title: Relationship between angiographic vasospasm and regional hypoperfusion in aneurysmal subarachnoid hemorrhage.
abstract: OBJECTIVE
  Angiographic vasospasm frequently complicates subarachnoid hemorrhage and has been implicated in the development of delayed cerebral ischemia. Whether large-vessel narrowing adequately accounts for the critical reductions in regional cerebral blood flow underlying ischemia is unclear. We sought to clarify the relationship between angiographic vasospasm and regional hypoperfusion.
  
  
  METHODS
  Twenty-five patients with aneurysmal subarachnoid hemorrhage underwent cerebral catheter angiography and 15O-positron emission tomographic imaging within 1 day of each other (median of 7 days after subarachnoid hemorrhage). Severity of vasospasm was assessed in each intracranial artery, whereas cerebral blood flow and oxygen extraction fraction were measured in 28 brain regions distributed across these vascular territories. We analyzed the association between vasospasm and perfusion and compared frequency of hypoperfusion (cerebral blood flow<25 mL/100 g/min) and oligemia (low oxygen delivery with oxygen extraction fraction≥0.5) in territories with versus without significant vasospasm.
  
  
  RESULTS
  Twenty-four percent of 652 brain regions were supplied by vessels with significant vasospasm. Cerebral blood flow was lower in such regions (38.6±12 versus 48.7±16 mL/100 g/min), whereas oxygen extraction fraction was higher (0.48±0.19 versus 0.37±0.14, both P<0.001). Hypoperfusion was seen in 46 regions (7%), but 66% of these were supplied by vessels with no significant vasospasm; 24% occurred in patients without angiographic vasospasm. Similarly, oligemia occurred more frequently outside territories with vasospasm.
  
  
  CONCLUSIONS
  Angiographic vasospasm is associated with reductions in cerebral perfusion. However, regional hypoperfusion and oligemia frequently occurred in territories and patients without vasospasm. Other factors in addition to large-vessel narrowing must contribute to critical reductions in perfusion.
authors.affiliation: Department of Neurology, Washington University School of Medicine, Campus Box 8111, 660 S Euclid Avenue, S Louis, MO 63110, USA. dharr@neuro.wustl.edu
authors.forename: Rajat
authors.initials: R
authors.lastname: Dhar
authors.forename: Michael T
authors.initials: MT
authors.lastname: Scalfani
authors.forename: Spiros
authors.initials: S
authors.lastname: Blackburn
authors.forename: Allyson R
authors.initials: AR
authors.lastname: Zazulia
authors.forename: Tom
authors.initials: T
authors.lastname: Videen
authors.forename: Michael
authors.initials: M
authors.lastname: Diringer
mesh_terms: D000368:Aged; D001783:Blood Flow Velocity / Q000502:physiology*; D002533:Cerebral Angiography / Q000379:methods; D002560:Cerebrovascular Circulation / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D049268:Positron-Emission Tomography / Q000379:methods; D012189:Retrospective Studies; D013345:Subarachnoid Hemorrhage / Q000000981:diagnostic imaging* / Q000503:physiopathology; D020301:Vasospasm, Intracranial / Q000000981:diagnostic imaging* / Q000503:physiopathology