Emerging evidence suggests COVID-19 may affect cardiac autonomic function; however, the limited findings in young adults with COVID-19 have been equivocal. Notably, symptomology and time since diagnosis appear to influence vascular health following COVID-19, but this has not been explored in the context of cardiac autonomic regulation. Therefore, we hypothesized that young adults who had persistent symptoms following COVID-19 would have lower heart rate variability (HRV) and cardiac baroreflex sensitivity (BRS) compared to those who had COVID-19 but were asymptomatic at testing and controls who never had COVID-19. Further, we hypothesized that there would be relationships between cardiac autonomic function measures and time since diagnosis. We studied 27 adults who had COVID-19 and were either asymptomatic (ASYM; n=15 (6 female); 21±4 years; 8.4±4.0 weeks from diagnosis) or symptomatic (SYM; n=12 (9 female); 24±3 years; 12.3±6.2 weeks from diagnosis) at testing, and 20 adults who reported never having COVID-19 (24±4 years, 11 female). Heart rate and beat-to-beat blood pressure were continuously recorded during 5-minutes of rest to assess HRV and cardiac BRS. HRV (root mean square of successive differences between normal heartbeats [RMSSD]; control: 73±50ms; ASYM: 71±47ms; SYM: 84±45ms; p=0.774) and cardiac BRS (overall gain; control: 22.3±10.1ms/mmHg; ASYM: 22.7±12.2ms/mmHg; SYM: 24.3±10.8ms/mmHg; p=0.871) were not different between groups. However, we found correlations with time since diagnosis for HRV (e.g., RMSSD: r=0.460, p=0.016) and cardiac BRS (overall gain, r=0.470, p=0.014). These data suggest a transient impact of COVID-19 on cardiac autonomic function that appears mild and unrelated to persistent symptoms in young adults.

Background The COVID‐19 pandemic has evolved into an unprecedented public health crisis, with over 255 million cases and over 5 million deaths worldwide. Emerging evidence indicates that many previously healthy young adults diagnosed with COVID‐19 experience persistent symptoms beyond the acute phase of the illness, a phenomenon coined “long‐COVID”. Several clinical reports suggest that long‐COVID may negatively impact the autonomic nervous system, leading to blood pressure (BP) dysregulation. However, the effects of COVID‐19 on indices of cardiac autonomic modulation (heart rate variability; HRV) and cardiac baroreflex sensitivity (cBRS) beyond the acute phase of the illness remain unclear. Likewise, the influence of COVID‐19 symptomology on these indices is also not well understood. Therefore, the purpose of this study was to determine the impact of COVID‐19 and persistent symptomology on cBRS and HRV in otherwise healthy young adults beyond the acute phase of illness. We hypothesized that young adults who have had COVID‐19 would exhibit attenuated cBRS and HRV compared to healthy controls and these impairments would be greatest in COVID‐19 subjects with persistent symptoms. Methods We studied 24 healthy adults (age = 22 ± 1 years; mean ± standard error) with a lab‐confirmed diagnosis of COVID‐19 (COVID; 11 ± 1 weeks from diagnosis) and twelve adults (age = 23 ± 1 years) who never had COVID‐19 (control). COVID subjects reported being either asymptomatic (n = 13) or symptomatic (n = 11) at the time of testing. Heart rate (ECG) and arterial BP (finger photoplethysmography) were continuously recorded during a ten‐minute resting baseline. The Sequence Method was used to estimate spontaneous cBRS for up gains (increase systolic BP: increase R‐R interval), down gains (decrease systolic BP: decrease R‐R interval), and for overall gains. HRV was determined using normalized high frequency power (HF; normalized units), the ratio between low frequency power and high frequency power (LF/HF; frequency‐domain) and root mean square of successive differences between normal heartbeats (RMSSD; time‐domain). Results We found that cBRS and HRV were not different between control and COVID subjects (P > 0.05 for all comparisons). Further, there were no significant differences in overall gains between controls (24 ± 3 ms/mmHg), asymptomatic COVID (24 ± 3 ms/mmHg), and symptomatic COVID (26 ± 3 ms/mmHg, P = 0.934) groups. Similarly, no group differences were found in up or down gains (both P > 0.05). Likewise, for HRV, no differences were observed in the HF power (control: 56 ± 6 n.u., asymptomatic: 60 ± 5 n.u., symptomatic: 63 ± 3 n.u., P = 0.580), LF/HF ratio (control: 1.19 ± 0.38, asymptomatic: 0.73 ± 0.14, symptomatic: 0.58 ± 0.09, P = 0.195) or RMSSD (control: 82 ± 16 ms, asymptomatic: 77 ± 14 ms, symptomatic: 86 ± 14 ms, P = 0.909) between groups. Conclusion These preliminary data suggest that beyond the acute phase of COVID‐19, cBRS and HRV are preserved in healthy young adults, regardless of persistent symptomology.