Novel inflammatory biomarkers in postural orthostatic tachycardia syndrome

Abstract

Abstract Funding Acknowledgements Type of funding sources: None. Introduction Postural Orthostatic Tachycardia Syndrome (POTS) is a disorder characterized by excessive orthostatic tachycardia and orthostatic intolerance. While traditional inflammatory biomarkers tend to be normal, a subclinical inflammatory process may be present in POTS. Purpose We aimed to analyse novel inflammatory biomarkers in POTS patients: Growth Differentiation Factor 15 (GDF15), Neutrophil Gelatinase Associated Lipocalin (NGAL), Intercellular Adhesion Molecule 1 (ICAM-1), Tumour Necrosis Factor Receptor 1 (TNFR1) and Tumour Necrosis Factor Receptor 2 (TNFR2) and compared them to healthy controls. These inflammatory biomarkers have been shown to be independent predictors of major adverse cardiovascular events in other populations. Methods An age- and sex-matched case-control study included 65 patients verified to have POTS by positive head-up tilt-testing and cardiovascular autonomic tests, and 65 healthy controls (mean age: 31.1 vs 31.5 years, 84% females) with negative active standing tests and no history of syncope, orthostatic intolerance, or endocrine disease. High-sensitivity chemiluminescence sandwich immunoassay was used to measure plasma levels of inflammatory biomarkers in a blinded fashion. Descriptive statistics compared groups and a univariate ANOVA was employed. Biomarker values were log-transformed. A score incorporating all biomarkers was generated to see if the totality of biomarkers discriminated POTS patients from controls. Results Baseline characteristics are displayed in Table 1. Mean levels of GDF15 (p=0.01), NGAL (p=0.003), ICAM-1 (p=0.04) and TNFR1 (p=0.03) were significantly higher in POTS vs controls, whereas TNFR2 (p=0.04) was significantly lower in POTS (p=0.04). The product of four upregulated biomarkers divided by TNFR2 produced a receiver operator curve (ROC) with an area under the curve (AUC) of 0.703 (p<0.001) (Fig.1). Conclusion POTS patients had increased GDF15, NGAL, TNFR1 and ICAM-1 levels and reduced TNFR2 levels suggesting underlying, yet undefined, subclinical inflammatory processes involving neutrophil and endothelial activation.