Reproducibility of asystole during head-up tilt testing in patients with neurally mediated syncope.

Tilt induced prolonged asystole has been considered to identify a distinct subgroup of patients with neurally mediated syncope and management including permanent pacemaker implantation has been suggested. To evaluate the reproducibility of asystolic response during head-up tilt testing (HUT), 33 patients with neurally mediated syncope and asystolic response (> or = 3 seconds) during HUT prospectively underwent two consecutive tests 13 +/- 15 days apart. On repeat tilt testing asystole was reproduced in 12 patients (36%), while 8 patients still had a positive HUT, but without asystole. Remarkably, 13 patients (40%) had a negative repeat HUT. Among 12 patients with asystole on both HUTs there was no significant difference in duration of asystole (14 371 +/- 11 430 ms vs 13 707 +/- 10 470 ms, P = ns) and time to syncope (36 +/- 20 min vs 37 +/- 20 min, P = ns) during initial and repeat HUTs. In conclusion, asystole during tilt testing does not seem to be a reproducible response.