Carotid cross-clamping intolerance during carotid endarterectomy: the role of Willis' Circle variations

BACKGROUND : Several authors have emphasized that different anatomical features regarding the Willis Circle (CoW) may represent risk factors in the development of cerebral ischemia during carotid cross-clamping (CCC). The aim of this study is to determine if the incompleteness of CoW assessed by computed tomography angiography (CTA) represents a risk factor for CCC intolerance (CCCi) during carotid artery endarterectomy (CEA). METHODS : We have conducted a retrospective study evaluating patients with a preoperative CTA of the extracranial and intracranial cerebral circulation, who underwent CEA under general anesthesia with preserved consciousness from 2012 to 2017. We considered patients who required shunt for CCCi (group A). We selected a control group with patient who tolerated CCC, homogenous to group A cardiovascular risk factors, contralateral carotid and vertebral arteries disease and operative technique (group B). On CTA we evaluated type (aplasia/hypoplasia) and side of the variations. Endpoints: evaluating CCCi risk in patients with at least one CoW variation; identifying the most common variation associated with CCCi. Statistical analysis was conducted using Fisher's Exact Test. RESULTS : Group A was composed by 17 patients, group B by 37. All group A patients owned at least one CoW variation vs. 70.3% of group B patients (P=0.01). The CoW variations resulted statistically significant were an aplasia/hypoplasia of contralateral anterior cerebral artery (cA1) (P=0.009) and the combination between cA1 and ipsilateral posterior communicating artery (iCoP) (P=0.008). CONCLUSIONS : By this preliminary experience it can be assumed that CCCi is more frequently associated with an incomplete CoW. In particular aplasia/hypoplasia of cA1 alone or associated with iCoP variation is statistically correlated with CCCi.