Pulse rate variability: a new biomarker, not a surrogate for heart rate variability

Abstract

With the popularization of pulse wave signals by the spread of wearable watch devices incorporating photoplethysmography (PPG) sensors, many studies are reporting the accuracy of pulse rate variability (PRV) as a surrogate of heart rate variability (HRV). However, the authors are concerned about their research paradigm based on the assumption that PRV is a biomarker that reflects the same biological properties as HRV. Because PPG pulse wave and ECG R wave both reflect the periodic beating of the heart, pulse rate and heart rate should be equal, but it does not guarantee that the respective variabilities are also the same. The process from ECG R wave to PPG pulse wave involves several transformation steps of physical properties, such as those of electromechanical coupling and conversions from force to volume, volume to pressure, pressure impulse to wave, pressure wave to volume, and volume to light intensity. In fact, there is concreate evidence that shows discrepancy between PRV and HRV, such as that demonstrating the presence of PRV in the absence of HRV, differences in PRV with measurement sites, and differing effects of body posture and exercise between them. Our observations in adult patients with an implanted cardiac pacemaker also indicate that fluctuations in R-R intervals, pulse transit time, and pulse intervals are modulated differently by autonomic functions, respiration, and other factors. The authors suggest that it is more appropriate to recognize PRV as a different biomarker than HRV. Although HRV is a major determinant of PRV, PRV is caused by many other sources of variability, which could contain useful biomedical information that is neither error nor noise.

Differential effects of the blood pressure state on pulse rate variability and heart rate variability in critically ill patients

“…Nonetheless, several processes take part in the information transmission from the pure electrical ECG and the R waves to the mechanical PPG pulse wave, as is explained in ref. 33 . These factors may also explain in part the differences observed between HRV and PRV, especially under non-resting conditions and in non-healthy, older subjects.…”

“…These factors may also explain in part the differences observed between HRV and PRV, especially under non-resting conditions and in non-healthy, older subjects. Hence, PRV should not be considered a surrogate of HRV, but should be treated as an independent biomarker instead, which may contain additional information not available in HRV 33 .…”

Assessment of Nocturnal Autonomic Cardiac Imbalance in Positional Obstructive Sleep Apnea. A Multiscale Nonlinear Approach

“…Therefore, further research is needed to assess additional definitions of POSA in order to ensure the generalizability of our results. Regarding the use of PRV as a surrogate of HRV, recent studies highlighted the usefulness of PRV recordings in the assessment of autonomic cardiac function in different physiological conditions [ 59 , 60 ], while significant differences between both approaches were also reported [ 61 , 62 ] due to additional sources of variability not present in HRV [ 62 ]. Accordingly, further research is needed on the reliability of PRV analyses in the context of POSA.…”

Diagnosing Parkinson’s Disease Using Multimodal Physiological Signals

“…After an offline bandpass filter with 0.1-30 Hz for PPG and respiratory signals, we normalized the data by subtracting the mean and dividing by the standard deviation. Then we calculated the pulse rate variability (PRV) [20], mean, and the standard deviation of pulse intervals, pulse rate, and respiratory. We calculated the spectral power of the normalized PPG signals and respiratory signals.…”