title: Diagnostic accuracy of a low-dose isoproterenol head-up tilt protocol.
abstract: The rate of positive head-up tilt (HUT), specificity, and same-day reproducibility of an HUT at 60 degrees combined with a low-dose isoproterenol infusion was assessed in the following patients: 120 consecutive patients with recurrent unexplained syncope, 30 healthy patients in a control group, and 30 patients with documented syncope not related to a vasodepressor reaction. HUT was positive in 61% (73 of 120) of patients with unexplained syncope. The false-positive rate in both the control and documented syncope groups was 6.6%. The mean isoproterenol dose infused was 1.4 +/- 0.5 microgram/min, 1.3 +/- 0.4 micrograms/min, 1.3 +/- 0.5 microgram/min, respectively (p = NS). HUT was positive during the drug free stage in 30 (25%) of 120 patients, and isoproterenol infusion was necessary in the remaining 43 (36%) patients. Immediate reproducibility was assessed in 75 patients, and HUT response was reproduced in 37 (82%) of 45 patients with a baseline positive HUT and in 28 (93%) of 30 patients with a baseline negative response. Overall, "sensitivity," specificity, and reproducibility were 61%, 93%, and 86%, respectively. Clinical variables that increased the probability of a positive outcome were age < or = 50 years and two or more syncopal episodes in the preceding 6 months in the absence of structural heart disease. These data support the use of an HUT protocol with low-dose isoproterenol infusion for the assessment of patients with recurrent syncope.
authors.affiliation: Department of Medicine, University of Western Ontario, London, Canada.
authors.forename: C A
authors.initials: CA
authors.lastname: Morillo
authors.forename: G J
authors.initials: GJ
authors.lastname: Klein
authors.forename: S
authors.initials: S
authors.lastname: Zandri
authors.forename: R
authors.initials: R
authors.lastname: Yee
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D016009:Chi-Square Distribution; D004562:Electrocardiography / Q000187:drug effects / Q000706:statistics & numerical data; D005189:False Positive Reactions; D005260:Female; D006801:Humans; D007545:Isoproterenol / Q000008:administration & dosage; D008297:Male; D008875:Middle Aged; D012008:Recurrence; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013575:Syncope / Q000175:diagnosis; D018667:Tilt-Table Test / Q000379:methods* / Q000706:statistics & numerical data
chemical_list: D007545:Isoproterenol