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

Cardiovascular Research Group, University of Calgary, Alberta, Canada.

OBJECTIVES. 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. BACKGROUND. 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. METHODS. Forty patients with recurrent syncope underwent both tests in a randomized crossover fashion. RESULTS. 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). CONCLUSIONS. 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.

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