Heart rate variability and cardiac autonomic functions in post-COVID period

C. P. Long-term cognitive and autonomic effects of COVID-19 in young adults: a cross-sectional study at 28 months

OBJECTIVES

The COVID-19 pandemic, caused by SARS-CoV-2, has had profound global impacts since its emergence in late 2019. Whilst acute symptoms are well-documented, increasing evidence suggests long-term consequences extending beyond the acute phase. This study aimed to investigate the long-term cognitive and autonomic effects of COVID-19 in young adults.

MATERIALS AND METHODS

We conducted a cross-sectional study comparing young adults with a history of COVID-19 (n = 34) to matched controls (n = 34). Cognitive function was assessed using the Sternberg Task, Stroop Task, and Go/No-Go Task (GNG). Autonomic function was evaluated using heart rate variability (HRV) parameters.

RESULTS

The average time interval between COVID-19 infection and testing was 28.2 months. The COVID-19 group showed significantly increased reaction time in the 2-item absent condition (p = 0.044) and errors in the 4-item present condition (p = 0.012) of the Sternberg Task and increased neutral response time (p = 0.028) and the normalized time for completing the task (p = 0.022) in the Stroop Task. No significant differences were found in the GNG Task. HRV parameters did not differ significantly between groups, although trends toward higher overall HRV were observed in the COVID-19 group.

CONCLUSION

Young adults who had COVID-19 infection approximately 28 months ago show minimal long-term impact on cognitive function and autonomic regulation. However, subtle cognitive inefficiencies persist, particularly in working memory and executive function tasks. These findings suggest a generally favorable long-term prognosis for young adults following mild to moderate COVID-19 but highlight the need for further investigation into persistent subtle cognitive effects and autonomic effects.

Heart rate variability in patients with atrial fibrillation of sinus rhythm or atrial fibrillation: chaos or merit?

Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia characterized by consistently irregular atrial and ventricular contractions. Heart rate variability (HRV) refers to the changes in the intervals between consecutive ventricular heartbeats. In sinus rhythm, HRV may be subtle and is quantitatively reflecting the dynamic interplay of the cardiac autonomic nervous system, which plays a crucial role in the onset, development, and maintenance of AF. HRV metrics, consisting of time-domain, frequency-domain, and nonlinear parameters, have been verified to vary significantly before and after AF episodes, and AF treatment-related procedures such as electrical cardioversion, ablation, and surgery of AF. Therefore, HRV may serve as a digital biomarker in predicting AF risk in long-term and acute risk period, identification of patients with AF risk in sinus rhythm and recurrence risk stratification after procedures. HRV in AF rhythm, predominantly influenced by dynamic atrioventricular node conduction under the onslaught of irregular atrial impulses, shows a huge disparity compared to that in sinus rhythm. Despite this, HRV in AF rhythm still provides valuable prognostic information, as reduced HRV may indicate a poor heart function and outcomes in patients with AF. Despite being influenced by lots of variables, HRV can still serve as an independent digital biomarker in the clinical management of AF throughout its entire lifecycle.

Heart Rate Variability Modulation Through Slow-Paced Breathing in Health Care Workers with Long COVID: A Case-Control Study

BACKGROUND

Long COVID is a syndrome persisting 12+ weeks after COVID-19 infection, impacting life and work ability. Autonomic nervous system imbalance has been hypothesized as the cause. This study aims to investigate cardiovascular autonomic function in health care workers (HCWs) with Long COVID and the effectiveness of slow-paced breathing (SPB) on autonomic modulation.

METHODS

From December 1, 2022 to March 31, 2023, 6655 HCWs of the University Hospitals of Trieste (Northeast Italy) were asked to participate in the study by company-email. Inclusion/exclusion criteria were assessed. Global health status and psychosomatic disorders were evaluated through validated questionnaires. Heart rate variability was assessed by finger-photoplethysmography during spontaneous breathing and SPB, which stimulate vagal response. Long COVID HCWs (G1) were contrasted with Never infected (G2) and Fully recovered COVID-19 workers (G3).

RESULTS

There were 126 HCWs evaluated. The 58 Long COVID were assessed at a median time because COVID-19 of 419.5 days (interquartile range 269-730) and had significantly more psychosomatic symptoms and lower detectability of spontaneous systolic pressure oscillation at 0.1 Hz (Mayer wave - baroreflex arc) during spontaneous breathing compared with 53 never-infected and 14 fully-recovered HCWs (19%, 42%, and 40%, respectively, P = .027). During SPB, the increase in this parameter was close to controls (91.2%, 100%, and 100%, respectively, P = .09). No other differences in heart rate variability parameters were found among groups.

CONCLUSIONS

Resting vascular modulation was reduced in Long COVID, while during SPB, baroreflex sensitivity effectively improved. Long-term studies are needed to evaluate whether multiple sessions of breathing exercises can restore basal vascular reactivity and reduce cardiovascular risk in these patients.

Cerebral Hemodynamic Alterations in Dialysis COVID-19 Survivors: A Transcranial Doppler Ultrasound Study on Intracranial Pressure Dynamics

Background

We observed a COVID-19 survivor with a ventriculoperitoneal shunt who developed increased intracranial pressure during hemodialysis. We hypothesized that post-SARS-CoV-2 infection, patients may have altered cerebral perfusion pressure regulation in response to intracranial pressure changes.

Methods

From April to July 2021, we recruited dialysis patients with prior COVID-19 from two Madrid nephrology departments. We also recruited age- and sex-matched dialysis patients without prior SARS-CoV-2 infection. Transcranial Doppler ultrasound was used to measure the middle cerebral artery velocity before dialysis and 30, 60, and 90 min after the initiation of dialysis.

Results

The final sample included 37 patients (16 post-COVID-19 and 21 without). The COVID-19 survivors showed a significant pulsatility index increase between 30 and 60 min compared to those without COVID-19. They also had lower heart rates.

Conclusions

We propose two mechanisms: an increase in intracranial pressure or a decreased arterial elasticity. A lower heart rate was also observed in the COVID-19 survivors. This study highlights SARS-CoV-2's multifaceted effects, including potential long-term vascular and cerebral repercussions.

Predictors and Clinical Impacts of Impaired Heart Rate Variability in Women with Breast Cancer

Background and Objectives: Breast cancer (BC) is the most prevalent cancer globally, with a significant mortality rate, especially among women. While advances in treatment have reduced BC mortality, cardiovascular complications resulting from anticancer therapies have become a major concern. The autonomic nervous system (ANS) may be affected in BC patients and it is assessed with heart rate variability (HRV). The aim of this study was to investigate the prevalence of impaired HRV, its predictors, and its clinical impacts in BC patients. Materials and Methods: We retrospectively screened all female BC patients and enrolled cases who underwent 24 h Holter electrocardiography monitoring with accessible clinical follow-up data. Results: This study included 136 BC patients, and the mean age was 56.8 ± 10.8 years old. Impaired HRV was present in 36.8% of patients, and hypertension was identified as a significant predictor of reduced HRV (OR = 3.61, CI: 1.01-12.92, p = 0.048). Furthermore, de novo atrial fibrillation (AF) occurred more frequently in patients with impaired HRV (20% vs. 8.1%; p = 0.044). None of the HRV parameters were associated with all-cause mortality, and cancer stage was found to be the only independent predictor of all-cause mortality (HR = 3.93, CI: 1.81-8.55; p < 0.001). Conclusions: HRV is impaired in a significant proportion of patients with BC. Hypertension plays a crucial role in the deterioration of HRV in patients with BC, and de novo AF is more common in patients with impaired HRV. However, HRV does not appear to predict all-cause mortality in patients with BC. This study highlights the importance of the optimal management of cardiovascular risk factors, such as hypertension, to prevent ANS dysfunction in cancer patients.

The impact of long COVID on heart rate variability: a cross-sectional study

BACKGROUND

Long-term COVID-19 (LC), which may affect the autonomic nervous system (ANS), is the term for the symptoms that some patients had for an additional month after contracting the virus. Therefore, during the LC phase, ANS status was evaluated in patients with mild-to-moderate COVID-19 using heart rate variability (HRV), a measurement of ANS function.

METHODS

A cross-sectional research with 173 participants - both positive and negative for COVID-19 - was conducted. Based on self-reports, patients with COVID-19 were classified as to whether they had LC or not. A 5-minute ECG recorder and data detection and response report were used to measure the ANS.

RESULTS

There were notable age differences across the groups (p = 0.034). Patients with LC under 25 years of age had a lower HRV categorized as a very-low-frequency (VLF) domain (p = 0.012). Compared to the group without LC, a higher number of people in the LC group had aberrant autonomic neuroactivity (p = 0.048).

CONCLUSION

Mild-to-moderate patients with COVID-19 in young to middle age may develop autonomic dysfunction one month after infection.

Effect of 24-hour heart rate fluctuations on mortality in patients with acute myocardial infarction: based on the MIMIC III database

BACKGROUND

Heart rate (HR) was one of the risk factors for cardiovascular disease, but there was insufficient evidence to demonstrate a relationship between heart rate fluctuations and the prognosis of patients with acute myocardial infarction (AMI). The objective of this study is to investigate the relationship between 24-h heart rate fluctuations after admission to the Intensive Care Unit (ICU) and 30-day, 1-year, and 3-year mortality rates in patients with AMI in order to examine its implications for prognosis in AMI patients.

METHODS

All data were obtained from the Medical Information Mart for Intensive Care III Database (MIMIC III). We calculated heart rate fluctuations using the maximum and minimum values of the patient's heart rate during the first 24 h after ICU admission and divided them into three groups (< 23beats/min, 23-33beats/min, > 33beats/min) according to tertiles. The COX risk regression model was applied to the analysis, and subgroup analyses were performed for use in testing the robustness of the results. Curve fitting was performed to explore whether there was a nonlinear relationship between heart rate fluctuations and mortality. Outcome measures were 30-day, 1-year, and 3-year mortality in patients with AMI.

RESULTS

After strict confounding adjustment, COX multifactorial analysis showed that patients' heart rate fluctuations were positively associated with 30-day, 1-year, and 3-year mortality rates (HR = 1.17, 95%CI: 1.11 ~ 1.23; HR = 1.17, 95%CI: 1.12 ~ 1.22; HR = 1.17, 95%CI: 1.12 ~ 1.21). In addition, the high heart rate fluctuation group (> 33 beats/min) had a significantly increased risk of death (HR = 1.76, 95%CI: 1.28 ~ 2.42; HR = 1.59, 95%CI: 1.25 ~ 2.03; HR = 1.43, 95%CI: 1.15 ~ 1.77). In the curve-fitting analysis, a J-shaped curve relationship among heart rate fluctuations and 1- and 3-year mortality was found (p for non-linearity = 0.049; p for non-linearity = 0.004), with an inflection point of 28 beats/min. In subgroup analyses, there was an interaction between heart rate fluctuations and age (P for interaction = 0.041).

CONCLUSIONS

Heart rate fluctuations within 24 h after ICU admission of AMI patients were associated with 30-day, 1-year, and 3-year mortality, which is a simple and stable predictor of patients' short- and long-term prognosis. Furthermore, 24-h heart rate fluctuations showed a "J" curve relationship with 1- and 3-year mortality, with fluctuations of 28 beats/min predicting the best prognosis.

Impact of COVID-19 on heart rate variability in post-COVID individuals compared to a control group

This study investigated the impact of mild COVID-19 on HRV in groups stratified by time after infection and to compare to a healthy group of the same age without previous virus infection and without need of hospitalization. This is a cross-sectional study. We divided the sample into four groups: control group (CG) (n = 31), group 1 (G1): ≤6 weeks (n = 34), group 2 (G2): 2-6 months (n = 30), group 3 (G3): 7-12 months (n = 35) after infection. For HRV analysis, we used the indices of linear (time and frequency domain) and non-linear analysis. For comparisons between groups, ANOVA one way test or Kruskal-Wallis was used according to the data distribution. The effect size was calculated based on Cohen's d or η2. Simple and multiple linear regressions were performed to investigate the interaction between clinical outcomes and HRV parameters. A total of 130 individuals were included. Groups G1 and G2 showed less parasympathetic modulation when compared to CG (p < 0.05), while G3 showed an increase in parasympathetic modulation when compared to G1 (p < 0.05). Moderate to large effect sizes were found according to Cohen d or η2. The multiple linear regression models identified age and infection duration as significant predictors for RMSSD (adjusted R2 = 0.227) and SD1 (adjusted R2 = 0.242), while age was significant for SDNN (adjusted R2 = 0.213). BMI, hypertension, and dyslipidemia were non-significant in all models. For HF (n.u.), infection duration was consistently significant, with stress emerging as a predictor in Model 2 (adjusted R2 = 0.143). The recovery time since diagnosis and age influences recovery from HRV, suggesting a transient effect of the disease on the autonomic nervous system.

Exploration of COVID-19 associated bradycardia using heart rate variability analysis in a case-control study of ARDS patients

BACKGROUND

Bradycardia and dysautonomia observed during SARS-Cov2 infection suggests involvement of the autonomic nervous system (ANS). Limited data exists on ANS dysregulation and its association with outcomes in patients with acute respiratory distress syndrome (ARDS) related to COVID-19 (C-ARDS) or other etiologies (NC-ARDS).

OBJECTIVES

We aimed to explore sympathovagal balance, assessed by heart rate variability (HRV), and its clinical prognostic value in C-ARDS compared with NC-ARDS.

METHODS

A single-center, prospective case-control study was conducted. Consecutive patients meeting ARDS criteria between 2020 and 2022 were included. HRV was assessed using 1-hour electrographic tracing during a stable, daytime period.

RESULTS

Twenty-four patients with C-ARDS and 19 with NC-ARDS were included. Age, sex and ARDS severity were similar between groups. The median heart rate was markedly lower in the C-ARDS group than in the NC-ARDS group (60 [53-72] versus 101 [91-112] bpm, p<.001). Most of HRV parameters were significantly increased in patients with C-ARDS. HRV correlated with heart rate only in patients with C-ARDS. A positive correlation was found between the low-to high-frequency ratio (LF/HF) and length of intensive care unit stay (r = 0.576, p<.001).

CONCLUSION

This study confirmed that C-ARDS was associated with marked bradycardia and severe ANS impairment, suggesting a sympathovagal imbalance with vagal overtone. Poor outcomes appeared to be more related to sympathetic rather than parasympathetic hyperactivation.

Comparative Analysis of Heart Rate Variability and Arterial Stiffness in Elite Male Athletes after COVID-19

This study investigated the long-term cardiovascular effects of coronavirus disease (COVID-19) in elite male athletes by comparing the heart rate variability (HRV), arterial stiffness, and other cardiovascular parameters between those with and without prior COVID-19 infection. Methods: This cross-sectional study evaluated 120 elite male athletes (60 post COVID-19, 60 controls) using anthropometric measurements, body composition analysis, pulmonary function tests, HRV analysis, arterial stiffness assessments, hemodynamic monitoring, and microcirculatory function tests. Results: Athletes post COVID-19 showed significantly higher lean mass (p = 0.007), forced vital capacity (p = 0.001), and forced expiratory volume in 1 s (p = 0.007) than controls. HRV parameters did not significantly differ between the groups. Post-COVID-19 athletes exhibited peripheral vascular resistance (p = 0.048) and reflection index (p = 0.038). No significant differences were observed in the blood pressure, cardiac output, oxygen saturation, or microcirculatory oxygen absorption. Conclusions: Elite male athletes showed notable cardiovascular resilience after COVID-19, with only minor differences in vascular function. The maintained cardiac autonomic function and improved lung parameters in post-COVID-19 athletes suggests an adaptive response. These findings support the cardiovascular health of elite athletes following COVID-19 but emphasize the importance of continued monitoring.

Genetic Algorithms for Feature Selection in the Classification of COVID-19 Patients

BACKGROUND

Severe Acute Respiratory Syndrome CoronaVirus-2 (SARS-CoV-2) infection can cause feared consequences, such as affecting microcirculatory activity. The combined use of HRV analysis, genetic algorithms, and machine learning classifiers can be helpful in better understanding the characteristics of microcirculation that are mainly affected by COVID-19 infection.

METHODS

This study aimed to verify the presence of microcirculation alterations in patients with COVID-19 infection, performing Heart Rate Variability (HRV) parameters analysis extracted from PhotoPlethysmoGraphy (PPG) signals. The dataset included 97 subjects divided into two groups: healthy (50 subjects) and patients affected by mild-severity COVID-19 (47 subjects). A total of 26 parameters were extracted by the HRV analysis and were investigated using genetic algorithms with three different subject selection methods and five different machine learning classifiers.

RESULTS

Three parameters: meanRR, alpha1, and sd2/sd1 were considered significant, combining the results obtained by the genetic algorithm. Finally, machine learning classifications were performed by training classifiers with only those three features. The best result was achieved by the binary Decision Tree classifier, achieving accuracy of 82%, specificity (or precision) of 86%, and sensitivity of 79%.

CONCLUSIONS

The study's results highlight the ability to use HRV parameters extraction from PPG signals, combined with genetic algorithms and machine learning classifiers, to determine which features are most helpful in discriminating between healthy and mild-severity COVID-19-affected subjects.

Reduced autonomic function in patients with long-COVID-19 syndrome is mediated by cardiorespiratory fitness

BACKGROUND

Long-COVID-19 syndrome (LCS) exhibits neurological problems such as peripheral neuropathy and autonomic nervous system (ANS) dysfunction. Exercise intolerance and, consequently, low cardiorespiratory fitness (CRF) are some of the most common symptoms of LCS. We describe a series of individuals exhibiting LCS symptoms compared to a control group and posit that this condition may be related to the exercise capacity-mediated disruption of the ANS resulting particularly in exercise intolerance.

METHODS

This study included 87 individuals with LCS and 71 control participants without COVID-19 diagnoses. Heart rate variability (HRV) in supine position is commonly measured to diagnose autonomic dysregulation and subsequently analyzed using the Kubios software (Kuopio, Finland). CRF (peak VO2), post-COVID-19 patient-reported symptoms, maximal muscle strength (grip strength, bilateral leg press, leg extension, pectoral press, and back press exercises), and body composition were also measured. Analysis of covariance (ANCOVA) and mediation analysis were employed to assess the associations among LCS, peak VO2, and HRV indicators. Two-sided p < 0.05 was considered as significant.

RESULTS

The HRV parameters-RR interval, RMSSD, SDNN, PNS index, LF, HF, total power, SD1, and SD2-were significantly elevated (p < 0.05) in the control group when compared to the LCS patients. In contrast, the HR, stress index, and SNS index parameters were significantly higher (p < 0.05) in the LCS group. When adjusted for RR intervals, these parameters remained statistically significant (p < 0.05). A partially mediated effect was found between peak VO2 and RMSSD (mediation effect = 24.4%) as well as peak VO2 and SDNN (mediation effect = 25.1%) in the LCS patients.

CONCLUSIONS

These findings contribute new insights on the interplay between CRF and HRV indicators as well as endorse that dysautonomia may be related to the low peak VO2 observed in long COVID-19 patients.

Pupillometry and autonomic nervous system responses to cognitive load and false feedback: an unsupervised machine learning approach

Objectives

Pupil dilation is controlled both by sympathetic and parasympathetic nervous system branches. We hypothesized that the dynamic of pupil size changes under cognitive load with additional false feedback can predict individual behavior along with heart rate variability (HRV) patterns and eye movements reflecting specific adaptability to cognitive stress. To test this, we employed an unsupervised machine learning approach to recognize groups of individuals distinguished by pupil dilation dynamics and then compared their autonomic nervous system (ANS) responses along with time, performance, and self-esteem indicators in cognitive tasks.

Methods

Cohort of 70 participants were exposed to tasks with increasing cognitive load and deception, with measurements of pupillary dynamics, HRV, eye movements, and cognitive performance and behavioral data. Utilizing machine learning k-means clustering algorithm, pupillometry data were segmented to distinct responses to increasing cognitive load and deceit. Further analysis compared clusters, focusing on how physiological (HRV, eye movements) and cognitive metrics (time, mistakes, self-esteem) varied across two clusters of different pupillary response patterns, investigating the relationship between pupil dynamics and autonomic reactions.

Results

Cluster analysis of pupillometry data identified two distinct groups with statistically significant varying physiological and behavioral responses. Cluster 0 showed elevated HRV, alongside larger initial pupil sizes. Cluster 1 participants presented lower HRV but demonstrated increased and pronounced oculomotor activity. Behavioral differences included reporting more errors and lower self-esteem in Cluster 0, and faster response times with more precise reactions to deception demonstrated by Cluster 1. Lifestyle variations such as smoking habits and differences in Epworth Sleepiness Scale scores were significant between the clusters.

Conclusion

The differentiation in pupillary dynamics and related metrics between the clusters underlines the complex interplay between autonomic regulation, cognitive load, and behavioral responses to cognitive load and deceptive feedback. These findings underscore the potential of pupillometry combined with machine learning in identifying individual differences in stress resilience and cognitive performance. Our research on pupillary dynamics and ANS patterns can lead to the development of remote diagnostic tools for real-time cognitive stress monitoring and performance optimization, applicable in clinical, educational, and occupational settings.

Assessment of parameters reflecting the reactivity of the autonomic nervous system of Polish firefighters on the basis of a test in a smoke chamber

Objective

Measurement and analysis of heart rate variability in a population of professional firefighters based on heart rate (RR) recording. Assessment based on a smoke chamber test in correlation with age, length of service, body mass index.

Materials and methods

The smoke chamber test for the officers of the State Fire Service (SFS) is aimed at improving the skills and techniques of working in special clothing and in a respiratory protection set (RPS) under high psychophysical burden. The study was divided into 3 stages: 1. measurement of parameters at rest - sitting position for 5 min, 2. measurement of parameters during the firefighter's activity, effort related to the training path and the test in the smoke chamber, indefinite time (different for each firefighter), 3. measurement of parameters at rest after exercise - sitting position for 5 min. Each firefighter included in the study had fitted onto his chest a Polar H10 band with a sensor (size XXL) that measures parameters HR, HRV (sensor connected via Bluetooth to an application on the phone of a person controlling the test).

Results

The study involved 96 firefighters aged 19-45 (Mean 27.9; SD 7.4), with 1-19 years of service (Mean 5.2; SD 4.6). The study included 75 firefighters who completed the entire activity and their results were recorded completely in a way that allowed for analysis and interpretation. Results of 17 firefighters were selected (parameters describing HRV changes was carried out, which are important from the authors' experience: RMSSD, HF ms2, DFA α1).

Conclusion

The presence of excessive body weight did not affect HR parameters, which may be related to the limited possibilities of using the BMI index among people with high muscle mass. Longer work experience has a health-promoting effect on heart rate values through increased adaptation of the circulatory system to increased effort and stress. HRV parameter and ANS activity have a wide range of clinical applications, in addition to monitoring health status in the course of diseases, ANS activity can be analyzed in correlation with occupational risk factors.

COVID-19-Associated Multisystem Inflammatory Syndrome in Children and Cardiovascular Autonomic Control: A Prospective Cohort Study Nine Months after SARS-CoV-2 Infection

Background: Multisystem Inflammatory Syndrome in Children (MIS-C) has emerged as a severe pediatric complication during the SARS-CoV-2 pandemic, with potential long-term cardiovascular repercussions. We hypothesized that heart rate and blood pressure control at rest and during postural maneuvers in MIS-C patients, months after the remission of the inflammatory syndrome, may reveal long-term autonomic dysfunctions. Methods: We assessed 17 MIS-C patients (13 males; 11.9 ± 2.6 years, m ± SD) 9 months after acute infection and 18 age- (12.5 ± 2.1 years) and sex- (13 males) matched controls. Heart rate and blood pressure variability, baroreflex function, and hemodynamic parameters were analyzed in supine and standing postures. Results: MIS-C patients exhibited reduced heart rate variability, particularly in parasympathetic parameters during standing (pNN50+: 6.1 ± 6.4% in controls, 2.5 ± 3.9% in MIS-C; RMSSD: 34 ± 19 ms in controls, 21 ± 14 ms in MIS-C, p < 0.05), with no interaction between case and posture. Blood pressure variability and baroreflex sensitivity did not differ between groups except for the high-frequency power in systolic blood pressure (3.3 ± 1.2 mmHg2 in controls, 1.8 ± 1.2 mmHg2 in MIS-C, p < 0.05). The MIS-C group also showed lower diastolic pressure-time indices (DPTI) and systolic pressure-time indices (SPTI), particularly in standing (DPTI: 36.2 ± 9.4 mmHg·s in controls, 29.4 ± 6.2 mmHg·s in MIS-C; SPTI: 26.5 ± 4.3 mmHg·s in controls, 23.9 ± 2.4 mmHg·s in MIS-C, p < 0.05). Conclusions: Altered cardiovascular autonomic control may persist in MIS-C patients with, however, compensatory mechanisms that may help maintain cardiovascular homeostasis during light autonomic challenges, such as postural maneuvers. These results highlight the importance of assessing long-term cardiovascular autonomic control in children with MIS-C to possibly identify residual cardiovascular risks and inform targeted interventions and rehabilitation protocols.

Does whole-body vibration improve risk of falls, balance, and heart rate variability in post-COVID-19 patients? A randomized clinical trial

INTRODUCTION

Whole-Body Vibration (WBV) can be a therapeutic recovery strategy for patients hospitalized for COVID-19.

OBJECTIVES

To evaluate the effects of a 36-session WBV protocol on the risk of falls, balance, mobility and heart rate variability (HRV).

STUDY DESIGN

A randomized clinical trial.

METHODS

13 patients affected by COVID-19, trained with WBV, 3×/week on alternate days, totaling 36 sessions, were evaluated before and after the intervention.

RESULTS

WBV training at 2 mm and 4 mm amplitude resulted in a reduction in the risk of falls when compared to Sham (p = 0.023), with effect size of 0.530. No changes were observed for mobility and balance outcomes (p = 0.127) or for any of the HRV variables (p = 0.386).

CONCLUSION

WBV training reduced the risk of falls in post-COVID patients. No changes were observed regarding balance and mobility, nor for HRV.

Composite Autonomic Symptom Score-31 for the diagnosis of cardiovascular autonomic dysfunction in long-term coronavirus disease 2019

BACKGROUND

Composite Autonomic Symptom Score-31 (COMPASS-31) is an easy-to-use screening tool for the evaluation of autonomic dysfunction in various diseases affecting neural function but has rarely been used in the assessment of long coronavirus disease 2019 (COVID-19). This study aimed to evaluate the diagnostic accuracy of the COMPASS-31 score in detecting dysfunction of the autonomic nervous system in patients 3 months after COVID-19 infection.

MATERIALS AND METHODS

Fifty-nine subjects were recruited and grouped into 2: (a) controls (n = 31) who had never had positive polymerase chain reaction results for COVID-19 before and (b) the post-COVID-19 patients (n = 28) who had confirmed COVID-19 infection 3-6 months before recruitment. COMPASS-31 questionnaire was utilized to evaluate subjective symptoms or evidence of autonomic dysfunction. Autonomic dysfunction was assessed objectively by cardiovascular autonomic reflex tests (CARTs) and heart rate variability (HRV). For comparison of quantitative variables between two groups, t-test or Mann-Whitney U test, as appropriate, were used. Sensitivity, specificity, negative predictive value (NPV), positive predictive value (PPV), negative likelihood ratio (LR), and positive LR were used as measures of diagnostic accuracy. Receiver operating characteristic (ROC) curve analysis determined the overall accuracy of COMPASS-31.

RESULTS

The median COMPASS score was found to be significantly higher in post-COVID-19 participants than controls (15.5 vs. 10, P = 0.021). The median total CART score was also significantly higher in post-COVID-19 participants (0 vs. 1, P < 0.001). Out of 6 domains of the COMPASS score, the median value for orthostatic dysfunction was found to be significantly higher in post-COVID-19 participants than controls (12 vs. 0, P = 0.008). There was significantly fair accuracy of the COMPASS score with an area under the receiver operating curve 0.68 (0.54-0.82) following the total CART score ≥2 as the gold standard in the diagnosis of autonomic dysfunction (P = 0.021). The best cutoff point of the total COMPASS score was 12.5, where the optimal values of sensitivity, specificity, and positive and negative predictive values were achieved. Nonsignificant and weak correlations between CARTs, HRV parameters, and COMPASS score were found.

CONCLUSION

COMPASS-31 could be used as a user-friendly screening tool to detect autonomic dysfunction in post-COVID-19 cases with acceptable sensitivity and specificity.

Agreement between Ultra-Short-Term and Standard Heart Rate Variability Analysis in Resting and Post-Exercise Conditions

BACKGROUND

Short-term (5 min) heart rate variability (HRV) analysis is widely used in assessing autonomic nervous system activity during exercise. While shortening the HRV measurement duration can help improve its application efficiency, its accuracy needs to be verified. This study investigated the agreement between ultra-short-term (UST) HRV (3 or 4 min) and standard 5 min HRV and explored the optimal recording duration under resting and post-exercise conditions.

METHODS

Fourteen participants exercised on a cycle ergometer at 60% of their maximum peak power. Data were collected during the rest condition (Pre-E) and three post-exercise conditions (Post-E1, Post-E2, and Post-E3), with indicators of the standard deviation (SDNN) of the ultra-short and short-term RR intervals and the root mean square (RMSSD) of the continuous difference between RR intervals. Repeated measures ANOVA, Cohen's d statistic, Bland-Altman analysis, and interclass correlation coefficients (ICC) assessed the agreement between UST-HRV and ST-HRV.

RESULTS

The consistency results of SDNN and RMSSD in resting and post-exercise were different. At the Pre-E, Post-E2, and Post-E3 phases, no statistical differences for SDNN and RMSSD were observed, with ICCs surpassing 0.9, indicating a high level of agreement. However, at Post-E2, there was a significant difference between 3 min RMSSD and 5 min RMSSD (p < 0.05), as well as between 3 min SDNN, 4 min SDNN, and 5 min SDNN (p < 0.05). Furthermore, the limits of agreement were observed to decrease as the time duration increased in Bland-Altman plots.

CONCLUSIONS

UST-HRV analysis is a reliable substitute for standard 5 min HRV assessment, particularly during resting conditions. For post-exercise measurements, assessing the appropriateness of a 3- or 4 min duration based on the exercise's length is recommended to ensure accuracy and reliability.

Impact of QRS misclassifications on heart-rate-variability parameters (results from the CARLA cohort study)

BACKGROUND

Heart rate variability (HRV), an important marker of autonomic nervous system activity, is usually determined from electrocardiogram (ECG) recordings corrected for extrasystoles and artifacts. Especially in large population-based studies, computer-based algorithms are used to determine RR intervals. The Modular ECG Analysis System MEANS is a widely used tool, especially in large studies. The aim of this study was therefore to evaluate MEANS for its ability to detect non-sinus ECG beats and artifacts and to compare HRV parameters in relation to ECG processing. Additionally, we analyzed how ECG processing affects the statistical association of HRV with cardiovascular disease (CVD) risk factors.

METHODS

20-min ECGs from 1,674 subjects of the population-based CARLA study were available for HRV analysis. All ECGs were processed with the ECG computer program MEANS. A reference standard was established by experienced clinicians who visually inspected the MEANS-processed ECGs and reclassified beats if necessary. HRV parameters were calculated for 5-minute segments selected from the original 20-minute ECG. The effects of misclassified typified normal beats on i) HRV calculation and ii) the associations of CVD risk factors (sex, age, diabetes, myocardial infarction) with HRV were modeled using linear regression.

RESULTS

Compared to the reference standard, MEANS correctly classified 99% of all beats. The averaged sensitivity of MEANS across all ECGs to detect non-sinus beats was 76% [95% CI: 74.1;78.5], but for supraventricular extrasystoles detection sensitivity dropped to 38% [95% CI: 36.8;38.5]. Time-domain parameters were less affected by false sinus beats than frequency parameters. Compared to the reference standard, MEANS resulted in a higher SDNN on average (mean absolute difference 1.4ms [95% CI: 1.0;1.7], relative 4.9%). Other HRV parameters were also overestimated as well (between 6.5 and 29%). The effect estimates for the association of CVD risk factors with HRV did not differ between the editing methods.

CONCLUSION

We have shown that the use of the automated MEANS algorithm may lead to an overestimation of HRV due to the misclassification of non-sinus beats, especially in frequency domain parameters. However, in population-based studies, this has no effect on the observed associations of HRV with risk factors, and therefore an automated ECG analyzing algorithm as MEANS can be recommended here for the determination of HRV parameters.

Cardiovascular autonomic dysfunction in post-COVID-19 syndrome: a major health-care burden

Cardiovascular autonomic dysfunction (CVAD) is a malfunction of the cardiovascular system caused by deranged autonomic control of circulatory homeostasis. CVAD is an important component of post-COVID-19 syndrome, also termed long COVID, and might affect one-third of highly symptomatic patients with COVID-19. The effects of CVAD can be seen at both the whole-body level, with impairment of heart rate and blood pressure control, and in specific body regions, typically manifesting as microvascular dysfunction. Many severely affected patients with long COVID meet the diagnostic criteria for two common presentations of CVAD: postural orthostatic tachycardia syndrome and inappropriate sinus tachycardia. CVAD can also manifest as disorders associated with hypotension, such as orthostatic or postprandial hypotension, and recurrent reflex syncope. Advances in research, accelerated by the COVID-19 pandemic, have identified new potential pathophysiological mechanisms, diagnostic methods and therapeutic targets in CVAD. For clinicians who daily see patients with CVAD, knowledge of its symptomatology, detection and appropriate management is more important than ever. In this Review, we define CVAD and its major forms that are encountered in post-COVID-19 syndrome, describe possible CVAD aetiologies, and discuss how CVAD, as a component of post-COVID-19 syndrome, can be diagnosed and managed. Moreover, we outline directions for future research to discover more efficient ways to cope with this prevalent and long-lasting condition.

Trimethylamine-N-oxide aggravated the sympathetic excitation in D-galactose induced aging rats by down-regulating P2Y12 receptor in microglia

This study aimed to determine whether trimethylamine N-oxide (TMAO) was involved in sympathetic activation in aging and the underlying mechanisms. Our hypothesis is TMAO reduces P2Y12 receptor (P2Y12R) and induces microglia-mediated inflammation in the paraventricular nucleus (PVN), then leading to sympathetic activation in aging. This study involved 18 young adults and 16 old adults. Aging rats were established by injecting D-galactose (D-gal, 200 mg/kg/d) subcutaneously for 12 weeks. TMAO (120 mg/kg/d) or 1% 3, 3-dimethyl-l-butanol (DMB) was administrated via drinking water for 12 weeks to investigate their effects on neuroinflammation and sympathetic activation in aging rats. Plasma TMAO, NE and IL-1β levels were higher in old adults than in young adults. In addition, standard deviation of all normal to normal intervals (SDNN) and standard deviation of the average of normal to normal intervals (SDANN) were lower in old adults and negatively correlated with TMAO, indicating sympathetic activation in old adults, which is associated with an increase in TMAO levels. Treatment of rats with D-gal showed increased senescence-associated protein levels and microglia-mediated inflammation, as well as decreased P2Y12R protein levels in PVN. Plasma TMAO, NE and IL-1β levels were increased, accompanied by enhanced renal sympathetic nerve activity (RSNA). While TMAO treatment exacerbated the above phenomenon, DMB mitigated it. These findings suggest that TMAO contributes to sympathetic hyperactivity in aging by downregulating P2Y12R in microglia and increasing inflammation in the PVN. These results may provide promising new target for the prevention and treatment of aging and aging-related diseases.

The Prevalence of Orthostatic Hypotension in Cancer Patients

BACKGROUND

Orthostatic hypotension (OH) is associated with a higher risk of mortality in the general population; however, it has not been studied in the cancer population. This study aimed to assess the prevalence of OH in cancer patients compared to that in the noncancer population.

METHODS

A total of 411 patients (mean age 63.5 ± 10.6 years) were recruited: patients with active cancer (n = 223) and patients hospitalised for other reasons, but without a cancer diagnosis (n = 188). Medical histories were collected and an orthostatic challenge test was performed. OH was defined as a blood pressure (BP) decrease upon standing of ≥20 mmHg for the systolic or ≥10 mmHg for the diastolic BP after 1 or 3 min; or a systolic BP decrease <90 mmHg.

RESULTS

The prevalence of OH in the subjects with cancer was significantly higher than in the subjects without cancer (28.7% vs. 16.5%, respectively, p = 0.003). OH was the most common in the lung cancer patients (57.5%). In a single-variable analysis, the predictors of OH were cancer presence, age ≥ 65 years, and body mass index (BMI) ≥ 30 kg/m2. In the multivariable model, the strongest independent predictor of OH was cancer status, which doubled the risk of OH, and BMI ≥ 30 kg/m2 and diabetes.

CONCLUSIONS

Cancer patients are characterised by a high prevalence of OH. In this population, the recommendation of routine orthostatic challenge tests should be considered.

Autonomic activity and cardiovascular system risk assessment in pediatric patients with hemolytic uremic syndrome

In pediatric patients with hemolytic uremic syndrome (HUS), cardiac involvement and autonomic nervous system function can be evaluated by a non-invasive method called heart rate variability (HRV). This study aims to evaluate heart rate variability and electrocardiography findings in patients with HUS by comparing a healthy group. Patients who are diagnosed with HUS at a university hospital from December 2020 to June 2022 are screened by electrocardiography (ECG), echocardiography, and 24-h Holter ECG. A healthy control group, compatible in age and gender with the patient group, was selected from healthy subjects. HRV parameters, laboratory values, and ECG findings were analyzed and compared with the healthy group and each other. There were 25 patients with HUS and 51 participants in the healthy control group. Statistically significant differences were found in some HRV parameters: standard deviation of normal to normal intervals, the mean of the 5-min RR interval standard deviations, the standard deviation of 5-min RR interval means, the triangular interpolation of normal to normal interval, and very-low-frequency power. HUS patients had impaired and declined HRV values compared to the healthy group. There was a significant decrease in the PR distance, while a significant increase in the corrected QT and QT dispersion values was detected in the electrocardiographic findings of the patient group. HRV values impaired as renal failure parameters increased.  Conclusion: Patients with HUS may have autonomic nervous system dysfunction. HRV measurement is a non-invasive method that can evaluate this. It can be thought that there may be an increased risk of cardiovascular events and arrhythmias in some patients with HUS. ECG should be also considered to detect arrhythmia. What is Known: • Hemolytic uremic syndrome (HUS) primarily effects the hematologic parameters and kidney. • Secondary cardiomyopathy with hypertension and renal failure could be observed in these patients. • Rhythm problems are not expected primarily in these patients. • There is very limited data in evaluating autonomic function and arrhythmia risk for these patients. What is New: • Patients with HUS may have autonomic nervous system dysfunction. • HRV measurement is a non-invasive method that can evaluate this. • Cardiovascular events and arrhythmias due to the deterioration of the balance between the sympathetic and parasympathetic systems could manifest in patients with HUS. • An ECG and screening patients for cardiac events, and monitoring them closely should be considered.

Developing effective strategies to optimize physical activity and cardiorespiratory fitness in the long Covid population- The need for caution and objective assessment

The Post Covid-19 Condition (commonly known as Long Covid) has been defined by the World Health Organisation as occurring in individuals with a history of probable or confirmed SARS CoV 2 infection, usually within 3 months from the onset of acute Covid-19 infection with symptoms that last for at least two months which cannot be explained by an alternative diagnosis. Long Covid is associated with over two hundred recognised symptoms and affects tens of millions of people worldwide. Widely reported reductions in quality of life(QoL) and functional status are caused by extremely sensitive and cyclical symptom profiles that are augmented following exposure to physical, emotional, orthostatic, and cognitive stimuli. This manifestation prevents millions of people from engaging in routine activities of daily living (ADLs) and has important health and well-being, social and economic impacts. Post-exertional symptom exacerbation (PESE) (also known as post-exertional malaise) is an exacerbation in the severity of fatigue and other symptoms following physical, emotional, orthostatic and cognitive tasks. Typically, this will occur 24-72 h after "over-exertion" and can persist for several days and even weeks. It is a hallmark symptom of Long Covid with a reported prevalence of 86%. The debilitating nature of PESE prevents patients from engaging in physical activity which impacts functional status and QoL. In this review, the authors present an update to the literature relating to PESE in Long Covid and make the case for evidence-based guidelines that support the design and implementation of safe rehabilitation approaches for people with Long Covid. This review also considers the role of objective monitoring to quantify a patient's response to external stimuli which can be used to support the safe management of Long Covid and inform decisions relating to engagement with any stimuli that could prompt an exacerbation of symptoms.

Assessing autonomic activity and prognostic risk factors comparing multisystem inflammatory syndrome and isolated viral myocarditis/myopericarditis

INTRODUCTION AND AIM

In pediatric multisystem inflammatory syndrome and isolated viral myocarditis/myopericarditis, autonomic nervous system function can be evaluated by a non-invasive method called heart rate variability. This study aims to evaluate heart rate variability in these two groups by comparing them with each other. This is the first study assessing these values in these two groups of patients.

METHOD

Patients who are diagnosed with multisystem inflammatory syndrome in children and isolated viral myocarditis/myopericarditis at a university hospital from September 2021 to February 2023 are screened by electrocardiography, echocardiography, and 24-hour Holter monitoring. A healthy control group, compatible in age and gender with the patient groups, was selected from healthy subjects that applied to the hospital for palpitation, murmur, and/or chest pain. Heart rate variability parameters and related laboratory markers were analyzed and compared among the three groups.

RESULTS

There were 30 patients with multisystem inflammatory syndrome in children, 43 patients with isolated viral myocarditis/myopericarditis, and 109 participants in the healthy control group. Statistically significant differences were found in most of the heart rate variability parameters: standard deviation of normal to normal intervals (SDNN), the mean of the 5- minute RR interval standard deviations (SDNNİ), the standard deviation of 5-minute R wave to R wave(RR) interval means (SDANN), the root mean square of successive RR interval differences (RMSSD), and the percentage of the beats with a consecutive RR interval difference of more than 50 ms (pNN50%), very low frequency, high frequency, low frequency, triangular index, and low frequency/high-frequency ratio. Multisystem inflammatory syndrome in children patients had impaired and declined heart rate variability values compared to the other two groups. In patients with myocarditis/myopericarditis, we couldn't find a significant difference in these parameters with the control group.

CONCLUSION

Heart rate variability can be used as an important non-invasive autonomic function parameter in determining prognosis and treatment plans, especially in patients diagnosed with multisystem inflammatory syndrome in children. This impairment of autonomic activity could be more prominent in patients with decreased left ventricular systolic functions.

Post-COVID dysautonomias: what we know and (mainly) what we don't know

Following on from the COVID-19 pandemic is another worldwide public health challenge that is referred to variously as long COVID, post-COVID syndrome or post-acute sequelae of SARS-CoV-2 infection (PASC). PASC comes in many forms and affects all body organs. This heterogeneous presentation suggests involvement of the autonomic nervous system (ANS), which has numerous roles in the maintenance of homeostasis and coordination of responses to various stressors. Thus far, studies of ANS dysregulation in people with PASC have been largely observational and descriptive, based on symptom inventories or objective but indirect measures of cardiovascular function, and have paid little attention to the adrenomedullary, hormonal and enteric nervous components of the ANS. Such investigations do not consider the syndromic nature of autonomic dysfunction. This Review provides an update on the literature relating to ANS abnormalities in people with post-COVID syndrome and presents a theoretical perspective on how the ANS might participate in common features of PASC.

Mechanisms underlying exercise intolerance in long COVID: An accumulation of multisystem dysfunction

The pathogenesis of exercise intolerance and persistent fatigue which can follow an infection with the SARS-CoV-2 virus ("long COVID") is not fully understood. Cases were recruited from a long COVID clinic (N = 32; 44 ± 12 years; 10 (31%) men), and age-/sex-matched healthy controls (HC) (N = 19; 40 ± 13 years; 6 (32%) men) from University College London staff and students. We assessed exercise performance, lung and cardiac function, vascular health, skeletal muscle oxidative capacity, and autonomic nervous system (ANS) function. Key outcome measures for each physiological system were compared between groups using potential outcome means (95% confidence intervals) adjusted for potential confounders. Long COVID participant outcomes were compared to normative values. When compared to HC, cases exhibited reduced oxygen uptake efficiency slope (1847 (1679, 2016) vs. 2176 (1978, 2373) mL/min, p = 0.002) and anaerobic threshold (13.2 (12.2, 14.3) vs. 15.6 (14.4, 17.2) mL/kg/min, p < 0.001), and lower oxidative capacity, measured using near infrared spectroscopy (τ: 38.7 (31.9, 45.6) vs. 24.6 (19.1, 30.1) s, p = 0.001). In cases, ANS measures fell below normal limits in 39%. Long COVID is associated with reduced measures of exercise performance and skeletal muscle oxidative capacity in the absence of evidence of microvascular dysfunction, suggesting mitochondrial pathology. There was evidence of attendant ANS dysregulation in a significant proportion. These multisystem factors might contribute to impaired exercise tolerance in long COVID sufferers.

Applicability of heart rate variability for cardiac autonomic assessment in long-term COVID patients: A systematic review

PURPOSE

To carry out a systematic review to determine the main methods used to study the heart rate variability (HRV) in individuals after the acute phase of COVID-19.

METHODS

The study followed the Preferred Items for Reporting for Systematic Reviews and Meta-Analyses (PRISMA) statement. PubMed, Web of Science, Scopus and CINAHAL electronic databases were searched from the inception to November 2022. The studies were included if they used HRV assessment based on linear and non-linear methods in long-term COVID-19 patients. Review studies, theses and dissertations, conference abstracts, longitudinal studies, studies conducted on animals and studies that included individuals in the acute phase of the COVID-19 were excluded. The methodological quality of the studies was analyzed using the Joanna Briggs Institute's critical evaluation checklist for cross-sectional analytical studies.

RESULTS

HRV was mainly assessed using 24-h Holter monitoring in 41.6% (5/12) of the studies, and 12‑lead ECG was used in 33.3% (4/12). Regarding the type of assessment, 66.6% (8/12) of the studies only used linear analysis, where 25% (3/12) used analysis in the time domain, and 41.6% (5/12) used both types. Non-linear methods were combined with the previously cited linear method in 25% (3/12) of the studies. Moreover, 50% (6/12) of the studies demonstrated post-COVID-19 autonomic dysfunction, with an increase in the predominance of cardiac sympathetic modulation. The average score of the evaluation checklist was 6.6, characterized as having reasonable methodological quality.

CONCLUSION

24-h Holter and 12‑lead ECG are considered effective tools to assess HRV in post-COVID-19 patients. Furthermore, the findings reveal diverse effects of COVID-19 on the autonomic nervous system's sympathovagal balance, which might be influenced by secondary factors such as disease severity, patients' overall health, evaluation timing, post-infection complications, ventilatory functions, and age.

Heart rate variability is reduced in COVID-19 survivors and associated with physical activity and fatigue

Reduced heart rate variability (HRV) and fatigue are common after COVID-19 infection and both are potentially influenced by physical activity (PA). We compared resting HRV, PA from accelerometers and questionnaires, and self-reported fatigue in 41 COVID-19 survivors (~8 months postinfection, 38 ± 17 years) with 41 matched controls. Differences in HRV were observed on acceleration capacity (p = 0.041), deceleration capacity (p = 0.032), high-frequency peak frequency (p = 0.019), absolute low-frequency power (p = 0.042), relative very low-frequency power (p = 0.012), SD2 (from Poincare plot; p = 0.047), and DFA2 (slope of long-term detrended fluctuation analysis; p = 0.004). Fatigue was greater in COVID-19 survivors (p < 0.001) with no differences in PA. Moderate-vigorous physical activity (MVPA) (Standardized Beta = -0.427, p = 0.003) and steps per day (Standardized Beta = -0.402, p = 0.007) were associated with DFA2 in COVID-19 survivors after controlling for age, sex, and body fat percentage. Fatigue was correlated to less MVPA (Spearman's rho = 0.342, p = 0.031) and fewer steps per day (rho = 0.329, p = 0.038) in COVID-19 survivors, and was indirectly linked to HRV through these PA mediators (Estimate = -0.20; p = 0.040). We present a model showing the complex relations between HRV, PA, and fatigue that provides the foundation for strategies to improve outcomes and rehabilitation after COVID-19 infection.

Interatrial Block and Electrocardiographic Markers of Repolarization in Patients Hospitalized with COVID-19: Classical and Bayesian Analysis

Objective

Coronavirus disease-2019 (COVID-19) is associated with atrial fibrillation (AF) and ventricular arrhythmias. Several electrophysiological abnormalities on surface electrocardiography (ECG) are associated with AF and ventricular arrhythmias, either as markers of abnormal interatrial conduction or abnormal repolarization. The present study sought to understand whether such ECG markers are more common in patients hospitalized with COVID-19 infection during the pandemic.

Methods

A total of 87 COVID-19 patients formed the study group, whereas 64 patients who were hospitalized for any reason other than COVID-19 infection served as controls. The frequency of partial and advanced interatrial block (IAB), QT and corrected QT (QTc) durations, QT dispersion (QTd), and T peak-to-end duration (Tpe) were measured from ECGs at admission.

Results

Both partial and advanced IAB were more common in patients with COVID-19, although statistical significance was only observed for advanced IAB (11.5% in COVID-19 patients vs. 0.0% in controls, p=0.005). There were no differences between the groups for QTc, QTd or Tpe. On Bayesian analyses, there was strong evidence favoring an association between COVID-19 and advanced IAB (BF10:16), whereas there was no evidence for an association for partial IAB, QTc, QTd, or Tpe (BF10<1 for all).

Conclusions

Patients hospitalized with COVID-19 were more likely to have advanced IAB, which may explain why AF is more frequent in these patients.

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

(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.

Impact of long COVID on the heart rate variability at rest and during deep breathing maneuver

While the majority of individuals with coronavirus disease 2019 (COVID-19) recover completely, a significant percentage experience persistent symptom, which has been characterized as Long COVID and may be associated with cardiac and autonomic dysfunction. We evaluated heart rate variability (HRV) at rest and during deep-breathing (M-RSA) in patients with Long COVID. Case-control design involved 21 patients with Long COVID and 20 controls; the HRV was evaluated (POLAR system) at rest in the supine position and during M-RSA and expressed in time domain and non-linear analysis. In the supine position we found a reduction HRV measures in Long COVID' patients compared to controls for: Mean_iRR (p < 0.001), STD_iRR (p < 0.001); STD_HR (p < 0.001); SD1 (p < 0.001); SD2 (p < 0.001); alpha2 (p < 0.001). In the M-RSA we found reduction Mean_iRR (p < 0.001), STD_iRR (p < 0.001), STD_HR (p < 0.001), rMSSD (p < 0.001), RR_tri-index (p < 0.001) in Long COVID' patients except for highest Mean_HR p < 0.001. In conclusion, Long COVID reduced HRV at rest and during deep breathing. These findings may imply impairment of cardiac autonomic control when symptoms of COVID-19 persist following initial recovery.

Autonomic Manifestations of Long-COVID Syndrome

PURPOSE OF REVIEW

Long-COVID is a novel condition emerging from the COVID-19 pandemic. Long-COVID is characterized by symptoms commonly seen in autonomic disorders including fatigue, brain fog, light-headedness, and palpitations. This article will critically evaluate recent findings and studies on Long-COVID and its physiological autonomic manifestations.

RECENT FINDINGS

Studies have reported on the prevalence of different symptoms and autonomic disorders in Long-COVID cohorts. Autonomic nervous system function, including both the parasympathetic and sympathetic limbs, has been studied using different testing techniques in Long-COVID patients. While numerous mechanisms may contribute to Long-COVID autonomic pathophysiology, it is currently unclear which ones lead to a Long-COVID presentation. To date, studies have not tested treatment options for autonomic disorders in Long-COVID patients. Long-COVID is associated with autonomic abnormalities. There is a high prevalence of clinical autonomic disorders among Long-COVID patients, with limited knowledge of the underlying mechanisms and the effectiveness of treatment options.

Heart Rate Variability in Psychiatric Disorders: A Systematic Review

Introduction

Heart rate variability (HRV) is a measure of the fluctuation in time interval between consecutive heart beats. Decreased heart rate variability has been shown to have associations with autonomic dysfunction in psychiatric conditions such as depression, substance abuse, anxiety, and schizophrenia, although its use as a prognostic tool remains highly debated. This study aims to review the current literature on heart rate variability as a diagnostic and prognostic tool in psychiatric populations.

Methods

A literature search was conducted using the MEDLINE, EMBASE, Cochrane, and PsycINFO libraries to identify full-text studies involving adult psychiatric populations that reported HRV measurements. From 1647 originally identified, 31 studies were narrowed down through an abstract and full-text screen. Studies were excluded if they enrolled adolescents or children, used animal models, enrolled patients with another primary diagnosis other than psychiatric as outlined by the diagnostic and statistical manual of mental disorders (DSM) V, or if they assessed HRV in the context of treatment rather than diagnosis. Study quality assessment was conducted using a modified Downs and Blacks quality assessment tool for observational rather than interventional studies. Data were reported in four tables: 1) summarizing study characteristics, 2) methods of HRV detection, 3) key findings and statistics, and 4) quality assessment.

Results

There is significant variability between studies in their methodology of recording as well as reporting HRV, which makes it difficult to meaningfully interpret data that is clinically applicable due to the presence of significant bias in existing studies. The presence of an association between HRV and the severity of various psychiatric disorders, however, remains promising.

Conclusion

Future studies should be done to further explore how HRV parameters may be used to enhance the diagnosis and prognosis of several psychiatric disorders.

Investigating autonomic nervous system dysfunction among patients with post-COVID condition and prolonged cardiovascular symptoms

Heart Rate Variability (HRV) and arterial pressure (AP) variability and their responses to head-up tilt test (HUTT) were investigated in Post-COVID-19 syndrome (PCS) patients reporting tachycardia and/or postural hypotension. Besides tachycardia, PCS patients also showed attenuation of the following HRV parameters: RMSSD [square root of the mean of the sum of the squares of differences between adjacent normal-to-normal (NN) intervals] from statistical measures; the power of RR (beat-to-beat interval) spectra at HF (high frequency) from the linear method spectral analysis; occurrence of 2UV (two unlike variation) pattern of RR from the nonlinear method symbolic analysis; and the new family of statistics named sample entropy, when compared to control subjects. Basal AP and LF (low frequency) power of systolic AP were similar between PCS patients and control subjects, while 0 V (zero variation) patterns of AP from the nonlinear method symbolic analysis were exacerbated in PCS patients. Despite tachycardia and a decrease in RMSSD, no parameter of HRV changed during HUTT in PCS patients compared to control subjects. PCS patients reassessed after 6 months showed higher HF power of RR spectra and a higher percentage of 2UV pattern of RR. Moreover, the reassessed PCS patients showed a lower occurrence of 0 V patterns of AP, while the HUTT elicited HR (heart rate) and AP responses identical to control subjects. The HRV and AP variability suggest an autonomic dysfunction with sympathetic predominance in PCS patients. In contrast, the lack of responses of HRV and AP variability indices during HUTT indicates a marked impairment of autonomic control. Of note, the reassessment of PCS patients showed that the noxious effect of COVID-19 on autonomic control tended to fade over time.

Autonomic dysregulation in long-term patients suffering from Post-COVID-19 Syndrome assessed by heart rate variability

Post-COVID-19 Syndrome (PCS) is a condition with multiple symptoms partly related to dysregulation of the autonomic nerve system. Assessment of heart rate variability (HRV) using 24 h Holter-ECG may serve as a surrogate to characterize cardiac autonomic activity. A prospective study including 103 PCS patients (time after infection = 252 days, age = 49.0 ± 11.3 years, 45.7% women) was performed and patients underwent detailed clinical screening, cardiopulmonary exercise testing, and 24 h Holter monitoring. Data of PCS patients was compared to 103 CAD patients and a healthy control group (n = 90). After correction for age and sex, frequency-related variables differed in PCS patients compared to controls including LF/HFpower, LF/HFnu, and LF/HF ratio (24 h; p ≤ 0.001). By contrast, these variables were largely comparable between PCS and CAD patients, while sympathetic activation was highest in PCS patients during the 24 h period. Overall, PCS patients showed disturbed diurnal adjustment of HRV, with impaired parasympathetic activity at night. Patients hospitalized during acute infection showed an even more pronounced overactivation of sympathetic activity compared to patients who underwent ambulant care. Our data demonstrate persistent HRV alterations in PCS patients with long-term symptom duration, suggesting a sustained impairment of sympathovagal balance. Moreover, sympathetic overstimulation and diminished parasympathetic response in long-term PCS patients are comparable to findings in CAD patients. Whether HRV variables have a prognostic value in PCS and/or might serve as biomarkers indicating a successful interventional approach warrants further longitudinal studies.

Cardiac Autonomic Function and Functional Capacity in Post-COVID-19 Individuals with Systemic Arterial Hypertension

Individuals diagnosed with systemic arterial hypertension (SAH) are considered risk groups for COVID-19 severity. This study assessed differences in cardiac autonomic function (CAF) and functional capacity (FC) in SAH individuals without COVID-19 infection compared to SAH individuals post-COVID-19. Participants comprised 40 SAH individuals aged 31 to 80 years old, grouped as SAH with COVID-19 (G1; n = 21) and SAH without COVID-19 (G2; n = 19). CAF was assessed via heart rate variability (HRV), measuring R-R intervals during a 10-min supine period. Four HRV indices were analyzed through symbolic analysis: 0V%, 1V%, 2LV%, and 2UV%. FC assessment was performed by a 6-min walk test (6MWT). G1 and G2 showed no significant differences in terms of age, anthropometric parameters, clinical presentation, and medication use. G2 exhibited superior 6MWT performance, covering more distance (522 ± 78 vs. 465 ± 59 m, p < 0.05). Specifically, G2 demonstrated a moderate positive correlation between 6MWT and the 2LV% index (r = 0.58; p < 0.05). Shorter walking distances were observed during 6MWT in SAH individuals post-COVID-19. However, the study did not find impaired cardiac autonomic function in SAH individuals post-COVID-19 compared to those without. This suggests that while COVID-19 impacted FC, CAF remained relatively stable in this population.

Impaired parasympathetic function in long-COVID postural orthostatic tachycardia syndrome - a case-control study

PURPOSE

Eighty percent of patients infected by SARS-CoV-2 report persistence of one symptom beyond the 4-week convalescent period. Those with orthostatic tachycardia and orthostatic symptoms mimicking postural tachycardia syndrome, they are defined as Long-COVID POTS [LCP]. This case-control study investigated potential differences in autonomic cardiovascular regulation between LCP patients and healthy controls.

METHODS

Thirteen LCP and 16 healthy controls, all female subjects, were studied without medications. Continuous blood pressure and ECG were recorded during orthostatic stress test, respiratory sinus arrhythmia, and Valsalva maneuver. Time domain and power spectral analysis of heart rate [HR] and systolic blood pressure [SBP] variability were computed characterizing cardiac autonomic control and sympathetic peripheral vasoconstriction.

RESULTS

LCP had higher deltaHR (+ 40 ± 6 vs. + 21 ± 3 bpm, p = 0.004) and deltaSBP (+ 8 ± 4 vs. -1 ± 2 mmHg, p = 0.04) upon standing; 47% had impaired Valsalva maneuver ratio compared with 6.2% in controls (p = 0.01). Spectral analysis revealed that LCP had lower RMSSD (32.1 ± 4.6 vs. 48.9 ± 6.8 ms, p = 0.04) and HFRRI, both in absolute (349 ± 105 vs. 851 ± 253ms2, p = 0.03) and normalized units (32 ± 4 vs. 46 ± 4 n.u., p = 0.02). LFSBP was similar between groups.

CONCLUSIONS

LCP have reduced cardiovagal modulation, but normal sympathetic cardiac and vasoconstrictive functions. Impaired parasympathetic function may contribute to the pathogenesis of Long-COVID POTS syndrome.

Cardiovascular autonomic dysfunction in "Long COVID": pathophysiology, heart rate variability, and inflammatory markers

Long COVID is characterized by persistent signs and symptoms that continue or develop for more than 4 weeks after acute COVID-19 infection. Patients with Long COVID experience a cardiovascular autonomic imbalance known as dysautonomia. However, the underlying autonomic pathophysiological mechanisms behind this remain unclear. Current hypotheses include neurotropism, cytokine storms, and inflammatory persistence. Certain immunological factors indicate autoimmune dysfunction, which can be used to identify patients at a higher risk of Long COVID. Heart rate variability can indicate autonomic imbalances in individuals suffering from Long COVID, and measurement is a non-invasive and low-cost method for assessing cardiovascular autonomic modulation. Additionally, biochemical inflammatory markers are used for diagnosing and monitoring Long COVID. These inflammatory markers can be used to improve the understanding of the mechanisms driving the inflammatory response and its effects on the sympathetic and parasympathetic pathways of the autonomic nervous system. Autonomic imbalances in patients with Long COVID may result in lower heart rate variability, impaired vagal activity, and substantial sympathovagal imbalance. New research on this subject must be encouraged to enhance the understanding of the long-term risks that cardiovascular autonomic imbalances can cause in individuals with Long COVID.

Physical Activity in Long COVID: A Comparative Study of Exercise Rehabilitation Benefits in Patients with Long COVID, Coronary Artery Disease and Fibromyalgia

Exercise in long COVID is poorly studied. Nevertheless, exerciserehabilitation could improve cardiorespiratory, muscular and autonomic functions. We aimed to investigate improvement in physical and autonomic performances of long COVID patients (n = 38) after a 4-week exercise rehabilitation program (3 sessions/week) compared to two control groups composed of coronary artery disease (n = 38) and fibromyalgia patients (n = 38), two populations for whom exercise benefits are well known. Efficacy of exercise training was assessed by a cardiopulmonary exercise test, a handgrip force test, and a supine heart rate variability recording at rest before and after the rehabilitation program. Cardiorespiratory and muscular parameters were enhanced after exercise rehabilitation in the three groups (p < 0.001). No significant difference was observed for the autonomic variables. Through this comparative study with control groups, we confirm and reinforce the interest of caring for long COVID patients without post-exertional symptom exacerbation by exercise rehabilitation of both strength and endurance training, by personalizing the program to the patient and symptoms.

The Cardiac Comeback-Beating Stronger: Exploring the Remarkable Resilience of the Heart in COVID-19 Recovery through Cardiac Autonomic Analysis

Background and Objectives: Analyzing the cardiac autonomic function in COVID-19 patients can provide insights into the impact of the virus on the heart's regulatory mechanisms and its recovery. The autonomic nervous system plays a crucial role in regulating the heart's functions, such as heart rate, blood pressure, and cardiac output. This study aimed to investigate the impact of COVID-19 on heart rate variability (HRV) during a 6-min walk test (6MWT). Materials and Methods: The study included 74 participants, consisting of 37 individuals who had recovered from mild to moderate COVID-19 and 37 healthy controls. The study assessed heart rate variability (HRV) and blood pressure both before and after a 6-min walk test (6MWT). Results: The study found significant differences in a few time domains (SDNN and pNN50) and all frequency domain measures, whereas there were no significant differences in demographic characteristics or blood pressure between COVID-19-recovered individuals and healthy controls at rest. There were significant 6MWT effects on average HR, time-domain (SDNN and pNN50) measures of HRV, and all frequency domain measures of HRV. A significant group × 6MWT interaction was found for SDNN, pNN50, total power, Ln total power, LF, HF, Ln LF, Ln HF, and LF nu. Conclusions: Cardiac Autonomic analysis through HRV is essential to ensure the continued health and well-being of COVID-19 survivors and to minimize the potential long-term impacts of the disease on their cardiovascular system. This suggests that HRV analysis during the recovery phase following exercise could serve as a valuable tool for evaluating the physiological effects of COVID-19 and monitoring the recovery process.

The Relationship between Paresthesia and the Presence of Cardiac Dysautonomia in Patients with Post-COVID-19 Syndrome: A Preliminary Observational Study

INTRODUCTION

Post-Coronavirus disease 2019 (Post-COVID-19) syndrome has neurological symptoms related to the dysfunction of the autonomous nerve system. However, a pathogenic relationship between post-COVID-19 syndrome and dysautonomia still remains to be demonstrated. Establishing a pathogenic relationship between paresthesia and the presence of cardiac dysautonomia in patients with post-COVID-19 syndrome is the objective of this study.

PARTICIPANTS AND METHODS

This observational study was carried out in the neurophysiology service wing of the Juan Bruno Zayas Hospital, Santiago de Cuba, in Cuba. The patients were recruited through a post-COVID-19 clinic at the same hospital. A variability study of cardiac frequency and a test of autonomic cardiovascular reflexes was carried out, which is composed of deep breathing, orthostatism, and the Valsalva maneuver.

RESULTS

The variability parameters of the cardiac frequency, the expiration-inspiration ratio between deep breaths, and the Valsalva Index showed no statistically significant differences between healthy participants and those with post-COVID-19 syndrome. During the Valsalva maneuver, there was a greater cardiac frequency response in participants with post-COVID-19 syndrome than in healthy subjects. The difference in supine and standing blood pressure was significantly minor in patients with post-COVID-19 syndrome. The logarithm of high frequency (log HF) increased significantly in patients with paresthesia when compared to patients without paresthesia.

CONCLUSIONS

In the autonomic function tests, no signs of dysautonomia were found in patients with post-COVID-19 syndrome. The presence of paresthesias is associated with differences in cardiac vagal activity, which may suggest that damage to peripheral sensory nerve fibers could be associated with an affectation to autonomic fibres.

[Neurological forms of long COVID in adults: Critical approach]

Now recognized by health authorities, long COVID is identified as a frequent condition complicating the evolution of SARS-CoV-2 infection. Its polymorphic and sometimes disconcerting clinical expression raises questions about its mechanism. Patterns of clinical expression suggest extensive involvement of the nervous system through an almost ubiquitous cognitive complaint. This article reviews the neurological symptoms and forms of these patients, and the neuropsychological explorations aimed at objectifying a cognitive deficit. The studies published until now confronted with the clinical mode of expression, did not make it possible to define a deficit neuropsychological profile at the level of the groups, and evoked more a functional impairment than a lesion. However, each series mentions a small number of patients in whom a cognitive deficit is objectified. The uncertainties about the causes of the prolonged forms of COVID, the heterogeneity of the published studies, and the virtual absence of temporal evolution data should make one cautious about the interpretation of these data but should in no way delay or prevent taking into account care of these patients.

Effects of Three-Hour Wearing Personal Protective Equipment on Heart Rate Variability in Healthcare Workers for the Treatment of COVID-19 Patients

Background

Personal protective equipment (PPE), an essential shield to protect healthcare workers (HCWs) during the COVID-19 pandemic, has been reported to affect their heart rate variability (HRV).

Objective

To investigate the changes of very short-term heart rate variability in HCWs after three hours of wearing PPE to treat COVID-19 patients at different working times and intensities, and related factors.

Methods

Sixty-five healthy HCWs were enrolled at the Number 2 Infectious Field Hospital (formed by Military Hospital 103), Vietnam. Two-minute 12-lead electrocardiograms were recorded before wearing and after removing PPE.

Results

After three hours of wearing PPE, the mean heart rate of HCWs increased (p = 0.048) meanwhile, the oxygen saturation decreased significantly (p = 0.035). Standard deviation of all normal to normal intervals (SDNN), mean intervals RR (mean NN), and root mean square successive difference (rMSSD) after wearing PPE was also reduced significantly. SDNN, Mean NN, and rMSSD decreased as the working intensity increased (as in mild, moderate, and severe patient departments). In univariate regression analysis, logSDNN, logmean NN and logrMSSD were positively correlated with SpO2 and QT interval (r = 0.14, r = 0.31, r = 0.25; r = 0.39, r = 0.77, r = 0.73, respectively) and were negatively correlated with ambient temperature inside PPE (r = -0.41, r = -0.405, r = -0.25, respectively) while logmean NN and log rMSSD were negatively correlated with diastolic blood pressure (r = -0.43, r = -0.39, respectively). In multivariable regression analysis, logSDNN and logmean NN were negatively correlated to ambient temperature inside PPE (r = -0.34, r = -0.18, respectively).

Conclusion

Time-domain heart rate variability decreased after wearing PPE. Time-domain HRV parameters were related to ambient temperature inside PPE, diastolic blood pressure, QT interval, and SpO2.

Evaluation of Outpatients in the Post-COVID-19 Period in Terms of Autonomic Dysfunction and Silent Ischemia

INTRODUCTION AND OBJECTIVE

In this context, the objective of this study is to evaluate the 24-hour ambulatory electrocardiography (ECG) recordings, autonomous function with heart rate variability (HRV), and silent ischemia (SI) attacks with ST depression burden (SDB) and ST depression time (SDT) of post-COVID-19 patients.  Materials and methods: The 24-hour ambulatory ECG recordings obtained >12 weeks after the diagnosis of COVID-19 were compared between 55 consecutive asymptomatic and 73 symptomatic post-COVID-19 patients who applied to the cardiology outpatient clinic with complaints of palpitation and chest pain in comparison with asymptomatic post-COVID-19 patients in Kars Harakani state hospital. SDB, SDT, and HRV parameters were analyzed. Patients who had been on medication that might affect HRV, had comorbidities that might have caused coronary ischemia, and were hospitalized with severe COVID-19 were excluded from the study.

RESULTS

There was no significant difference between symptomatic and asymptomatic post-COVID-19 patients in autonomic function. On the other hand, SDB and SDT parameters were significantly higher in symptomatic post-COVID-19 patients than in asymptomatic post-COVID-19 patients. Multivariate analysis indicated that creatine kinase-myoglobin binding (CK-MB) (OR:1.382, 95% CI:1.043-1.831; p=0.024) and HRV index (OR: 1.033, 95% CI:1.005-1.061; p=0.019) were found as independent predictors of palpitation and chest pain symptoms in post-COVID-19 patients.

CONCLUSION

The findings of this study revealed that parasympathetic overtone and increased HRV were significantly higher in symptomatic patients with a history of COVID-19 compared to asymptomatic patients with a history of COVID-19 in the post-COVID-19 period. Additionally, 24-hour ambulatory ECG recordings and ST depression analysis data indicated that patients who experienced chest pain in the post-COVID-19 period experienced silent ischemia (SI) attacks.

Using Machine Learning Algorithms to Determine the Post-COVID State of a Person by Their Rhythmogram

This study introduces a novel method for detecting the post-COVID state using ECG data. By leveraging a convolutional neural network, we identify "cardiospikes" present in the ECG data of individuals who have experienced a COVID-19 infection. With a test sample, we achieve an 87 percent accuracy in detecting these cardiospikes. Importantly, our research demonstrates that these observed cardiospikes are not artifacts of hardware-software signal distortions, but rather possess an inherent nature, indicating their potential as markers for COVID-specific modes of heart rhythm regulation. Additionally, we conduct blood parameter measurements on recovered COVID-19 patients and construct corresponding profiles. These findings contribute to the field of remote screening using mobile devices and heart rate telemetry for diagnosing and monitoring COVID-19.

The Use of Photoplethysmography in the Assessment of Mental Health: Scoping Review

BACKGROUND

With the rise in mental health problems globally, mobile health provides opportunities for timely medical care and accessibility. One emerging area of mobile health involves the use of photoplethysmography (PPG) to assess and monitor mental health.

OBJECTIVE

In recent years, there has been an increase in the use of PPG-based technology for mental health. Therefore, we conducted a review to understand how PPG has been evaluated to assess a range of mental health and psychological problems, including stress, depression, and anxiety.

METHODS

A scoping review was performed using PubMed and Google Scholar databases.

RESULTS

A total of 24 papers met the inclusion criteria and were included in this review. We identified studies that assessed mental health via PPG using finger- and face-based methods as well as smartphone-based methods. There was variation in study quality. PPG holds promise as a potential complementary technology for detecting changes in mental health, including depression and anxiety. However, rigorous validation is needed in diverse clinical populations to advance PPG technology in tackling mental health problems.

CONCLUSIONS

PPG holds promise for assessing mental health problems; however, more research is required before it can be widely recommended for clinical use.

Parasympathetic autonomic dysfunction is more often evidenced than sympathetic autonomic dysfunction in fluctuating and polymorphic symptoms of "long-COVID" patients

Several disabling symptoms potentially related to dysautonomia have been reported in "long-COVID" patients. Unfortunately, these symptoms are often nonspecific, and autonomic nervous system explorations are rarely performed in these patients. This study aimed to evaluate prospectively a cohort of long-COVID patients presenting severe disabling and non-relapsing symptoms of potential dysautonomia and to identify sensitive tests. Autonomic function was assessed by clinical examination, the Schirmer test; sudomotor evaluation, orthostatic blood pressure (BP) variation, 24-h ambulatory BP monitoring for sympathetic evaluation, and heart rate variation during orthostatism, deep breathing and Valsalva maneuvers for parasympathetic evaluation. Test results were considered abnormal if they reached the lower thresholds defined in publications and in our department. We also compared mean values for autonomic function tests between patients and age-matched controls. Sixteen patients (median age 37 years [31-43 years], 15 women) were included in this study and referred 14.5 months (median) [12.0-16.5 months] after initial infection. Nine had at least one positive SARS-CoV-2 RT-PCR or serology result. Symptoms after SARS-CoV-2 infection were severe, fluctuating and disabling with effort intolerance. Six patients (37.5%) had one or several abnormal test results, affecting the parasympathetic cardiac function in five of them (31%). Mean Valsalva score was significantly lower in patients than in controls. In this cohort of severely disabled long-COVID patients, 37.5% of them had at least one abnormal test result showing a possible contribution of dysautonomia to these nonspecific symptoms. Interestingly, mean values of the Valsalva test were significantly lower in patients than in control subjects, suggesting that normal values thresholds might not be appropriate in this population.