${\mathsf{\Psi }}_{\pi \mathrm{CA}}$	Transformation matrix to perform Periodic Component Analysis
$\left[K^{+}\right]$	Blood potassium concentration
$\mathsf{\Delta }\left[K^{+}\right]$	Blood potassium concentration variations
ECG	Electrocardiogram
ESRD	End Stage Renal Disease
ESRD-HD patients	End Stage Renal Disease patients undergoing hemodialysis
HD	Hemodialysis
IQR	Interquartile range
MWTW	Mean Warped T-wave
PCA	Principal Component Analysis
$\pi$ CA	Periodic Component Analysis
$\pi C^{\mathrm{T}}$	Periodic Component Analysis evaluated over the T-wave
$\rho$	Spearman’s correlation coefficient
r	Pearson’s correlation coefficient