SPECT evaluation of cerebral blood flow during arm exercise in patients with subclavian steal.

Objectives: To explore the cerebral hemodynamics in subclavian steal syndrome, we examined the cerebral perfusion of seven patients with subclavian steal (one symptomatic and six asymptomatic) using single-photon emission computed tomography (SPECT) during resting, arm exercise, and acetazolamide-activated conditions.
Methods: The regional CBF (rCBF) was measured with SPECT under all conditions, and region of interest (ROI) analysis was performed using a three-dimensional stereotaxic ROI template (3DSRT). We evaluated the relationship between arm exercise-induced rCBF change and (1) presence of subclavian artery stenosis, (2) vertebral reverse flow severity, (3) presence of vertebro-basilar insufficiency (VBI) symptoms, and (4) cerebrovascular reactivity (CVR) to acetazolamide.
Results: Overall, no arm exercise-induced rCBF reduction was observed on either the affected or the unaffected side, even in patients with severe vertebral reverse flow. One patient with VBI symptoms showed an arm exercise-induced global rCBF reduction in the cerebrum and cerebellum, whereas the other asymptomatic patients did not. The %rCBF changes in segments with severely impaired CVR (-8.6%+/-10.7%, mean+/-SD) were significantly lower than those in other segments with less impaired CVR (P<0.01).
Conclusions: Our results suggest that subclavian steal is a benign condition in asymptomatic patients. On the other hand, arm exercise-induced rCBF reduction can occur in the cerebrum and cerebellum in patients with VBI symptoms possibly related to low CVR.