Plasma Cytokine and Caspase-1p20 Profiles in Pre-Pandemic and Long COVID-Associated Postural Orthostatic Tachycardia Syndrome

Background: Prior to the COVID-19 pandemic, the etiology of postural orthostatic tachycardia syndrome (POTS) remained elusive. Since the pandemic, a newly recognized disorder, termed Long COVID, has emerged with a significant subset of patients developing dysautonomia and a multitude of comorbidities consistent with POTS. Aim: The aim of this study was to determine if pre-pandemic POTS and Long COVID POTS share a common inflammatory-associated biomarker profile. Methods: Volunteers were recruited for four study groups; patients diagnosed with POTS prior to the pandemic, Long COVID-associated POTS, SARS-CoV-2-recovered controls, and naïve controls. All participants completed a COMPASS-31 survey and a medical history questionnaire. Plasma biomarkers of the innate and adaptive immune system were quantified using a custom multiplex bead assay and ELISAs. Results: Both POTS cohorts demonstrated indistinguishable and significant elevations in 14 of the 15 measured biomarkers including markers of the NLRP3 axis (Caspase-1p20, interleukins IL-1β, IL-18), regulatory cytokine IL-10, and immune activation markers (sCD40L, sCD40, sCD30) compared to controls. Multivariate PERMANOVA analysis revealed no significant difference in global cytokine profiles between the two POTS cohorts. Random Forest classification accurately distinguished POTS from controls, with IL-18 emerging as the most important feature. Conclusions: These associative findings suggest that pre-pandemic POTS and Long COVID-associated POTS share a distinct inflammatory profile among measured cytokines. The identification of IL-18 as a key biomarker, alongside Caspase-1p20 and other inflammatory cytokines, are compatible with inflammasome-related signaling. Further investigation is necessary to characterize the role of the inflammasome, platelet activation, and immune dysregulation in POTS and Long COVID.