Isoproterenol tilt-table testing provides a diagnosis of
neurocardiogenic syncope in patients with
syncope or near-
syncope. Although acute beta-blockade may prevent the development of
syncope during
isoproterenol tilt-table testing, the use of beta-blockers for chronic prophylaxis may not be effective for some patients who show a positive response to
isoproterenol tilt-table testing. We evaluated whether the efficacy of intravenous
metoprolol in preventing symptoms during repeated tests would be helpful in selecting patients suitable for long-term
therapy.
METHODS AND RESULTS: We studied 55 patients (35 females, 20 males; mean age 36+/-11 years) who had been chosen from a group referred to our institute with a history of unexplained
syncope (> or = 2
syncopal episodes) and a positive response to
isoproterenol tilt-table testing. After a positive response to
isoproterenol tilt-table testing, 5 mg
metoprolol was infused intravenously as a bolus and the test repeated. Thirty-five patients (group 1) showed a positive response again and 20 (group 2) showed a negative response. We started 50 mg
metoprolol once a day for patients in group 1 while group 2 was divided into 2 subgroups: the first subgroup (group 2a, 12 patients) was started on 50 mg
sertraline or 20 mg
paroxetine once a day and the second subgroup (group 2b, 8 patients) was started on 5 mg
midodrine orally once a day. Two months later,
isoproterenol tilt-table testing was repeated. In group 1, 13 of 35 patients (37%) were positive on
isoproterenol tilt-table testing while in group 2, 8 of 20 patients (40%) were positive on
isoproterenol tilt-table testing (p not statistically significant). The
therapies of the two groups were then interchanged. Two months later (4 months from the beginning of the study), the
isoproterenol tilt-table test was repeated. Eleven patients in group 1 (31%) and 6 in group 2 (30%, p not statistically significant) showed a positive response again.
CONCLUSIONS: