Influence of plasma potassium changes on the myocardial cell repolarization during hemodialysis

Dialysis therapy has a strong impact on cardiac excitability and the frequency of ectopic beats increases in the course of the session. Dispersion of ventricular repolarization could be a cause of the dialysis arrhythmogenic effect. In fact, QT dispersion increases during dialysis and this increase seems to be related to electrolyte, particularly potassium and calcium, concentration changes. However, some concerns have been raised about uncertainty of the QT dispersion measurement. Principal component analysis of the T wave applied to 12-lead ECG recording has been proposed as a novel approach to study the complexity of repolarization without having to determine the end of T-wave. The aim of this study was to assess and quantify the 24-hour changes in the complexity of ventricular repolarization in patients undergoing hemodialysis by means of principal components analysis. The effects of two dialysis protocols leading to different plasma potassium levels were also analyzed. Twelve patients were studied during Acetate Free Biofiltration with K+ profiling (AFBK). AFBK sessions were classified as Klow and Khigh on the basis of the dialyzate K+ concentration set at the start of the treatment. For each patient four sessions (2 Klow and 2 Khigh) were analysed. Holter 24-hour recordings were collected starting with the dialysis session. Principal components analysis was applied to the T wave automatically extracted from each beat and the repolarization complexity was quantified by the ratio of the second to the first eigenvalue (PCA ratio). Hemodialysis caused a significant increase in the PCA ratio (+50% at the end of the sessions). The PCA ratio recovered to the basal value during the first hour post-dialysis and kept stable during the subsequent 19 hours. When comparing Klow and Khigh sessions the PCA ratio increase was similar during the first two hours of dialysis but it was significantly higher in Klow sessions in the last two hours of dialysis, then the PCA ratio recovered to the same basal value. A difference in the occurrence of ventricular ectopic beats was also pointed out, being the number of premature ventricular contractions (PVCs) significantly higher in Klow sessions in the last three hours of treatment (p<0.05). Results show that hemodialysis significantly increases the T wave complexity. Such an increase is related to the therapy-induced potassium depletion, with greater complexity when lower potassium levels are reached. Moreover, it can be hypothesized that repolarization dispersion changes underlie the observed increase in PVCs occurrence.