Abstract P198: Vitamin D Supplementation Improves Autonomic Response To Head Up Tilt In Adolescents Suffering From Orthostatic Intolerance

Abstract

Background: We have previously shown in a group of adolescents who are suffering from orthostatic intolerance (OI) and syncope that they exhibited impairment in autonomic function in supine position and greater loss of baroreflex sensitivity (BRS) and heart rate variability (HRV) measures upon head up tilt (HUT). They also had low vitamin D level that correlated with the severity of symptoms on tilt. In this pilot study we hypothesized that vitamin D supplementation to normal levels will improve the autonomic response to change in position. Methods: In a pilot group of eight female adolescents (mean age= 16.0 years) who are vitamin D deficient, head up tilt was done at baseline and after two months of vitamin D supplementation (2000-5000 IU daily based on baseline level). Heart rate, blood pressure, BRS measured as Sequence Up (parasympathetic) and Sequence down (sympathetic), HRV measured as SDNN and rMSSD, and sympathovagal balance (LF/HF ratio) were assessed both in supine and HUT positions. Results: As shown in the table, compared to baseline, vitamin D supplementation improved vitamin D level, minutes standing on tilt, BRS, HRV and sympathovagal balance measures at baseline and reduced the loss in BRS and HRV measures upon standing. There were no changes in blood pressure measures between pre and post treatment. Conclusions: Vitamin D supplementation for two months restored vitamin D to normal levels and was associated with improvement in the hemodynamic response to standing. These data provide evidence of potential therapeutic benefit of vitamin D supplementation for patients suffering from orthostatic intolerance who are vitamin D deficient,