Are ultra‐short heart rate variability features good surrogates of short‐term ones? State‐of‐the‐art review and recommendations

Abstract

Ultra-short heart rate variability (HRV) analysis refers to the study of HRV features in excerpts of length <5 min. Ultra-short HRV is widely growing in many healthcare applications for monitoring individual's health and well-being status, especially in combination with wearable sensors, mobile phones, and smart-watches. Long-term (nominally 24 h) and short-term (nominally 5 min) HRV features have been widely investigated, physiologically justified and clear guidelines for analysing HRV in 5 min or 24 h are available. Conversely, the reliability of ultra-short HRV features remains unclear and many investigations have adopted ultra-short HRV analysis without questioning its validity. This is partially due to the lack of accepted algorithms guiding investigators to systematically assess ultra-short HRV reliability. This Letter critically reviewed the existing literature, aiming to identify the most suitable algorithms, and harmonise them to suggest a standard protocol that scholars may use as a reference in future studies. The results of the literature review were surprising, because, among the 29 reviewed papers, only one paper used a rigorous method, whereas the others employed methods that were partially or completely unreliable due to the incorrect use of statistical tests. This Letter provides recommendations on how to assess ultra-short HRV features reliably and proposes an inclusive algorithm that summarises the state-of-the-art knowledge in this area.

Optimal fiducial points for pulse rate variability analysis from forehead and finger photoplethysmographic signals

“…First, the classical time and frequency variability indices were estimated for each fiducial point in the three phases of the tilt table test. In order to measure P LF and P HF , at least 1 minute of HRV and PRV signals is needed (Pecchia et al, 2018). Therefore, due to the nature of this study, the length of the segments and the Hamming window were chosen to provide a reliable estimation of the P LF power (McNames et al, 2006;Baek et al, 2015) and an accurate comparison between the variability signals.…”

“…In each phase of the protocol, HRV and PRV indices have been calculated in short segments whose length is in the range of 1 to 2 minutes due to the nature of the study (McNames et al, 2006;Salahuddin et al, 2007;Baek et al, 2015;Pecchia et al, 2018), where stationarity is assumed and considering a valid segment when there are no artifacts during at least 1 min of PPG signal. Otherwise, that segment is discarded for the variability analysis from all signals in the database.…”

Feasibility of assessing ultra-short-term pulse rate variability from video recordings

“…Ultra-short-term (UST; <5 minutes) HRV has been investigated as an alternative to standard HRV analysis (for a full review of this topic, see Pecchia et al (2018)). One of the most relevant studies considering the validity of UST recordings for HRV measurements was conducted by Munoz et al (2015).…”

“…The authors reported that an average of multiple 10 s recordings efficiently captures the standard deviation of normal-to-normal (NN) intervals (SDNN), whereas an average of multiple 10 s recordings or one single 30 s recording is recommended for accurately measuring the root mean square of successive NN interval differences (RMSSD). The study's large sample (3,387 subjects) and the rigorous method applied to assess the validity of UST-HRV mean the study gives strong support for the adoption of these HRV metrics (Pecchia et al, 2018). Recently, Castaldo et al (2019) examined the validity of UST-HRV metrics derived from 0.5-, 1-, 2-, 3-, and 5-minute-long ECG recordings.…”

“…only a correlation test) the results with sufficient rigor. This issue was identified by Shaffer & Ginsberg (2017), Londhe & Atulkar (2018) and is thoroughly addressed by Pecchia et al (2018). The adoption (and standardization) of UST-HRV would be highly beneficial because in certain clinical applications, for example, routine check-ups and check-ups of patients with atrial fibrillation (Camm et al, 2010), ECG recordings of less than 5 min are recorded.…”