The usefulness of
esmolol in predicting the efficacy of treatment with an oral
beta-adrenergic blocking agent was evaluated in 27 consecutive patients with
neurocardiogenic syncope. Seventeen patients had a positive head-up tilt test response at baseline and 10 patients required intravenous
isoproterenol for provocation of
hypotension. All patients were then given a continuous
esmolol infusion (500 micrograms/kg per min loading dose for 3 min followed by 300 micrograms/kg per min maintenance dose) and rechallenged with a head-up tilt test at baseline or with
isoproterenol. Of the 17 patients with a positive baseline tilt test response, 11 continued to have a positive response to
esmolol challenge. Sixteen patients (including all 10 patients with a positive tilt test response with
isoproterenol) exhibited a negative response to upright tilt during
esmolol infusion. Irrespective of their response to
esmolol infusion, all patients had a follow-up tilt test with oral
metoprolol after an interval of greater than or equal to 5 half-lives of the
drug. All 16 patients (100%) with a negative tilt test response during
esmolol infusion had a negative tilt test response with oral
metoprolol. Of the 11 patients with a positive tilt test response during
esmolol infusion, 10 (90%) continued to have a positive response with oral
metoprolol. It is concluded that in the electrophysiology laboratory,
esmolol can accurately predict the outcome of a head-up tilt response to oral
metoprolol. This information may be helpful in formulating a therapeutic strategy at the initial head-up tilt test in patients with
neurocardiogenic syncope.