title: Duration of head-up tilt test for patients with suspected vasovagal syncope.
abstract: OBJECTIVE
  To investigate the appropriate duration of head-up tilt test (HUTT) needed to induce a positive reaction in patients with suspected vasovagal syncope.
  
  
  RESULTS
  Consecutive patients referred to the syncope unit of our centre for recurrent unexplained syncope were studied. The HUTT included a 30 min passive basic phase and a 20 min sublingual nitroglycerin provocation phase if syncope did not develop during the passive phase. We studied 773 consecutive patients, and 427 (55.2%) patients had a positive HUTT, including 46 patients (10.8%) during the passive basic phase and 381 patients (89.2%) during the nitroglycerin provocation phase. During the basic phase, positive reaction appeared at 7.5 min, and the percentage of positive cases increased with the duration of the test, reaching a peak (20.9%) at 22.5 min, and then decreasing gradually. Most positive reactions (96.1%) occurred between 10 and 25 min during the basic phase. During the nitroglycerin provocation phase, however, the percentage of positive reactions increased rapidly after sublingual nitroglycerin, peaking (35.7%) at 10 min, followed by a sharp decline. Most positive reactions (96.1%) occurred in the first 15 min of the provocation phase.
  
  
  CONCLUSIONS
  The HUTT was a useful diagnostic test in patients with suspected vasovagal syncope, and sublingual nitroglycerin increased the rate of positive reactions. The appropriate duration for HUTT required at least 25 min during the passive basic phase and 15 min during the nitroglycerin provocation phase.
authors.affiliation: Cardiac Function Test Center, Peking Union Medical College and Chinese Academy of Medical Sciences, 167 North Lishi Road, Xicheng State, Beijing, 100037 China.
authors.forename: Jun
authors.initials: J
authors.lastname: Liu
authors.forename: Pihua
authors.initials: P
authors.lastname: Fang
authors.forename: Yue
authors.initials: Y
authors.lastname: Liu
authors.forename: Guoying
authors.initials: G
authors.lastname: Lu
authors.forename: Zhi
authors.initials: Z
authors.lastname: Li
authors.forename: Xiaofeng
authors.initials: X
authors.lastname: Li
authors.forename: Yushan
authors.initials: Y
authors.lastname: Wang
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D002648:Child; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D005996:Nitroglycerin; D012189:Retrospective Studies; D019462:Syncope, Vasovagal / Q000175:diagnosis* / Q000503:physiopathology*; D018667:Tilt-Table Test / Q000379:methods*; D013997:Time Factors; D014665:Vasodilator Agents; D055815:Young Adult
chemical_list: D014665:Vasodilator Agents; D005996:Nitroglycerin