title: Watershed strokes after cardiac surgery: diagnosis, etiology, and outcome.
abstract: OBJECTIVE
  Watershed strokes are more prevalent after cardiac surgery than in other stroke populations, but their mechanism in this setting is not understood. We investigated the role of intraoperative blood pressure in the development of watershed strokes and used MRI to evaluate diagnosis and outcomes associated with this stroke subtype.
  
  
  METHODS
  From 1998 to 2003 we studied 98 patients with clinical stroke after cardiac surgery who underwent MRI with diffusion-weighted imaging. We used logistic regression to explore the relationship between mean arterial pressure and watershed infarcts, between watershed infarcts and outcome, and chi(2) analyses to compare detection by MRI versus CT of watershed infarcts.
  
  
  RESULTS
  Bilateral watershed infarcts were present on 48% of MRIs and 22% of CTs (P<0.0001). Perioperative stroke patients with bilateral watershed infarcts, compared with those with other infarct patterns, were 17.3 times more likely to die, 12.5 and 6.2 times more likely to be discharged to a skilled nursing facility and to acute rehabilitation, respectively, than to be discharged home (P=0.0004). Patients with a decrease in mean arterial pressure of at least 10 mm Hg (intraoperative compared with preoperative) were 4.1 times more likely to have bilateral watershed infarcts than other infarct patterns.
  
  
  CONCLUSIONS
  Bilateral watershed infarcts after cardiac surgery are most reliably detected by diffusion-weighted imaging MRI and are associated with poor short-term outcome, compared with other infarct types. The mechanism may include an intraoperative drop in blood pressure from a patient's baseline. These findings have implications for future clinical practice and research.
authors.affiliation: Johns Hopkins Medical Institutions, Baltimore, MD, USA.
authors.forename: Rebecca F
authors.initials: RF
authors.lastname: Gottesman
authors.forename: Paul M
authors.initials: PM
authors.lastname: Sherman
authors.forename: Maura A
authors.initials: MA
authors.lastname: Grega
authors.forename: David M
authors.initials: DM
authors.lastname: Yousem
authors.forename: Louis M
authors.initials: LM
authors.lastname: Borowicz
authors.forename: Ola A
authors.initials: OA
authors.lastname: Selnes
authors.forename: William A
authors.initials: WA
authors.lastname: Baumgartner
authors.forename: Guy M
authors.initials: GM
authors.lastname: McKhann
mesh_terms: D000368:Aged; D006348:Cardiac Surgical Procedures / Q000009:adverse effects*; D002544:Cerebral Infarction / Q000175:diagnosis / Q000209:etiology / Q000401:mortality / Q000503:physiopathology; D016009:Chi-Square Distribution; D038524:Diffusion Magnetic Resonance Imaging; D005260:Female; D006801:Humans; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D010351:Patient Discharge; D011379:Prognosis; D012047:Rehabilitation Centers; D012866:Skilled Nursing Facilities; D020521:Stroke / Q000175:diagnosis* / Q000209:etiology* / Q000401:mortality / Q000503:physiopathology; D014057:Tomography, X-Ray Computed