R. Brooks et al., PROSPECTIVE EVALUATION OF DAY-TO-DAY REPRODUCIBILITY OF UPRIGHT TILT-TABLE TESTING IN UNEXPLAINED SYNCOPE, The American journal of cardiology, 71(15), 1993, pp. 1289-1292
To evaluate the day-to-day reproducibility of upright tilt-table testi
ng, 109 patients with unexplained syncope prospectively underwent test
ing on 2 consecutive days using a uniform protocol. Results of testing
on 2 separate days were concordant in 69 of 109 patients (63%), and d
iscordant in 40 of 109 patients (37%). Thirty-six of 109 patients (33%
) had vasodepressor syncope on 1 or both days of testing. Nineteen of
30 patients (63%) with vasodepressor responses on the first day did no
t response this response during the second day of testing. An addition
al 6 patients with an initial negative tilt test had a vasodepressor r
esponse on the second day. Only 11 of 36 patients (31%) had reproducib
le vasodepressor responses on both days of testing. Patients with repr
oducible vasodepressor responses had a significantly higher mean numbe
r of preceding clinical syncopal events than patients with 2 normal te
sts (p < 0.02) or nonreproducible results (p < 0.04). In addition, the
se patients had a significantly longer duration of clinical symptoms r
elative to patients with 2 tests that yielded negative results (p < 0.
008) and nonreproducible results (p < 0.01). The elapsed time between
the most recent clinical event and the performance of tilt-table testi
ng was not significantly different among the 3 groups, and did not app
ear to influence the outcome of testing. These data show that vasodepr
essor responses elicited by upright tilt-table testing show day-to-day
variability in many patients, a finding that may limit the interpreta
tion of initial and follow-up test results.