Postural tachycardia during head-up tilt test predicts persistent orthostatic intolerance in young adults

Background: Head-up tilt (HUT) test is an important tool in establishing the cause of past syncope. As postural tachycardia is associated with orthostatic intolerance, we hypothesise that heart rate (HR) increase during the early phase of HUT can be used as a surrogate test outcome to predict future orthostatic intolerance in an individual patient. Methods: Patients aged 18 to 40 years who had undergone HUT test at our centre were included in the cross-sectional study. Telephone interviews about orthostatic symptoms and recurrent syncope were performed 9 to 12 months after HUT with 73 consecutive patients in the exploratory and 67 consecutive patients in the confirmatory cohort. Data from interviews were related to past HUT test results. Results: Orthostatic intolerance was reported by 52 (71 %) patients in the exploratory and 41 (61 %) in the confirmatory cohort. Positive predictive value (PPV) of HR increase ≥ 30 bpm for orthostatic intolerance in confirmatory cohort was 0.88 (only one patient had this level of tachycardia in the exploratory cohort). HR increase ≥ 23 bpm was established as cut-off value with high specificity for orthostatic intolerance, its PPV was 0.89 in exploratory and 0.87 in confirmatory cohort. PPVs of HUT test outcome for orthostatic intolerance were 0.84 and 0.62, respectively. Both prominent HR increase and HUT test outcome had low PPV for recurrent syncope. Conclusions: In young adults referred for HUT test postural tachycardia in the early phase of HUT predicts orthostatic intolerance a year after testing independently of test outcome.