ANS	Autonomic Nervous System
BMI	Body Mass Index
CR	Cardiac Remodeling
ECG	Electrocardiogram
HF	Heart Failure
HFimpEF	Heart Failure with Improved Ejection Fraction
HFpEF	Heart Failure with Preserved Ejection Fraction
HFrEF	Heart Failure with Reduced Ejection Fraction
HFn	Normalized High Frequency
HFab	Absolute High Frequency
HR	Heart Rate
HRV	Heart Rate Variability
LFab	Low Frequency
LFn	Normalized Low Frequency
MESOR	Midline Estimating Statistic of Rhythm
NN	Normal-to-Normal (RR) intervals
PNSi	Parasympathetic Nervous System Index
RAAS	Renin–Angiotensin–Aldosterone System
RMSSD	Root Mean Square of Successive Differences
SDNN	Standard Deviation of NN intervals
SNSi	Sympathetic Nervous System Index
STi	Stress Index
VLF	Very Low Frequency
AmpEN	Amplitude Entropy
SampEn	Sample Entropy
ShannonE	Shannon Entropy
CorrDim	Correlation Dimension
REC	Recurrence
DET	Determinism
SD1	Poincaré short-term variability
SD2	Poincaré long-term variability
DFA	Detrended Fluctuation Analysis
SCN	Suprachiasmatic Nucleus
Φ	Acrophase