Angiographic Predictors of Outcomes After Balloon Test Occlusion

Balloon test occlusion (BTO) with adjunctive single-photon emission computed tomography has been used to predict tolerance after permanent internal carotid artery occlusion. Anatomic characteristics of the cerebral circulation might predict BTO outcomes and identify patients susceptible to test failure.

We performed a single-center retrospective analysis of patients who underwent internal carotid artery BTO from July 2013 to June 2020. Patients who passed the clinical BTO underwent single-photon emission computed tomography imaging; technetium-99m-ethyl cysteinate dimer was injected intravenously after 15 to 30 minutes of occlusion and induced hypotension. The diameter of the vessels of the circle of Willis was measured angiographically. Single-photon emission computed tomography imaging hypoperfusion severity was classified as none, mild, low intermediate, high intermediate, and severe. A threshold vessel diameter with most predicted accuracy for BTO failure was created using the Youden index. The threshold value was tested in a logistic regression for prediction of BTO failure and accuracy as represented with a receiver operator curve.

Fifty-seven patients underwent BTO. Neoplasia was the most common indication (n=43, 75%). Twelve (21.1%) patients failed the clinical BTO. Contralateral dominant vertebral artery (P=0.02), smaller anterior communicating artery (ACom; P=0.002), and ipsilateral posterior communicating artery (P=0.03) diameters were correlated with clinical BTO failure. Smaller ACom was most predictive with an area under the curve of 0.907. The Youden index identified an ACom diameter threshold of 1.1 mm, with a sensitivity of 91.7% and specificity of 77.8% (odds ratio, 0.026 [95% CI, 0.003-0.226]; receiver operating characteristic, 0.847) for predicting BTO failure. Patients with severe single-photon emission computed tomography asymmetry had significantly smaller-caliber ACom arteries (ACom median diameter, 0.95 versus 1.4 mm; P=0.0073).

Angiographic findings can be used to predict BTO results. A small ipsilateral posterior communicating artery, and more significantly, a small ACom (<1.1 mm) can be used to identify patients who are likely to fail BTO.