Table 1.

Summary of clinical reports and case series of patients with autonomic dysfunction post-COVID-19. Abbreviations: POTS: postural orthostatic tachycardia syndrome; ECG: Electrocardiogram; OH: orthostatic hypotension; QSART: Quantitative Sudomotor Axon Reflex Testing; HRV: heart rate variability; SDNN: Standard Deviation of NN intervals; SDANN: Standard Deviation of the Average NN intervals; LF/HF: Low Frequency/High Frequency Ratio; SNS: sympathetic nervous system; PNS: peripheral nervous system; ANS: autonomic nervous system; NCS: Neurocardiogenic Syncope.

Number of participants	Age and gender	Clinical findings post-COVID-19 infection	Reference
1	36-year-old female	3–4 weeks post-COVID-19 diagnosis: Fatigue, dizziness, headache, orthostatic chest pain, and palpitations Diagnosis of POTS	(Kanjwal et al., 2020)
1	26-year-old female	Day 7 Shortness of breath, palpitations, burning chest pains upon inhalation, and anorexia Day 14 Fatigue, tachycardia, shortness of breath, exercise intolerance, chest pains, and insomnia Day 19 Orthostatic presyncope and lightheadedness Day 22 Pressured speech and restlessness Day 24 Adrenaline surges and restlessness Day 30 Worsening of orthostatic intolerance Day 45 Non-pruritic hives, facial flushing, dermatographia Day 107 (over 3 months after symptoms onset) Diagnosis of POTS	(Miglis et al., 2020)
1	58-year-old female	Headache, somnolence, and hypertensive palpitations at rest Diagnosis: acute dysautonomia with sympathetic overactivity	(Abdelnabi et al., 2021)
1	22-year-old female	Day 21 post infection Chest tightness, palpitations, dyspnea, and fatigue upon mild exertion ECG: Sinus tachycardia Electrocardiography: Hyperdynamic left ventricle	(O'Sullivan et al., 2021)
1	67-year-old male	OH, lightheadedness, generalized weakness, shortness of breath, and anorexia Day 6 of hospitalization Syncopal episode	(Suresh et al., 2021)
1	27-year-old female	5 weeks after infection: Headache, fatigue upon exertion, weakness, blurry vision, slow cognition, heart palpitations 2 months after initial symptoms: worsening initial symptoms, burning in lower extremities, muscle spasms and twitches 5 months after initial symptoms: worsening initial symptoms, diarrhea, extreme exhaustion, uncontrollable shaking Diagnosis of POTS	(Bosco and Titano, 2022)
27	59 % are females and 41 % are males with an average age of 30 years old	Autonomic symptoms onset during infection: 41 % of patients Autonomic symptoms onset 0–122 days post-infection: 59 % of patients: lightheadedness (93 %), burning pain (11 %), orthostatic headache (22 %), orthostatic tachycardia (7 %), syncope (11 %), flushing (7 %), hyperhidrosis (11 %), and weight loss (7 %) Abnormal autonomic test (63 %), abnormal QSART (36 %), abnormal cardiovagal test (27 %), abnormal cardiovagal adrenergic function (7 %)	(Shouman et al., 2021)
40	57.5 % are females and 42.5 % are males with an average age of 55 years	6 months post-discharge from COVID-19 hospitalization Fever (2.5 %), cough (30 %), breathing difficulties (40 %), diarrhea (20 %), muscle pain (25 %), ventilation dysfunction (17.5 %), diffuse dysfunction (55 %), and pulmonary fibrosis (57.5 %) Patients with Ventilation Dysfunction SDNN: 28.6 % had an abnormal HRV SDANN: 14.3 % had an abnormal circadian HRV LF/HF: 14.3 % had a SNS/PNS imbalance Patients with Diffuse Dysfunction SDNN: 40.91 % had an abnormal HRV SDANN: 30 % had an abnormal circadian HRV LF/HF: 9.1 % had a SNS/PNS imbalance Patients with Pulmonary Fibrosis SDNN: 38.1 % had an abnormal HRV SDANN: 14.3 % had an abnormal circadian HRV LF/HF: 4.5 % had a SNS/PNS imbalance	(Bai et al., 2021)
152	Mild group: 30 patients who had COVID-19 without pneumonia 53.33 % are males and 46.67 % are females with an average age of 42 years Severe group: 45 patients who had COVID-19 with interstitial pneumonia 53.33 % are males and 46.67 % are females with an average age of 51 years Control group: 77 healthy controls matched by sex and age with infected groups	Sympathetic function tests: OH: -Control group: 2.6 % -Mild group: 46.3 % -Severe group: 25 % Hand grip test: -Control group: 76.9 % -Mild group: 94.4 % -Severe group: 84.6 % Parasympathetic function tests: Heart rate response to Valsalva maneuver: -Control group: 24.4 % -Mild group: 28.9 % -Severe group: 18.2 % Heart rate response to deep breathing: -Control group: 11.5 % -Mild group: 41.7 % -Severe group: 25.8 % ANS Impairment Parasympathetic dysfunction -Control group: 14.1 % -Mild group: 26.6 % -Severe group: 12.10 % Combined dysfunction -Control group: 11.8 % -Mild group: 73.20 % -Severe group: 53.5 % Autonomic neuropathy -Control group: 55.8 % -Mild group: 76.7 % -Severe group: 51.5 %	(Milovanovic et al., 2021)
20	30 % are males and 70 % are females with average age of 40 years	During COVID-19 Infection Acute respiratory syndrome (75 %), anosmia (50 %), ageusia (50 %), and pneumonia (10 %) 6–8 months Post-COVID-19 Infection: Fatigue, orthostatic intolerance, dizziness, postural tachycardia, and exercise intolerance POTS (75 %), NCS (15 %), and OH (10 %)	(Blitshteyn and Whitelaw, 2021)
9	Females with average age of 35.8 years	0.8 ± 0.3 years after a mild COVID-19 infection: 100 %: Autonomic symptoms, gastrointestinal symptoms, pain, brain fog, fatigue, and dyspnea Mean Reduction in Orthostatic cerebral blood flow velocity: −20 % Dysautonomia: 100 % Small fiber neuropathy: 89 % Presence of inflammatory markers: 67 %	(Novak et al., 2022)
218	112 patients who recovered from COVID-19: 61 % females, 39 % males Average age of 40 years 106 healthy controls: 60 % females, 40 % males Average age of 46 years	3.7 ± 1.7 months after COVID-19 infection: Symptoms: Fatigue (73.2 %), headache (66 %), anosmia (65.1 %), ageusia (59.8 %), fever (58.9 %), cough (48.2 %), pharyngitis (47.4 %), myalgia (46.4 %), dyspnea (29 %), rhinitis (25.9), diarrhea (21.8 %). Significant averages of SCOPA-AUT autonomic symptoms: -COVID-19 group: Pupillomotor 0.4 ± 0.7 Sudomotor 3.1 ± 2.5 Urinary 3.6 ± 3.2 -Control group: Pupillomotor 0.6 ± 0.7 Sudomotor 1.7 ± 1.8 Urinary 2.5 ± 2.2	(Erdal et al., 2022)