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Introduction: This study aimed to evaluate the effects of dialysis on change of QT interval in pre-dialysis, 1 h after dialysis initiation, and post-dialysis period in patients on maintenance dialysis (MHD). Methods: An observational prospective study was conducted, including 61 patients, on thrice-weekly MHD ≥3 months, and without acute diseases, at the Nephrology-Dialysis Department of a tertiary hospital in Vietnam. The exclusive criteria were atrial fibrillation, atrial flutter, branch block, prolonged QT recorded in medical history, and taking antiarrhythmic drugs lengthening QT interval before entering the study. Twelve-lead electrocardiographs and blood chemistries were done simultaneously before, 1 h after initiation, and after the dialysis session. Results: The proportion of patients with prolonged QT interval increased significantly from 44.3% in pre-dialysis to 77% 1 h after dialysis initiation and 86.9% in post-dialysis session. Immediately after dialysis, the QT and QTc intervals on all 12 leads were significantly longer. Post-dialysis levels of potassium, chloride, magnesium, and urea decreased significantly from 3.97 (0.7), 98.6 (4.7), 1.04 (0.2), and 21.4 (6.1) to 2.78 (0.4), 96.6 (2.5), 0.87 (0.2), and 6.33 (2.8) mmol/L, respectively, whereas the calcium increased significantly from 2.19 (0.2) to 2.57 (0.2) mmol/L. There were significant differences in the potassium level at the dialysis initiation and its speed of reduction between the group without and with prolonged QT interval. Conclusions: There was an increased risk of prolonged QT interval in MHD patients regardless of the absence of the previous abnormal QT interval. Notably, this risk increased rapidly 1 h after the initiation of dialysis. [ABSTRACT FROM AUTHOR]

Objectives: An increased dispersion of myocardial repolarization represents one of the mechanisms underlying the arrhythmic risk in hypertrophic cardiomyopathy (HCM). We investigated spatial myocardial repolarization dispersion indices in HCM patients with nonsustained ventricular tachycardia (NSVT) and, contextually, their main clinical determinants. Methods: Fifty-two well-matched HCM outpatients were categorized into two groups according to the presence or the absence of NSVT at 24-hour Holter electrocardiogram (ECG) monitoring. Each patient underwent a clinical examination, including Doppler echocardiogram integrated with tissue Doppler imaging, cardiac magnetic resonance, and 12-lead surface ECG to calculate the dispersion for the following intervals: QRS, Q-Tend (QTe), Q-Tpeak, Tpeak-Tend (TpTe), J-Tpeak, and J-Tend. Results: The NSVT group showed only QTe dispersion and TpTe dispersion values to be significantly higher than their counterparts. NSVT occurrence was independently predicted by late gadolinium enhancement presence (p = 0.021) and QTe Bazett dispersion (p = 0.030), the latter strongly associated with the myocardial performance index (MPI) obtained at the basal segment of the interventricular septum (p = 0.0004). Conclusion: Our data support QTe dispersion as an easy and noninvasive tool for identifying HCM patients with NSVT propensity. The strong relationship between QTe dispersion and MPI allows us to hypothesize an intriguing link between electrical instability and confined myocardial areas of systodiastolic dysfunction. © 2015 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

Background/Aims: Evidence suggests that vascular calcification (VC) portends poor cardiovascular (CV) prognosis in patients undergoing maintenance dialysis (CKD-5). Nonetheless, how VC might predispose to CV mortality still remains to be clarified. Herein, we report on the association between coronary artery calcification (CAC) progression and changes in cardiac repolarization as well as arterial stiffness. Methods: 132 patients new to dialysis were identified. Demographic and clinical characteristics were collected at study entry and during the 12-month follow-up. CAC, 12-lead ECG and pulse wave velocity (PWV) were assessed at baseline and study completion. Uni- and multivariable analyses were applied to detect factors associated with worsening of cardiac repolarization (QTd) and arterial stiffness (PWV). Results: Uni- and multivariable analyses revealed that CAC progression was associated with a significant increase in both QTd and PWV. Every 20-unit increase in the CAC score corresponded to a significant 23% (95% CI 1.12-1.27; p < 0.001) and 32% (95% CI 1.09-1.37; p < 0.01) increase in the risk of experiencing a 1-m/s increase in PWV and 1 ms in QTd, respectively. Conclusion: VC is a marker of vasculopathy and appears to be associated with cardiac repolarization and arterial stiffness abnormalities in CKD-5 patients. Copyright © 2011 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

Objectives: QT dispersion (QTd) measures the variability of the ventricular recovery time. QTd may identify patients at risk for ventricular arrhythmias and sudden cardiac death (SCD). The purpose of our study was to determine the effect of obstructive sleep apnea (OSA) on QTd. Methods: There were 199 patients studied: 101 patients (28 women, 73 men) with OSA diagnosed in our sleep center and 98 patients (49 women, 49 men) without OSA from the outpatient clinic, representing the control group. QT intervals (milliseconds) were measured in each of the 12 leads of a standard surface electrocardiogram during wakefulness and QTd calculated (QTmax - QTmin). QTcd, which corrects for heart rate, was also calculated. Results: Mean age and heart rate were similar in men and women with or without OSA. Control patients exhibited a significant difference (p < 0.001) in QTd between men (48 ± 19) and women (31 ± 13). Men and women with OSA had similar QTd (56 ± 35 vs. 54 ± 21) but higher QTd compared to the control group. QTcd results were similar to QTd. Conclusions: Patients with OSA and no structural heart disease have a higher QTd/QTcd compared to an overtly healthy patient population, possibly serving as a marker for an increased risk of SCD. Copyright © 2011 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

Objectives: To determine, in patients with ST-segment elevation myocardial infarction (STEMI) treated with primary percutaneous coronary intervention (PPCI), the mechanisms and clinical implications of the acute changes in QT dispersion (QTd). Methods: In this prospective study we included 216 patients admitted with a STEMI of <12 h of evolution. All were treated with PPCI. QTd was measured prior to PPCI and within 1 h after. Results: The ratio of QTd reduction after PPCI (QTd-R) – defined as [(QTd before PPCI – QTd after PPCI)/QTd before PPCI] ×100 – was significantly correlated with the percentage of ST-segment elevation resolution (ST-R; p < 0.001). To determine the significance of the different values of QTd-R, we further subdivided our population into 3 groups according to the tertiles of QTd-R (<10, 11–49, ≥50%). Patients with longer QTd-R had higher percentages of ST-R: 32 ± 43 for QTd-R <10% vs. 60 ± 21 for 11–49% vs. 71 ± 12 for ≥50% (p < 0.05). By logistic regression, patients with QTd-R ≥50% had a reduction of 75% in the adjusted frequency of death or severe heart failure during hospitalization (95% CI 13–73%, p = 0.03). Conclusion: QTd-R after PPCI occurs early, is closely related to the restoration of reperfusion at the microvascular level and provides additional prognostic information. Copyright © 2009 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

Objectives: Carvedilol and bisoprolol reduce QT dispersion (QTD) in chronic heart failure (CHF). However, it is unclear whether there is a difference between the effects of the two drugs. The aim of the present study was to compare the long-term effects of carvedilol and bisoprolol on QTD in patients with CHF. Methods: Eighty-one patients with CHF with no previous β-blocker therapy were included in this prospective study. The patients were randomly allocated to carvedilol or bisoprolol therapy. Left ventricular ejection fraction (LVEF), heart rate (HR), QTD, and corrected QTD (QTcD) were calculated at baseline and at the 6th month of therapy. Results: In comparison to baseline values in both therapy groups, LVEF was significantly improved, and a statistically significant decrease was found in HR (carvedilol from 76 ± 12 to 65 ± 10 beats/min, p < 0.001; bisoprolol from 78 ± 13 to 65 ± 8 beats/min, p < 0.001) and QTcD (carvedilol from 85 ± 28 to 65 ± 22 ms, p < 0.001; bisoprolol from 83 ± 22 to 61 ± 20 ms, p < 0.001). In our study, carvedilol and bisoprolol were found to have similar effects on LVEF, HR, and QTcD. Conclusions: Carvedilol and bisoprolol decrease HR and QTcD in patients with CHF, and there is no meaningful difference between the two β-blockers as regards their effects on these parameters. Copyright © 2008 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

Background: A circadian and seasonal variation of QT dispersion (QTd) has been shown in healthy individuals. Nevertheless, no data exist regarding the weekly influences on the QTd in healthy individuals and in patients with coronary heart disease (CHD). Design: This study was designed to determine whether there is a weekly variability of QTd in healthy individuals and in patients with CHD. Methods: In this prospective registry study, 53 patients with documented CHD and 57 healthy control subjects were involved. Resting electrocardiograms (ECGs) with double amplitude were recorded at a speed of 50 mm/s on Monday and Friday mornings. QT intervals were measured and QTd were determined by calculating the difference between maximum and minimum QT intervals. Then, rate-corrected QTd (QTcd) were calculated using Bazett’s formula. Results: There was a significant weekly variation of QTd in control subjects (39.3 ± 6.3 vs. 36.2 ±6.1 ms) (p < 0.05) and in patients (56 ± 7.3 vs. 47.4 ± 5.4 ms) (p < 0.0001). There was also a significant weekly variation of QTcd both in control subjects (33 ± 5.3 vs. 30.7 ± 5.6 ms) (p < 0.05) and in patients (47.4 ± 6.4 vs. 41.9 ± 5.4 ms) (p < 0.0001). Conclusions: There is a weekly variation of QTd and QTcd in healthy individuals and in patients with CHD, both with a Monday preference. This fact should be taken into consideration during the chronopharmacological treatment or advisal of primary or secondary preventive measures to these subjects or patients. [ABSTRACT FROM AUTHOR]

Background: QT dispersion has been proposed to be a predictor of adverse outcomes in a variety of cardiac disease states. The objective of this study was to examine QT dispersion in patients with sickle cell disease (SCD) and to assess the effect of pulmonary hypertension (PHT) on QT dispersion. Methods: We performed Doppler echocardiographic assessments of pulmonary artery systolic pressure in 73 (mean age 18.5 ± 8.0 years) steady-state SCD patients and 25 (mean age 19.6 ± 7.2 years) healthy subjects. Resting 12-lead electrocardiogram was recorded and QT dispersion was calculated as the difference between maximum and minimum QT intervals. Bazett’s formula was used to obtain a rate-corrected value of the QT interval (QTc). Results: Maximum QTc, minimum QTc and QTc dispersion were significantly increased in SCD patients compared to the control subjects (p < 0.0001, p < 0.05, p < 0.0001, respectively). Among SCD patients, patients with PHT had higher maximum QTc and QTc dispersion than patients without PHT (p < 0.0001). However, minimum QTc showed no significant differences between the two patient groups. Conclusion: QTc dispersion is significantly increased in SCD patients, especially those with PHT indicating regional inhomogeneity of ventricular repolarization. Copyright © 2007 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

Background: Electrolyte impairments are common in hemodialysis (HD) patients. Consequently, QT dispersion (QTd) is prolonged, correlating with high intracellular magnesium. In patients with cardiac disorders, renin-angiotensin system (RAS) inhibition reduces QTd. Aim: To compare the effects of ACE inhibition or AT-1 blockade on QTd duration and intracellular magnesium (Mg)/calcium (Ca) in peripheral blood mononuclear cells (PBMC) from chronic HD patients. Methods: 24 HD patients received cilazapril for 8 weeks and, following a 2-week withdrawal, were switched to valsartan for additional 8 weeks. QTd measurements and PBMC isolation were performed at the beginning and the end of each period. Total intracellular Ca and Mg were assessed by atomic spectrometer, and cytosolic free Ca2+ by fluorocytometer. Results: Both treatments significantly decreased QTd, demonstrating similar reduction magnitudes. In both groups, PBMC exhibited basally low cytosolic Ca2+ and undisturbed high transmembrane Ca2+ influx following phytohemagglutinin stimulation. Total intracellular Ca was increased, while Mg was reduced, following either treatment. The total intracellular Ca/Mg ratio inversely correlated with QTd duration. Conclusions: (1) RAS inhibition reduces prolonged QTd in HD patients. (2) In PBMC from ordinarily Ca-depleted HD patients, RAS suppression brings about elevation of total intracellular Ca. (3) RAS blockade decreases high intracellular Mg in PBMC from HD patients. Consequently, the Ca/Mg ratio increases, inversely correlating with QTd reduction. Copyright © 2006 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

Objective: We attempted to observe the alterations in QTd and QTcd in chronic renal failure (CRF) patients before and after hemodialysis (HD) to determine the relevant determinants of QTc duration in HD. Methods: The HD was carried out 2 or 3 times/week in a standard setting for 4–4.5 h. No drug therapy was applied during HD, except for isotonic NaCl infusions and sodium heparin. Maintenance drug therapy, including digitalis, antihypertensive, anti-anginal, and β-blocking agents, was not changed. In the study, we investigated the alterations in QTd and QTcd in 68 CRF patients before and after HD with 12-lead ECG. Plasma Na+, K+, ionized Ca, creatinine, urea nitrogen, and hemoglobin were also controlled before and after HD. Results: In our study QTd and QTcd significantly increased at the end of HD (p < 0.01). Plasma Na+ and K+ decreased, and ionized Ca increased after HD (p < 0.05, 0.01). Plasma Na+, K+, ionized Ca levels, ultrafiltration volume and myocardial ischemia appear to be the main determinants of QTc duration in HD, not hypertension, gender, patient age, or duration of chronic HD. Conclusion: Changes in plasma Na+, K+ and ionized Ca, the ultrafiltration volume and presence of ischemic heart disease in HD have significant effects on QTcd. ECG data demonstrate that the risk of arrhythmia could be higher with decreased plasma Na+ and K+, increased ionized Ca, the presence of ischemic heart disease and an increased ultrafiltration rate during HD. These results might provide some valuable references for proper HD programs. Copyright © 2006 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

Background: Sudden cardiac death is common in patients on hemodialysis (HD), and its rate is as high as 25% of all cardiac deaths associated with left ventricular hypertrophy (LVH) and secondary hyperparathyroidism. A prolonged QT interval on standard electrocardiography is related to an increase in sudden death in various patient groups. It is also well known that LVH has been noted in uremic patients with high parathyroid hormone levels. Methods: To evaluate the response of intravenous calcitriol treatment on the QT interval and LVH in HD patients with secondary hyperparathyroidism (intact parathyroid hormone, iPTH, >450 ng/ml), echocardiographic, electrocardiographic (ECG), and biochemical assessments were performed over a 15-week period in 25 HD patients before and after intravenous calcitriol treatment. We also evaluated 25 age-, sex-, HD duration-, and BMI-matched HD control patients with secondary hyperparathyroidism. Results: In patients receiving intravenous calcitriol, a significant reduction in iPTH levels (p < 0.05) and alkaline phosphatase levels (p < 0.01) was found without changes in values of serum calcium and ionized Ca2+, phosphorus, Na+, K+, Mg2+, hematocrit, blood pressure, or other hemodynamic changes. Echocardiograms showed significant decreases in the thickness of the interventricular septum (p < 0.05), left posterior wall thickness (p < 0.05), and left ventricle mass index (LVMi, p < 0.01). In addition, sequential ECG measurement in patients with calcitriol treatment showed significant reductions in QTcmax (QTmax interval corrected for heart rates, p < 0.01) and QTc dispersion (QT dispersion corrected for heart rates, p < 0.01). However, in the control patients, biochemical, hemodynamic, and ECG changes, as well as myocardial structural and functional changes were not seen. Multiple regression analysis in all patients indicated that iPTH and LVMi levels were independent predictors of QTcmax while the LVMi level was the only independent predictor of QTc dispersion (p < 0.05). Conclusions: Our study showed a significant correlation between LVMi and QT dispersion in HD patients with secondary hyperparathyroidism. Intravenous calcitriol treatment, to be used for the control of secondary hyperparathyroidism, was found to cause regression of myocardial hypertrophy and a reduction in the QTc interval and dispersion, without biochemical and hemodynamic changes. These findings suggest that an active vitamin D metabolite has a cardioprotective action in HD patients. [ABSTRACT FROM AUTHOR]

Recent studies have indicated increased ventricular repolarisation dispersion in haemodialysis (HD) patients. The purpose of this study was to estimate the effect of the HD process on parameters of regional and transmyocardial repolarisation inhomogeneities. Thirty-two selected HD patients (without relevant diseases and medication known to affect the QT interval) were included. Dispersion of the QT corrected interval (QT-c-D) and the corrected interval between the peak and the end of the T wave (Tpe-c-D) were evaluated before and after HD, and in controls. Blood chemistry and extracellular body water (ECW) were evaluated before and after HD. Predialysis QT-c-D and Tpe-c-D were higher in patients (53.40 ± 17.39 and 47.50 ± 13.68 ms, respectively) than in controls (34.91 ± 17.70 ms, p < 0.001 and 31.9 ± 16.76 ms, p < 0.001, respectively). HD induced an increase in the QT-c-D (67.59 ± 19.40 ms; p < 0.001) and Tpe-c-D (62.89 ± 14.33 ms; p < 0.001). Stepwise multiple regression identified the independent risk factors of QT-c-D (the differences between pre- and postdialysis phosphorus, potassium and calcium levels and ECW values) and Tpe-c-D (the differences between pre- and postdialysis phosphorus levels, calcium levels and ECW values) increases, induced by the HD process. The HD process increases regional and transmyocardial repolarisation phase inhomogeneities in HD patients. Changes of phosphorus, calcium and potassium levels plus ECW values seem to be important predisposing factors as far as the increase in ventricular inhomogeneities in HD patients is concerned. Copyright © 2005 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

An increased QT dispersion (QTd) is associated with a variety of cardiac diseases and predicts sudden death. Although chronic renal failure patients and patients on hemodialysis are shown to have an increased QTd, evidence of increased QTd in renal transplant patients is scarce. In this study, renal transplant patients were evaluated to find out if they had an increased QTd. Thirty-four renal transplant recipients aged 35 ± 8 years and 34 healthy control subjects aged 34 ± 8 years were included in the study. The mean time after transplantation was 51.8 ± 40.4 (range 5–154) months. The QT interval was measured by 12-lead electrocardiogram, and the QTd was defined as the difference between the maximum and minimum QT interval. Bazett’s formula was used to correct for the heart rate (QTc). Both QTd and QTc dispersion (QTcd) in renal transplant patients were compared with those of control subjects. All patients underwent transthoracic echocardiographic assessment and 24-hour ambulatory blood pressure monitoring. Renal transplant recipients had similar QTd (37 ± 15 vs. 39 ± 17 ms) and QTcd (50 ± 18 vs. 55 ± 20 ms) compared to control subjects. QTd and QTcd were similar in patients with and without left ventricular hypertrophy (QTd 37 ± 14 vs. 36 ± 17 ms and QTcd 50 ± 14 vs. 49 ± 21 ms, respectively). No association was found between QTd and left ventricular mass index or blood pressure measurements. The QTd was not found to be increased in renal transplant recipients as compared with that of healthy controls in this study. Normalization of the QTd after renal transplantation may be through the correction of several factors responsible for increased QTd in uremic patients.Copyright © 2002 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

In a group of 193 postinfarction patients with ventricular premature beats on a resting 12-lead ECG, the dispersion of QT and JT intervals was calculated as a difference between maximum and minimum QT and JT intervals in ventricular premature beats. During a follow-up of 38 ± 17 months, death from all causes was noted in 56 patients. Univariate predictors of mortality included QT dispersion ≥100 ms, JT dispersion ≥100 ms, left ventricular ejection fraction <40%, complete bundle branch block, ‘R-on-T’ index of ventricular premature beats <1 and age of patients >60 years. At multivariate Cox proportional hazards survival analysis, only QT dispersion ≥100 ms, left ventricular ejection fraction <40% and complete bundle branch block had an independent relation to postinfarction mortality. The final model selected increased QT dispersion as the prognostic factor which was the most strongly related to mortality (χ[sup 2] = 23.60, p = 0.0000). [ABSTRACT FROM AUTHOR]

Prolonged QT dispersion is a risk factor for cardiac arrhythmias and sudden death in patients with cardiac and peripheral artery diseases, but there is no study about prolonged QT dispersion in patients with ischaemic strokes. The insular cortex may play an important role in the genesis of cardiac arrhythmias and sudden death. In our study with 40 patients suffering from unilateral hemispheric ischaemic stroke, the QT dispersion was analysed and correlated to the location of the cerebral lesion. We found that in patients with involvement of the insular cortex, the QT dispersin is significantly longer than in those without insular involvement.Copyrightz1999S.KargerAG,Basel [ABSTRACT FROM AUTHOR]

The QTc dispersion reflects the underlying regional heterogeneity of the recovery of the ventricular excitability, thereby it is considered as a novel marker of risk of ventricular arrhythmias. Because a higher incidence of ventricular arrhythmias is described during and after hemodialysis, the aim of this study has been to evaluate the QTc dispersion before and after uncomplicated hemodialysis session. Twenty chronic uremics without heart failure, ischemic heart disease or dialysis hypotension were selected. The QTc dispersion was determined as the difference between the longer and the shorter QTc interval measured on a 12-lead electrocardiogram. Following the hemodialysis session, the QTc dispersion increased from 30 ± 9 to 54 ± 17 ms (p < 0.001) associated with the expected reduction of potassium and magnesium and with the increase of extracellular calcium concentration. However, no correlation has been observed between the QTc dispersion increase and the degree of the intradialytic changes of plasma electrolytes, blood pressure or body weight. In summary, the hemodialysis treatment per se does induce an increase of the QTc dispersion, likely due to the rapid changes of electrolyte plasma concentrations. This can potentially contribute to the arrhythmogenic effect of the hemodialysis procedure, reflecting an enhanced regional heterogeneity of ventricular repolarization. The clinical importance of the increase of QTc dispersion as risk factor of ventricular arrhythmias, particularly in hemodialyzed patients suffering from ischemic or hypertrophic heart diseases, should be the matter of further investigations. [ABSTRACT FROM AUTHOR]

Prolongation of repolarization dispersion (QT interval dispersion) measured from the 12-lead surface ECG has been associated with sudden cardiac death and ventricular tachyarrhythmias in a variety of cardiac disorders. The aim of our study was to assess the effects of hemodialysis (HD) and continuous ambulatory peritoneal dialysis (CAPD) on QT dispersion in end-stage renal disease patients. 20 chronic HD patients (mean age 57.75 ± 13.79 years) and 20 CAPD patients (mean age 50.79 ± 14.94 years) who had no complaints and symptoms of cardiac arrhythmias as well as 20 healthy volunteers (mean age 48.74 ± 10.88 years) underwent ECG testing. All HD patients were on bicarbonate three times weekly with cuprophane capillaries. 12-lead ECGs were recorded on the day after HD. The CAPD patients were on a standard CAPD program (four times daily with 2,000 cm[sup 3] peritoneal fluid). ECGs were recorded when the patients were receiving their regular standard CAPD program. All ECGs were analyzed manually by one observer. There were no statistically significant differences in dialysis duration, blood urea nitrogen, creatinine, sodium, calcium, and parathormone values between the HD and CAPD patients. The serum potassium values were significantly higher in HD patients when compared to CAPD patients. There was no difference in the mean of maximal QT among all three groups. The rate of QT interval dispersions was significantly higher in HD and CAPD patients as compared with healthy controls (p < 0.05). There was no statistically significant difference in the QT dispersion rates between HD and CAPD patients. In conclusion, there is a tendency to cardiac arrhythmias in HD patients during the postdialysis period. Although CAPD patients are receiving dialysis daily, they also have higher rates of QT dispersions and accordingly a tendency to arrhythmias.Copyright © 2002 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]