Asymptomatic Autonomic Dysregulation after Recovery from Mild COVID-19 Infection Revealed by Analysis of Heart Rate Variability Responses to Task Load

Abstract

(1) Background: The coronavirus disease 2019 (COVID-19) infection is often followed by various complications, which can cause disturbances in daily life after recovery from the infectious state, although etiological mechanisms are not fully elucidated. Previous studies have indicated that autonomic dysregulation is an underlying factor, and it is of interest to clarify whether autonomic dysregulation is also present in the asymptomatic subjects after COVID-19 infection (post-COVID-19) for early detection of post-COVID-19 complications. (2) Methods: In the present study, autonomic activity was assessed using heart rate variability (HRV) analysis in the workers who recovered from mild COVID-19 infection (n = 39). They took a leave of absence for an average of 11.9 days and returned to the original work without complications. HRV was measured after an average of 9.3 days from return. High-frequency (HF) and low-frequency (LF) HRV parameters and heart rate (HR) were recorded during a three-behavioral-state paradigm of approximately 5 min length composed of initial rest, task load, and post-task rest periods and were compared with the data of the workers without the history of COVID-19 infection (normal, n = 38). (3) Results: The HRV and HR scores at the initial rest in the post-COVID-19 subjects showed no difference from those in the control. It is found that the post-COVID-19 subjects exhibited an attenuation of LF/HF increment during the task load and an excessive increase of HF together with a decrease of LF, LF/HF and HR during the post-task rest period in comparison with the initial rest scores. (4) Conclusions: These abnormalities are evaluated as asymptomatic autonomic dysregulation in response to task load, are frequently present after COVID-19 infection, and could be related to the generation of complications.

Keywords: asymptomatic autonomic dysregulation; heart rate variability; post-COVID-19; task load.

Figure 1

Heart rate variability (HRV) indices and heart rate (HR) profiles during the initial rest (R), the random generation task (T), and the rest-after-task (A) conditions in the normal control and post-COVID-19 subjects. HRV indices include low-frequency component (LF), high-frequency component (HF), and their ratio (LF/HF). Each filled circle indicates individual data, and the data from the same individuals are connected by lines. Significant increases and decreases from the score during the rest (R) are represented by upward and downward arrows, respectively (p < 0.05, Tukey multiple comparison test), above the data during the task (T) and the rest after the task (A). The filled reversed triangle indicates that the data of post-COVID-19 in the behavioral state are significantly lower than that of the normal control analyzed with the Mann–Whitney U-test (p < 0.05).

Figure 2

The ratio of the data during the task to that during the rest (Task/Rest) and the ratio of the data during the rest after the task to that during the rest (After/Rest). The ratios were compared between the normal control (N) and post-COVID-19 (COVID) subjects for HRV indices, low frequency (LF), high frequency (HF), and their ratio (LF/HF) together with heart rate (HR). The data were presented in box/whisker format of Tukey’s format. A significant difference between the data of normal control and post-COVID-19 subjects was indicated by an asterisk (Mann–Whitney U-test, p < 0.05).