Significant Difference In QT Dispersion Research Articles

Exercise-Induced Repolarization Changes in Patients with Isolated Myocardial Bridging.

BackgroundAlthough myocardial bridging (MB) is defined as an angiographic phenomenon with a benign course, it has also been associated with adverse cardiovascular events. The effects of exercise on myocardial repolarization in patients with MB were tested in this study, with Tp-e and Tp-e/QT repolarization indexes.Material/MethodsA total of 50 patients in whom isolated MB was diagnosed at coronary angiography (CAG) (Group I) and 48 patients with normal CAG results (Group II) were included in this study. The participants underwent treadmill exercise stress testing according to the Bruce protocol. QT dispersion (QTd) was defined as the minimum QT interval subtracted from the maximum. The Tp-e interval was defined as the difference between the QT and the QT peak time period. QTd and Tp-e intervals were calculated for all patients before and after exercise testing and differences between groups were compared.ResultsAt peak exercise, QTd and cQTd showed a significant increase in comparison to baseline values in the group of patients with myocardial bridges. Significant increases were also found with exercise in the Tp-e, cTp-e durations and Tp-e/QT ratio of the MB patient group in comparison to the baseline values. On the other hand, significant differences in QTd, cQTd, Tp-e, cTp-e intervals, and Tp-e/QT ratio during peak exercise in comparison with baseline values were not detected in the control group (p>0.05).ConclusionsSignificant increases in QTd, cQTd, Tp-e and cTp-e intervals and Tp-e/QT ratio were detected in the MB patients during exercise testing.

Study on corrected QT interval before and after haemodialysis among patients on beta blocker therapy

Introduction : In recent days patients with end stage renal disease on maintenance hemodialysis is emerging.In the conventional ECG the prolonged QT interval has been associated with arrhythmogenesis in a number of cardiac disorders.It has been documented that dialysis patients exhibit sustained activation of the sympathetic nervous system and that the diseased kidney themselves are the trigger of this overactivity 106,107 .The sympathetic over activity is associated with mortality and worse cardiovascular outcomes. 19 So the study to assess the effect of beta blockers in chronic renal failure patients using QT interval is taken up. Materials & methods : A cross sectional hospital based study was done on fifty adult patients on hemodialysis for more than three months at associate hospitals of Kasturba Medical College, Mangalore.Informed consent was taken from them.Twelve-lead electrocardiographs were performed at 10mm/mv and 25mm/s using software based digital ECG recorder (Schiller Healthcare India Pvt Ltd.)10 minutes before and 10 min after a single hemodialysis session. The automatic QT interval was obtained. Statistical analysis was done using Students t-test and chi-square test. P value of ?0.05 was considered significant. Discussion : This study demonstrates that QT interval increases significantly after hemodialysis.There was no significant differences in QT dispersion in end stage renal disease patients on beta blockers and those patients not on beta blockers in our study.However, long term clinical trials are desperately needed to evaluate the safety and efficacy of beta blockers in chronic dialysis patients.

2013 Late-Breaking Basic Science Abstracts

### 21998 #### Enhanced Myocardial Repair with CardioChimeras Pearl J Quijada, Jonathan D Cubillo, Claudio Staub, Mark A Sussman; San Diego State Univ, San Diego, CA Dual stem cell transplantation of c-kit positive cardiac progenitor cells (CPCs) and mesenchymal stem cells (MSCs) after infarction support modest improvements in cardiac function, however there are currently no reports substantiating a single stem cell type supporting both direct and indirect mechanisms of myocardial repair. Therefore we created a CardioChimera, a stem/progenitor cell formed by fusion between CPCs and MSCs, resulting in a unique progeny superior to either individual precursor. CardioChimeras were purified after cell fusion with Hemagglutinating virus of Japan and expanded clonally based on dual expression of fluorescent proteins mCherry and eGFP from CPCs and MSCs respectively. CardioChimeras are mono-nucleated, have comparable growth kinetics to parental CPCs and MSCs and display increased cellular size unrelated to cell cycle arrest and/or senescence. CardioChimeras have increased expression of cardiomyogenic lineage markers cardiac troponin T (2.5-fold), smooth muscle 22 (9.3-fold), and CD31 (10.7-fold) concomitantly associated with decreased c-kit protein expression (50%) relative to parent CPCs. Lineage commitment of CardioChimeras is bolstered by dexamethasone treatment measured by mRNA levels of cardiogenic genes and increases in active mitochondria (2.2-fold) after labeling with MitoTracker. Induction of apoptosis is blunted in cardiomyocytes co-cultured with CardioChimeras compared to co-culturing with CPCs and MSCs alone, or combination of non-fused parent cells. CardioChimeras enhance cardiomyocyte growth similar to parent MSCs owing to an increased propensity to secrete pro-growth factors. Collectively, CardioChimeras represent an adaptable cell therapy combining the beneficial properties of CPCs to undergo cardiac specific commitment as well as MSCs that foster an improved microenvironment with protective paracrine secretion. Clinically, CardioChimeras merge the application of distinct cell types into a single entity for increased engraftment, mitigation of inflammation and blunting the progression of heart failure by promoting myocardial regeneration. …

OP-072 QT DISPERSION INCREASES WITH LOW GLOMERULAR FILTRATION RATE IN PATIENTS WITH CORONARY ARTERY DISEASE

Objective: We aimed to evaluate the relationship between estimated glomerular filtration rate (eGFR) and QT dispersion (QTd) in patients with coronary artery disease (CAD). Methods: Sixty patients(mean age 62.72 ± 12.48 years) included 46 male, (mean age 60.89 ± 12.70 years) and 14 female (mean age 68.71± 9.86 years) were enrolled in this study. Patients were divided into 2 groups according to their eGFR using the 6 variable MDRD equation. Group 1 consisted of patients with estimated eGFR 0.05) QTd values were found higher in group 1 than those of group 2 (57.23 ± 40.65 ms vs. 31.23 ± 14.47 ms, p = 0.002). After adjustment for age, gender and smoking using one-way ANCOVA test, statistically significant difference in QTd still existedbetween the groups (p=0.038). Conclusion:QTd tends to be higher in patients with poor renal function independent of severity of angiographical CAD. QTd may be a potentially useful non-invasive test in the management of patients with poor renal function, especially those with CAD.

Novel Electrocardiographic Parameters of Altered Repolarization in Uncomplicated Overweight and Obesity

In addition to well-known electrocardiographic measurements, as QT, QT dispersion, and QT apex dispersion, new parameters such as Tpeak-Tend, Tpeak-Tend dispersion, and Tpeak-Tend/QT ratio have been recently introduced as indexes of increased arrhythmic risk. The aim of the present study was to test, in overweight and obese subjects not affected by conditions of comorbidity, the aforementioned markers of ventricular repolarization. We studied 60 athletic subjects with normal body weight (21 females and 39 males, BMI between 19 and 24, mean BMI 22.0 ± 2.0kg/m(2), aged 14-64 years, mean age 32 ± 13.59) and 60 sedentary and overweight/obese subjects (34 overweight and 26 obese, 22 females, and 38 males, BMI between 26 and 55, mean BMI 30.7 ± 5.7kg/m(2), aged 14-64, mean age 38 ± 14.49). Each subject underwent anthropometric measurements and a 12-lead electrocardiogram, from which the following different parameters were calculated: QT, corrected QT, QT dispersion, QT apex dispersion, Tpeak-Tend, Tpeak-Tend dispersion and Tpeak-Tend/QT ratio were calculated. The aforementioned repolarization markers resulted, respectively: 340.2 ± 25.1, 373.8 ± 25.9, 29 ± 16.2, 23.5 ± 14.6, 87.3 ± 12.8, 26.5 ± 16.8, and 0.22 ± 0.03ms in control subjects and 362.5 ± 28.5, 397.4 ± 35.4, 34.5 ± 16.8, 30.7 ± 16.3, 90.5 ± 15.2, 27 ± 17.1, and 0.22 ± 0.04ms in overweight/obese subjects. Neither uncomplicated obesity nor overweight were associated with a statistically significant difference in QT dispersion, QT apex dispersion, Tpeak-Tend, Tpeak-Tend dispersion, and Tpeak-Tend/QT ratio; QT and corrected QT were the only parameters that showed statistically significant variations between normal weight and overweight/obese subjects.

QT dispersion failed to estimate the global dispersion of ventricular repolarization measured using monophasic action potential mapping technique in swine and patients

The aim of this study was to evaluate whether the QT dispersion measured from 12-lead electrocardiogram (ECG) can estimate the global dispersion of ventricular repolarization (DVR) measured using a monophasic action potential (MAP) mapping technique. Monophasic action potentials were recorded from 75 ± 12 left ventricular sites in 10 pigs and from 48 ± 16 left or right ventricular sites in 15 patients using the CARTO mapping system. The maximum DVRs in both end-of-repolarization and MAP duration among all the mapped sites were calculated and termed as global DVR for each measurement. QT intervals, QT peak and QT end, were measured from the 12-lead ECG, and QT dispersions; namely the differences between the maximum and the minimum of the QT peak and QT end were calculated. We found that QT dispersions were significantly smaller than ( P < .05) and poorly correlated with the global DVRs both in pigs and patients. Bland-Altman agreement analysis demonstrated a marked variation of the differences and an obvious lack of agreement between the results obtained using the ECG and the MAP methods. In our patients, the global DVR increased markedly during ventricular tachycardia as compared with that during sinus rhythm ( P < .05), whereas there was no significant difference in QT dispersion between these 2 subgroups. In conclusion, QT dispersion on the surface ECG could not estimate the global DVR measured using the MAP mapping technique. These findings are not consistent with some previously reported observations, suggesting the need for reappraisal of the electrophysiological implications of QT dispersion.

QT dispersion in the risk stratification of patients with unstable angina: correlation with clinical course, troponin T and scintigraphy

Objective — This study sought to evaluate the potential prognostic usefulness of QT dispersion (QTd) in patients with unstable angina.Methods and results — QTd was calculated and plasma troponin T (TnT) level was measured and rest perfusion imaging with Tc-99m sestamibi was performed in 62 patients admitted with chest pain at rest. All patients had a follow-up during one month in order to assess cardiac events. Cardiac events occurred in 41 patients (no deaths, 11 myocardial infarctions (MI), 4 urgent and 26 planned revascularizations).The mean QTd in patients with cardiac events was significantly higher than in those without cardiac events (68 ± 28 vs. 54 ± 14 ms; p = 0.01).When patients were divided into subgroups according to the cardiac events, the mean QTd in MI and revascularization were 90 ± 25 ms and 60 ± 25 ms, respectively. QTd in patients with MI was higher than in patients without cardiac events (p = 0.001). There was no significant difference in QTd between the revascularization subgroup and patients without cardiac events. Nineteen patients with elevated TnT had a greater QTd compared to patients with normal TnT (74 ± 29 vs. 56 ± 20 ms; p = 0.008). Additionally, the mean QTd in 46 patients with perfusion defects was slightly higher than in patients without (66 ± 27 vs. 53 ± 17 ms; p = 0.03).There was also a moderate correlation between QTd and the number of perfusion defects (r = 0.31, p = 0.01). On the other hand, most of the patients who had a MI or urgent revascularization had a QTd greater than 75 ms.Conclusion — The measurement of QTd in patients with unstable angina may help to stratify patients at high risk for cardiac events, in particular MI and urgent revascularization.

Accuracy of electrocardiographic and echocardiographic indices in predicting life threatening ventricular arrhythmias in patients operated for tetralogy of Fallot

OBJECTIVETo validate the accuracy of the prognostic significance of non-invasive clinical diagnostic indices as predictors of sustained ventricular tachycardia (sVT) or fibrillation (VF) in patients undergoing repair for tetralogy of...

This month in J Lab Clin Med

This month in J Lab Clin Med

QT Dispersion as a Noninvasive Arrhythmiogenic Marker in Acute Myocardial Infarction

Backround: Prolongation of QT dispersion (QTD), defined as the difference between maximum and minimum QT intervals on surface ECG, has been proposed as a noninvasive arrythmogenic marker. The aim of this study was to estimate the value of QTD in identifing patients susceptible to ventricular fibrillation or ventricular tachycardia (VF/VT) after an acute myocardial infarction (AMI) and to evaluate the behavior of QTD in relation to the thrombolytic therapy.Methods: We studied 108 consecutive patients with AMI. All patients had a 12‐lead surface ECG recorded upon admission and a second ECG 24 hours later. QT interval was measured from the onset of Q to the end of T in each of 12 standard ECG leads. QTD was the difference between the longest and shortest values of QT. All QTD measurements were corrected for heart rate (QTcD) using QTc values according to Bazzet formula.Results: Fifteen patients (13.8%) developed VF/VT in the first week after AMI (group 1A) and 93 patients (86.2%) did not have VF/NT (group 1B). QTD and QTcD values were significantly greater in group 1A in comparison to group 1B on admission and 24 hours later. Sixty‐five patients (60%) received intravenous thrombolysis in the acute phase of AMI (group 2A) and 43 patients (40%) did not (group 2B). No significant difference in QTD and QTcD was observed in the first ECG on admission between the two groups. Conversely, QTD and QTcD were lower in group 2A patients in the second ECG 24 hours after admission.Conclusions: These results provide evidence that increased values of QTD are correlated well with occurrence of malignant ventricular arrhythmias after acute myocardial infarction while lower values associated with the thrombolytic therapy. A.N.E. 1999;4(1):35–38

Increased ventricular repolarization inhomogeneity during postural changes in patients with syndrome X

The interlead variation in QT interval (QT dispersion) can be used to assess regional inhomogeneity of ventricular repolarization under a variety of conditions, including stress. Patients with syndrome X may have increased sympathetic activity that could change QT interval regionally and give rise to an increase in QT dispersion under exercise testing. To test the hypothesis, 26 consecutive patients with syndrome X (group 1) were studied. Two additional groups matched in terms of age, sex, and left ventricular mass index consisting of 26 nonconsecutive patients with coronary artery disease (group 2) and 20 normal subjects (group 3) were studied for comparison. Standing induced a significantly higher increase of heart rate in group 1 than in groups 2 and 3 (7.5 ± 6.0 vs 4.0 ± 6.3 and 1.1 ± 3.6 beats/min; p = 0.05 and 0.003, respectively). There were significant differences in QT dispersion between groups 1 and 2 on upright standing (48 ± 12 vs 34 ± 14 ms, p = 0.0003), but not at baseline (33 ± 14 vs 38 ± 11 ms, p = NS) or at peak exercise (38 ± 9 vs 38 ± 9 ms, p = NS). Results did not change when QT c dispersion was substituted for QT dispersion. From a conditional multivariate logistic regression analysis, the only independent predictor of occurrence of syndrome X on upright standing was QT c dispersion (odds ratio = 1.255, p = 0.01). Electrocardiographic QT c dispersion provides important clinical information. Patients with syndrome X had a higher increase of heart rate and QT c dispersion in response to standing from the supine position compared with patients with coronary artery disease and normal subjects.

Electrophysiologic effects of ischemic preconditioning on QT dispersion during coronary angioplasty

Objectives. The aim of this study was to examine the effect of ischemic preconditioning on the manner of ventricular repolarization by assessing the change in QT dispersion during coronary angioplasty.Background. QT interval dispersion regional variations in ventricular repolarization and cardiac electrical instability. Previous studies have suggested that increased QT dispersion is associated with an increased incidence of malignant ventricular arrhythmias, whereas brief episodes of myocardial ischemia can render the heart more resistant to subsequent ischemic episodes, a phenomenon called ischemic preconditioning.Methods. To assess the effects of ischemic preconditioning on myocardial repolarization by examining the change in QT dispersion during coronary angioplasty, we studied 47 consecutive patients (39 men and 8 women; mean age 57 ± 16 years). QT dispersion was measured after each balloon inflation during coronary angioplasty. Statistical analysis was performed by using repeated measurement of analysis of variance.Results. There were significant differences in QT dispersion as the number of balloon inflations increased (mean ± SD 52 ± 14, 42 ± 11, 36 ± 9, 31 ± 10 and 29 ± 11 ms, respectively [p < 0.01], for the first, second, third, fourth and fifth balloon inflations). The magnitude of decrease in QT dispersion was significant in the first and second balloon inflations, then became insignificant with later inflations.Conclusions. These data indicate that the gradual decrease in OT dispersion provoked by coronary artery occlusion and reperfusion during coronary angioplasty may be associated with electrophysiologic effects of ischemic preconditioning on myocardium in the human heart.

QT dispersion and RR variations on 12-lead ECGs in patients with congestive heart failure secondary to idiopathic dilated cardiomyopathy.

Increased QT dispersion, which has been proposed as a marker of ventricular repolarization inhomogeneity, may predispose to ventricular arrhythmias. Data on QT dispersion in patients with congestive heart failure are scarce. In this study, conventional 12-lead ECGs were recorded in 135 consecutive patients with congestive heart failure secondary to idiopathic dilated cardiomyopathy. Seventy-five patients were excluded from QT interval assessments due to one or more of the following reasons: (1) low amplitude of the T wave (n = 3), (2) atrial fibrillation (n = 26) and (3) bundle branch block (n = 46). QT dispersion was calculated as (1) QT-range: the difference between the maximum and minimum QT intervals on any of the 12 leads and (2) QT-SD: the standard deviation of the QT interval in all the 12 leads. RR intervals were measured in leads II, aVL, V2 and V5. QT-SD (20.85 +/- 5.00 ms) was significantly (r = 0.8997, P < 0.001) related to QT-range (65.65 +/- 15.77 ms), but not to the QT interval. Neither QT-range nor QT-SD was significantly related to age, left ventricular dimensions, left ventricular end diastolic pressure, left ventricular ejection fraction or left ventricular wall thickness. There was no significant difference in QT dispersion between survivors and those who died (n = 8) or were transplanted (n = 9) during 34 +/- 23 month follow-up. No significant difference in QT dispersion was observed between patients with and without ventricular tachycardia (> or = three consecutive beats) detected on 24-h Holter ECGs. RR interval variation was significantly lower in patients who died compared with survivors (standard deviation: 10.37 +/- 3.61 vs 36.02 +/- 35.03 ms, P < 0.001; coefficient of variance: 1.87 +/- 0.7% vs 4.50 +/- 4.9%, P = 0.001). This was also true in patients with bundle branch block. These observations suggest that QT dispersion in idiopathic dilated cardiomyopathy is not significantly related to either QT interval or cardiac size and function and does not predict death. The application of QT dispersion assessment is limited by the commonly encountered atrial fibrillation and bundle branch block in this patient population. However, reduced RR variation on standard 12-lead ECGs has important prognostic implications in these patients.

QT dispersion increases with low glomerular filtration rate in patients with coronary artery disease

We aimed to evaluate the relationship between estimated glomerular filtration rate (eGFR) and QT dispersion (QTd) in patients with coronary artery disease (CAD). Sixty patients(mean age 62.72 ± 12.48 years) included 46 male, (mean age 60.89 ± 12.70 years)and 14 female (mean age 68.71± 9.86 years) were enrolled in this study. Patients were divided into 2 groups according to their eGFR using the 6 variable MDRD equation. Group 1 consisted of patients with estimated eGFR<60 ml/min/1.73m(2) and Group 2 consisted of patients witheGFR ≥ 60 ml/min/1.73m(2). Baseline patient characteristics were homogeneous in both groups except for age, gender and smoking.Also, the extent of CAD was similar in both groups (p > 0.05) QTd values were found higher in group 1 than those of group 2 (57.23 ± 40.65 ms vs. 31.23 ± 14.47 ms, p = 0.002). After adjustment for age, gender and smoking using one-way ANCOVA test, statistically significant difference in QTd still existedbetween the groups (p=0.038). QTd tends to be higher in patients with poor renal function independent of severity of angiographical CAD. QTd may be a potentially useful non-invasive test in the management of patients with poor renal function, especially those with CAD.