Transmural Ventricular Heterogeneities Play a Major Role in Determining T-Wave Morphology at Different Extracellular Potassium Levels

End-stage renal disease (ESRD) affects more than 10% of the world population. ESRD patients present impaired potassium homeostasis, which increases the risk for ventricular arrhythmias and sudden cardiac death. Noninvasive estimation of serum potassium, [K
⁺
], before the patient experiences serious consequences is of major importance. In this study, we investigated the relationship of [K
⁺
] with three T-wave morphological descriptors: the T-wave width (T
w
), slope-to-amplitude ratio (T
SA
) and temporal morphological variability (d
w
) from ECGs of 12 ESRD patients undergoing hemodialysis and from simulated ECGs. Spearman’s correlation coefficients between the descriptors T
w
, T
SA
and d
w
and [K
⁺
] were –0.5, 0. 8 and 0.65, respectively. These associations were, however, highly patient-dependent. The high inter-individual variability in T-wave morphology, particularly observed at high [K
⁺
], was reproduced in the simulations and could be explained by differences in transmural heterogeneities, with 10% variations in the proportion of midmyocardial cells leading to changes larger than 15% in T-wave morphology. In conclusion, T-wave morphological descriptors have the potential to be used as predictors of [K
⁺
] in ESRD patients, but their associated inter-individual variability should be taken into account, especially under hyperkalemic conditions.