A cross sectional study of the autonomic function at different recovery phases in SARS-CoV-2 patients without...

Autonomic nervous system involvement in COVID-19 survivors has been reported. This study aimed to assess heart rate variability (HRV) and baroreflex sensitivity (BRS) in COVID-19 survivors without orthostatic symptoms at different times after infection. Participants were classified as post-acute (PA, < 120 days) or long-term (LT, ≥ 120 days) according to time since positive swab. Mean heart rate (HR), time- (SDNN, RMSSD, pNN50) and frequency-domain (LF power, HF power, LF/HF) were computed. BRS was assessed by the sequence (BRS_seq) and the transfer function (BRS_TF) methods. We studied 37 PA and 36 LT patients and 50 age- and sex-matched healthy controls (HC). Compared to HC, PA patients exhibited significantly lower values for SDNN, RMSSD, pNN50, log-transformed LF and HF power, BRS_TF and BRS_seq, and higher HR and LF/HF ratio. Similar trends were observed in LT patients, with the exception of HR and LF/HF, where differences were not significant. Significant differences between PA and LT were found in HR (77.2 ± 10.7 vs. 69.8 ± 10.7 bpm, p = 0.002), log-transformed HF power (3.1 ± 1.2 vs. 3.8 ± 1.2 log-ms², p = 0.010), LF/HF (1.97 ± 1.76 vs. 1.31 ± 0.97, p = 0.035) and BRS_TF (2.00 ± 1.62 vs. 3.18 ± 2.53 ms/mmHg, p = 0.042). This study may support the notion that survivors of COVID-19 without orthostatic symptoms may show a decrease in parasympathetic and an increase in sympathetic modulation, which is more relevant in the post-acute phase of the disease.