-wave variables: QTmax and Tpe (P = 0.015), QTd and Tpe (P = 0.022) and Ta (P = 0.004), and Tpe with QTd and T0e (P < 0.05). A moderate but significant correlation was found between Tpe and QTmax, Tpe and QTII, and Ta and QTd. A prolonged QTc was more prevalent in hypertensive patients with LVH (85%), compared to hypertensive patients without LVH (50%). QTm, QTd, QTII, Tpe, Tpem were significantly elevated (P < 0.05) in patients with LVH.

CONCLUSIONS

Hypertension is associated with an increased prevalence of prolonged QT intervals. QT intervals and T-wave variables are closely connected in hypertensive patients. QTm, T0em, Tpem, and Tam, do not provide significant additional information compared to QTmax, T0e, Tpe, and Ta. Left ventricular hypertrophy is associated with prolonged QT interval and Tpeak-Tend interval in hypertensive patients.

Assessing QT interval prolongation and its associated risks with antipsychotics

Several antipsychotics are associated with the ventricular tachycardia torsade de pointes (TdP), which may lead to sudden cardiac death (SCD), because of their inhibition of the cardiac delayed potassium rectifier channel. This inhibition extends the repolarization process of the ventricles of the heart, illustrated as a prolongation of the QT interval on a surface ECG. SCD in individuals receiving antipsychotics has an incidence of approximately 15 cases per 10,000 years of drug exposure but the exact association with TdP remains unknown because the diagnosis of TdP is uncertain. Most patients manifesting antipsychotic-associated TdP and subsequently SCD have well established risk factors for SCD, i.e. older age, female gender, hypokalaemia and cardiovascular disease. QT interval prolongation is the most widely used surrogate marker for assessing the risk of TdP but it is considered somewhat imprecise, partly because QT interval changes are subject to measurement error. In particular, drug-induced T-wave changes (e.g. flattening of the T-wave) may complicate the measurement of the QT interval. Furthermore, the QT interval depends on the heart rate and a corrected QT (QTc) interval is often used to compensate for this. Several correction formulas have been suggested, with Bazett's formula the most widely used. However, Bazett's formula overcorrects at a heart rate above 80 beats per minute and, therefore, Fridericia's formula is considered more appropriate to use in these cases. Several other surrogate markers for TdP have been developed but none of them is clinically implemented yet and QT interval prolongation is still considered the most valid surrogate marker. Although automated QT interval determination may offer some assistance, QT interval determination is best performed by a cardiologist skilled in its measurement. A QT interval >500 ms markedly increases the risk for TdP and SCD, and should lead to discontinuation of the offending drug and, if present, correction of underlying electrolyte disturbances, particularly serum potassium and magnesium derangements. Before prescribing antipsychotics that may increase the QTc interval, the clinician should ask about family and personal history of SCD, presyncope, syncope and cardiac arrhythmias, and recommend cardiology consultation if history is positive.

Alterations in QT interval in patients undergoing living donor liver transplantation

BACKGROUND

QT interval prolongation, predisposing to ventricular tachyarrhythmia, has frequently been observed in patients with liver cirrhosis. During liver transplantation (LT) surgery, electrolyte imbalance and hemodynamic instability may affect QT interval changes. We evaluated the alterations in QT parameters at each stage of LT surgery.

METHODS

We assessed 50 living donor LT recipients without overt heart disease for the corrected QT (QTc) and the interval from peak to the end of the T wave (T(p-e)) automatically using Bazett's formula with LabChart software. QT parameters, laboratory and hemodynamic data were simultaneously collected in the following stages of LT: before anesthetic induction (baseline), pre-anhepatic, anhepatic, 1 hour postreperfusion, and after hepatic artery anastomosis. Recipients were allocated into 2 groups according to their baseline QTc: ≥440 versus <440 msec.

RESULTS

QTc progressively rose from the pre-anhepatic stage remaining prolonged in each stage of LT surgery compared with the baseline. In the anhepatic stage, 54% of recipients showed marked prolongation of QTc ≥500 msec (522 ± 14), which indicated the potential for a fatal ventricular dysrhythmia: 77% and 36% in groups with QTc ≥440 and <440 msec, respectively. As opposed to changes in QTc, T(p-e) in the anhepatic stage decreased significantly; however, it returned to the baseline level in the neohepatic stage.

CONCLUSION

A prolonged QTc interval (≥500 msec) was frequently observed throughout the procedure of LT, even among patients with baseline QTc <440 msec, emphasizing the importance of optimizing electrolyte balance and hemodynamic status to reduce greater risk of perioperative arrhythmias.

Behavior of the electrocardiographic T peak to end interval in childhood

BACKGROUND

The T-wave peak to T-wave end (TpTe) interval reflects spatial and transmural dispersion in repolarization and serves as an arrhythmogenic index. Normal TpTe interval data in children are lacking. We evaluated the effects of age, gender, heart rate, leads (II and V(5)) on TpTe and T-wave voltage.

METHODS

Four hundred healthy children (age 4 days to 16.7 years) were enrolled. From a resting 12-lead digital ECG, TpTe, RR, QT, JT intervals, and T amplitude were measured (leads II and V(5)). Bazett and Fridericia formulas were applied to TpTe for heart rate correction and TpTe/QT and TpTe/JT were calculated. Descriptive and analytical statistics were applied, significance level set at P < or = 0.05.

RESULTS

TpTe in leads II and V(5) correlate well. Contrary to adults, no gender differences in TpTe were observed in childhood. TpTe lengthens with increasing age, and is inversely related to heart rate. TpTe 98th percentile is 85 msec in first 5 years, increasing to 92 msec in adolescence. TpTe Fridericia is a good correction formula in childhood; TpTe Bazett overcorrects in the younger age. TpTe/QT and TpTe/JT are longer in younger subjects due to greater QT shortening than the TpTe interval at higher heart rates.

CONCLUSIONS

In children, TpTe in lead II and V(5) correlate well. The TpTe interval lengthens with advancing age as heart rate diminishes. TpTe Fridericia is a good correction formula in children. Younger subjects have higher TpTe/QT and TpTe/JT indices compared to older children. T-wave voltage increases with age, tallest in the 5-10-year-age group particularly in V(5).

Reference values of electrocardiogram repolarization variables in a healthy population

INTRODUCTION

Reference values for T-wave morphology analysis and evaluation of the relationship with age, sex, and heart rate are lacking in the literature. In this study, we characterized T-wave morphology in a large sample of healthy individuals.

METHOD

A total of 1081 healthy subjects (83% men; range, 17-81 years) were included. T-wave morphology variables describing the duration, area, slopes, amplitude, and distribution were calculated using 10-second digital electrocardiogram recordings. Multivariate regression was used to test for dependence of T-wave variables with the subject age, sex, and heart rate.

RESULTS

Lead V5 (men vs women) T-wave variables were as follows: amplitude, 444 versus 317 muV; area, 48.4 versus 33.2 ms mV; Tpeak-Tend interval, 94 versus 92 milliseconds; maximal descending slope, -5.15 versus -3.69 muV/ms; skewness, -0.24 versus -0.22; and kurtosis, -0.36 versus -0.35. Tpeak-Tend interval, skewness, and kurtosis were independent of age, sex, and heart rate (r(2) < 0.05), whereas Bazett-corrected QT-interval was more dependent (r(2) = 0.40).

CONCLUSION

A selection of T-wave morphology variables is found to be clinically independent of age, sex, and heart rate, including Tpeak-Tend interval, skewness, and kurtosis.

The prognostic value of the Tpeak-Tend interval in patients undergoing primary percutaneous coronary intervention for ST-segment elevation myocardial infarction

INTRODUCTION

The Tpeak-Tend interval (TpTe) has been linked to increased arrhythmic risk. TpTe was investigated before and after primary percutaneous coronary intervention (pPCI) in patients with ST-segment elevation myocardial infarction (STEMI).

METHOD

Patients with first-time STEMI treated with pPCI were included (n = 101; mean age 62 years; range 39-89 years; 74% men). Digital electrocardiograms were taken pre- and post-PCI, respectively. Tpeak-Tend interval was measured in leads with limited ST-segment deviation. The primary end point was all-cause mortality during 22 +/- 7 months (mean +/- SD) of follow-up.

RESULTS

Pre- and post-PCI TpTe were 104 milliseconds [98-109 milliseconds] and 106 milliseconds [99-112 milliseconds], respectively (mean [95% confidence interval], P = .59). A prolonged pre-PCI TpTe was associated with increased mortality (hazard ratio, 10.5 [1.7-20.4] for a cutoff value of 100 milliseconds). Uncorrected QT and heart rate-corrected QT intervals (Fridericia-corrected QT) were prolonged after PCI (QT: 401 vs 410 milliseconds, P = .022, and Fridericia-corrected QT: 430 vs 448 milliseconds, P < .0001).

CONCLUSION

In patients with STEMI undergoing pPCI, pre-PCI TpTe predicted subsequent all-cause mortality, and the QT interval was increased after the procedure.

Risk stratification for sudden cardiac death

Recent advances in pharmacological and device-based therapies have provided a range of management options for patients at risk of sudden cardiac death (SCD). Since all such interventions come with their attendant risks, however, stratification procedures aimed at identifying those who stand to benefit overall have gained a new degree of importance. This review assesses the value of risk stratification measures currently available in clinical practice, as well as of others that may soon enter the market. Parameters that may be obtained only by performing invasive cardiac catheterisation procedures are considered separately from those that may be derived using more readily available non-invasive techniques. It is concluded that effective stratification is likely to require the use of composite parameters and that invasive procedures might only be justified in specific sub-groups of patients.