T-Wave Morphology Changes as Surrogate for Blood Potassium Concentration in Hemodialysis Patients

Flavio Palmieri1, Pedro Gomis2, José Esteban Ruiz3, Beatriz Bergasa3, Ferreira Dina4, Alba Martin5, Syed Hassaan Ahamed6, Esther Pueyo6, Juan Pablo Martínez7, Julia Ramírez8, Pablo Laguna9
1Universitat Politècnica de Catalunya, 2Universitat Politecnica de Catalunya, 3Nephrology Department, Hospital Clínico Universitario Lozano Blesa, 4Laboratorios Rubio,, 5Biomedical Signal Interpretation and Computational Simulation Group (BSICoS), Universidad de Zaragoza, 6University of Zaragoza, 7jpmart@unizar.es, 8Queen Mary University London, 9Zaragoza University


INTRODUCTION: Patients at end-stage renal disease (ESRD) undergoing hemodialysis (HD) are at high cardiovascular mortality risk due to potassium concentration ([K+]) changes out of normal ranges. The assessment of [K+] levels is limited as it can only be performed through blood tests in a hospital environment. Since [K+] levels are reflected on the T-wave in the electrocardiogram (ECG) signal, we hypothesized the T-wave morphology could be used to monitor [K+] changes in ESRD patients during HD. The aim of this study was to investigate whether dw, a time-warping-based ECG marker of T-wave morphology changes, with known association with ventricular repolarization dispersion, can monitor changes in [K+] levels. METHODS:We used 48-h long ECG recordings and [K+] measurements from a set of blood samples collected from 12 ESRD patients undergoing HD. An average T-wave (ATW) was obtained every hour of the ECG recordings and a reference T-wave was taken at the end of the HD session.The morphological changes between each ATW and the reference one were quantified with dw. The relative variations (Δ[K+]) in [K+] with respect to the reference values (end of treatment), during the HD session were computed. Spearman's correlation was computed between dw and Δ[K+]. RESULTS: The Figure shows the evolution of the distribution of Δ[K+] and dw during the HD session across all patients. The values of dw were significantly correlated with Δ[K+] (median [interquartile range] correlation coefficient of 0.95 [0.15]). CONCLUSIONS:T-wave morphology changes, quantified by dw, exhibit high correlation with [K+] changes. The results of this study support the use of dw to track changes in [K+] in ESRD patients undergoing HD.