ABSTRACT
Interlead variability of the QT interval in surface electrocardiogram (ECG), i.e., QT dispersion, reflects regional differences in ventricular recovery time, and it has been linked to the occurrence of malignant arrhythmias in different cardiac diseases. The purpose of the study was to assess the effect of hemodialysis on QT and corrected QT (QTc) interval and dispersion in chronic hemodialyzed patients. Data of 34 nondiabetic patients (male/female = 21/13; mean age, 54 +/- 15 yr) on chronic hemodialysis were studied. Polysulfone capillaries and bicarbonate dialysate containing (in mEq/L) 135 Na+, 2.0 K+, 1.5 Ca2+, and 1.0 Mg2+ were used. Simultaneous 12-lead ECG were recorded before and after hemodialysis in a standard setting. The QT intervals for each lead were measured manually on enlarged (x3) ECG by one observer using calipers. Each QT interval was corrected for patient heart rate: QTc = QT/square root of RR (in milliseconds [ms]). The average cycle intervals were 853 +/- 152 ms predialysis and 830 +/- 173 ms postdialysis; the difference was not significant. The maximal QT interval changed significantly from 449 +/- 43 to 469 +/- 41 ms (P < 0.01). The corrected maximal QT interval increased significantly from 482 +/- 42 to 519 +/- 33 ms (P < 0.01). The QT dispersion changed from 56 +/- 15 to 85 +/- 12 ms (P < 0.001) and the corrected QT interval dispersion from 62 +/- 18 to 95 +/- 17 ms (P < 0.001). During hemodialysis, the serum potassium and phosphate levels decreased from 5.5 +/- 0.8 to 3.9 +/- 0.5 (mM) and from 2.3 +/- 0.5 to 1.6 +/- 0.4 (mM), respectively, whereas calcium increased from 2.2 +/- 0.23 to 2.5 +/- 0.22 (mM). It is concluded that hemodialysis increases the QT and QTc interval and QT and QTc dispersion in patients with end-stage renal failure. Thus, it may be stated that the nonhomogeneity of regional ventricular repolarization increases during hemodialysis. Measurement of QT and QTc dispersion is a simple bedside method that can be used for analyzing ventricular repolarization during hemodialysis.
Subject(s)
Cardiovascular Diseases/diagnosis , Electrocardiography , Kidney Failure, Chronic/complications , Kidney Failure, Chronic/therapy , Renal Dialysis , Adult , Aged , Analysis of Variance , Cardiovascular Diseases/etiology , Female , Humans , Incidence , Kidney Failure, Chronic/diagnosis , Linear Models , Male , Middle Aged , Observer Variation , Renal Dialysis/methods , Reproducibility of Results , Risk FactorsABSTRACT
Interlead variability of the QT interval in surface 12-lead ECG (i.e. QT dispersion) reflects regional differences in ventricular recovery time and it has been linked to the occurrence of malignant arrhythmias in different cardiac diseases. The purpose of the study was to assess the effect of hemodialysis on QT dispersion in chronic hemodialyzed patients. The data of 34 patients (Male/Female = 21/13, mean age 54 +/- 15 years) on chronic hemodialysis were studied. Simultaneous 12 lead ECGs were recorded pre- and post-hemodialysis in a standard setting. The QT intervals for each lead were measured manually by one observer. Each QT interval was corrected for patient's heart rate: QTc = QT/square route of RR (sec). The maximal QT interval changed from 449 +/- 43 to 469 +/- 41 ms (p < 0.01). The maximal QTc interval increased from 482 +/- 42 to 519 +/- 33 ms (p < 0.01). The QT dispersion changed rom 56 +/- 15 to 85 +/- 12 ms (p < 0.001), and the QTc interval from 62 +/- 18 to 95 +/- 17 ms (p < 0.001). During hemodialysis the serum potassium and phosphate decreased from 5.5 +/- 0.8 to 3.9 +/- 0.5 (p < 0.001), and from 2.3 +/- 0.5 to 1.6 +/- 0.4, respectively, whereas calcium level increased from 2.2 +/- 0.23 to 2.5 +/- 0.22 (p < 0.001). It can be concluded that the hemodialysis increased the inhomogeneity of regional ventricular repolarization. Measurement of QT and QTc dispersion by a cheap and simple bedside method could predict the increased myocardial inhomogeneity in dialyzed patients.
