Reproducibility and Reliability Of QTc and QTcd Measurements and Their Relationships with Left Ventricular Hypertrophy in Hemodialysis Patients

Abstract

BackgroundLeft ventricular hypertrophy (LVH) is very common in hemodialysis patients and an independent risk factor for mortality in this population. The myocardial remodeling underlying the LVH can affect ventricular repolarization causing abnormalities in QT interval.Objectiveto evaluate the reproducibility and reliability of measurements of corrected QT interval (QTc) and its dispersion (QTcd) and correlate these parameters with LVH in hemodialysis patients.MethodsCase-control study involving hemodialysis patients and a control group. Clinical examination, blood sampling, transthoracic echocardiogram, and electrocardiogram were performed. Intra- and interobserver correlation and concordance tests were performed by Pearson´s correlation, Cohen’s Kappa coefficient and Bland Altman diagram. Linear regression was used to analyze association of QTc or QTcd with HVE.ResultsForty-one HD patients and 37 controls concluded the study. Hemodialysis patients tended to have higher values of QTc, QTcd and left ventricular mass index (LVMi) than controls but statistical significance was not found. Correlation and concordance tests depicted better results for QTc than for QTcd. In HD patients, a poor but significant correlation was found between QTc and LVMi (R2 = 0.12; p = 0.03). No correlation was found between values of QTcd and LVMi (R2= 0.00; p=0.940). For the control group, the correspondent values were R2= 0.00; p = 0.67 and R2= 0.00; p = 0.94, respectively.ConclusionWe found that QTc interval, in contrast to QTcd, is a reproducible and reliable measure and had a weak but positive correlation with LVMi in HD patients.

Increased Dispersion of Ventricular Repolarization as an Arrhythmic Risk Marker in Drug-free Patients With Major Depressive Disorder: A Preliminary Comparative Study

“…Increased QTcd reflects the presence of complex repolarization patterns, especially a certain degree of fusion of the T and U waves, which may characterize various proarrhythmic conditions better than QT/QTc duration 41,42 . This is possibly due to the fact that QT (or QTc) duration is vulnerable to intrinsic and extrinsic factors, such as myocardium characteristics and changes, cell death, biochemical alterations, and disturbances in neurohormonal regulation, unlike dispersion of QTc 43,44 . Moreover, prolonged QT may sometimes be associated with inherited long QT syndromes 43 .…”

“…41,42 This is possibly due to the fact that QT (or QTc) duration is vulnerable to intrinsic and extrinsic factors, such as myocardium characteristics and changes, cell death, biochemical alterations, and disturbances in neurohormonal regulation, unlike dispersion of QTc. 43,44 Moreover, prolonged QT may sometimes be associated with inherited long QT syndromes. 43 Therefore, it has been reported that, compared with QTc prolongation, increased dispersion of QT/QTc was a more powerful predictor of susceptibility to ventricular tachyarrhythmias, suggesting that lack of homogeneity of repolarization is more closely associated with arrhythmic risk than is the prolongation of repolarization itself.…”

Haemodialysis Alters the Index of Cardiac-Electrophysiological Balance

“…Among HD-dependent patients, longer QTc intervals are associated with thicker left posterior ventricular walls as the utmost marker of mortality. 19 However, we did have any such echocardiographic information available for our patients.…”

QTc and QTcd Measurements and Their Relationships with Left Ventricular Hypertrophy in Hemodialysis Patients

“…We read the publication on "QTc and QTcd Measurements and Their Relationships with Left Ventricular Hypertrophy in Hemodialysis Patients", which is very interesting. 1 Alonso et al 1 concluded that "We found that QTc interval, in contrast to QTcd, is a reproducible and reliable measure and had a weak but positive correlation with LVMi in HD patients." This report used an unmatched control group; hence, the selection bias can be expected.…”