Correlation Between Orthostatic Symptoms and Autonomic Parameters During the Head-Up Tilt Test

ABSTRACT

BACKGROUND: The aims of the present study were to identify the orthostatic symptoms occurring during the head-up tilt (HUT) test and to compare the autonomic parameters in patients with and without symptoms during the HUT test. METHODS: We retrospectively collected autonomic data from patients presenting with autonomic symptoms including orthostatic dizziness over a 1-year period. A standardized battery of autonomic tests was performed, including the HUT test, Valsalva maneuver (VM), heart rate (HR) deep breathing test, and quantitative sudomotor axon reflex test (QSART) using Finometer devices to record the beat-to-beat blood pressure (BP) and HR response. We also investigated the patients' symptoms during the HUT test and compared the autonomic parameters between patients with and without orthostatic symptoms. RESULTS: In total, 898 patients who submitted to autonomic function tests were included in this study. Of these, 17% (157/898) complained of various kinds of symptoms during tilting, while the remainder denied any symptoms. Patients complained of atypical symptoms, such as leg or back pain, tingling sensation in the leg, and difficulty breathing or chest tightness, as well as typical orthostatic symptoms. The BP decrease and the HR increase during the HUT test were greater in the symptomatic group. A prolonged pressure recovery time during VM, a lower sweat output during QSART, and a higher composite autonomic severity score were observed in the symptomatic group. CONCLUSIONS: Approximately one-fifth of the patients complained of symptoms during the HUT test, and those symptoms were strongly correlated with the autonomic parameters suggestive of impaired compensative mechanisms in response to a BP fall.