RESUMO
BACKGROUND: To evaluate the impact of anatomical variations in the Circle of Willis (CoW) on immediate neurological events (INEs) after carotid endarterectomy (CEA) without shunting in patients with contralateral carotid occlusion (CCO). METHODS: Single-center retrospective study. Patient's demographic and clinical outcomes data were prospectively collected. CoW segments were reviewed retrospectively. Between January 2013 and May 2018, 2090 patients underwent CEA under general anesthesia, CCO was found in 113 (5.4%) patients. CoW segments were classified as normal, hypoplastic (diameter Ë0.8 mm), or absent based on computed tomography angiography. We studied the CoW segments as 2 collateral networks connecting the basilar artery and the ipsilateral middle cerebral artery: a short semicircle (first segment of the ipsilateral posterior cerebral artery [P1] and posterior communicating artery [Pcom] segment) and a long semicircle (contralateral P1, Pcom, and both first segments of the anterior cerebri artery (A1) anterior communicating artery (Acom)). INE was defined as any transient ischemic attack or stroke diagnosed immediately after the procedure. RESULTS: Out of the 113 patients, 46 underwent endarterectomy with shunting. We further excluded 16 patients from the assessment of the CoW due to unavailability or inadequate quality of computed tomography angiography. Of the 113 patients, 2 had strokes, 1 with shunting that occurred hrs after surgery. Besides the other stroke case, 4 INE were observed, all without the use of a shunt. Of the 51 patients with CoW assessment, 10 (19.6%) had a complete CoW, while 21 (41.2%) patients had only 1 semicircle intact (10 short and 11 long intact semicircles), and none of these patients experienced an INE. A total of 20 (39%) patients had both the long and short semicircles incomplete, of which 4 (7.8%) cases had an INE. In all INE cases, at least 1 of the Pcom was absent or hypoplastic. The absence of both Pcom was a strong predictor of incident INE [odds ratio = 11.10 (confidence interval: 1.04-118.60)] for INE. CONCLUSIONS: Patients with CCO and insufficient CoW collateral flow support are at an increased risk of INE, including stroke, in the absence of shunt protection during CEA cross-clamping. Shunting should always be considered when the collateral flow between the ipsilateral middle cerebral artery and the basilar artery is compromised in CCO patients.