Evidence-Based Clinical Utility of Heart Rate Variability Across Populations, Including Long COVID

Purpose: Heart rate variability (HRV) has been used for decades as a tool for measuring systemic health through the autonomic nervous system (ANS). The purpose of this paper was to examine the literature on HRV and to investigate its use in the long COVID (LC) population. Summary of Key Points: Measurement devices vary significantly in their validity and reliability when compared with the gold standard of electrocardiogram (ECG). Wrist and hand devices typically demonstrate diminished validity for capturing HRV signal, while chest strap devices often exhibit high reliability and validity. Lack of transparency in third-party software used to clean and analyze HRV data makes assessment for accuracy problematic. This is of particular concern when single beat miscalculations can result in significantly dissimilar output. The conditions under which HRV data are collected, such as natural or paced breathing, activity intensity, and patient position, can dramatically affect HRV readings. While some individual HRV metrics have consistently been shown to reflect certain components of the ANS, such as high-frequency power as a measure of parasympathetic function, the meaning of other metrics is less clear. Recommendations for Clinical Practice: Heart rate variability can be an extraordinarily valuable tool to measure systemic function. However, it is recommended that clinicians be judicious in the interpretation of HRV, considering inconsistencies in presentation. This is particularly true in LC, where individual HRV varies greatly. In all populations, clinicians should consider using valid devices to assess trends in HRV values over time, along with consideration of unique physical conditions.