Sivakoti, Kirti

Abstract Purpose: Adolescents with chronic orthostatic intolerance (COI) experience symptoms related to impaired tolerance of upright posture. Postural Orthostatic Tachycardia Syndrome (POTS) is a specific type of COI, marked by an excessive increase in heart rate (≥40 bpm or an absolute HR >120 bpm) when standing. This study compares Functional Disability Inventory (FDI) scores between adolescents with COI with and without excessive postural tachycardia (POTS subtype). Methods: Patients ≤19 years referred to our POTS program (Aug 2024–Mar 2025) with orthostatic symptoms for>3 months were included. Based on active stand HR, patients were categorized as POTS (HR ≥40 bpm) or COI without excessive postural tachycardia (HR <40 bpm). FDI scores were collected. Chi-square tests assessed group differences. A two-sample t-test compared FDI severity. Linear regression evaluated the association between HR change and FDI score. Results: All data were normally distributed, allowing the use of parametric analyses. Of the 92 patients (46 per group), 78% were female. The mean age was 16.0 ± 1.48 years in the COI group and 16.3 ± 1.7 years in the POTS group, with no significant sex differences between groups. The COI group had a higher mean FDI score than the POTS group, but this difference was not statistically significant. The distribution of FDI severity (mild, moderate, severe) was similar between groups. Linear regression showed a non-significant trend of a 1 bpm increase in heart rate associated with a 0.1055-point decrease in FDI score Conclusion: Functional disability was similar between the COI and POTS groups.