Comparison of the active standing test and head-up tilt test for diagnosis of syncope in childhood and adolescence.

We examined 51 children and adolescents with orthostatic symptoms using two orthostatic tests, the active standing test (the AS test) and head-up tilt test (HUT), and compared circulatory responses, autonomic function in addition to the induction rate of syncope during short-time orthostasis. Syncope was induced in eight patients with both tests, in only six patients with the AS test and in only one patient with HUT. The induction rate was significantly higher with the AS test (p<0.0001). In addition, the AS test is common and daily postural motion and does not require a tilt table. We calculated percent changes in systolic blood pressure at the initial drop (DeltaID-SBP), in systolic blood pressure (DeltaSBP), in diastolic blood pressure (DeltaDBP), in heart rate (DeltaHR), component coefficient variation LF/HF (DeltaLF/HF) from supine to upright. DeltaHR were significantly larger in fainters than in non-fainters with both tests, although there was no difference in DeltaSBP and in DeltaDBP. In six fainters only with the AS test, DeltaHR was significantly larger with the AS test than with HUT. With the AS test DeltaID-SBP were correlative with DeltaLF/HF, and DeltaLF/HF were correlative with DeltaHR, whereas these relations were not clear in HUT. These results indicated the AS test caused cardiac sympathetic activation associated with an initial pressure drop, and was more prone to induce syncope with a greater HR increase in some patients. We conclude the AS test is as potential as HUT as a diagnostic test for syncope.