Is QT interval a marker of subclinical atherosclerosis in nondiabetic subjects? The Insulin Resistance Atherosclerosis Study (IRAS)

Investigation of carotid intima-media thickness in patients with schizophrenia

BACKGROUND

Patients with schizophrenia (SCZ) have a higher risk of cardiovascular diseases than the average population. Early diagnosis of SCZ patients with subclinical atherosclerosis is great importance in reducing cardiovascular morbidity and mortality. The aim of this study was to investigate some clinical risk factors for atherosclerosis in patients with SCZ.

METHODS

Fifty-one SCZ patients (20 females, 31 males) and 55 healthy controls (HCs) (25 females, 30 males) were included in the study. Electrocardiography (ECG), lipid parameters, hemogram, and biochemistry values of the participants were taken. Low-density lipoprotein (LDL), high-density lipoprotein (HDL), fasting triglycerides, and total cholesterol were measured. The arrhythmogenic index of plasma (AIP) was analyzed. The recorded right and left carotid intima-media thickness (CIMT) measurements by carotid ultrasonography were scanned.

RESULTS

QT interval (p = 0.035), CIMT-left (p = 0.008), CIMT-right (p = 0.002), fasting triglyceride (p = 0.005), AIP (p = 0.005) in the SCZ group compared to HCs (< 0.001) was statistically higher, while HDL (p = 0.003) was statistically lower. Smoking rates, QT interval (p = 0.035), CIMT-left (p = 0.008), and CIMT-right (p = 0.002) were significantly higher in the the SCZ group than in the HCs. According to odds ratios, individuals with SCZ have a 6.3-fold higher smoking rate. According to Pearson correlation analysis, CIMT-left was positively correlated with age and QT interval (r = 0.568, p < 0.001 and r = 0.589, p < 0.001, respectively). CIMT-right value was also positively correlated with age and QT interval (r = 0.533, p < 0.001 and r = 0.555, p < 0.001, respectively). QT interval positively and significantly predicted CIMT-left and CIMT-right (p < 0.001, β = 0.549 and p = 0.001 and β = 0.506 accordingly).

CONCLUSION

In this study, a close relationship was found between the QT interval and CIMT in SCZ patients. This finding could be valuable for using an easy-to-calculate data such as QT in place of a laborious test such as CIMT.

Prolongation of the QTc interval is associated with an increased risk of cardiovascular diseases: The Hoorn study

BACKGROUND/OBJECTIVE

Prolonged heart rate-corrected QT interval (QTc) on the electrocardiogram (ECG) is maybe associated with the occurrence of cardiovascular diseases (CVD), but the evidence is inconsistent. Therefore, we investigated whether baseline prolongation of the QTc interval is associated with CVD morbidity and mortality and its subtypes and whether glucose tolerance modifies this association in a population-based cohort study with a mean follow-up of 10.8 years.

METHODS

We analyzed a glucose tolerance stratified sample (N = 487) from the longitudinal population-based Hoorn Study cohort (age 64 ± 7 years, 48% female). Cox regression was used to investigate the association between sex-specific baseline QTc quartiles and CVD morbidity and mortality. The risk was also estimated per 10 ms increase in QTc. All analyses were adjusted for age, sex, smoking status, systolic blood pressure, prevalent CVD, glucose tolerance status, hypertension and total cholesterol. In addition, stratified analyses were conducted for glucose tolerance status.

RESULTS

During a mean follow-up of 10.8 years, 351 CVD events were observed. The adjusted hazard ratios (95% CI) for each 10 ms increase in QTc interval were 1.06 (95% CI: 1.02-1.10) for CVD, 1.06 (95% CI: 0.97-1.15) for acute myocardial infarction, 1.07 (95% CI: 1.01-1.13) for stroke, 1.12 (95% CI: 1.06-1.19) for heart failure, 1.04 (95% CI: 0.96-1.12) for peripheral arterial disease and 1.01 (95% CI:0.95-1.08) for coronary heart disease. Glucose tolerance status did not modify the association (P > 0.2).

CONCLUSION/INTERPRETATION

Prolongation of the QTc interval is associated with morbidity and mortality due to general CVD. Glucose tolerance status did not modify these associations.

Cardio-ankle brachial index is associated with prolonged Tp-e interval in patients with arterial hypertension

AIM

The cardio-ankle vascular index (CAVI) is a marker of arterial stiffness, and elevated CAVI values have been reported to be associated with an increased risk of cardiovascular mortality and cardiac arrhythmia. This study aimed to evaluate the relationship between Tp-e interval and CAVI, which is associated with cardiac arrhythmia on electrocardiography (ECG).

METHOD

The study included patients with hypertension whose blood pressure values were taken under control with optimal medical treatment. Arterial stiffness and CAVI were measured using the vascular scanning system VaSera VS-1000. The patients were divided into two groups as CAVI<9 and CAVI≥9. Ventricular repolarization markers QT and QTc intervals, Tp-e interval, and Tp-e/QT and Tp-e/QTc ratios were measured using 12‑lead ECG.

RESULTS

Tp-e interval (78.7 ± 10.3 vs. 63.6 ± 9.1, p < 0.001), Tp-e/QT ratio (0.018 ± 0.02 vs. 0.015 ± 0.02, p < 0.001), and Tp-e/QTc ratio (0.17 ± 0.02 vs. 0.14 ± 0.04, p = 0.025) were statistically significantly higher in the CAVI≥9 group compared to the CAVI<9 group. In the prediction of patients in the CAVI≥9 group, Tp-e interval had an area under the curve value of 0.862 (0.784-0.940, p < 0.001) at the cut-off point of >72.5 msec, indicating a statistically significant result. Left CAVI and right CAVI were found to be significantly correlated with Tp-e interval (r = -0.650, p < 0.001 and r = -0.663, p < 0.001, respectively).

CONCLUSION

We found that elevated CAVI values were associated and positively correlated with prolonged Tp-e interval values in patients with hypertension. Patients with elevated CAVI values should be followed up closely to prevent cardiac arrhythmic events.

Prolongation of the heart rate-corrected QT interval is associated with cardiovascular diseases: Systematic review and meta-analysis

BACKGROUND

Conflicting findings have described the association between prolonged heart rate-corrected QT interval (QTc) and cardiovascular disease.

AIMS

To identify articles investigating the association between QTc and cardiovascular disease morbidity and mortality, and to summarize the available evidence for the general and type 2 diabetes populations.

METHODS

A systematic search was performed in PubMed and Embase in May 2022 to identify studies that investigated the association between QTc prolongation and cardiovascular disease in both the general and type 2 diabetes populations. Screening, full-text assessment, data extraction and risk of bias assessment were performed independently by two reviewers. Effect estimates were pooled across studies using random-effect models.

RESULTS

Of the 59 studies included, 36 qualified for meta-analysis. Meta-analysis of the general population studies showed a significant association for: overall cardiovascular disease (fatal and non-fatal) (hazard ratio [HR] 1.68, 95% confidence interval [CI] 1.33-2.12; I²=69%); coronary heart disease (fatal and non-fatal) in women (HR 1.27, 95% CI 1.08-1.50; I²=38%; coronary heart disease (fatal and non-fatal) in men (HR 2.07, 95% CI 1.26-3.39; I²=78%); stroke (HR 1.59, 95% CI 1.29-1.96; I²=45%); sudden cardiac death (HR 1.60, 95% CI 1.14-2.25; I²=68%); and atrial fibrillation (HR 1.55, 95% CI 1.31-1.83; I²=0.0%). No significant association was found for cardiovascular disease in the type 2 diabetes population.

CONCLUSION

QTc prolongation was associated with risk of cardiovascular disease in the general population, but not in the type 2 diabetes population.

Electrocardiogram Risk Score and Prevalence of Subclinical Atherosclerosis: A Cross-Sectional Study

Integrated abnormal electrocardiogram (ECG) parameters predict the risk of cardiovascular disease (CVD); however, its relationship with subclinical CVD is unknown. We aimed to evaluate the association between the integrated ECG risk score and the prevalence of coronary artery calcium (CAC). A cross-sectional study comprised 134,802 participants with no known CVD who underwent ECG and CAC computed tomography. The ECG risk score was the sum of five ECG abnormalities: heart rate of >80 beats, QRS of >110 ms, left ventricular hypertrophy, T-wave inversion, and prolonged QTc. A multinomial regression model was used to estimate the prevalence ratios (PRs) and their 95% confidence intervals (CIs) for prevalent CAC. The prevalence of CAC progressively increased as the ECG risk score increased. After adjustment for conventional CVD risk factors and other confounders, the multivariable-adjusted PRs (95% CI) for a CAC of 1−100 in the 1, 2, and ≥3 ECG risk score groups were 1.06 (1.02−1.10), 1.12 (1.03−1.22), and 1.19 (1.00−1.42), respectively, while the corresponding PRs for a CAC of >100 were 1.03 (0.95−1.12), 1.44 (1.25−1.66), and 1.75 (1.33−2.29), respectively. Integrative ECG scoring may help identify individuals requiring lipid-lowering medications, even in young and asymptomatic populations.

The best QT correction formula in a non-hospitalized population: the Fasa PERSIAN cohort study

Background

QT interval as an indicator of ventricular repolarization is a clinically important parameter on an electrocardiogram (ECG). QT prolongation predisposes individuals to different ventricular arrhythmias and sudden cardiac death. The current study aimed to identify the best heart rate corrected QT interval for a non-hospitalized Iranian population based on cardiovascular mortality.

Methods

Using Fasa PERSIAN cohort study data, this study enrolled 7071 subjects aged 35–70 years. Corrected QT intervals (QTc) were calculated by the QT interval measured by Cardiax® software from ECGs and 6 different correction formulas (Bazett, Fridericia, Dmitrienko, Framingham, Hodges, and Rautaharju). Mortality status was checked using an annual telephone-based follow-up and a minimum 3-year follow-up for each participant. Bland–Altman, QTc/RR regression, sensitivity analysis, and Cox regression were performed in IBM SPSS Statistics v23 to find the best QT. Also, for calculating the upper and lower limits of normal of different QT correction formulas, 3952 healthy subjects were selected.

Results

In this study, 56.4% of participants were female, and the mean age was 48.60 ± 9.35 years. Age, heart rate in females, and QT interval in males were significantly higher. The smallest slopes of QTc/RR analysis were related to Fridericia in males and Rautaharju followed by Fridericia in females. Thus, Fridericia’s formula was identified as the best mathematical formula and Bazett’s as the worst in males. In the sensitivity analysis, however, Bazett’s formula had the highest sensitivity (23.07%) among all others in cardiac mortality. Also, in the Cox regression analysis, Bazett’s formula was better than Fridericia’s and was identified as the best significant cardiac mortality predictor (Hazard ratio: 4.31, 95% CI 1.73–10.74, p value = 0.002).

Conclusion

Fridericia was the best correction formula based on mathematical methods. Bazett’s formula despite its poorest performance in mathematical methods, was the best one for cardiac mortality prediction. Practically, it is suggested that physicians use QTcB for a better evaluation of cardiac mortality risk. However, in population-based studies, QTcFri might be the one to be used by researchers.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12872-022-02502-2.

Rare variants in previously identified linkage regions associated with carotid plaque in Dominican Republic families

Carotid plaque is a subclinical measure of atherosclerosis. We have previously shown measures of carotid plaque to be heritable in a sample of 100 Dominican families and found evidence for linkage and association of common variants (CVs) on 7q36, 11p15, 14q32 and 15q23 with plaque presence. Our current study aimed to refine these regions further and identify rare variants (RVs) influencing plaque presence. Therefore, we performed targeted sequencing of the one LOD unit down region on 7q36, 11p15, 14q32 and 15q23 in 12 Dominican families with evidence for linkage to plaque presence. Gene-based RV analyses were performed using the Sequence Association Test for familial data (F-SKAT) under two filtering algorithms; 1. all exonic RVs and 2. non-synonymous RVs. Replication analyses were performed using a sample of 22 Dominican families and 556 unrelated Dominicans with Exome Array data. To identify additional non-synonymous RVs influencing plaque, we looked for co-segregation of RVs with plaque in each of the sequenced families. Our most strongly associated gene with evidence for replication was AMPD3 which showed suggestive association with plaque presence in the sequenced families (exonic RV p = 0.003, nonsynonymous RV p = 0.005) and replication families (exonic RV p = 0.04, nonsynonymous RV p = 0.02). Examination of the sequenced family pedigrees revealed two missense variants on chromosome 11 which co-segregated with plaque presence in one of our families; rs61751342 (located in DENND2B), and rs61760882 (located in RNF141). The rs61751342 missense variant is an eQTL for SCUBE2 in the atrial appendage. Notably, SCUBE2 encodes a protein which interacts with vascular endothelial growth factor (VEGF) receptor 2 to regulate VEGF-induced angiogenesis, thus providing biologic plausibility for this gene in atherosclerosis. In conclusion, using targeted sequencing of previously-identified linkage regions, we have identified suggestive evidence for the role of RVs in carotid plaque pathogenesis.

Prognostic Significance of Prolonged Corrected QT Interval in Acute Ischemic Stroke

Background and Purpose: The aim of this study was to determine the relationship between the heart rate-corrected QT (QTc) interval and the risk of incident long-term mortality in patients with acute ischemic stroke (AIS), considering the impact of sex differences on clinical characteristics, outcomes, and QTc intervals.

Methods: We analyzed prospectively registered data included patients with AIS who visited the emergency room within 24 h of stroke onset and underwent routine cardiac testing, such as measurements of cardiac enzymes and 12-lead ECG. QTc interval was corrected for heart rate using Fridericia's formula and was stratified by sex-specific quartiles. Cox proportional hazards models were used to examine the association between baseline QTc interval and incident all-cause death.

Results: A total of 1,668 patients with 1,018 (61.0%) men and mean age 66.0 ± 12.4 years were deemed eligible. Based on the categorized quartiles of the QTc interval, cardiovascular risk profile, and stroke severity increased with prolonged QTc interval, and the risk of long-term mortality increased over a median follow-up of 33 months. Cox proportional hazard model analysis showed that the highest quartile of QTc interval (≥479 msec in men and ≥498 msec in women; hazard ratio [HR]: 1.49, 95% confidence interval [CI]: 1.07–2.08) was associated with all-cause death. Furthermore, dichotomized QTc interval prolongation, defined by the highest septile of the QTc interval (≥501 ms in men and ≥517 m in women: HR: 1.33, 95% CI: 1.00–1.80) was significantly associated with all-cause mortality after adjusting for all clinically relevant variables, such as stroke severity.

Conclusions: Prolonged QTc interval was associated with increased risk of long-term mortality, in parallel with the increasing trend of prevalence of cardiovascular risk profiles and stroke severity, across sex differences in AIS patients.

It's Time to Add Electrocardiography and Echocardiography to CVD Risk Prediction Models: Results from a Prospective Cohort Study

Objective

To develop and validate a new prediction model for the general population based on a large panel of both traditional and novel factors in cardiovascular disease (CVD).

Design and Setting

We used a prospective cohort in the Northeast China Rural Cardiovascular Health Study (NCRCHS).

Participants

A total of 11,956 participants aged ≥35 years were recruited between 2012 and 2013, using a multistage, randomly stratified, cluster-sampling scheme. In 2015 and 2017, the participants were invited to join the follow-up study for incident cardiovascular events. The loss to follow-up number was 351. At the study’s end, we obtained the CVD outcome events for 10,349 participants.

Primary and Secondary Outcome Measures

The prediction model was developed using demographic factors, blood biochemical indicators, electrocardiographic (ECG) characteristics, and echocardiography indicators collected at baseline (Model 1). Framingham-related variables, namely age, sex, smoking, total and high-density lipoprotein cholesterol and diabetes status were used to construct the traditional model (Model 2).

Results

For the observed population (n = 10,349), the median follow-up time was 4.66 years. The total incidence of CVD was 1.1%/year, including stroke (n = 342) and coronary heart disease (n = 175). The results of Model 1 indicated that in addition to the traditional risk factors, QT interval (p < 0.001), aortic root diameter (p < 0.001), and ventricular septal thickness (p < 0.001) were predictive factors for CVD. Decision curve analysis (DCA) showed that the net benefit with Model 1 was higher than that of Model 2.

Conclusion

QT interval from electrocardiography and aortic root diameter and ventricular septal thickness from echocardiography should be included in the CVD risk prediction models.

Corrected QT Interval Is Associated With Stroke but Not Coronary Heart Disease: Insights From a General Chinese Population

Background: Prolonged heart rate-corrected QT (QTc) interval has been associated with incident cardiovascular diseases (CVD) in general Western populations. However, this association is unclear in Asian population. We aim to estimate the association between QTc interval and incident CVD in a general Chinese population.

Methods: We analyzed 8,867 participants age ≥35 years and free of CVD at baseline in the Northeast China Rural Cardiovascular Health Study. A resting 12-lead electrocardiogram was performed on all participants, and QTc interval computed using the Framingham formula. Cox proportional hazards models were used to calculate hazard ratios (HRs) with 95% confidence intervals (CIs) for associations between QTc interval and incident stroke, coronary heart disease, and combined CVD events.

Results: Over a median follow-up of 4.66 years, a total of 439 CVD events occurred (298 stroke cases and 152 CHD cases). After full adjustment, prolonged QTc defined by a sex-specific cutoff was associated with increased risk of developing stroke (HR: 1.82, 95% CI 1.20–2.75, P = 0.004) and combined CVD (HR: 1.52, 95% CI 1.05–2.19, P = 0.026). Spline analyses demonstrated no clear thresholds; when modeled as a linear relationship, each 10 ms increase of QTc interval was associated with an HR of 1.12 (95% CI 1.06–1.19, P < 0.001) for stroke and an HR of 1.10 (95% CI 1.05–1.15, P < 0.001) for combined CVD. Baseline QTc interval was not associated with incident CHD with either modeling strategy.

Conclusions: Baseline QTc interval is associated with incident stroke and CVD in adults without prior CVD from a general Chinese population.

Effect of Intensive Glycemic and Blood Pressure Control on QT Prolongation in Diabetes: The ACCORD Trial

Compared with standard glycemic control, intensive glycemic control caused increased mortality in the Action to Control Cardiovascular Risk in Diabetes (ACCORD) trial. Preliminary data from several studies suggest that intensive glycemic control is associated with QT prolongation, which may lead to ventricular arrhythmias as a possible explanation of this increased mortality. We sought to assess the effects of intensive glycemic control and intensive blood pressure control on the risk of incident QT prolongation. Cox proportional hazards models were used to compare the risk of incident QT prolongation (>460 ms in women or >450 ms in men) in the intensive versus standard glycemic control arms. Over a combined 48,634 person-years of follow-up (mean 4.9), 634 participants (6.4%) developed a prolonged QTc. Participants in the intensive glycemic control arm did not have an increased risk of QT prolongation. Similarly, a strategy of intensive blood pressure control did not result in a significant change in risk of prolonged QTc. Sensitivity analyses using alternative QT correction formulas (Hodges and Bazett) yielded overall similar findings. In conclusion, the increased mortality observed in the intensive glycemic control arm in the ACCORD trial is not likely to be explained by QT prolongation leading to lethal ventricular arrhythmias.

Predictive role of ventricular repolarization parameters for the occurrence of complete heart block in patients undergoing transcatheter aortic valve implantation

Background

We investigated the role of ventricular repolarization parameters to predict complete atrioventricular block in patients undergoing transcatheter aortic valve implantation (TAVI).

Methods

A total of 150 patients undergoing TAVI due to severe aortic stenosis were included in this retrospective cohort study. Patients were assigned in two groups based on the presence (n: 49) or absence (n: 101) of complete atrioventricular block after TAVI. Ventricular repolarization intervals (QT, QTc, JT, JTc, TP‐E), indices (QT dispersion), and ratios (TP‐E/QT, TP‐E/QTc, TP‐E/JTc) were measured.

Results

Electrocardiographic repolarization parameters such as Tp‐e interval: 74.2 ± 5.1 versus 59.2 ± 6.1 ms, p < .001; QTc interval: 397.6 ± 3.4 versus 368.1 ± 7.8 ms, p < .001; JTc interval: 317.4 ± 11.3 versus 291.1 ± 6.7 ms, p < .001; Tp‐e/QT ratio: 0.28 ± 0.04 versus 0.20 ± 0.04, p < .001; Tp‐e/QTc ratio: 0.29 ± 0.04 versus 0.19 ± 0.03, p < .001; Tp‐e/JT ratio: 0.32 ± 0.03 versus 0.23 ± 0.03, p < .001; Tp‐e/JTc ratio: 0.30 ± 0.02 versus 0.2 ± 0.03, p < .001; and QT dispersion: 34.4 ± 3.0 versus 17.8 ± 3.6 ms, p < .01 were significantly higher in post‐TAVI permanent pacemaker group. In a univariate regression analysis, pulmonary artery pressure, heart rate, coronary artery disease, Tp‐e/QTc, Tp‐e/JTc, and PR interval were significantly associated with complete heart block. Tp‐e/JTc (OR 0.373, p = .067) and PR interval (OR 0.898, p = .079) were found to be independent predictors of these type of arrhythmias in a multivariate analysis. But it is not statistically significant.

Conclusion

Our results suggest that repolarization parameters may play a role in predicting complete atrioventricular block. Tp‐e/JTc was found to be potential independent risk marker for this setting.

Electrocardiographic predictors of mortality in patients after percutaneous coronary interventions - a nested case-control study

Background: The outcome of patients undergoing percutaneous coronary interventions (PCIs) varies considerably. Several ECG parameters have recently emerged (PQ interval, P-wave, T-peak-to-T-end interval, T-wave, T/R ratio, J-wave) beyond traditional markers (rhythm, QRS, Q-wave, QT interval, ST segment) and were attributed important prognostic value in the setting of coronary artery disease. The present study integrated for the first time these ECG parameters altogether with the aim to determine their role in predicting patients' outcome after a PCI. Methods: A total of 3342 patients were enrolled in the present study between 2009 and 2013. In a nested case-control design, 644 patients who died within a year post-PCI (cases) were matched 1:4 with patients alive at that particular date (controls). Results: Our data showed that only the presence of a longer QT interval (heart rate-corrected using Bazett formula) was associated with increased risk of death after adjusting for multiple clinical and angiographic risk factors (adjusted OR 1.07; 95%CI 1.01-1.12, p = .022). Conclusion: Our study emphasises the prognostic importance of the QT interval in identifying patients at increased risk of death during the first year after PCI. Clinical Trial Registration - URL: https://www.clinicaltrials.gov . Unique identifier: NCT02241291.

QT-interval parameters are increased in systemic lupus erythematosus patients

Systemic lupus erythematosus (SLE) patients have increased cardiovascular morbidity and mortality. QT-interval parameters are presumed markers of cardiovascular risk and have not been previously evaluated in SLE. Standard 12-lead ECGs were obtained from 140 female SLE outpatients and 37 age and body mass index-matched controls. QT interval was measured in each lead and heart rate-corrected maximum QT-interval duration (QTcmax) and QT-interval dispersion (QTd) were calculated. Risk factors for cardiovascular disease and lupus clinical features, disease treatment, disease activity and damage index were recorded. SLE patients have increased QT-interval parameters when compared to controls (QTcmax: 427.91 31.53 ms1/2 versus 410.05 15.45 ms1/2, P 0.001; QTd: 52.38 22.21 ms versus 37.12 12.88 ms, P 0.001). These differences persisted after excluding those patients with arterial hypertension, diabetes and with ECG abnormalities (QTcmax: 419.90 28.78 ms1/2 versus 409.15 15.85 ms1/2, P 0.041; QTd: 54.74 26.00 ms versus 37.96 13.05 ms, P 0.001). Multivariate linear regression for factors associated with QTcmaxselected the presence of electrocardiographic left ventricular hypertrophy (ECG-LVH) ( P 0.003), nonspecific ST-T-wave abnormalities ( P 0.022) and left atrial enlargement ( P 0.044). Multivariate associates with QTd were age ( P 0.018), ECG-LVH ( P 0.022) and ST-T abnormalities ( P 0.031). In conclusion, SLE patients have increased QT interval parameters when compared to controls. This prolongation may lead to an increased cardiovascular risk. This finding might be due to subclinical atherosclerotic cardiovascular disease.

Longitudinal Community-Based Study of QT Interval and Mortality in Southeast Asians

Introduction

The prognostic impact of QT interval prolongation has not been well studied in healthy Asians. We investigated the association between the QT interval with mortality and cardiovascular events in a healthy Southeast Asian population.

Methods

The QT interval corrected for heart rate using the Bazett’s formula (QTc) was measured in 2536 (825 men, mean age 65.7±7.5 years) Singaporean adults free of cardiovascular disease in the population-based Singapore Longitudinal Ageing Study. Outcomes were all-cause mortality and incident cardiovascular events (cardiovascular mortality, myocardial infarction (MI) and/or stroke).

Results

Over a mean 7.78 years (19695 person-years) of follow-up, there were 202 deaths (45 from cardiovascular causes), 62 cases of myocardial infarction and 64 cases of stroke. Adjusting for age, sex, and cardiovascular risk factors, QTcB prolongation remained independently associated with increased all-cause mortality (HR(per standard deviation) 1.27 (1.10–1.48), p = 0.0015), as well as increased risk of cardiovascular events (HR 1.20 (1.01–1.43), p = 0.0415) and MI/stroke (HR 1.22 (1.01–1.47), p = 0.0455), but not cardiovascular mortality alone (HR 1.05 (0.77–1.44), p = 0.7562).

Conclusions

We provide the first community-based estimates of the independent association of QT prolongation with all-cause mortality and cardiovascular events in Southeast Asians.

Relationship between QT Interval Length and Arterial Stiffness in Systemic Lupus Erythematosus (SLE): A Cross-Sectional Case-Control Study

INTRODUCTION AND OBJECTIVES

The QT interval on the electrocardiogram has been shown to be longer in patients with systemic lupus erythematosus (SLE) compared to that of the general population. The clinical significance of this finding is unknown. The aim of this study was to assess the relationship between QT interval and subclinical atherosclerosis, measured by carotid-femoral pulse-wave velocity.

MATERIAL AND METHODS

93 patients with SLE and 109 healthy women with similar basal characteristics were studied. All patients underwent a 12- lead electrocardiogram, and corrected QT interval (QTc) was measured using the Bazett's formula. The presence of atherosclerosis was evaluated by carotid-femoral pulse-wave velocity.

RESULTS

Clinical basal characteristics were similar in both groups. QTc interval was 415 ± 21.4 milliseconds in all patients, and 407 ± 19.1 milliseconds in the control group (p = 0.007). There was a positive correlation between QTc interval and carotid-femoral pulse-wave velocity (r = 0.235; p = 0.02) in patients with SLE. This association was independent of hypertension and age in a multivariate analysis.

CONCLUSION

QTc interval measured by electrocardiogram is prolonged in SLE patients; it is related to subclinical atherosclerosis, measured by carotid-femoral pulse-wave velocity. This measure may help stratify risk in routine clinical practice and select the patients that might benefit from a more aggressive therapy in the prevention of cardiovascular events.

Interrelationship between electrocardiographic left ventricular hypertrophy, QT prolongation, and ischaemic stroke: the REasons for Geographic and Racial Differences in Stroke Study

AIMS

To determine if the association between electrocardiographic left ventricular hypertrophy (ECG-LVH) and ischaemic stroke is partially explained by the concomitant presence of QT prolongation.

METHODS AND RESULTS

A total of 24 948 (mean age = 65 ± 9.4 years; 40% black; 55% women) participants from the REasons for Geographic And Racial Differences in Stroke (REGARDS) study were included in this analysis. Electrocardiographic left ventricular hypertrophy was defined by the Sokolow-Lyon criteria. Heart rate-adjusted QT (QTa) was computed using a linear regression model. Adjudicated ischaemic stroke events were the outcome of interest. Cox regression was used to compute hazard ratios (HRs) and 95% confidence intervals (CIs) for associations between ECG-LVH and prolonged QTa, in isolation and combined, with ischaemic stroke. There were 2422 (9.7%) participants with ECG-LVH, 820 (3.3%) with prolonged QTa, and 161 (0.6%) with both. Over a median follow-up of 7.6 years, 714 (2.9%) ischaemic stroke events occurred. After adjustment for stroke risk factors and potential confounders, an increased risk of ischaemic stroke was observed among participants with ECG-LVH and prolonged QTa (HR = 1.85, 95% CI = 1.04-3.30), isolated ECG-LVH (HR = 1.40, 95% CI = 1.13-1.75), and isolated prolonged QTa (HR = 1.45, 95% CI = 1.04-2.03) compared with participants without either condition. When ECG-LVH and prolonged QTa were examined as separate variables, the risk of ischaemic stroke for each condition remained statistically significant.

CONCLUSION

The combination of ECG-LVH and prolonged QT is associated with a higher risk of ischaemic stroke compared with either condition in isolation, and the stroke risk for each condition does not depend on the presence of the other.

Considerations for assessing the potential effects of antidiabetes drugs on cardiac ventricular repolarization: A report from the Cardiac Safety Research Consortium

Thorough QT studies conducted according to the International Council on Harmonisation E14 guideline are required for new nonantiarrhythmic drugs to assess the potential to prolong ventricular repolarization. Special considerations may be needed for conducting such studies with antidiabetes drugs as changes in blood glucose and other physiologic parameters affected by antidiabetes drugs may prolong the QT interval and thus confound QT/corrected QT assessments. This review discusses potential mechanisms for QT/corrected QT interval prolongation with antidiabetes drugs and offers practical considerations for assessing antidiabetes drugs in thorough QT studies. This article represents collaborative discussions among key stakeholders from academia, industry, and regulatory agencies participating in the Cardiac Safety Research Consortium. It does not represent regulatory policy.

The link between ventricular repolarization variables and arterial function

AIM

To assess the relationship between repolarization variables and arterial function.

METHODS

A total of 54 participants, aged 33±10years, underwent arteriography and standard 12-lead electrocardiography (ECG). Arteriography was performed using a noninvasive automated oscillometric method, assessing: brachial (Aix Brach) and aortic augmentation index (Aix Ao), pulse wave velocity (PWV), arterial age (AA), diastolic reflection area (DRA) and diastolic area index (DAI). Standard 12-lead ECG enabled measurement of QT and Tpeak-Tend (TpTe) intervals and TpTe/QT ratios.

RESULTS

QT interval was prolonged in patients with elevated blood pressure or body mass index. Significant associations were found between electrocardiographic repolarization parameters, such as QT intervals, TpTe and TpTe/QT and arteriography variables, such as Aix Brach, Aix Ao, PWV and AA.

CONCLUSION

Prolonged QTc and Tpe are associated with endothelial dysfunction, arterial stiffness, impaired coronary perfusion and accelerated arterial aging.

Factors associated with abnormal T-wave axis and increased QRS-T angle in type 2 diabetes

Frontal plane T-wave axis and QRS-T angle are novel electrocardiographic ventricular repolarization parameters that have been scarcely evaluated in type 2 diabetes. The aim was to investigate the factors associated with these parameters of abnormal ventricular repolarization in a cross-sectional analysis of 594 patients with type 2 diabetes. Clinical, laboratory, 2D-echocardiographic, ambulatory blood pressure (BP) monitoring, aortic pulse wave velocity (PWV) and carotid ultrasonographic data were obtained. Digital 12-lead ECG was recorded, and frontal plane T-wave axis and QRS-T angle were automatically measured. T-wave axis was considered abnormal if >75° or <15° and QRS-T angle if ≥73° in men and ≥67° in woman. Associations were assessed by bivariate tests and multivariate logistic regressions. One hundred and four (20.9 %) patients had abnormal T-wave axis, and 84 (14 %) had increased QRS-T angle. Patients with abnormal ventricular repolarization were older and had greater prevalence of micro- and macrovascular diabetic complications than patients with normal repolarization. They had higher office and ambulatory BPs, greater prevalence of the non-dipping pattern, and greater left ventricular mass, aortic PWV and carotid intima-media thickness. On multivariate analysis, abnormal ventricular repolarization parameters were independently associated with left ventricular hypertrophy, non-dipping pattern, higher ambulatory systolic BPs, glycated hemoglobin and common carotid intima-media thickness, and with the presence of coronary artery disease. In conclusion, abnormal frontal plane T-wave axis and QRS-T angle are independently associated with several markers of pre-clinical atherosclerotic disease; whether these associations represent additional cardiovascular risk in type 2 diabetes shall be confirmed in prospective studies.

Prevalence and risk factors of prolonged QTc interval among Chinese patients with type 2 diabetes

Objectives. The aim of this study was to evaluate the prevalence and the risk factors of prolonged QTc interval among Chinese patients with type 2 diabetes. Methods. The retrospective study included 3156 outpatients from the Diabetes Centre, the 306th Hospital of PLA, during the period from September 2003 to June 2010. QT interval was measured manually in the 12-lead conventional electrocardiogram. The QT interval corrected for heart rate (QTc) was calculated using Bazett's formula. Additional demographic and laboratory data were also collected. Potential risk factors of prolonged QTc interval were assessed using multivariable regression. Results. The prevalence of prolonged QTc interval among Chinese patients with type 2 diabetes was 30.1%. Height (OR 0.156, 95% CI 0.032~0.748), waist circumference (OR 1.025, 95% CI 1.010~1.040), diastolic blood pressure (OR 1.016, 95% CI 1.007~1.026), postprandial glucose (OR 1.040, 95% CI 1.022~1.059), fasting insulin (OR 1.014, 95% CI 1.003~1.025), and presence of microalbuminuria (OR 1.266, 95% CI 1.033~1.551) were significant risk factors. Conclusions. The prevalence of prolonged QTc interval among Chinese patients with type 2 diabetes is high. Risk factors for prolongation of QTc interval were low height, high waist circumference, increasing diastolic blood pressure levels, high postprandial glucose levels, high fasting insulin levels, and presence of microalbuminuria.

Prolongation of QTc and risk of stroke: The REGARDS (REasons for Geographic and Racial Differences in Stroke) study

OBJECTIVES

The purpose of this study was to examine the association between prolongation of QT interval corrected for heart rate (QTc) with incident stroke.

BACKGROUND

Unlike cardiovascular morbidity and mortality, little is known about the relationship between QTc and risk of stroke.

METHODS

A total of 27,411 participants age 45 years and older without previous stroke from the REGARDS (REasons for Geographic and Racial Differences in Stroke) study were included in this analysis. QTc was calculated using Framingham formula (QTc(Fram)). Stroke cases were identified and adjudicated during up to 8.2 years of follow-up (median, 5.1 years).

RESULTS

The risk of incident stroke in study participants with prolonged QTc(Fram) was almost 3 times the risk in those with normal QTc(Fram) (hazard ratio [HR] [95% confidence interval (CI)]: 2.88 [2.12 to 3.92], p < 0.0001). After adjustment for demographics (age, race, and sex), traditional stroke risk factors (antihypertensive medication use, systolic blood pressure, current smoking, diabetes, left ventricular hypertrophy, atrial fibrillation, and previous cardiovascular disease), warfarin use, aspirin use, QRS duration and use of QTc-prolonging drugs, the risk of stroke remained significantly high (HR [95% CI]: 1.67 [1.16 to 2.41], p = 0.0061) and was consistent across several subgroups of REGARDS study participants. Similar results were obtained when the risk of stroke was estimated per 1-SD increase in QTc(Fram), (HR [95% CI]: 1.12 [1.03 to 1.21], p = 0.0053 in multivariable-adjusted model) and when other QTc correction formulas including those of Hodge, Bazett, and Fridericia were used.

CONCLUSIONS

QTc prolongation is associated with a significantly increased risk of incident stroke independent of traditional stroke risk factors. Examining the risk of stroke associated with QTc-prolonging drugs may be warranted.

Genetic locus on mouse chromosome 7 controls elevated heart rate

Elevated heart rate (HR) is a risk factor for cardiovascular diseases. The goal of the study was to map HR trait in mice using quantitative trait locus (QTL) analysis followed by genome-wide association (GWA) analysis. The first approach provides mapping power and the second increases genome resolution. QTL analyses were performed in a C3HeB×SJL backcross. HR and systolic blood pressure (SBP) were measured by the tail-cuff plethysmography. HR was ∼80 beats/min higher in SJL compared with C3HeB. There was a wide distribution of the HR (536-763 beats/min) in N2 mice. We discovered a highly significant QTL (logarithm of odds = 6.7, P < 0.001) on chromosome 7 (41 cM) for HR in the C3HeB×SJL backcross. In the Hybrid Mouse Diversity Panel (58 strains, n = 5-6/strain) we found that HR (beats/min) ranged from 546 ± 12 in C58/J to 717 ± 7 in MA/MyJ mice. SBP (mmHg) ranged from 99 ± 6 in strain I/LnJ to 151 ± 4 in strain BXA4/PgnJ. GWA analyses were done using the HMDP, which revealed a locus (64.2-65.1 Mb) on chromosome 7 that colocalized with the QTL for elevated HR found in the C3HeB×SJL backcross. The peak association was observed for 17 SNPs that are localized within three GABA(A) receptor genes. In summary, we used a combined genetic approach to fine map a novel elevated HR locus on mouse chromosome 7.

Impact of vascular calcification on corrected QT interval at the time of renal transplantation

BACKGROUND/AIMS

Sudden death is the major cause of cardiac mortality in dialysis patients, accounting for approximately 60% of cardiovascular deaths. A prolonged QT interval and arterial calcification have been associated with increased cardiovascular morbidity and mortality in different patient populations including patients with chronic kidney disease (CKD). In the present study, we aimed to elucidate the association of vascular calcification with corrected QT interval duration in patients with end-stage renal disease.

METHODS

We performed a single-center cross-sectional study in patients referred for renal transplantation. Patients taking QT-prolonging agents or with conduction abnormalities were excluded. Aortic calcifications were scored by means of lumbar X-rays.

RESULTS

In the final analysis, 193 patients (118 men, 52 years old) were included. A prolonged QT interval was observed in 26% of the patients. Multivariate analysis showed an independent and direct association between corrected QT duration and the extent of aortic calcifications (p = 0.0004) independent of age, gender, cardiovascular history, electrolytes and parameters of mineral metabolism.

CONCLUSIONS

A prolonged QT interval is prevalent in patients with CKD stage 5D. Aortic calcification is associated with a prolonged QT duration, independent of traditional determinants.

Utility of nonspecific resting electrocardiographic features for detection of coronary artery stenosis by computed tomography in acute chest pain patients: from the ROMICAT trial

Twelve-lead surface electrocardiography (ECG) and computed tomography (CT) are used to evaluate for myocardial ischemia and coronary artery disease (CAD), respectively. We aimed to determine features on resting ECG that predict coronary artery stenosis by cardiac CT. In 309 acute chest pain patients, we compared the initial triage resting ECG to contrast-enhanced 64-slice cardiac CT angiography. We assessed for 6 quantitative (QT interval, QTc interval, QTc > 440 ms, gender-specific QTc, QT dispersion and QRS duration) and 4 qualitative ECG parameters (ST depression >0.05 to ≤0.1 mV, T wave inversion ≥0.1 mV, T wave flattening, and any T wave abnormalities) and for the presence of coronary stenosis by CT (>50% luminal narrowing). Specificities of these ECG parameters were excellent (83.6-97.0%) while sensitivities were poor (12.2-29.3%). For coronary stenosis detection, the ECG features with the greatest performance were the presence of ST depression (positive likelihood ratio [LR+] 4.09) and T wave inversion (LR+ 4.58). In multivariable analyses, the risk for coronary stenosis increased by 33-41% for every 20 ms prolongation of the QTc interval after adjusting for age, gender, and cardiac risk factors or adjustment for Framingham risk score. Similarly, there was an increase of fourfold with the presence of ST depression >0.05 to ≤0.1 mV or T wave inversion ≥0.1 mV. In acute chest pain patients, resting ECG features of QTc interval prolongation, mild ST depression, and T wave inversion are independently associated with the presence of CT coronary stenosis and their presence suggests an increase risk of CAD.

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.

Association between the corrected QT interval and carotid artery intima-media thickness in obese children

OBJECTIVE

Sudden death has been reported in asymptomatic obese adults and the mechanism is unclear. In recent years, obesity has shown a dramatic increase in children and this enhances the risk factors for the development of cardiovascular disease. The aim of this study was to investigate whether there is repolarization abnormality and any potential risk factor such as increase in intima-media thickness (IMT) of carotid artery for corrected QT (QTc) prolongation among obese children.

METHODS

A total of 60 obese children, 30 of which had features of metabolic syndrome (MS), and 23 age-matched controls were included in the study. QTc interval was calculated at rest. The IMT of both common carotid arteries (CCA) was measured. The relationship between QTc, IMT of right and left CCA and insulin sensitivity indices were evaluated in the study group.

RESULTS

The QTc interval of the children with simple exogenous obesity (SEO) were longer than in the controls (p=0.024). The IMT of both carotid arteries of the obese girls and boys with and without MS were higher than the controls (p=<0.001). The QTc was significantly affected by the parameters pertaining to the right carotid artery IMT, to chronologic age and HDL-C.

CONCLUSION

Since obesity may cause subclinical atherosclerotic disease regardless of sex, obese children must be followed closely for early cardiovascular problems.

Prognostic value of ventricular repolarization prolongation in resistant hypertension: a prospective cohort study

OBJECTIVE

The prognostic value of prolonged ventricular repolarization in patients with resistant hypertension is unknown. The aim of this prospective study was to investigate the usefulness of electrocardiographic QT-interval parameters as predictors of cardiovascular morbidity and mortality.

METHODS

At baseline, 538 resistant hypertensive patients had five QT-interval components measured in standard 12-lead ECGs: maximum QRS, QTpeak, QTend, JT and Tpeak-to-end-interval durations. Primary endpoints were a composite of fatal and nonfatal cardiovascular events, all-cause and cardiovascular mortalities. Multiple Cox regression assessed the associations between QT-interval parameters and subsequent endpoints.

RESULTS

After a median follow-up of 4.8 years, 69 (12.8%) patients died, 46 from cardiovascular causes, and 107 (19.9%) fatal or nonfatal cardiovascular events occurred. After adjustment for several traditional risk factors, including 24-h ambulatory systolic blood pressure, an increment of 1 SD (35 ms) in QTcend-interval was associated with hazard ratios of 1.38 (1.15-1.67), 1.51 (1.16-1.98) and 1.30 (1.03-1.64), respectively, for the composite endpoint, cardiovascular mortality and all-cause mortality. Further adjustment for left ventricular hypertrophy attenuated the relative risks, but they remained significant for cardiovascular mortality (1.45, 1.07-1.97) and for the composite endpoint (1.35, 1.11-1.66). After full adjustment, a prolonged QTcend-interval (> or =460 ms) conferred a 1.7-fold (1.1-2.6) higher risk of having a future fatal or nonfatal cardiovascular event. No other QT-interval component added further prognostic information to QTcend-interval duration.

CONCLUSIONS

Prolonged ventricular repolarization is a risk marker for cardiovascular morbidity and mortality in patients with resistant hypertension, over and beyond traditional cardiovascular risk factors, including ambulatory blood pressure and left ventricular hypertrophy.

Epoxyeicosatrienoic acid prevents postischemic electrocardiogram abnormalities in an isolated heart model

Cytochrome P450 epoxygenases metabolize arachidonic acid (AA) to epoxyeicosatrienoic acids (EETs) which are in turn converted to dihydroxyeicosatrienoic acids (DHETs) by soluble epoxide hydrolase (sEH). The main objective of this study was to investigate the protective effects of EETs following ischemic injury using an ex vivo electrocardiogram (EKG) model. Hearts from C57Bl/6, transgenic mice with cardiomyocyte-specific overexpression of CYP2J2 (Tr) and wildtype (WT) littermates were excised and perfused with constant pressure in a Langendorff apparatus. Electrodes were placed superficially at the right atrium and left ventricle to assess EKG waveforms. In ischemic reperfusion experiments hearts were subjected to 20 min of global no-flow ischemia followed by 20 min of reperfusion (R20). The EKG from C57Bl/6 hearts perfused with 1 microM 14,15-EET showed less QT prolongation (QTc) and ST elevation (STE) (QTc=41+/-3, STE=2.3+/-0.3; R20: QTc=42+/-2 ms, STE=1.2+/-0.2mv) than control hearts (QTc=36+/-2, STE=2.3+/-0.2; R20: QTc=53+/-3 ms; STE=3.6+/-0.4mv). Similar results of reduced QT prolongation and ST elevation were observed in EKG recording from CYP2J2 Tr mice (QTc=35+/-1, STE=1.9+/-0.1; R20: QTc=38+/-4 ms, STE=1.3+/-0.2mv) compared to WT hearts. The putative epoxygenase inhibitor MS-PPOH (50 microM) and EET antagonist 14,15-EEZE (10 microM) both abolished the cardioprotective response, implicating EETs in this process. In addition, separate exposure to the K(ATP) channel blockers glibenclamide (1 microM) and HMR1098 (10 microM), or the PKA protein inhibitor H89 (50 nM) during reperfusion abolished the improved repolarization in both the models. Consistent with a role of PKA, CYP2J2 Tr mice had an enhanced activation of the PKAalpha regulatory II subunit in plasma membrane following IR injury. The present data demonstrate that EETs can enhance the recovery of ventricular repolarization following ischemia, potentially by facilitating activation of K(+) channels and PKA-dependent signaling.

Gender-specific effect of metabolic syndrome on rate adjusted QT interval in middle-aged participants of an atherosclerosis prevention program

INTRODUCTION

The metabolic syndrome is a matter of immense public concern for atherosclerosis prevention. Key features are visceral obesity, dyslipidemia, hyperglycemia in the non-diabetic range, and arterial hypertension. Subclinical atherosclerosis is the clinical consequence of metabolic syndrome, which may influence the QT interval. The aim was to investigate the rate corrected QT interval in subjects with metabolic syndrome in comparison to those without cardiometabolic risk factor clusters, and to explore gender differences in cardiac repolarization between the two groups.

PATIENTS, MATERIALS AND METHODS

Heart rate and QT interval were automatically measured from surface ECG in 1086 participants (767 men, 319 women) from the Salzburg-Atherosclerosis-Prevention-program-in-subjects-at-High-Individual-Risk (SAPHIR). To omit the QT adjustment bias inherent in Bazett's formula we used a QT adjustment method with linear scaling as described by Rautaharju.

RESULTS

The prevalence of metabolic syndrome was 13.8% among males and 10% among females. Mean rate adjusted QT (QTa) intervals were longer in women than in men. Presence of metabolic syndrome, however, was associated with significantly prolonged QTa only in men but not in women. Adjustment for relevant confounders reduced the difference of mean QTa in men from 9.24 to 5.83 ms (95% CI 0.9-10.8), but this difference was still statistically significant (p = 0.021). The effect of metabolic syndrome on QTa was only partly mediated by hypertension and insulin resistance. In females, however, no relevant differences were detected for QTa interval between subjects categorized by presence or absence of metabolic syndrome.

CONCLUSIONS

The findings indicate a significant association between metabolic syndrome and rate-invariant QT in middle-aged men after adjustment for other risk factors. QT measurement may provide additive diagnostic and prognostic information in populations undergoing cardiovascular risk screening. However, the effect of metabolic and hormonal factors on ventricular repolarization seems to differ between the sexes.

[QTc interval and traditional risk factors to atherosclerotic disease in patients with type 1 diabetes]

To evaluate the QTc interval and its relation with clinical, laboratorial variables and LDL susceptibility to in vitro oxidation in patients with type 1 DM, we studied 40 diabetics and 33 non diabetics with 24.83 +/- 10.21 and 23.51 +/- 7.28 years old, respectively matched by sex, age and body mass index (BMI). We evaluated metabolic control, A and B apolipoproteins, LDL oxidation coefficient for spectrophotometry and electrocardiogram (ECG). Interval QTc was calculated by the Bazetts formula. There was no difference in QTc between diabetic and non diabetic groups (394.43 +/- 19.98 ms versus 401.31 +/- 17.83 ms; p = 0.2065). Five diabetics showed increased QTc (396.76 +/- 14.63 ms versus 429.75 +/- 1.89 ms; p < 0.001) and lesser A apolipoprotein levels than rest of diabetic group (74.60 +/- 25.42 mg/dL versus 113.64 +/- 29.79 mg/dL; p = 0,011). In pooled sample, there was correlation between QTc and BMI (rho = -0.288; p = 0.045), pot-prandial glycemia (rho = 0.357; p = 0.016) and 3 h oxidation coefficient (OxC3h) (r = -0.293; p = 0.039). In diabetics, there was correlation between QTc and triglycerides (rho = -0.420; p = 0.023) and OxC3h (r = -0.427; p = 0.021). Although there was no difference between QTc of diabetics and the non diabetics subjects studied, there was correlation with risk factors for the atherosclerotic disease. Further studies are necessary to establish the real predictive value of QTc for this type of disease in the patients with type 1 DM.

Genetic determinants of vascular remodelling

Vascular remodelling is an important physiological mechanism that occurs as a result of changes in hemodynamics, and is a pathological process that plays a major role in the clinical manifestations of cardiovascular diseases. Using a mouse model, it was recently established that vascular remodelling is partially based on ligation of the carotid. In this model, low flow was associated with intima media thickening (IMT). IMT is a major manifestation of atherosclerosis of the carotid artery, and it is an important predictor of cardiovascular events. Carotid IMT has a strong genetic component. It was hypothesized that there would be genetically determined differences in outward remodelling and IMT induced by carotid flow alterations. Vascular remodelling among five inbred strains of mice were compared. Despite similar changes in flow in the left carotid among the strains, dramatic differences in remodelling of the partially ligated left carotid relative to control were observed. IMT correlated significantly with heart rate, outward remodelling and changes in plasminogen activator expression, cell proliferation and apoptosis. There were significant strain-dependent differences in the remodelling index (measured as the ratio of vessel area to IMT), which suggest fundamental alterations in sensing or transducing hemodynamic signals among strains. This model should be useful to identify and characterize the role of genes that mediate vascular remodelling.

Subclinical coronary atherosclerosis and resting ECG abnormalities in an unselected general population

OBJECTIVES

Exposure to cardiovascular (CV) risk factors may result in coronary atherosclerosis and myocardial disease, which is reflected in the extent of coronary artery calcification (CAC) and resting ECG abnormalities, respectively. We studied the association of CAC with ECG abnormalities in a general population without myocardial infarction or revascularization.

METHODS

The total cohort of 4814 subjects (45-75 years) were randomly selected from the general population for the Heinz Nixdorf Recall Study, an ongoing study designed to assess the prognostic value of modern risk stratification methods. In addition to measuring standard risk factors, digitized resting ECGs and the EBT-based Agatston score were obtained. Subjects were separated into those without (n=1929) and with CV disease (CVD) or treated risk factors (tRF) (n=2558).

RESULTS

In both groups, a positive CAC-score was more frequent and CAC-scores were higher in men and women with ECG abnormalities as compared to those with normal ECGs (p<0.05 each). In persons without CVD/tRF, a CAC > or =75th percentile was more frequent in those with LVH (42.4%) and QTc >440 ms (34.2%) as compared to normal ECGs (23.0%, p<0.01 for both). In persons with CVD/tRF, a CAC-score > or =75th percentile was found in subjects with A-Fib (46.3%), borderline-LVH (39.1%), ECG signs of MI (40.5%) and major ECG abnormalities (40.3%) versus 31.2% in those with normal ECGs (p<0.03 for all). In multivariate analysis, LVH (p=0.025) and major ECG abnormalities (p=0.04) remained independently associated with CAC in subjects without and with CVD/tRF, respectively.

CONCLUSIONS

ECG-based evidence of myocardial disease is often associated with an elevated CAC burden, suggesting a link between epicardial and myocardial manifestations of risk factor exposure. The association of CAC burden with different ECG abnormalities in different clinical groups may have implications for the interpretation of the resting ECG and CAC burden in risk stratification.

Short- and long-term prognostic value of the corrected QT interval in the non–ST-elevation acute coronary syndrome

BACKGROUND AND PURPOSE

Myocardial ischemia prolongs the QTc interval. Very little data exists about its prognostic implications in the non-ST-elevation acute coronary syndromes (NST-ACS).

METHODS

This is and observational and prospective study in which we evaluated the prognostic implications of the QTc obtained at admission (AQTc) in the short- and long-term of the NST-ACS. The median of the follow-up was 17 months.

RESULTS

AQTc correlated adequately with the incidence of adverse events in the short- and long-term (P < .001), with the best cut-off point in 450 milliseconds. Patients with AQTc > or =450 presented higher frequency of in-hospital death: 8.8% vs 1.2%; P = .001, and MACE (death, recurrent ischemia, or urgent coronary revascularization): 72% vs 25%; P < .001. In a Cox regression analysis, we found 3 independent predictors of cardiovascular death after discharge: AQTc > or =450 (14.7% vs 2.1%; P < .0001), age >65 years and left ventricular ejection fraction <40%. Coronary revascularization reduced the risk of posthospitalary cardiovascular death in AQTc > or =450 milliseconds (5% vs 24%; P < .0001) but had no significant effect in AQTc<450 milliseconds.

CONCLUSION

These findings provide a new evidence supporting the prognostic value of the AQTc in predicting unfavorable events in the short- and long-term of the NST-ACS.

Insular involvement in brain infarction increases risk for cardiac arrhythmia and death

OBJECTIVE

Brain injuries may induce cardiac dysrhythmias and sudden cardiac death.

METHODS

We analyzed 12-lead electrocardiograms of 493 consecutive patients with brain infarction (BI) proved by an magnetic resonance imaging and 493 control subjects matched for age, sex, and center. Insular involvement (insula (+/-)) was assessed by two independent readings of the magnetic resonance imaging scans. Cases were followed for 5 years.

RESULTS

Acute BI was independently associated with heart rate (< or = 64 beats/min), abnormal repolarization, atrial fibrillation, and ventricular and supraventricular ectopic beats. Lower heart rate in BI patients was due to an interaction with smoking (p for interaction = 0.004). Insula(+) group was significantly associated with abnormal repolarization with no interaction with infarct side. Atrial fibrillation by history was also more frequent in the insula(+) than in the insula(-) group (p = 0.07). After adjustment for age, sex, cardiovascular history, and handicap at admission, right insula(+) BI was significantly associated with 2-year all-cause death (hazard ratio, 2.11; 95% confidence interval, 1.27-3.52) and with vascular death (hazard ratio, 2.00; 95% confidence interval, 1.00-3.93). In multivariate analysis including age, sex, cardiovascular history, handicap at admission, and lesion side, increased QTc interval and left bundle branch block were independent predictors of all-cause and vascular mortality at 2 years in right insula(+) patients.

INTERPRETATION

These findings support the notion that right insular involvement may lead to electrocardiographic abnormalities with potential prognostic implications. This could be important for optimal care in patients with right insular infarct.

QTc interval and survival in 75-year-old men and women from the general population

AIMS

The study concerns the relationship of the corrected QT (QTc) interval to 6.4 years of survival and to measures of cardiac function, such as echocardiographic variables and plasma levels of brain natriuretic peptide (BNP), in 75-year-old people.

METHODS AND RESULTS

QTc was measured in a 12-lead electrocardiogram (ECG) in 210 men and 223 women, comprising a randomly selected sample from the general population (70% participation rate). The Sicard 440/740 computer-analysis program, with Hodges' formula for heart rate-based QT correction, was used. The optimal cut-off point for predicting survival according to the receiver operating characteristic curve was found between 429 and 430 ms. Individuals with a QTc interval of > or =430 ms (n = 115) had decreased survival when compared with those with shorter QTc interval (n = 318); the relative risk was 2.4 (95% confidence interval 1.5-3.7). The predictive ability of QTc reflects an association between QTc and the following variables: BNP, left ventricular mass, and left ventricular ejection fraction (but not diastolic filling patterns). Both Hodges' and Bazett's formulae for heart rate correction of the QT interval were useful for predicting survival. The median QTc was 415 ms using Hodges' formula and 430 ms with Bazett's formula. The QRS component of QTc predicted survival better than the rest of the QTc interval and was approximately as useful as the QTc interval itself.

CONCLUSION

The computer-derived QTc obtained from the ordinary 12-lead ECG identifies high-risk individuals among elderly people from the general population.

Relationship between QT interval and cardiovascular risk factors in healthy young subjects

A prolongation of QT interval increases the risk for coronary heart disease, ventricular arrhythmias, and sudden death in diabetic patients, after myocardial infarction, and in the elderly. An association between QT prolongation and cardiovascular risk factors has been demonstrated in middle-aged and elderly subjects. Aims of this study were to evaluate the prevalence of a prolonged corrected QT interval (QTc) in a healthy young population (n=170, age 22-25 years, 84 males) and to investigate the association of QTc and QT dispersion (QTd) with cardiovascular risk factors (body mass index, blood pressure, fasting blood glucose and cholesterol, smoking habits, and hypertensive familiarity). A prolonged QTc was observed in 10% of female and 5% of male subjects; in multiple regression analysis, QTc showed a significant positive relationship with blood glucose in females (P=0.04) and systolic blood pressure in male subjects (P=0.03), while QTd was not significantly related with any of the factors. In conclusion, the association between QTc length, glucose levels, and blood pressure is present also in young healthy subjects. QT measurement may represent a useful marker in the screening of young subjects for cardiovascular prevention. Journal of Human Hypertension (2005) 19, 623-627. doi:10.1038/sj.jhh.1001874; published online 19 May 2005.

Free Fatty Acids, Insulin Resistance, and Corrected QT Intervals in Morbid Obesity: Effect of Weight Loss During 6 Months With Differing Dietary Interventions

OBJECTIVE

To assess whether shortening of the corrected QT (QTc) interval is most closely associated with changes in weight, insulin resistance, or free fatty acids (FFAs) (or some combination of these factors).

METHODS

We randomized 75 severely obese subjects without diabetes to either a low-carbohydrate or a conventional low-fat weight-loss diet for 6 months. We measured QTc, insulin sensitivity, body mass index, and FFAs at baseline and at 6 months. Analysis was performed to determine whether improvement in weight, in insulin resistance, or in FFAs has the greatest effect on reducing the QTc interval.

RESULTS

"Completers" of both the low-carbohydrate diet (N = 25) and the low-fat diet (N = 22) had a decrease in weight, but the weight loss was greater in the low-carbohydrate group. A statistically significant decrease in QTc from baseline was observed only in the low-carbohydrate group. QTc in the low-carbohydrate group correlated with improvement in insulin resistance, but this finding was not significant after correction for the greater weight loss. FFAs or weight loss was not correlated with QTc in either dietary group.

CONCLUSION

Low-carbohydrate dieting is associated with a greater decrease in the QTc interval in comparison with low-fat dieting. Improvements in insulin resistance seem to have a relatively weak mechanistic role, and a decrease in FFAs has no apparent role in the reduction of the QTc interval.

Relationship of QT interval duration with carotid intima media thickness in a clinically healthy population undergoing cardiovascular risk screening

OBJECTIVES

To investigate the relationship between cardiac repolarization (QT interval duration) and intima media thickness (IMT) of the carotid arteries as surrogate measures of subclinical atherosclerosis.

DESIGN

Prospective study with consecutive subjects enrolled in the SAPHIR program (Salzburg Atherosclerosis Prevention Program in Subjects at High Individual Risk).

SETTING

The analysis of the material was performed at the departments of medicine and neurology of a university hospital.

SUBJECTS

The study cohort comprises a population-based sample of 1199 clinically healthy subjects (851 men and 348 women; age 39-66 years). Exclusion criteria were cardiovascular disease, diabetes, atrial fibrillation, bundle branch block and use of medication affecting QT interval duration.

MAIN OUTCOME MEASURES

IMT of common (CCA) and internal carotid arteries (ICA) was measured by B-mode ultrasound. QT interval duration was determined in the resting 12-lead electrocardiogram by an automatic analysis program. The QT intervals were corrected for heart rate with five standard equations (QTc-Bazett, -Fridericia, -Framingham, -Hodges and -Rautaharju) and tested for their relationship with carotid IMT after adjustment for clinical and metabolic variables. Results. Females had higher heart rates than males (64 +/- 10 b min(-1) vs. 60 +/- 9 b min(-1), P <0.0005), with longer mean QT (410 +/- 28 ms vs. 404 +/- 28 ms, P=0.003) and QTc intervals in all correction formulae (P <0.0005). Significant correlations between QT/QTc and ICA IMT (r=0.14-0.16) were found in males. In the general linear model the association between QTc (except for Bazett) and ICA IMT remained significant after adjusting for age, BMI and further cardiovascular risk factors. In females the crude correlations between QT/QTc and ICA IMT were lower than those with CCA IMT. Only the correlation between uncorrected QT and CCA IMT (r=0.15, P=0.006) remained significant after adjustment for covariates.

CONCLUSIONS

The results of the present study demonstrate that QT and QTc prolongation are in part associated with IMT of carotid arteries, which is an established risk marker of subclinical atherosclerosis. In men the data support the hypothesis of an association between QTc and ICA IMT. In women a statistically significant relationship was found between the uncorrected QT interval and CCA IMT. These findings suggest that differences in carotid IMT and ventricular repolarization between genders might be related to hormonal and nonhormonal effects.

Association between the corrected QT intervals and combined intimal-medial thickness of the carotid artery in patients with type 2 diabetes

The main purpose of this study was to determine whether cardiac autonomic neuropathy or coronary atherosclerosis is the more important factor affecting prolongation of the corrected QT interval (QTc) in patients with type 2 diabetes. We studied the association between QTc and the coefficient of variance of the heart rate variation (CV(RR)), which reflects cardiac autonomic neuropathy, and the combined intimal-medial thickness (IMT) of the common carotid artery, which reflects coronary atherosclerosis. In addition, we also investigated the relationship between the QTc and blood pressure, serum lipid concentrations, hemoglobin A(1C) (HbA(1C)) concentration, and duration of diabetes. We studied 75 patients with type 2 diabetes and 30 age-matched healthy individuals. The QT interval was measured in lead II of the electrocardiogram (ECG) and was corrected using Bazett's formula. Cardiac neuropathy was assessed by measuring CV(RR). Atherosclerosis was evaluated by measuring the combined IMT of the common carotid artery using B-mode ultrasonography. The QTc in patients with type 2 diabetes was significantly longer than in healthy individuals (P <.0001). The QTc more closely correlated with the IMT of the carotid artery (r = 0.7206, P <.0001), compared with CV(RR) (r = -0.3188, P =.0053), although both were statistically significant. The QTc also correlated positively with the systolic (SBP) and diastolic blood pressure (DBP) (r = 0.4371, P <.0001, r = 0.3632, P =.0014, respectively). Based on stepwise regression analysis with the QTc interval as the dependent variable, the IMT of the carotid artery had the most significant association with the QTc (beta = 0.6882, P =.0004). In conclusion, QTc prolongation in the setting of diabetes might be caused primarily by coronary atherosclerosis rather than by cardiac autonomic neuropathy.

Heart rate-corrected QT interval prolongation predicts risk of coronary heart disease in black and white middle-aged men and women: the ARIC study

OBJECTIVES

We aimed to study the predictive value of heart rate-corrected QT interval (QTc) for incident coronary heart disease (CHD) and cardiovascular disease (CVD) mortality in the black and white general population, and to validate various QT measurements.

BACKGROUND

QTc prolongation is associated with higher risk of mortality in cardiac patients and in the general population. Little is known about the association with incident CHD. No previous studies included black populations.

METHODS

We studied the predictive value of QTc prolongation in a prospective population study of 14,548 black and white men and women, age 45 to 64 year. QT was determined by the NOVACODE program in the digital electrocardiogram recorded at baseline.

RESULTS

In quintiles of QTc, cardiovascular risk profile deteriorated with longer QTc, and risk of CHD and CVD mortality increased. The high risk in the upper quintile was mostly explained by the 10% with the longest QTc. The age-, gender-, and race-adjusted hazard ratios for CVD mortality and CHD in subjects with the longest 10% relative to the other 90% of the gender-specific QTc distribution were 5.13 (95% confidence interval 3.80 to 6.94) and 2.14 (95% confidence interval 1.71 to 2.69), respectively. The increased risk was partly, but not completely, attributable to other risk factors or the presence of chronic disease. The association was stronger in black than in white subjects. Manual- and machine-coded QT intervals were highly correlated, and the method of rate correction did not affect the observed associations.

CONCLUSIONS

Long QTc is associated with increased risk of CHD and CVD mortality in black and white healthy men and women.