Head-up tilt table test: How far and how long?

There is great variation between laboratories in the angle and duration of tilt used in the head-up tilt table test. We compared the hemodynamic response to three sequential randomized 20-min tilts of 60°, 80° and 90° in 20 normal subjects. We studied 66 patients to determine the duration of tilt needed to document three types of orthostatic intolerance. Blood pressure and heart rate were monitored non-invasively. Thirty-nine patients with orthostatic hypotension of diverse causes and 17 patients with orthostatic tachycardia plus were tilted to 90° for 10 min. Ten patients with vasovagal syncope were tilted to 90° for 30 min. A muitivariate analysis of variance performed to assess the hemodynamic responses to 60°, 80° and 90° tilts did not show a statistically significant difference (F = 0.459). Logistic regression analyses revealed that the duration of tilt required to document orthostatic hypotension was 5 min (73% cases correctly identified), orthostatic tachycardia plus 10 min (86.5% cases correctly identified) and neurally mediated syncope 10 min (86.5% cases correctly identified). Tilt duration is a more important variable than tilt angle and the duration of the tilt should depend on the suspected cause of orthostatic intolerance.