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.