Changes in the QT intervals, QT dispersion, and amplitude of T waves after hemodialysis

Background: Increased QT dispersion (QTd) has been associated with an increased risk for ventricular arrhythmias and sudden death in the general population and in various clinical states. Methods: We investigated the impact of hemodialysis (HD) on QT, QTd, and T-wave amplitude in subjects with end-stage renal failure. Data on 49 patients on chronic HD were studied. The QT, QTd, and the sum of amplitude of T waves (ET) in millimetre in the 12 ECG leads, along with a host of other ECG parameters, body weight, blood pressure, heart rate, electrolytes, and hemoglobin/hematocrit were measured before and immediately after HD. Results: QT decreased (380.9 +/- 38.4-363.5 +/- 36.8 ms, P = 0.001), the QTc did not change (406.2 +/- 30.8-405.4 +/- 32.2 ms, P 0.8), the QTd increased (31.3 +/- 14.6-43.9 +/- 18.6 ms, P = 0.003), and the Sigma T decreased (32.3 +/- 15.7-25.9 +/- 12.6 mm, P = 0.0001) after HD. There was no correlation between the change in QTd and the changes in serum cations, heart rate, the subjects' weight, T-wave duration, and ET. However, the change in QTc correlated inversely with the change in serum Ca++ (r = -0.339, P = 0.021). Conclusion: QTd increased, the ET decreased, and the QTc and T-wave duration remained stable, after HD. The QTd increase, although may be real, could also reflect measurement errors stemming from the decrease in the amplitude of T waves (as shown recently), imparted by HD; this requires clarification, to use QTd in patient on HD.