This In Focus article reviews sources of heart rate variability, its role as a prognostic marker for cardiovascular diseases, and its application in estimation of cardiac autonomic nervous system activity.
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heart rate variability
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Supporting Sources
Linked Claims
Heart rate variability is reduced in patients with mild hypertension compared with normal values.
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Heart rate variability (variance of R-R intervals) was reduced in patients with mild hypertension (29) compared with normal values (1,134 ± 202 vs. 3,466 ± 1,018 ms2)
Simple time-domain statistics of heart rate variability such as the standard deviation of R-R intervals can reliably predict prognosis in cardiovascular disease.
Quoted textsource-backed
Simple statistics of heart rate variability, such as the standard deviation of R-R intervals in the ECG, can reliably predict the prognosis of cardiovascular diseases.
Heart rate variability does not reliably reflect the sympathetic response to orthostatic stress.
Quoted textsource-backed
Thus heart rate variability does not reliably reflect the sympathetic response to orthostatic stress.
LF and HF spectral components do not always reliably reflect cardiac sympathetic and parasympathetic tone.
Quoted textsource-backed
the LF and HF spectral components of heart rate variability may not always be very reliable markers for cardiac sympathetic and parasympathetic "tone"
HF heart rate variability is synchronized to respiration and is primarily modulated by cardiac parasympathetic innervation.
Quoted textsource-backed
high frequencies (HF; 2.5- to 6.0-s cycle length in humans) that are synchronized to the respiratory rhythm and are primarily modulated by cardiac parasympathetic innervation
LF heart rate variability is sensitive to changes in cardiac sympathetic activity and may also include parasympathetic contributions.
Quoted textsource-backed
low frequencies (LF; >6-s cycle length in humans) that are sensitive to changes in cardiac sympathetic (and presumably parasympathetic) nerve activity
Frequency components of heart rate variability are classified into ULF, VLF, LF, and HF bands with distinct physiological associations.
Quoted textsource-backed
these frequencies are classified into 1) ultra-low frequencies (ULF...); 2) very low frequencies (VLF...); 3) low frequencies (LF...); and 4) high frequencies (HF...)
Heart rate variability is generated by multiple factors and is not exclusively limited to autonomic nervous system activity.
Quoted textsource-backed
heart rate variability is generated by multiple factors not exclusively limited to the autonomic nervous system
Loss of heart rate variability is associated with severe cardiovascular disease and predicts poor outcome.
Quoted textsource-backed
loss of heart rate variability can indicate severe cardiovascular diseases and reliably predict poor outcome of such conditions