A randomized study of tilt test angle in patients with undiagnosed syncope

BACKGROUND: A widely used tilt test protocol involves passive head-up tilt followed by tilt with isoproterenol infusion if necessary. Little is known about the effects of passive tilt angle and duration, duration of isoproter enol infusion or hemodynamic diagnostic criteria. OBJECTIVES: To assess whether tilt angle and duration of isoproterenol infu sion affected test outcomes in patients with undiagnosed syncope. PATIENTS AND METHODS: Two hundred one syncope patients (87 men, age 45 +/- 20 years, median five faints) were randomly assigned to undergo 60 degrees versus 80 degrees tilt for 45 min, then, if necessary, to receive isoproter enol 30 ng/kg/min for 20 min or less. Positive tests ended in presyncope or syncope. RESULTS: Overall, 49% and 71% of patients fainted at 60 degrees and 80 degr ees, respectively (P=0.002). In the drug-free stage, 27% and 50% of patient s fainted at 60 degrees and 80 degrees, respectively (P=0.0005). In the 119 patients who received isoproterenol, there was no significant difference i n the probability of a positive isoproterenol test at 60 degrees and 80 deg rees, respectively (31% compared with 43% of exposed patients, P=0.25). Sym ptoms developed in adults during drug-free tilt linearly with time at both 60 degrees and 80 degrees at 0.6% and 1.1%/min, respectively, while symptom s during isoproterenol tilt reached an asymptote after about 10 min. Rate-s ystolic pressure products of 7000 mmHg/min and 9000 mmHg/min best distingui shed positive from negative passive and isoproterenol stages, respectively. CONCLUSIONS: The positive yield of passive tilt tests is higher at 80 degre es and increases linearly with the duration of tilt. A subsequent 10 min is oproterenol infusion maximizes positive yield. Evidence-based outcome crite ria accurately distinguish negative from positive tilt tests.