title: Circle of Willis Collateral During Temporary Internal Carotid Artery Occlusion I: Observations From Digital Subtraction Angiography.
abstract: BACKGROUND
  Impaired collateral circulation can lead to stroke during carotid endarterectomy. Carotid stump pressure (CSP) is used as a surrogate measure of collateral flow. The objective was to determine whether anatomical features obtained from digital subtraction angiography correlate with CSP during temporary internal carotid artery occlusion. The second objective was to use these features in combination to predict CSP.
  
  
  METHODS
  Digital subtraction angiographies from 102 patients obtained before endarterectomy were reviewed for anatomical variables including: degree of ipsilateral and contralateral carotid artery stenosis; patency of the anterior communicating artery; presence of cross-flow into ipsilateral middle cerebral artery branches; and size (< or ≥1 mm calibre) of the ipsilateral proximal anterior cerebral (A1), the contralateral A1, and the ipsilateral posterior communicating arteries. At surgery, systemic mean arterial pressure (MAP) and CSP were recorded. Multiple regression analysis was used to assess for anatomical features significantly associated with CSP. A "predicted CSP" equation was applied to 54 subsequent patients and correlated with measured CSP.
  
  
  RESULTS
  Variables correlating with CSP included MAP (p=0.001); the presence of severe contralateral carotid stenosis (p=0.002); patency of the anterior communicating artery (p=0.013); and the size of the contralateral A1 segment (p=0.029). Angiographic cross-flow, ipsilateral A1 size, and ipsilateral posterior communicating artery size were not significant. Predicted CSP correlated significantly with measured CSP (p<0.0001; R 2=0.34).
  
  
  CONCLUSIONS
  Anatomical features and systemic MAP are associated with carotid stump pressure during internal carotid artery occlusion and account for a significant amount of its variation.
authors.affiliation: 1Departments of Clinical Neurological Sciences and Medical Imaging,University of Western Ontario,London Health Sciences Centre,London OntarioCanada.
authors.forename: Stephen P
authors.initials: SP
authors.lastname: Lownie
authors.affiliation: 2Department of Radiology,McMaster University,Hamilton Health Sciences,Hamilton OntarioCanada.
authors.forename: Ramiro
authors.initials: R
authors.lastname: Larrazabal
authors.affiliation: 3Department of Neurosurgery,Henry Ford Health Sciences Center,Detroit,Michigan.
authors.forename: Maximilian K
authors.initials: MK
authors.lastname: Kole
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D015901:Angiography, Digital Subtraction / Q000379:methods*; D001794:Blood Pressure / Q000502:physiology; D016893:Carotid Stenosis / Q000000981:diagnostic imaging / Q000473:pathology* / Q000503:physiopathology* / Q000601:surgery; D002560:Cerebrovascular Circulation / Q000502:physiology*; D002941:Circle of Willis / Q000000981:diagnostic imaging*; D003097:Collateral Circulation / Q000502:physiology*; D004691:Endarterectomy / Q000379:methods; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results
keywords: Carotid stenosis; carotid endarterectomy; carotid stump pressure; cerebral collateral circulation; circle of Willis