Patients with long COVID may demonstrate persistent autonomic dysfunction that is similar to patients with pure autonomic failure when adjusted for age and sex, according to a study published Dec. 10 in JACC. It remains unclear whether autonomic dysfunction is directly responsible for long COVID symptoms.

Ciana Keller, MD, et al., examined autonomic testing results in 341 patients aged ≥18 years who were referred to the M Health Fairview University Medical Center between 2019 and 2023. Patients were referred for symptoms such as heart palpitations, lightheadedness, syncope and positional palpitations. Included individuals had not undergone autonomic testing previously and were not receiving autonomic dysfunction treatment.

Researchers classified the included patients into three groups: long COVID (78 patients included, acute COVID-19 infection ≥12 weeks before testing), control subjects (25 patients included, COVID-19 negative, normal autonomic tests) and pure autonomic failure (38 patients included, COVID-19 negative, abnormal autonomic testing). Of note, blood pressure and heart rate were recorded during tilt-table testing, respiratory sinus arrhythmia, Valsalva maneuver and active standing.

Study results showed that patients with long COVID (median age of 36 years; 84% women) exhibited a greater heart rate increase and blood pressure drop with tilt-table testing and active standing (all p<0.05), and they had lower respiratory sinus arrhythmia values and Valsalva ratios vs. patients in the control group (median age of 32 years; 76% women) (both p<0.05).

Additionally, patients with long COVID had a greater heart rate increase but a lower blood pressure drop with tilt-table testing and active standing than patients with pure autonomic failure (median age of 64 years; 53% women), and lesser respiratory sinus arrhythmia values and Valsalva ratios (all p<0.001).

Autonomic dysfunction measures in patients with long COVID were comparable with patients with pure autonomic failure after age and sex adjustment, and abnormalities in autonomic testing were observed in patients up to 40 months after infection.

The authors note several limitations of this study, including small sample size, potential selection bias and the potential of previous asymptomatic or subclinical COVID-19 infection across the three groups. "Nonetheless, the quantitative measures of autonomic function reported here support the presence of substantial and persistent autonomic nervous system disturbances in patients with long COVID," they write.