title: Noninvasive fractional flow on MRA predicts stroke risk of intracranial stenosis.
abstract: OBJECTIVE
  Fractional flow may identify hemodynamic effects and ischemic risk beyond percent stenosis of an artery. We hypothesized that diminished TOF-MRA signal intensity distal to an intracranial stenosis predicts stroke risk.
  
  
  METHODS
  TOF-MRA was acquired prospectively in the SONIA-WASID trials. The distal/proximal signal intensity ratio (SIR) was calculated from 3 mm regions of interest, blinded to outcome. Univariate and multivariate analyses included clinical variables, SIR, and invasive angiography measures to identify predictors for risk of stroke in the territory.
  
  
  RESULTS
  189 patients with 50-99% symptomatic intracranial stenosis in SONIA-WASID had TOF-MRA available. In univariate analysis, the hazard ratio (HR) for stroke in the territory of the symptomatic artery with SIR < .9 was 5.2 (1.8, 15.3; P < .001) as compared to SIR ≥ .9. Multivariate analysis correcting for baseline systolic blood pressure, LDL, centrally measured percent stenosis, recency of symptoms, TICI and downstream collaterals, the HR for SIR < .9 was 10.9 (2.0, 58.9; P < .001). In those with <70% stenosis, a SIR < .9 maintained a significant association with recurrent stroke in the territory (P = .006), with a 2-year event rate of 17.3%.
  
  
  CONCLUSIONS
  Fractional flow assessed by TOF-MRA SIR may be a useful noninvasive tool to identify high-risk intracranial lesions.
  
  
  BACKGROUND
  This trial was not registered because enrollment began prior to July 1, 2005.
authors.affiliation: UCLA Stroke Center, Los Angeles, CA.
authors.forename: David S
authors.initials: DS
authors.lastname: Liebeskind
authors.forename: Andrzej S
authors.initials: AS
authors.lastname: Kosinski
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Lynn
authors.forename: Fabien
authors.initials: F
authors.lastname: Scalzo
authors.forename: Albert K
authors.initials: AK
authors.lastname: Fong
authors.forename: Pari
authors.initials: P
authors.lastname: Fariborz
authors.forename: Marc I
authors.initials: MI
authors.lastname: Chimowitz
authors.forename: Edward
authors.initials: E
authors.lastname: Feldmann
mesh_terms: D001783:Blood Flow Velocity; D002560:Cerebrovascular Circulation; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D002537:Intracranial Arteriosclerosis / Q000150:complications / Q000175:diagnosis* / Q000503:physiopathology*; D018810:Magnetic Resonance Angiography / Q000379:methods*; D011379:Prognosis; D015203:Reproducibility of Results; D018570:Risk Assessment; D012680:Sensitivity and Specificity; D020521:Stroke / Q000175:diagnosis* / Q000209:etiology / Q000503:physiopathology*; D014481:United States
keywords: Intracranial atherosclerosis; MRA; fractional flow; stenosis; stroke