Are Wearable Photoplethysmogram-Based Heart Rate Variability Measures Equivalent to Electrocardiogram? A Simulation...

Area of Science:

• Cardiovascular Physiology
• Biomedical Engineering
• Signal Processing

Background:

• Electrocardiography (ECG)-derived heart rate variability (HRV) and photoplethysmography (PPG)-derived "HRV" (PRV) are often used interchangeably.
• Variability in pulse arrival time (PAT) may cause dissociation between HRV and PRV.

Purpose of the Study:

• To determine if PRV is equivalent to ECG-derived HRV.
• To assess if PRV's inherent error qualifies it as a distinct, high-quality measurement separate from HRV.

Main Methods:

• Bayesian simulation using ECG data from 1084 subjects.
• Incorporated individual PAT dispersions (wrist and finger) to model PPG wave arrival times.
• Calculated root mean square of successive differences (RMSSD) and standard deviation of N-N intervals (SDNN) for both HRV and PRV, comparing them within predefined equivalence bounds (ROPE).

Main Results:

• At the lowest PAT variability (2.0 SD), SDNN equivalence was 88.4% and RMSSD was 21.4%.
• Increasing PAT variability significantly decreased the equivalence between PRV and HRV for both SDNN and RMSSD.
• Pulse arrival time variability increased the uncertainty (HDI width) in PRV measurements, particularly for RMSSD.

Conclusions:

• PRV is not a reliable surrogate for HRV in individuals with significant PAT variability.
• When PRV is considered a unique biometric, SDNN demonstrates potentially more favorable measurement properties than RMSSD, despite both metrics exhibiting non-uniform errors.