Analysis of T Wave Nonlinear Dynamics for Serum Potassium Monitoring in End-Stage Renal Disease Patients

Non-invasive estimation of serum potassium, [K+], is of major importance to prevent associated risks, but current ambulatory estimation methods are limited. We investigated changes in T wave nonlinear dynamics by quantifying a divergence-related marker ψ on electrocardiograms (ECGs) from 15 end-stage renal disease (ESRD) patients undergoing hemodialysis (HD) and we assessed the relationship between ψ and [K+]. ECGs from 22 simulated transmural ventricular fibers were additionally calculated. In ESRD patients, ψ took the largest values at the beginning and end of the HD session, corresponding to the highest and lowest [K+] values. The median correlation coefficient over patients between the change in ψ and the change in [K+] was 0.92 and decreased to 0.74 after controlling for the effects of [Ca2+] and heart rate. These associations were, however, highly patient-dependent. Both the strength and variability of the ψ -[K+] relationship was reproduced in the simulations, with the variability explained by differences in transmural heterogeneities: 10% variations in the proportion of epicardial and midmyocardial cells led to more than 10% and 8% changes in ψ, respectively. In conclusion, changes in the nonlinear dynamics of the ECG T waves can be related to [K+] variations in ESRD patients, despite the high inter-individual variability.