QTc interval prolongation is a predictor of future strokes in patients with type 2 diabetes mellitus

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.

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.

Fluoxetine Treatment Decreases Cardiac Vagal Input and Alters the Serotonergic Modulation of the Parasympathetic Outflow in Diabetic Rats

Comorbid diabetes and depression constitutes a major health problem, worsening associated cardiovascular diseases. Fluoxetine's (antidepressant) role on cardiac diabetic complications remains unknown. We determined whether fluoxetine modifies cardiac vagal input and its serotonergic modulation in male Wistar diabetic rats. Diabetes was induced by alloxan and maintained for 28 days. Fluoxetine was administered the last 14 days (10 mg/kg/day; p.o). Bradycardia was obtained by vagal stimulation (3, 6 and 9 Hz) or i.v. acetylcholine administrations (1, 5 and 10 μg/kg). Fluoxetine treatment diminished vagally-induced bradycardia. Administration of 5-HT originated a dual action on the bradycardia, augmenting it at low doses and diminishing it at high doses, reproduced by 5-CT (5-HT_1/7 agonist). 5-CT did not alter the bradycardia induced by exogenous acetylcholine. Decrease of the vagally-induced bradycardia evoked by high doses of 5-HT and 5-CT was reproduced by L-694,247 (5-HT_1D agonist) and blocked by prior administration of LY310762 (5-HT_1D antagonist). Enhancement of the electrical-induced bradycardia by 5-CT (10 μg/kg) was abolished by pretreatment with SB269970 (5-HT₇ receptor antagonist). Thus, oral fluoxetine treatment originates a decrease in cardiac cholinergic activity and changes 5-HT modulation of bradycardic responses in diabetes: prejunctional 5-HT₇ receptors augment cholinergic-evoked bradycardic responses, whereas prejunctional 5-HT_1D receptors inhibit vagally-induced bradycardia.

Exercise Training Attenuates the Development of Cardiac Autonomic Dysfunction in Diabetic Rats

BACKGROUND/AIM

Exercise training usually complements pharmacological therapy of type 1 diabetes mellitus, however, little is known about its impact on cardiac autonomic neuropathy. Our aim was to evaluate the impact of exercise on electrocardiographic parameters and heart rate variability in diabetic rats.

MATERIALS AND METHODS

Wistar rats were randomly assigned to four groups (n=12): Sedentary control (SC), sedentary diabetic (SD), exercise control (EC), and exercise diabetic (ED). Diabetes was induced by a single intraperitoneal injection of streptozotocin (45 mg/kg). Exercise groups underwent 8 weeks of training on a treadmill. At the end of the study, echocardiography was performed and continuous electrocardiographic recording was obtained by intra-abdominally implanted telemetric devices. Diabetes induction significantly reduced the heart rate and increased the blood glucose level (p<0.001) and R-wave amplitude (p<0.05). Frequency-domain spectral variables were also analyzed. The SD group had a significantly lower absolute high-frequency component (p<0.05) and higher normalized low-frequency component, as well as low-frequency power divided by the high-frequency power ratio when compared to the SC and EC groups (p<0.05). All these diabetes-related adverse changes in heart rate variability parameters were significantly reversed by exercise training (p<0.05). Overall, our study shows that early initiation of systemic exercise training prevents the development of cardiac autonomic neuropathy in rats with type 1 diabetes mellitus, by favorable change in the balance between parasympathetic and sympathetic activity.

The Effects of Trimetazidine on QT-interval Prolongation and Cardiac Hypertrophy in Diabetic Rats

Background

Trimetazidine (TMZ) is an anti-ischemic drug. In spite of its protective effects on cardiovascular system, there is no scientific study on the usefulness of TMZ treatment for prolonged QT interval and cardiac hypertrophy induced by diabetes.

Objectives

To evaluate the effects of TMZ on QT interval prolongation and cardiac hypertrophy in the diabetic rats.

Methods

Twenty-four male Sprague-Dawley rats (200-250 g) were randomly assigned into three groups (n = 8) by simple random sampling method. Control (C), diabetic (D), and diabetic administrated with TMZ at 10 mg/kg (T10). TMZ was administrated for 8 weeks. The echocardiogram was recorded before isolating the hearts and transfer to a Langendorff apparatus. Hemodynamic parameters, QT and corrected QT interval (QTc) intervals, heart rate and antioxidant enzymes were measured. The hypertrophy index was calculated. The results were evaluated by one-way ANOVA and paired t-test using SPSS (version 16) and p < 0.05 was regarded as significant.

Results

The diabetic rats significantly indicated increased hypertrophy, QT and QTc intervals and decreased Left ventricular systolic pressure (LVSP), Left ventricular developed pressure (LVDP), rate pressure product (RPP), Max dp/dt, and min dp/dt (±dp/dt max), heart rate, superoxide dismutase (SOD), glutathione peroxidase (GPx) and catalase in the heart. Treatment with TMZ in the diabetic animals was significantly improved these parameters in comparison to the untreated diabetic group.

Conclusions

TMZ improves QTc interval prolongation and cardiac hypertrophy in diabetes.

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.

Monoamine oxidase-A is an important source of oxidative stress and promotes cardiac dysfunction, apoptosis, and fibrosis in diabetic cardiomyopathy

Oxidative stress is closely associated with the pathophysiology of diabetic cardiomyopathy (DCM). The mitochondrial flavoenzyme monoamine oxidase A (MAO-A) is an important source of oxidative stress in the myocardium. We sought to determine whether MAO-A plays a major role in modulating DCM. Diabetes was induced in Wistar rats by single intraperitoneal injection of streptozotocin (STZ). To investigate the role of MAO-A in the development of pathophysiological features of DCM, hyperglycemic and age-matched control rats were treated with or without the MAO-A-specific inhibitor clorgyline (CLG) at 1 mg/kg/day for 8 weeks. Diabetes upregulated MAO-A activity; elevated markers of oxidative stress such as cardiac lipid peroxidation, superoxide dismutase activity, and UCP3 protein expression; enhanced apoptotic cell death; and increased fibrosis. All these parameters were significantly attenuated by CLG treatment. In addition, treatment with CLG substantially prevented diabetes-induced cardiac contractile dysfunction as evidenced by decreased QRS, QT, and corrected QT intervals, measured by ECG, and LV systolic and LV end-diastolic pressure measured by microtip pressure transducer. These beneficial effects of CLG were seen despite the persistent hyperglycemic and hyperlipidemic environments in STZ-induced experimental diabetes. In summary, this study provides strong evidence that MAO-A is an important source of oxidative stress in the heart and that MAO-A-derived reactive oxygen species contribute to DCM.

The association of the QT interval with atrial fibrillation and stroke: the Multi-Ethnic Study of Atherosclerosis

BACKGROUND

Prolongation of the QT interval is associated with an increased risk of atrial fibrillation (AF) and stroke.

OBJECTIVES

The purpose of this analysis was to determine if AF explains the association between prolonged QT and stroke.

METHODS

A total of 6305 participants (mean age 62 ± 10 years; 54% women; 38% whites; 27% blacks; 23% Hispanics; 12% Chinese-Americans) from the Multi-Ethnic Study of Atherosclerosis (MESA) were included in this analysis. A linear scale was used to compute heart rate-adjusted QT (QT(a)). Prolonged QT(a) was defined as ≥ 460 ms in women and ≥ 450 ms in men. Incident AF cases were identified using hospital discharge records and Medicare claims data. Vascular neurologists adjudicated stroke events by medical record review. Cox regression was used to examine the association between prolonged QT(a) and stroke with and without AF.

RESULTS

A total of 216 (3.4%) of study participants had prolonged QT(a). Over a median follow-up of 8.5 years, 280 (4.4%) participants developed AF and 128 (2.0%) participants developed stroke. In a multivariable Cox regression analysis adjusted for socio-demographics, cardiovascular risk factors, and potential confounders, prolonged QT(a) was associated with an increased risk of AF (HR = 1.7, 95% CI 1.1, 2.6) and stroke (HR = 2.3, 95% CI 1.3, 4.1). When AF was included as a time-dependent covariate, the association between prolonged QT(a) and stroke was not substantively altered (HR = 2.4, 95% CI 1.3, 4.3).

CONCLUSION

The increased risk of stroke in those with prolonged QT potentially is not explained by documented AF. Further research is needed to determine if subclinical AF explains the association between the QT interval and stroke.

Prolonged QTc Interval Predicts Poststroke Paroxysmal Atrial Fibrillation

Background and Purpose—

Paroxysmal atrial fibrillation (PAF) is often difficult to detect in patients with acute ischemic stroke. We aimed to assess the predictive value of a prolonged QT interval corrected for heart rate (QTc) in PAF detection after acute ischemic stroke.

Methods—

We enrolled 972 patients with acute ischemic stroke consecutively extracted from our observational stroke registry system. Exclusion criteria were as follows: (1) AF on the initial 12-lead ECG (n=171); (2) previously diagnosed PAF (n=47); and (3) the use of a cardiac pacemaker (n=10). Of the 972 patients, 744 (mean age, 67.6 years; men, 62.6%) were eligible for analysis. The clinical characteristics and 12-lead ECG findings of the patients with and without PAF were compared, and multiple logistic regression analysis was performed to identify predictors of poststroke PAF.

Results—

The poststroke cardiac work-up yielded 69 (9.3%) de novo PAF cases among the 744 patients. The QTc interval was significantly longer in patients with PAF than in those without PAF (436 versus 417 ms; P <0.001). Each 10-ms increase in the QTc interval was associated with an increased risk of PAF after multivariate adjustments (odds ratio, 1.41; 95% confidence interval, 1.24–1.61; P <0.001). The optimal threshold value of QTc interval calculated by a receiver-operating characteristic curve was 438 ms, and the area under the curve was 0.73 in this data set.

Conclusions—

The QTc interval prolongation is potentially a strong and useful predictor for poststroke PAF.

Prolonged corrected QT interval is predictive of future stroke events even in subjects without ECG-diagnosed left ventricular hypertrophy

We attempted to evaluate whether subjects who exhibit prolonged corrected QT (QTc) interval (≥440 ms in men and ≥460 ms in women) on ECG, with and without ECG-diagnosed left ventricular hypertrophy (ECG-LVH; Cornell product, ≥244 mV×ms), are at increased risk of stroke. Among the 10 643 subjects, there were a total of 375 stroke events during the follow-up period (128.7±28.1 months; 114 142 person-years). The subjects with prolonged QTc interval (hazard ratio, 2.13; 95% confidence interval, 1.22-3.73) had an increased risk of stroke even after adjustment for ECG-LVH (hazard ratio, 1.71; 95% confidence interval, 1.22-2.40). When we stratified the subjects into those with neither a prolonged QTc interval nor ECG-LVH, those with a prolonged QTc interval but without ECG-LVH, and those with ECG-LVH, multivariate-adjusted Cox proportional hazards analysis demonstrated that the subjects with prolonged QTc intervals but not ECG-LVH (1.2% of all subjects; incidence, 10.7%; hazard ratio, 2.70, 95% confidence interval, 1.48-4.94) and those with ECG-LVH (incidence, 7.9%; hazard ratio, 1.83; 95% confidence interval, 1.31-2.57) had an increased risk of stroke events, compared with those with neither a prolonged QTc interval nor ECG-LVH. In conclusion, prolonged QTc interval was associated with stroke risk even among patients without ECG-LVH in the general population.

Sudden cardiac death and diabetes mellitus

Sudden cardiac death (SCD) affects a significant percentage of diabetic patients. SCD in these patients can be due to several factors, such as diastolic dysfunction, heart failure, altered platelet function, inflammation, sympathetic nervous stimulation and other factors. In the present review, we discuss the association between diabetes mellitus and SCD.

QTc-prolongation in posterior circulation stroke

BACKGROUND AND PURPOSE

To evaluate the relationship between infarct location and QTc-prolongation in patients with posterior circulation strokes.

METHODS

Admission electrocardiograms (ECG) of 131 patients among a prospective sample of 407 consecutive adult patients in the New England Medical Center Posterior Circulation Registry were retrospectively analyzed. The QT interval (ms) was measured and corrected using Bazett's formula (QTcBazett) as well as linear regression functions (QTcLinear). QTcBazett > 440 ms and QTcLinear ≥ 450 ms for men (≥460 ms for women) were considered prolonged. Multivariable linear and logistic regression analyses were used to identify independent predictors of the QTc.

RESULTS

Overall, 34% of patients had a prolonged QTcBazett and 7% had a prolonged QTcLinear noted on the admission ECG. There was a significant association between temporal lobe infarction and QTcBazett and QTcLinear (p < 0.001 for both) in multivariable linear regression analyses adjusting for demographics, ECG parameters, and preadmission medication use. In multivariable logistic regression analysis, temporal lobe infarction emerged as an independent predictor of prolonged QTcBazett (p = 0.009) and QTcLinear (p = 0.008), respectively. Sensitivity analyses excluding patients with transient ischemic attack yielded similar results. Exploratory analyses indicated that patients with temporal lobe infarction had worse functional 30-day outcomes in multivariable logistic regression (p = 0.022). However, there was no significant association between QTc and 30-day functional outcome.

CONCLUSIONS

QTc-prolongation is common after posterior circulation stroke and associated with temporal lobe infarction. Prospective studies are needed to confirm these preliminary findings and to examine potential long-term consequences.

The absence of insulin signaling in the heart induces changes in potassium channel expression and ventricular repolarization

Diabetes mellitus increases the risk for cardiac dysfunction, heart failure, and sudden death. The wide array of neurohumoral changes associated with diabetes pose a challenge to understanding the roles of specific pathways that alter cardiac function. Here, we use a mouse model with cardiomyocyte-restricted deletion of insulin receptors (CIRKO, cardiac-specific insulin receptor knockout) to study the specific effects of impaired cardiac insulin signaling on ventricular repolarization, independent of the generalized metabolic derangements associated with diabetes. Impaired insulin action caused a reduction in mRNA and protein expression of several key K(+) channels that dominate ventricular repolarization. Specifically, components of transient outward K(+) current fast component (Ito,fast; Kv4.2 and KChiP2) were reduced, consistent with a reduction in the amplitude of Ito,fast in isolated left ventricular CIRKO myocytes, compared with littermate controls. The reduction in Ito,fast resulted in ventricular action potential prolongation and prolongation of the QT interval on the surface ECG. These results support the notion that the lack of insulin signaling in the heart is sufficient to cause the repolarization abnormalities described in other animal models of diabetes.

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.

Probable quetiapine-mediated prolongation of the QT interval

PURPOSE

QT prolongation can occur with both first- (FGA) and second-generation antipsychotics (SGA). QT prolongation was identified in an adult patient who presented to the emergency room with schizophrenia, fluid and electrolyte imbalances, and pneumonia. Quetiapine, an SGA, was a component of the pharmacotherapy regimen. Based on the Naranjo adverse drug reaction probability scale rating criteria, a probable causal association was made.

METHODS

PubMed and Ovid were searched using the terms antipsychotic, psychotropic, QT interval, corrected QT interval (QTc) prolongation, and quetiapine. References were examined for additional articles related to antipsychotic drugs and the QT interval.

DISCUSSION

In this patient, the use of quetiapine was identified as a contributing factor in QT prolongation. Prior QT prolongation was experienced with ziprasidone, another SGA. The antidepressant and dose remained consistent throughout the inpatient course of treatment. Other risk factors in this patient included hypokalemia, dehydration, pneumonia, age, gender, and concurrent usage of an antidepressant. Dual psychiatric diagnoses, preexisting cardiovascular disease, and electrolyte disturbances may increase this risk potential.

CONCLUSION

Psychiatric patients may be more at risk of cardiovascular complications, such as QT interval prolongation. The pharmacist can help evaluate risk factors and provide input into the care of all patients, particularly those identified as at risk.

Electrocardiographic changes with the onset of diabetes and the impact of aerobic exercise training in the Zucker Diabetic Fatty (ZDF) rat

BACKGROUND

Early markers of diabetic autonomic neuropathy (DAN) in an electrocardiogram (ECG) include elevated R wave amplitudes, widening of QTc intervals and decreased heart rate variability (HRV). The severity of DAN has a direct relationship with mortality risk. Aerobic exercise training is a common recommendation for the delay and possible reversal of cardiac dysfunction. Limited research exists on ECG measures for the evaluation of aerobic exercise training in Zucker Diabetic Fatty (ZDF) rat, a model of type 2 diabetes. The objective of this study was to assess whether aerobic exercise training may attenuate diabetes induced ECG changes.

METHODS

Male ZDF (obese fa/fa) and control Zucker (lean fa/+) rats were assigned to 4 groups: sedentary control (SC), sedentary diabetic (SD), exercised control (EC) and exercised diabetic (ED). The exercised groups began 7 weeks of treadmill training after the development of diabetes in the ED group. Baseline (prior to the training) and termination measurements included body weight, heart weight, blood glucose and glycated hemoglobin levels and ECG parameters. One way repeated measures ANOVA (group) analyzed within and between subject differences and interactions. Pearson coefficients and descriptive statistics described variable relationships and animal characteristics.

RESULTS

Diabetes caused crucial changes in R wave amplitudes (p < 0.001), heart rate variability (p < 0.01), QT intervals (p < 0.001) and QTc intervals (p < 0.001). R wave amplitude augmentation in SD rats from baseline to termination was ameliorated by exercise, resulting in R wave amplitude changes in ED animals similar to control rats. Aerobic exercise training neither attenuated QT or QTc interval prolongation nor restored decreases in HRV in diabetic rats.

CONCLUSION

This study revealed alterations in R wave amplitudes, HRV, QT and QTc intervals in ZDF rats. Of these changes, aerobic exercise training was able to correct R wave amplitude changes. In addition, exercise has beneficial effect in this diabetic rat model in regards to ECG correlates of left ventricular mass.

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.

Determinants of prolonged QT interval and their contribution to sudden death risk in coronary artery disease: the Oregon Sudden Unexpected Death Study

BACKGROUND

In a recent cohort study, prolongation of the corrected QT interval (QTc) was associated with an independent increased risk of sudden cardiac death (SCD). We evaluated determinants of prolonged QTc and the relationship of prolonged QTc to SCD risk among patients with coronary artery disease in the general population.

METHODS AND RESULTS

A case-control design was used. Cases were SCD patients with coronary artery disease among a metropolitan area of 1 000 000 residents (2002 to 2006); controls were area residents with coronary artery disease but no history of SCD. All cases were required to have an ECG suitable for QTc analysis before and unrelated to the occurrence of SCD. A total of 373 cases and 309 controls met criteria for analysis. Mean QTc was significantly longer in cases than in controls (450+/-45 versus 433+/-37 ms; P<0.0001). In a multivariate model, gender, diabetes mellitus, and QTc-prolonging drugs were significant determinants of QTc prolongation in controls. In a logistic regression model predicting SCD, diabetes mellitus (odds ratio, 1.97; 95% confidence interval, 1.32 to 2.96) and use of QTc-prolonging drugs (odds ratio, 2.90; 95% confidence interval, 1.92 to 4.37) were significant predictors of SCD among subjects with normal or borderline QTc. However, abnormally prolonged QTc in the absence of diabetes and QT-prolonging medications was the strongest predictor of SCD (odds ratio, 5.53; 95% confidence interval, 3.20 to 9.57).

CONCLUSIONS

Diabetes mellitus and QTc-affecting drugs determined QTc prolongation and were predictors of SCD in coronary artery disease. However, idiopathic abnormal QTc prolongation was associated with 5-fold increased odds of SCD. A continued search for novel determinants of QTc prolongation such as genomic factors is likely to enhance risk stratification for SCD in coronary artery disease.

Epidemiology of sudden cardiac death: clinical and research implications

The current annual incidence of sudden cardiac death in the United States is likely to be in the range of 180,000 to 250,000 per year. Coinciding with the decreased mortality from coronary artery disease, there is evidence pointing toward a significant decrease in rates of sudden cardiac death in the United States during the second half of the 20th century. However, the alarming rise in prevalence of obesity and diabetes in the first decade of the new millennium both in the United States and worldwide, would indicate that this favorable trend is unlikely to persist. We are likely to witness a resurgence of coronary artery disease and heart failure, as a result of which sudden cardiac death will have to be confronted as a shared and indiscriminate, worldwide public health problem. There is also increasing recognition of the fact that discovery of meaningful and relevant risk stratification and prevention methodologies will require careful prospective community-wide analyses, with access to large archives of DNA, serum, and tissue that link with well-phenotyped databases. The purpose of this review is to summarize current knowledge of sudden cardiac death epidemiology. We will discuss the significance and strengths of community-wide evaluations of sudden cardiac death, summarize recent observations from such studies, and finally highlight specific potential predictors that warrant further evaluation as determinants of sudden cardiac death in the general population.

Sudden cardiac death: influence of diabetes

This article reviews current thinking on the problem of sudden cardiac death (SCD) within community settings, highlighting progress in understanding risks and mechanisms. Information available on the influence of diabetes as a risk factor for SCD and the question of whether this disease enhances susceptibility to ventricular arrhythmias is summarized as are central strategies in risk stratification and mortality prevention.

Cardiac autonomic neuropathy in diabetes mellitus: prevalence, risk factors and utility of corrected QT interval in the ECG for its diagnosis

OBJECTIVES

To study the prevalence and risk factors for cardiac autonomic neuropathy (CAN) and the utility of prolongation of corrected QT interval (QTc) in the ECG to diagnose CAN in patients with diabetes mellitus.

DESIGN AND SETTING

Cross-sectional study conducted among patients attending the diabetic clinic of a teaching hospital.

METHODS

The prevalence of CAN among 100 patients with type 1 and type 2 diabetes mellitus was assessed by the five autonomic function tests by Eving's methodology. The CAN score in each patient and its relationship to the QTc interval were analysed. Possible influences of age, duration of diabetes and coexistent peripheral neuropathy on the occurrence of CAN also were studied.

RESULTS

The prevalence of CAN was 60%. Univariate analysis showed a significant association between CAN and higher age (odds ratio (OR) 15.75), prolongation of QTc (OR 5.55), duration of disease over 10 years (OR 2) and peripheral neuropathy (p<0.001) in patients with type 1 diabetes. Significant risks for CAN among patients with type 2 diabetes were coexistent peripheral neuropathy (OR 14), prolonged QTc (OR 9.75), higher age (OR 7.2) and disease duration over 10 years (OR 1.92) in univariate analysis, but none of them showed independent risk in multivariate analysis. Disease duration over 10 years resulted in QTc prolongation in a significant numbers of cases with type 1 (p<0.001) and type 2 (p = 0.006) diabetes. The sensitivity, specificity and positive predictive value of QTc prolongation for the diagnosis of CAN were 77%, 62.5% and 77% in type 1 and 76.5%, 75% and 81.3% in type 2, respectively. Higher CAN scores correlated with longer QTc intervals (coefficient of correlation 0.73; p<0.001).

CONCLUSIONS

The prevalence of CAN in diabetes mellitus is high. Higher age, longer duration of diabetes and peripheral neuropathy are significant risk factors. QTc interval in the ECG can be used to diagnose CAN with reasonable sensitivity, specificity and positive predictive value.

Is there a relationship between the blood cholinesterase and QTc interval in the patients with acute organophosphate poisoning?

Organophosphates cause poisoning as a result of the excessive accumulation of acetylcholine at the cholinergic synapses due to inhibition of acetylcholinesterase (ChE). In the literature, it has been reported that there have been electrocardiographic abnormalities, including QT-interval prolongation in most patients with acute organophosphate poisoning (OPP), and a relation between blood ChE level and clinical severity in acute OPP. The aim of this study is to assess the relationship between blood ChE level and QTc interval in the patients with acute OPP. This retrospective study consists of 20 patients admitted to the emergency intensive care unit. A total of 93 QTc interval and blood ChE measures obtained on the same day from 20 cases were compared for their correlation. There were prolonged QTc intervals in 35.4% of the ECGs. There was a negative correlation between QTc interval and blood ChE measures. In following up the patients with acute OPP, QTc interval may be useful when blood ChE levels are low and may provide complementary information concerning the severity of poisoning. However, further prospective studies, supporting the present results, are needed.

MicroRNA miR-133 represses HERG K+ channel expression contributing to QT prolongation in diabetic hearts

We have previously found that the ether-a-go-go related gene (ERG), a long QT syndrome gene encoding a key K(+) channel (I(Kr)) in cardiac cells, is severely depressed in its expression at the protein level but not at the mRNA level in diabetic subjects. The mechanisms underlying the disparate alterations of ERG protein and mRNA, however, remained unknown. We report here a remarkable overexpression of miR-133 in hearts from a rabbit model of diabetes, and in parallel the expression of serum response factor (SRF), which is known to be a transactivator of miR-133, was also robustly increased. Delivery of exogenous miR-133 into the rabbit myocytes and cell lines produced post-transcriptional repression of ERG, down-regulating ERG protein level without altering its transcript level and caused substantial depression of I(Kr), an effect abrogated by the miR-133 antisense inhibitor. Functional inhibition or gene silencing of SRF down-regulated miR-133 expression and increased I(Kr) density. Repression of ERG by miR-133 likely underlies the differential changes of ERG protein and transcript thereby depression of I(Kr), and contributes to repolarization slowing thereby QT prolongation and the associated arrhythmias, in diabetic hearts. Our study provided the first evidence for the pathological role of miR-133 in adult hearts and thus expanded our understanding of the cellular function and pathophysiological roles of miRNAs.

Clinical studies on chromium picolinate supplementation in diabetes mellitus--a review

Chromium (Cr) picolinate (CrPic) is a widely used nutritional supplement for optimal insulin function. A relationship among Cr status, diabetes, and associated pathologies has been established. Virtually all trials using CrPic supplementation for subjects with diabetes have demonstrated beneficial effects. Thirteen of 15 clinical studies (including 11 randomized, controlled studies) involving a total of 1,690 subjects (1,505 in CrPic group) reported significant improvement in at least one outcome of glycemic control. All 15 studies showed salutary effects in at least one parameter of diabetes management, including dyslipidemia. Positive outcomes from CrPic supplementation included reduced blood glucose, insulin, cholesterol, and triglyceride levels and reduced requirements for hypoglycemic medication. The greater bioavailability of CrPic compared with other forms of Cr (e.g., niacin-bound Cr or CrCl(3)) may explain its comparatively superior efficacy in glycemic and lipidemic control. The pooled data from studies using CrPic supplementation for type 2 diabetes mellitus subjects show substantial reductions in hyperglycemia and hyperinsulinemia, which equate to a reduced risk for disease complications. Collectively, the data support the safety and therapeutic value of CrPic for the management of cholesterolemia and hyperglycemia in subjects with diabetes.

Risk factors for prolonged QTc among US adults: Third National Health and Nutrition Examination Survey

BACKGROUND

QT interval prolongation can lead to torsades de pointes, a potentially fatal arrhythmia. Although research exists on the relationship between QT prolongation and clinical outcome, few studies have described risk factors for prolonged QT interval in the general population.

METHODS

The Third National Health and Nutrition Examination Survey (NHANES III) collected electrocardiogram interval data on 8561 subjects over 40 years of age and projected results to the US population. QT was corrected for heart rate using Fridericia's formula. Logistic regression analyses were performed to identify factors independently associated with prolonged QTc interval, defined as being in the upper 5% of the population QTc interval distribution. Analyses were conducted separately for women and men as a result of differences in the QT distribution between the sexes and also because of potential effect modification. Analytical variables included age, race/ethnicity, electrolyte measurements, body mass index, the recent use of QT-prolonging drugs and past medical histories of stroke, thyroid disease, hypertension, diabetes and myocardial infarction.

RESULTS

Age, female sex, hypocalcemia (men), hypokalemia (women), and a history of thyroid disease and myocardial infarction (men) were associated with a prolonged QTc interval. In addition, taking QT-prolonging medications in the past month was associated with more than a twofold increase in the odds of prolonged QTc interval in both men and women.

CONCLUSIONS

Healthcare practitioners should be aware that a prolonged QTc interval is a potential indicator of cardiovascular risk, and should exercise caution in prescribing potentially QT-prolonging medications to certain patients.

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.

Coronary artery disease alters ventricular repolarization dynamics in type 2 diabetes

Ventricular repolarization dynamics (VRD) is an important predictor of outcome in diabetes. We examined the potential impact of coronary artery disease (CAD) on VRD in type 2 diabetic patients. We recorded 5-minute high-resolution resting electrocardiograms in 38 diabetic patients undergoing elective coronary angiography, and in 38 age- and gender-matched apparently healthy subjects (controls). Using leads-I and -II, time-domain indices of VRD were calculated. Coronary angiography was regarded as positive if >/= 50% stenosis was found. Angiography was positive in 21 diabetic patients (55%). Patients with CAD had a significantly higher degree of VRD than controls (SDNN(QT): 15.81 +/- 7.22 ms versus 8.94 +/- 6.04 ms; P < 0.001, rMSSD(QT): 21.02 +/- 7.07 ms versus 11.18 +/- 7.45 ms; P < 0.001). Ventricular repolarization dynamics in diabetic patients with negative angiograms did not differ from VRD in controls (SDNN(QT): 8.94 +/- 6.04 ms versus 7.44 +/- 5.72 ms; P = 0.67, rMSSD(QT): 11.18 +/- 7.45 ms versus 10.22 +/- 5.35 ms; P = 0.82). CAD increases VRD in patients with type 2 diabetes. Therefore, changes in ventricular repolarization in diabetic patients may be due to silent CAD rather than due to diabetes per se.

Chromium supplementation shortens QTc interval duration in patients with type 2 diabetes mellitus

BACKGROUND

We investigated the potential effects of chromium supplementation on QTc interval duration in type 2 diabetic patients.

METHODS

Of 60 patients with type 2 diabetes mellitus, 30 were randomly assigned to group A, and 30 to group B. Group A received 1000 microg of chromium picolinate (CrPic) daily for 3 months, followed by placebo in the next 3 months; group B was treated with placebo for the first 3 months and CrPic in the next 3 months. At each visit, QT interval was measured on a standard electrocardiogram by averaging 3 consecutive beats in leads II and V4 and corrected for heart rate with Bazett formula.

RESULTS

Although baseline QTc interval was similar in both groups (422 +/- 34 milliseconds in group A vs 425 +/- 24 milliseconds in group B, P = .77), QTc interval at 3 months was shorter in group A (406 +/- 35 milliseconds) than in group B (431 +/- 26 milliseconds, P = .01). In the following 3 months, QTc interval shortened in group B but not in group A, which resulted in a comparable QTc interval duration of both groups at the end of the study (414 +/- 28 milliseconds in group A vs 409 +/- 22 milliseconds in group B, P = .50). Apart from body mass index (31.4 +/- 4.2 kg/m2 in patients with QTc shortening vs 28.7 +/- 4.2 kg/m2 in patients without QTc shortening, P = .03), none of the clinical and laboratory variables predicted QTc interval shortening in our patient cohort.

CONCLUSIONS

Short-term chromium supplementation shortens QTc interval in patients with type 2 diabetes mellitus.

Usefulness of QT-interval parameters for cardiovascular risk stratification in type 2 diabetic patients with arterial hypertension

QT-interval parameters are potential indicators of increased cardiovascular risk. We evaluated prospectively their prognostic value, in relation to other risk markers, for cardiovascular fatal and nonfatal events in a cohort of 271 hypertensive type 2 diabetic outpatients. QT intervals were measured from 12-lead standard ECGs obtained on admission and maximum rate-corrected QT-interval duration and QT-interval dispersion (QTd) calculated. Clinical and laboratory data and 2-D echocardiograms (available in 126 patients) were recorded. Survival analyses included Kaplan-Meier survival curves, uni and multivariate Cox proportional-hazards models. After a median follow-up of 55 months (range 2-84), 68 total fatal or nonfatal cardiovascular events and 34 cardiovascular deaths (24 of them from cardiac causes) were observed. In multivariate Cox analysis, QTd was an independent predictor for total cardiovascular events (HR: 1.16, 95% CI: 1.01-1.34, for each 10 ms increments) and for cardiac deaths (HR: 1.28, 95% CI: 1.01-1.60). Other independent risk indicators for cardiovascular morbidity and mortality were echocardiographic left ventricular hypertrophy (Echo-LVH), serum triglycerides, presence of pre-existing cardiac and peripheral arterial disease, age, diabetes duration, heart rate and the presence of frequent ventricular premature contractions on ECG. The combination of QTd and Echo-LVH improved cardiovascular risk stratification compared with either alone, the presence of both prolonged QTd (>65 ms) and Echo-LVH was associated with a 3.2-fold (95% CI: 1.7-6.1) increased risk of a first cardiovascular event and a 5.9-fold (95% CI: 2.1-16.4) increased risk of cardiovascular death. Thus, QT provided additive prognostic information for cardiovascular morbidity and mortality beyond that obtained from conventional risk markers, including Echo-LVH, in type 2 diabetic patients with arterial hypertension.

Mortality and predictors of mortality in a cohort of Brazilian type 2 diabetic patients

OBJECTIVE

To investigate mortality rates and predictors of mortality in Brazilian type 2 diabetic patients.

RESEARCH DESIGN AND METHODS

A prospective follow-up study was carried out with 471 type 2 diabetic outpatients. Primary end points were all-cause, diabetes-related, and cardiovascular deaths. Excess mortality in this cohort was evaluated by calculating standardized mortality ratios (SMRs) in relation to those of the Rio de Janeiro population. Predictors of mortality were assessed by Kaplan-Meier survival curves and by uni- and multivariate Cox survival analyses.

RESULTS

During a median follow-up of 57 months (range 2-84 months), 121 (25.7%) patients died, 91 (75.2%) from diabetes-related causes and 44 (36.4%) from cardiovascular diseases. After adjusting for age and sex, the all-cause SMR was 3.36 (95% confidence interval [CI] 2.81-4.02) and the cardiovascular SMR was 3.28 (CI 2.44-4.41). In the Cox multivariate analysis, the predictors of mortality were older age, increased 24-h proteinuria, preexisting vascular disease, presence of frequent ventricular premature contractions and prolonged maximum heart rate-corrected QT interval on baseline electrocardiogram, and decreased serum HDL cholesterol. The use of beta-blockers was a protective factor. In Kaplan-Meier curves, these variables were capable of distinguishing subgroups of patients with significantly different prognoses.

CONCLUSIONS

Brazilian type 2 diabetic patients had a more than threefold excess mortality than the general population, largely because of increased cardiovascular mortality risk. Several clinical, laboratory, and electrocardiographic predictors of mortality were identified that could possibly be modified to decrease the mortality burden of type 2 diabetes in Brazil.