title: Cerebrovascular blood flow during the near syncopal phase of head-up tilt test: a comparative study in different types of neurally mediated syncope.
abstract: OBJECTIVE
  This study analyses the changes in cerebral blood flow (CBF) velocity occurring in the near syncopal phase of head-up tilt test (HUT) to determine whether their appearance during the premonitory symptoms permits the differentiation of the different types of haemodynamic response.
  
  
  RESULTS
  Six hundred and nineteen patients aged 35.9 +/- 16.4 with a prior history of syncope (55%) or presyncope (45%) were studied. Head-up tilt test was positive in 585 patients. The test was interrupted before syncope, once hypotension was evident and CBF changed. A vasovagal reaction (VVR) was observed in 245 patients. They had a 59% fall in diastolic CBF velocity, whereas systolic CBF velocity decreased by 12%. Postural orthostatic tachycardia syndrome (POTS) was observed in 82, systolic and diastolic CBF velocity decreased 44 and 60%, respectively. A similar response was observed in 258 patients with the orthostatic intolerance (OI) pattern. No significant changes were observed in the negative group.
  
  
  CONCLUSIONS
  Patients with VVR had changes in CBF velocity, which are different from those presented by patients with POTS and OI pattern. Cerebral blood flow monitoring is useful to increase the yield of HUT and may allow early interruption before syncope occurs, reducing patient discomfort.
authors.affiliation: Department of Electrocardiology, Instituto Nacional de Cardiología Ignacio Chávez, Juan Badiano #1, Sección XVI Tlalpan CP 14080, México DF. aghermo@yahoo.com
authors.forename: Antonio G
authors.initials: AG
authors.lastname: Hermosillo
authors.forename: José Luis
authors.initials: JL
authors.lastname: Jordan
authors.forename: Maite
authors.initials: M
authors.lastname: Vallejo
authors.forename: Andrei
authors.initials: A
authors.lastname: Kostine
authors.forename: Manlio F
authors.initials: MF
authors.lastname: Márquez
authors.forename: Manuel
authors.initials: M
authors.lastname: Cárdenas
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001783:Blood Flow Velocity; D002560:Cerebrovascular Circulation; D002648:Child; D005260:Female; D006801:Humans; D007022:Hypotension / Q000503:physiopathology; D007547:Isosorbide / Q000494:pharmacology; D008297:Male; D008875:Middle Aged; D019462:Syncope, Vasovagal / Q000503:physiopathology*; D013610:Tachycardia / Q000503:physiopathology; D018667:Tilt-Table Test; D017585:Ultrasonography, Doppler, Transcranial
chemical_list: D007547:Isosorbide