HRV Advanced Parameters

The Heart Rate Variability points described below are a collection of statistics related to changes occurring in the measured timing interval between one heartbeat and the next. The points are available in addition to HRV_SDNN.

IDAcronymFeature DomainUnitAvailable After (seconds)RangeAlso Needs
HRV_ALPHAαNonlinear-1200 to 2-
HRV_ALPHA1α1Nonlinear-1200 to 3-
HRV_ALPHA2α2Nonlinear-120-1 to 3-
HRV_HFHFFrequency domainms²1208 to 6319-
HRV_HFNUHFnuFrequency domainnu1200 to 53-
HRV_LFLFFrequency domainms²1202 to 100-
HRV_LF_HFLF/HFFrequency domain-12010 to 9935-
HRV_LFNULFnuFrequency domainnu1200 to 98-
HRV_MEAN_RRIMean RRITime domainms30128 to 946-
HRV_MHRMean HRTime domainbpm3064 to 529-
HRV_NN50NN50Time domain-600 to 28-
HRV_PEAK_HFPeak HFFrequency domainpeak1200 to 0.4-
HRV_PEAK_HF_ARPeak HF (AR)Frequency domainpeak1200 to 0.15-
HRV_PEAK_LFPeak LFFrequency domainpeak1200 to 0.4-
HRV_PEAK_LF_ARPeak LF (AR)Frequency domainpeak1200 to 0.15-
HRV_PNN50pNN50Time domain%600 to 76-
HRV_RMSSDRMSSDTime domainms6012 to 118-
HRV_SD1SD1Nonlinearms1209 to 85-
HRV_SD2SD2Nonlinearms1208 to 185-
HRV_SD1_DIV_SD2SD1/SD2Nonlinear-1200 to 2-
HRV_SDNNSDNNTime domainms301 to 80-
HRV_TOTAL_POWERTotal PowerFrequency domainms²300 to 3535-
HRV_VLFVLFFrequency domainms²1200 to 9086-

Definitions

The points in the table are defined below. Please note that in all cases, the definition is the DeepAffex Cloud's estimate.

  • HRV_ALPHA: Scaling exponent of RR intervals over different time series based on Detrended Fluctuation Analysis.
  • HRV_ALPHA1: Short-term fluctuations from Detrended Fluctuation Analysis.
  • HRV_ALPHA2: Long-term fluctuations from Detrended Fluctuation Analysis.
  • HRV_HF: Power measured in high-frequency band.
  • HRV_HFNU: Proportion of power in the high-frequency band (0.15–0.40 Hz) to summation of powers in low- and high-frequency bands, expressed in normal units (nu)
  • HRV_LF_HF: Ratio of power in low-frequency band to power in high-frequency band.
  • HRV_LF: Power measured in low-frequency band.
  • HRV_LFNU: Proportion of power in the low-frequency band (0.04–0.15 Hz) to the summation of powers in low- and high-frequency bands, expressed in normal units (nu)
  • HRV_MEAN_RRI: Average RR interval.
  • HRV_MHR: Average heart rate.
  • HRV_NN50: Number of adjacent NN intervals that differ from each other by more than 50ms.
  • HRV_PEAK_HF_AR: Highest amplitude frequency in the high-frequency band using autoregressive power spectral density estimate using Burg's method.
  • HRV_PEAK_HF: Highest amplitude frequency in the high-frequency band using Welch's power spectral density estimate.
  • HRV_PEAK_LF_AR: Highest amplitude frequency in the very-low-frequency (VLF) band using autoregressive power spectral density estimate using Burg's method.
  • HRV_PEAK_LF: Highest amplitude frequency in the low-frequency band using Welch's power spectral density estimate.
  • HRV_PNN50: Percentage of adjacent NN intervals that differ more than 50ms.
  • HRV_RMSSD: Root mean square of successive RR interval differences.
  • HRV_SD1_DIV_SD2: Ratio of SD1 to SD2, both obtained from Poincaré Plot.
  • HRV_SD1: Standard deviation of points along the line of identity on the Poincaré Plot.
  • HRV_SD1: Standard deviation of points perpendicular to the line of identity on the Poincaré Plot.
  • HRV_SDNN: Standard deviation of NN intervals.
  • HRV_TOTAL_POWER: Summation of power measures in all frequency bands.
  • HRV_VLF: Power measured in the very-low-frequency (VLF) band.

Background

Heart Rate Variability (HRV) is a measure of the variation in time between successive heartbeats and is influenced by various physiological factors that impact heart rate and variability, including breathing patterns, blood pressure regulation, and natural daily rhythms such as sleep-wake cycles, physical activity, and food intake. HRV can be analyzed in three main domains: time domain, frequency domain, and non-linear domain.

In the time domain, HRV is measured through various statistical measures of the inter-beat intervals, such as the standard deviation of the RR intervals (SDNN), root mean square of successive RR interval differences (RMSSD), and the percentage of successive RR intervals that differ by more than 50 ms (pNN50). In the frequency domain, HRV is analyzed by looking at the power of the ECG signal in different frequency bands, which are called VLF, LF, and HF. These bands represent different ranges of frequencies, with VLF being the lowest, and HF being the highest. In the non-linear domain, HRV is analyzed using more complex mathematical methods like DFA and entropy measures. These methods provide information on how the inter-beat intervals vary in complexity and randomness.

Overall, HRV analysis provides important information about cardiovascular function and overall health and can help guide interventions to improve overall health and well-being.

There is no interpretation table for HRV Advanced Parameters.

Note

TOI is designed to provide quick HRV measurements in just 30 seconds, but it's important to recognize that HRV analysis is typically performed over much longer periods of time to obtain accurate results. In general, electrocardiograms of at least 240-300 seconds are needed to reliably measure HRV. While short-term HRV measurements such as SDNN and RMSSD can be a useful approximation of longer-term HRV, there are some limitations. RMSSD is generally considered to be a more reliable measure than SDNN and averaging multiple 10-second ECG recordings can help to improve accuracy. However, it's important to use caution when interpreting the results of TOI, as it is subject to limitations similar to other short-term HRV analysis methods.