Evaluation of a single-stage isoproterenol-tilt table test in patients with syncope

The purpose of this study was to compare clinical outcomes and tilt test variables between a single-stage tilt test with an infusion of 5 micrograms/min of isoproterenol and a conventional multistage test with infusions of 0, 2 and 5 micrograms/min of isoproterenol in three successive stages.

The diagnosis of neuromediated syncope is often established with isoproterenol--head-up tilt table testing. Previous work has suggested that a single infusion of 5 micrograms/min of isoproterenol during 80 degrees head-up tilt for < or = 10 min should be sufficient to establish the diagnosis.

Forty patients with recurrent syncope underwent both tests in a randomized crossover fashion.

Of 24 patients with positive findings on a multistage test, 19 (79%) had positive findings on a single-stage test, whereas 13 (81%) of 16 patients with negative results on a multistage test had negative results on a single-stage test (p < 0.001, chi-square analysis). Presyncope developed monoexponentially with time at similar rates in both tests, with half-times to presyncope of 1.3 and 2 min for the single-stage and multistage test, respectively. Intertest intrapatient times to presyncope correlated well (r = 0.74, p = 0.001). Finally, peak and trough heart rates each were similar and correlated well between tests. The mean peak heart rate was 136 +/- 25 and 133 +/- 18 beats/min for the single-stage and multistage test, respectively (p = NS, t test; r = 0.50, p = 0.002, linear regression). The mean trough heart rate was 76 +/- 31 and 78 +/- 36 beats/min for the single-stage and multistage test, respectively (p = NS, t test; r = 0.86, p < 0.001, linear regression analysis).

The single-stage and multistage tilt tests are equivalent with regard to clinical outcome and tilt test variables, although the single-stage test is considerably less time-consuming.