Cerebral blood flow during HUTT in young patients with orthostatic intolerance

Purpose: To investigate patterns of change in cerebral perfusion during head-up tilt testing (HUTT) in children and young adults with autonomic dysfunction.

Methods: We utilized near-infrared spectroscopy (NIRS) to estimate bilateral cerebral perfusion patterns during HUTT in 71 adolescents and young adults with a diagnosis of autonomic dysfunction. In addition, we used transthoracic impedance to measure cardiac stroke volume and thus infer autonomic tone, heart rate, and blood pressure during the test. Cerebral blood-flow wave-patterns were then visually analyzed and associated with clinical symptoms and measures of cardiovascular and autonomic function.

Results: Visual analysis of contour changes in head NIRS values during phases of HUTT revealed variable patterns of cerebral blood flow, some specifically associated with severe symptomatology (i.e., syncope). We also observed an inequality in blood flow of the cerebral hemispheres in many patients. Finally, we observed changes in cardiac stroke volume during HUTT, as previously reported, that related to changes in head NIRS.

Conclusion: These results confirm a decrease in cerebral blood flow during HUTT as assessed by head NIRS in patients with autonomic dysfunction. Specifically, we have profiled the cerebral blood flow contours throughout the phases of HUTT, which add insight into the clinical spectrum of the disorder and may correlate with clinical severity.