Specificity of Head-Up Tilt Testing in Adolescents: Effect of Various Degrees of Tilt Challenge in Normal Control Subjects

Objectives. This study sought to determine the specificity of commonly used tilt protocols in children. Background. Tilt table testing is commonly utilized in the evaluation of children and adolescents with syncope despite a lack of uniformity in tilt protocols and a lack of studies of specificity in normal control subjects. Methods. Sixty-nine normal control volunteers (12 to 18 years old, 38 male, 31 female) with no previous history of syncope, presyncope or arrhythmia underwent tilting to 80°, 70° or 60° for a maximum of 30 min on a motorized table with a footboard support. Autonomic maneuvers, including deep breathing, carotid massage, Valsalva maneuver and diving reflex, were performed before tilt testing to determine whether the response to these maneuvers could identify subjects prone to fainting during tilt testing. Results. Symptoms of presyncope and frank syncope were elicited in 24 of 69 subjects (13 male, 11 female): 6 (60%) of 10 were tilted at 80°, 9 (29%) of 31 at 70° and 9 (32%) of 28 at 60°. Tilt testing at 80° was terminated after the tenth subject by the institutional review board. The mean time to a positive test response was 10.5 min at 80°, 14.2 min at 70° and 13.2 min at 60°. In the 80° tilt, 4 of 10 subjects had a positive response within 10 minutes, whereas only 3 of 31 and 2 of 28 had a positive response within <10 min at 70° and 60° tilt angles, respectively. Subjects with and without a positive response to tilt testing were similar with respect to age; gender; PR, QRS and QT intervals; and baseline heart rate and blood pressure. Likewise, responses to other autonomic function tests performed were similar in tilt-positive and tilt-negative patients. The power for detecting a significant difference between patients tilted at 80° versus 60° and 70° was 0.45 and for detecting differences in autonomic tone between tilt-positive (n = 24) and tilt-negative (n = 45) subjects was 0.8. Conclusions. Children appear to be more susceptible to orthostatic stress than adults. Therefore, tilt protocols commonly used in adults lack specificity in teenage patients. A specificity >85% may be obtained by performing the tilt test at 60° or 70° for no longer than 10 min.