Assessing Autonomic Nervous System Imbalance in Post-COVID-19 Patients through Heart Rate Variability during Tilt Testing

Samuel Camargo1, Beatriz Silva2, Matheus Pereira3, Ana dos Santos4, Stella Maximo5, William Watanabe6, Jose Puglisi7, Daniel Goroso8
1Facultad de Medicina, Centro de Investigación Tecnológica, Universidad de Mogi das Cruzes., 2Faculty of Medicine, University of Mogi das Cruzes, 3Faculty of Medicine, University of Mogi das Cruzes., 4Faculty of Biomedicine, University of Mogi das Cruzes, 5Faculty of Medicine São Leopoldo Mandic de Araras, 6Technological Research Center, 7College of Medicine California North State University., 8University of Mogi das Cruzes


The COVID-19 has affected millions of people globally, and new symptoms and syndromes, such as "long COVID," are emerging. It is thought that autonomic nervous system instability, as a result of the virus, may explain these new patterns. However, there is still much to learn about the influence of SARS-CoV-2 on heart rate regulation and the sympathetic/parasympathetic system. This study aimed to evaluate heart rate variability (HRV) in post-COVID-19 patients during tilt test. The study involved five healthy volunteers (Control Group) and five individuals with confirmed COVID-19 history (Study Group). HRV was calculated in time domain, frequency domain, and nonlinear parameters, followed by a tilt test to assess dysautonomia affecting the autonomic nervous system. The results showed significant quantitative differences in the HRV parameters between the groups, including: VLF: 795.9 ± 276.3 ms² (GC) vs 643.1 ± 395.4 ms² (GE); LF 731.8 ± 205.3 ms² (GC) vs 541.2 ± 371.7 ms² (GE); HF 2016.7 ± 475.8 ms² (GC) vs 357 ± 387.8 ms² (GE); and LF/HF ratio 0.36 ± 0.9 (GC) vs 2.9 ± 1.9 (GE). The study found that an LF/HF ratio <1.0 in a healthy individual suggests that parasympathetic activity is relatively higher than sympathetic activity, indicating good cardiovascular health and autonomic nervous system balance. However, an LF/HF ratio > 1.0 in post-COVID-19 patients may indicate autonomic nervous system dysfunction, and a high LF/HF value may indicate an excessive sympathetic nervous system response. In conclusion, this study suggests that autonomic dysfunctions may exist in post-COVID-19 patients, as demonstrated by the significant changes in HRV parameters. However, caution should be taken in interpreting these results due to the variability of the LF/HF ratio value in different individuals' conditions. Further research is needed to better understand the impact of COVID-19 on the autonomic nervous system and heart rate regulation.