EFFECT OF HEMODIALYSIS ON THE DISPERSION OF THE QTC INTERVAL

The QTc dispersion reflects the underlying regional heterogeneity of t he recovery of the ventricular excitability, thereby it is considered as a novel marker of risk of ventricular arrhythmias. Because a higher incidence of ventricular arrhythmias is described during and after he modialysis, the aim of this study has been to evaluate the QTc dispers ion before and after uncomplicated hemodialysis session. Twenty chroni c uremics without heart failure, ischemic heart disease or dialysis hy potension were selected. The QTc dispersion was determined as the diff erence between the longer and the shorter QTc interval measured on a 1 2-lead electrocardiogram. Following the hemodialysis session, the QTc dispersion increased from 30 +/- 9 to 54 +/- 17 ms (p < 0.001) associa ted with the expected reduction of potassium and magnesium and with th e increase of extracellular calcium concentration. However, no correla tion has been observed between the QTc dispersion increase and the deg ree of the intradialytic changes of plasma electrolytes, blood pressur e or body weight. In summary, the hemodialysis treatment per se does i nduce an increase of the QTc dispersion, likely due to the rapid chang es of electrolyte plasma concentrations. This can potentially contribu te to the arrhythmogenic effect of the hemodialysis procedure, reflect ing an enhanced regional heterogeneity of ventricular repolarization. The clinical importance of the increase of QTc dispersion as risk fact or of ventricular arrhythmias, particularly in hemodialyzed patients s uffering from ischemic or hypertrophic heart diseases, should be the m atter of further investigations.