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QRS Slopes for Potassium and Calcium Monitoring in End-Stage Renal Disease Patients

Abstract:

Non-invasive estimation of serum potassium, [K+], and calcium, [Ca2+], are of major importance to prevent ventricular arrhythmias and sudden cardiac death, but current ambulatory estimation methods, mostly based on T wave properties, are limited. We present an analysis based on QRS slopes to detect and quantify electrolyte abnormalities in end-stage renal disease (ESRD) patients. We applied principal component analysis to 12-lead electrocardiograms (ECGs) of 29 ESRD patients undergoing hemodialysis (HD). In the first principal component, we analyzed two-minute segments at the end of each HD hour and computed a mean warped QRS complex (MWQRS) representing an optimal average of QRS complexes. We calculated the upward (I{text{US}}) and downward (I{text{DS}}) slope of the MWQRS and we quantified the relative slope changes with respect to the end of the HD session (Delta I{text{US}} and Delta I{text{DS}}). Delta I{text{US}} and Delta I{text{DS}} significantly increased and decreased, respectively, during HD in association with decreasing [K+] and increasing [Ca2+]. The median correlation coefficients of Delta I{text{US}} and Delta I{text{DS}} with the change in [K+] were -0.84 and 0.88, respectively. Corresponding correlation coefficients with the change in [Ca2+] were 0.78 and -0.91. The quantified QRS slope changes were related to both amplitude and duration changes in the QRS complex during HD. Changes in QRS slopes are strongly related to variations in [K+] and [Ca2+] during HD and could be used to monitor electrolyte concentrations in ESRD patients.