Hemodynamic and cerebral oxygenation predictors of visual darkening in pediatric POTS: a cross-sectional study

In pediatric postural tachycardia syndrome (POTS), presyncope is important yet undercharacterized. It undermines school participation and daily function, while objective bedside markers remain limited. We aimed to delineate clinically usable predictors by integrating cardiovascular responses and cerebral oxygenation during active standing. We operationalized presyncope as visual darkening and examined three physiological correlates: heart rate change (ΔHR), recovery time, and cerebral oxygenation (ΔOxyHb).

We conducted a cross-sectional study of 49 pediatric patients with POTS (median age 14.2 years, 46.9% male). Continuous heart rate, blood pressure, and cerebral oxygenation were recorded during a 10-min active standing test; body mass index, inferior vena cava collapsibility index, and urinary sodium were also obtained. Robust regression identified independent predictors of visual darkening.

ΔHR emerged as the strongest predictor of visual darkening (coefficient 0.017, 95% CI 0.005-0.030, p = 0.004), followed by recovery time (coefficient 0.005, 95% CI 0.000-0.010, p = 0.055) and ΔOxyHb (coefficient 0.029, 95% CI  - 0.005 to 0.064, p = 0.098). The final model demonstrated strong discriminative ability (AUC 0.842). Patients reporting visual darkening exhibited significantly higher ΔHR (49 [42-59] vs. 41 [38-46] bpm, p = 0.009), longer recovery time (21 [19-28] vs. 19 [17-22] s, p = 0.041), and greater ΔOxyHb reduction (- 8.7 [ - 10.4 to - 2.4] vs. - 3.5 [- 7.0 to - 2.5] μmol/L, p = 0.039).

Heart rate change upon standing is the most significant and clinically accessible predictor of visual darkening in pediatric POTS. The combined assessment of ΔHR, recovery time, and cerebral oxygenation offers a comprehensive evaluation of the risk of visual darkening, enabling personalized management strategies for pediatric patients.