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Heart Rate Variability (HRV) Analysis: FAQs

The following FAQs refer to PLUX’s Heart Rate Variability (HRV) Analysis add-on for OpenSignals (r)evolution (more information | buy add-on).

What is Heart Rate Variability?

ECG is a periodic signal, where specific physiological events (atrium depolarization/repolarization and ventricular depolarization/repolarization) can be monitored through the characteristic complexes and segments, observable in ECG. However, for HRV analysis we should only be concerned with the concept of “periodicity” and how the duration of the cardiac cycle varies. 

For this purpose, it is only necessary to choose a reference event on ECG, being the most characteristic one the QRS Complex and the R-Peak that it contains (due to ventricular depolarization) which acts as a commonly used heart rate marker. By detecting the time instant of each R peak, the duration of all cardiac cycles is easily determined through the difference between consecutive time instants, which leads to the tachogram (time series that shows the evolution of RR interval duration along with the acquisition). 

For analyzing Heart Rate Variability (HRV) the Electrocardiography (ECG) data acquired using a PLUX Electrocardiography (ECG) sensor needs to be pre-processed before the parameters extraction begins. 

All parameters returned by OpenSignals HRV add-on are determined to take into consideration the information contained in the tachogram. In spite of not being common, some abnormal heartbeats can happen ectopic beats which generally affect drastically the HRV analysis. It is advisable to filter the tachogram (RR tachogram), ensuring that these “outliers” are removed from our HRV analysis. After filtering the tachogram is typically called NN tachogram. !

What sensors can I use with the HRV add-on?
How can I use the HRV add-on?

The following animation shows you the essential steps to run the add-on.

Does the HRV add-on use NN-Interval or RR-Interval data?

The data used for calculating frequency parameters is taken from the NN tachogram.

How does the add-on handle R-peak outliers?

An ectopic beat is a point in our RR tachogram, that is simply deleted if it does not meet the inclusion criteria specified in the interface

When calculating LF, HF, etc. from NN data, what is the method of processing after deleting outliers?

After deleting the outliers an estimate of Power Spectral Density (PSD) is done using the Welch’s method.

With the resulting power spectrum, the area under the curve (integration using the composite Simpson’s rule) is determined for the following frequency bands:

  • Very Low Frequency (VLF): [0.003 Hz; 0.040 Hz]
  • Low Frequency (LF) Band: [0.040 Hz; 0.150 Hz]
  • High Frequency (HF) Band: [0.150 Hz; 0.400 Hz]
Is the Poincaré Plot calculated using NN-Interval or RR-Interval data?

As is the case for temporal and spectral parameters, the Poincaré parameters are also determined through NN tachogram.

Updated on 29 de December de 2021

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