Objective: Noninvasive screening of hypo- and hyperkalemia can prevent fatal arrhythmia in end-stage renal disease (ESRD) patients, but current methods for monitoring of serum potassium (K + ) have important limitations. We investigated changes in nonlinear dynamics and morphology of the T wave in the electrocardiogram (ECG) of ESRD patients during hemodialysis (HD), assessing their relationship with K + and designing a K + estimator.
Methods: ECG recordings from twenty-nine ESRD patients undergoing HD were processed. T waves in 2-min windows were extracted at each hour during an HD session as well as at 48 h after HD start. T wave nonlinear dynamics were characterized by two indices related to the maximum Lyapunov exponent (λ t , λ wt ) and a divergence-related index (η). Morphological variability in the T wave was evaluated by three time warping-based indices (d w , reflecting morphological variability in the time domain, and d a and d a NL , in the amplitude domain). K + was measured from blood samples extracted during and after HD. Stage-specific and patient-specific K + estimators were built based on the quantified indices and leave-one-out cross-validation was performed separately for each of the estimators.
Results: The analyzed indices showed high inter-individual variability in their relationship with K + . Nevertheless, all of them had higher values at the HD start and 48 h after it, corresponding to the highest K + . The indices η and d w were the most strongly correlated with K + (median Pearson correlation coefficient of 0.78 and 0.83, respectively) and were used in univariable and multivariable linear K + estimators. Agreement between actual and estimated K + was confirmed, with averaged errors over patients and time points being 0.000 ± 0.875 mM and 0.046 ± 0.690 mM for stage-specific and patient-specific multivariable K + estimators, respectively.
Conclusion: ECG descriptors of T wave nonlinear dynamics and morphological variability allow noninvasive monitoring of K + in ESRD patients.
Significance: ECG markers have the potential to be used for hypo- and hyperkalemia screening in ESRD patients.
(Copyright © 2022 The Authors. Published by Elsevier Ltd.. All rights reserved.)