Prospective evaluation of high-dose or low-dose isoproterenol upright tilt protocol for unexplained syncope in young adults,☆☆,

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Abstract

The sensitivity of the passive head-up tilt test (HUT) in the evaluation of unexplained short-lasting syncope in young adults remains insufficient. The infusion of isoproterenol was proposed to improve the benefit. To evaluate the sensitivity-specificity relationship during isoproterenol dosing, we studied 76 young adults (aged 20.9 ± 1.7 years) (group S) with recurrent (mean 3.8 ± 1.6) losses of consciousness that remained unexplained after clinical and noninvasive assessment and 35 young healthy volunteers (aged 22.6 ± 2.7 years) (group V). Subjects underwent either passive HUT (45 min, 60 degrees without drug dosing for 48 subjects in group S (S1) and 17 in group V (V1), or HUT with isoproterenol infusion at progressive doses (2 then 5 μg/min) after 30 minutes of passive tilting for 28 patients in group S (S2) and 18 in group V (V2). During passive HUT, the test was positive (asystole, bradycardia, or fall in systolic blood pressure) in 2 of 17 (11.8%) patients in group V1 and in 7 of 48 (14.6%) in group S1 before 30 minutes, and in 3 of 17 (17.6%) in group V1 compared with 10 of 48 (20.8%) in group S1 at the end of the 45-minute infusion, with no difference in delay before the appearance of a positive result. During HUT with isoproterenol dosing, the test was positive in 2 of 18 (11.1%) patients in group V2 and in 18 of 28 (64.2%) in group S2 before 45 minutes (2 μg/min; p < 0.01) in 7 of 18 (38.8%) in group V2 compared with 24 of 28 (85.7%) in group S2 before 60 min (5 μg/min; p < 0.01). In both cases the mean delay in evoking a positive response was significantly shorter. No asystolic response was observed in the volunteers regardless of the protocol used. The most characteristic response to isoproterenol injection was the appearance of a junctional escape rate with a fall in systolic blood pressure (61.5% of subjects in group S2). The infusion of isoproterenol considerably improves the sensitivity of the HUT with satisfactory specificity if low doses are used (<3 μg/min). These results support the use of HUT with isoproterenol in the evaluation of unexplained syncope in young adults. (Am Heart J 1997; 133:346-52.)

Section snippets

Definitions

Syncope was defined as a brief loss of consciousness appearing suddenly or preceded by short prodromes (<10 seconds) with loss of postural tonus and spontaneous recovery of consciousness without therapeutic intervention.

Patient selection (group S)

From January 1992 to February 1994, 76 patients were enrolled in the study. Each was aged <30 years and had experienced at least one syncope of unexplained cause. Data included a complete history of past incidents, clinical examination, blood tests, a search for carotid sinus

RESULTS

Table I lists the main characteristics of each group. The mean age of patients in groups S and V was similar (between 20.7 and 22.4 years). Both groups were almost exclusively male (two women in the entire study). The difference between the average number of syncopes in group S1 (2.4) and group S2 (5.2) was not significant. The mean delay in carrying out HUT after the most recent syncopal event did not differ significantly in groups S1 and S2 (30.6 and 20.6 days, respectively.

DISCUSSION

Recurring losses of consciousness in children and young adults are a frequent reason for consultation in neurology or cardiology. 1, 17 Because the critical symptoms are fairly unspecific, multiple examinations are performed. These are certainly costly and do not necessarily provide precise and definite diagnoses. 1

Acknowledgements

We thank Mrs. Sylvie Favry, Corinne Blavot, Sylvie Fabick, and Colette Verdière for assistance in this work.

References (30)

  • CA Morillo et al.

    Diagnostic accuracy of a low-dose isoproterenol head-up tilt protocol

    Am Heart J

    (1995)
  • R Sheldon et al.

    Methodology of isoproterenol tilt table in patients with syncope

    J Am Coll Cardiol

    (1992)
  • R. Sheldon

    Effects of aging on responses to isoproterenol tilt-table testing in patients with syncope

    Am J Cardiol

    (1994)
  • DM Bloomfield et al.

    Vagal modulation of RR intervals during head-up tilt and the infusion of isoproterenol

    Am J Cardiol

    (1995)
  • TA Gordon et al.

    A retrospective analysis of the cost effective work up of syncope in children

    Cleveland Clin Q

    (1987)
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    From the Department of Cardiology, H.I.A. Percy, Clamart, and Department of Cardiology, Faculté Libre de Médecine de Lille, Lomme.

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    Reprint requests: Roland Carlioz, MD, Department of Cardiology, H.I.A. Percy, 101 Avenue Henri Barbusse, F 92141 Clamart Cedex, France.

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