title: Collaterals dramatically alter stroke risk in intracranial atherosclerosis.
abstract: OBJECTIVE
  Stroke risk due to intracranial atherosclerosis increases with degree of arterial stenosis. We evaluated the previously unexplored role of collaterals in modifying stroke risk in intracranial atherosclerosis and impact on subsequent stroke characteristics.
  
  
  METHODS
  Collateral flow was graded in blind fashion on 287 of 569 baseline angiograms (stenoses of 50-99% and adequate collateral views) in the Warfarin--Aspirin Symptomatic Intracranial Disease (WASID) trial. Statistical models predicted stroke in the symptomatic arterial territory based on collateral flow grade, percentage of stenosis, and previously demonstrated independent covariates.
  
  
  RESULTS
  Across all stenoses, extent of collaterals was a predictor for subsequent stroke in the symptomatic arterial territory (hazard ratio [HR] none vs good, 1.14; 95% confidence interval [CI], 0.39-3.30; poor vs good, 4.36; 95% CI, 1.46-13.07; p < 0.0001). For 70 to 99% stenoses, more extensive collaterals diminished risk of subsequent territorial stroke (HR none vs good, 4.60; 95% CI, 1.03-20.56; poor vs good, 5.90; 95% CI, 1.25-27.81; p = 0.0427). At milder degrees of stenoses (50-69%), presence of collaterals was associated with greater likelihood of subsequent stroke (HR none vs good, 0.18; 95% CI, 0.04-0.82; poor vs good, 1.78; 95% CI, 0.37-8.57; p < 0.0001). In multivariate analyses, extent of collaterals was an independent predictor for subsequent stroke in the symptomatic arterial territory (HR none vs good, 1.62; 95% CI, 0.52-5.11; poor vs good, 4.78; 95% CI, 1.55-14.7; p = 0.0019).
  
  
  CONCLUSIONS
  Collateral circulation is a potent determinant of stroke risk in intracranial atherosclerosis, demonstrating a protective role with severe stenoses and identifying more unstable milder stenoses.
authors: UCLA Stroke Center, Los Angeles, CA 90095, USA. davidliebeskind@yahoo.com
authors: David S
authors: DS
authors: Liebeskind
authors: George A
authors: GA
authors: Cotsonis
authors: Jeffrey L
authors: JL
authors: Saver
authors: Michael J
authors: MJ
authors: Lynn
authors: Tanya N
authors: TN
authors: Turan
authors: Harry J
authors: HJ
authors: Cloft
authors: Marc I
authors: MI
authors: Chimowitz
mesh_terms: D000368:Aged; D003097:Collateral Circulation / Q000187:drug effects / Q000502:physiology*; D003251:Constriction, Pathologic / Q000150:complications; D017023:Coronary Angiography / Q000379:methods; D004311:Double-Blind Method; D005260:Female; D005343:Fibrinolytic Agents / Q000494:pharmacology / Q000627:therapeutic use; D006801:Humans; D002537:Intracranial Arteriosclerosis / Q000150:complications*; D002546:Ischemic Attack, Transient / Q000150:complications / Q000188:drug therapy; D053208:Kaplan-Meier Estimate; D008279:Magnetic Resonance Imaging; D008297:Male; D015201:Meta-Analysis as Topic; D008875:Middle Aged; D011446:Prospective Studies; D012044:Regression Analysis; D012307:Risk Factors; D012720:Severity of Illness Index; D020521:Stroke / Q000209:etiology*; D014057:Tomography, X-Ray Computed
chemical_list: D005343:Fibrinolytic Agents