Background and Aim: Non-invasive monitoring of serum potassium and calcium concentration ([K+] and [Ca2+]) can help to prevent arrhythmia in kidney patients. Current electrocardiogram (ECG) markers, including the width Tw and the time-warped temporal morphological variability dwu of the T wave, correlate significantly with [K+] and [Ca2+] but these relations are highly variable between patients. We hypothesized that inter-individual differences in cell type distribution across the ventricular wall can explain this variability.
Methods: We computed Tw and dwu in ECGs simulated with human heart-torso models with different proportions of endocardial, midmyocardial, and epicardial cells, while varying [K+] (3-6.2mM) and [Ca2+] (1.4-3.2mM). Electrical activity was simulated with a reaction-diffusion model with modified Ten Tusscher-Panfilov dynamics. Results were compared to measurements from 29 end-stage renal disease patients undergoing hemodialysis.
Results: Tw and dwu correlated strongly with [K+] (absolute median Pearson correlation coefficient r ranging from 0.70 to 0.93) and [Ca2+] (r ranging from 0.69 to 0.86) in the simulated cases and patients. Different cell type distributions reproduced inter-patient variability, with the same sign and magnitude of r in simulations as in patients.
Conclusion: Variations in the morphology and duration of the T wave were related to [K+] and [Ca2+] variations in our models and in the patients, with the observed high inter-individual variability in patients well reproduced by variations in cell type distribution across the ventricular wall.